Research Article Assignment of O O and Mo=O Stretching ...Molybdenum and Tungsten complexes studied...

Research ArticleAssignment of OndashO and Mo=O Stretching Frequencies ofMolybdenumTungsten Complexes Revisited

Choon Wee Kee

Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University 21Nanyang Link Singapore 637371

Correspondence should be addressed to Choon Wee Kee cwkeentuedusg

Received 22 December 2014 Revised 25 March 2015 Accepted 2 April 2015

Academic Editor Arturo Espinosa Ferao

Copyright copy 2015 Choon Wee Kee This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The assignment of peroxo stretching frequencies forMolybdenumandTungsten complexes is studied byDFT andMP2 calculationsWe found that M06 functional is unsuitable for assignment of Mo=O and OndashO stretches in CpMo(1205782-O

2)OCH

3and we found

that MP2 and even the def2-TZVP do not give accurate order of asymmetric and symmetric Mo=O stretching We recommendthe M06L which is a good compromise between speed and accuracy for works involving these complexes For a series of tenMolybdenum and Tungsten complexes studied we found that for MoW=O stretching frequencies at M06Ldef2-TZVP afterscaling a small RMSD of 15 cmminus1 could be obtained However peroxo stretching frequencies RMSD remains high at 40 cmminus1 afterscaling This could potentially point out the need for reassignment of experimental peroxo frequencies in some of the works citedin this report

1 Introduction

IR spectroscopy is an important characterization techniquein chemistry and it has been extensively employed in varioussubdisciplines of chemistry such as organic inorganic andorganometallic chemistry In this work we are interested inthe assignment of vibrational modes (MoW=O and OndashOstretching modes) in Molybdenum and Tungsten complexeswhich are efficient catalysts in epoxidation and oxidation [1ndash4]

We had been working on the use of Molybdenum basedcatalyst in both epoxidation [5] and oxidation of phenol[6] Computational studies on the epoxidation of olefinscatalyzed by Molybdenum complexes have been reportedby the groups of Costa et al [7] Drees et al [8] andComas-Vives et al [9] Generally the B3LYP functionalis employed in these studies and while B3LYP is one ofthe main driven forces for the early popularity of employ-ing DFT in chemistry [10] its shortcoming when appliedto kinetics and interactions which involves dispersion iswell documented in the literature [11ndash16] Therefore wedecided to revisit these reactions with the Minnesota den-sity functionals which have broad accuracy for application

in thermochemistry kinetics and noncovalent interactions[17]

During the course of our study we found that not allMinnesota density functionals are suitable for the assignmentof Mo=O stretching and OndashO stretching in Molybdenumand Tungsten complexes which contain these groups Wealso found that some literature assignments of asymmetricand symmetric Mo=O stretching frequencies to observedbands in the IR spectrum do not agree with those calculatedwith modern DFT functionals Relevant results would bepresented in the rest of this work

2 Material and Methods

All calculations were performed with Gaussian 09 A02 orC01 [18] on NUSHPC (National University of SingaporeHigh Performance Computing)

Def2-SVP def2-SVPD def2-TZVP def2-TZVPD anddef2-QZVPD basis sets [19] were obtained from basis setexchange [20 21] The DFT functionals used were imple-mented in Gaussian 09 C01 [18]

The DFT functionals employed in this study are Min-nesota series [11] (M06L [22] M06-2X andM06) PBE0 [23]

Hindawi Publishing CorporationJournal of ChemistryVolume 2015 Article ID 439270 10 pageshttpdxdoiorg1011552015439270

2 Journal of Chemistry

B3LYP [24] CAM-B3LYP [25] B3PW91 [26] and wB97xD[27] More detailed references to theoretical methods couldbe found in theDFT andMP2 section of Gaussian 09 website

Frequency calculations were performed at the defaultatmosphere and temperature as implemented in GaussianDefault convergence criteria and integration grid were usedunless otherwise stated For tighter convergence criteriaand larger integration grid the keywords ldquoopt=tightrdquo andldquoint=ultrafinerdquo were used in Gaussian 09

For the study of solvent effect two approaches wereadopted For explicit solvation three solvent molecules(acetonitrile or water) were added For implicit solvationmodel the PCM model implemented in Gaussian 09 wasused Geometries optimization and frequencies calculationsfor explicit solvation are the same as in the gas phasecalculations For implicit solvation model optimization andfrequencies calculations are performed with PCM via thekeywords ldquoscrf=(solvent=acetonitrile)rdquo Note that for watertighter convergence criteria and larger integration grid werespecified via ldquoopt=tightrdquo and ldquoint=ultrafinerdquo in addition toldquoscrf=(solvent=water)rdquo

The isotopes used for frequency calculations are thedefault in Gaussian 09 unless otherwise stated

Geometries for 1-CF3 (see Table 5) 1-Cl (see Table 6) 8(see Table 9 and Figure 6) 9 (see Table 9 and Figure 6) and10 (see Table 9 and Figure 6) were obtained from XRD

Anharmonic correction is generally neglected in thisstudy We attempted to fit the calculated harmonic frequen-cies to the fundamental frequencies observed experimentally

3D images of optimized geometries are created withCYLview v10562 beta [28] which generates the script forPOYRAY Images showing normal modes are generated withGaussView 509

3 Results and Discussion

31 Vibrational Modes of CpMo(1205782-O2)OCH

3 Synthesis and

characterization of CpMo(1205782-O2)OCH

31 were reported by

Legzdins et al [29] and Al-Ajlouni et al [30] Relevant IRbands and their assignment by Al-Ajlouni et al are tabulatedin Table 2 Legzdins and coworkers assignment was similar

During the course of our study we explored the useof M06 functional as recommended by Zhao and Truhlarfor transition metal [11] We found that with the M06functional IR frequencies of Mo=O stretch and OndashO stretchfor 1 obtained do not agree with assignments made in theliterature [30 31] More specifically we found that the OndashOstretching frequency is higher than that of Mo=O in termsof wavenumber which contradicts the generally acceptedassignment that M=O stretch is higher in wavenumber thanOndashO stretch for Molybdenum complexes of the generalformula Cp1015840Mo(1205782-O

2)OR

In our calculations the geometry optimization and sub-sequent frequency analysis were performed with M06 func-tional and the family of basis sets defined by Weigend andAhlrichs [19] The optimized geometries of 1 at def2-TZVPare depicted in Figure 1 Two distinct conformations could belocated They are very close in energy with 1-C2 being morestable at M06def2-TZVP (Δ119867C1-C2 = +004 kcalmol and

1-C1 1-C2

ΔG = +038kcalmol ΔG = +00 kcalmol

Figure 1 Illustrating the conformation differences

Table 1 Key vibrational modes and their calculated frequencies

1-C1 1-C2]MondashO 64035 62581 63575 61686

OOP CndashH bending of Cp 8498882984 81868

84710 83087821

]Mo=O 103234 102821In-plane CndashH bending of Cp 103802 103912]OndashO 104144 104097

Δ119866C1-C2 = +038 kcalmol)The effect of the Cp conformationon the vibrational frequencies is generally small (Table 1)

Thenormalmodes of various key vibrationalmodes listedin Table 1 are depicted in Figures 2 and 3 In general MondashOMo=O and OndashO stretches are strongly coupled to vibrationmodes of the Cp ring (Figure 2) but the bendingmodes of Cpring are not strongly coupled to theMo(1205782-O

2)OCH

3portion

of 1The normalmodes associatedwith the bending of Cp ring

are shown in Figure 3 The IP CndashH bending was predicted tohave a relative high intensity

The various isotopes of Molybdenum have negligibleeffect on the frequencies The difference is generally less than10 cmminus1 therefore we would not be considering the effect ofisotope in the calculations

The effects of size of basis sets on the vibrational modesof interest and their frequencies are tabulated in Table 2 TheOndashO stretch is in all cases higher than the M=O stretchexcept in the case of the smallest basis set def2-SVPHoweverthe result at M06def2-SVP is unlikely to be accurate as theaddition of diffuse function reversed the order (M06def2-SVPD) Larger basis sets def2-TZVP and def2-TZVPD gavethe same order as def2-SVPD

When the numerical accuracy is increased by employinga larger integration grid and tighter convergence criteriaas implemented in Gaussian 09 the Mo=O stretch andOndashO stretch become strongly coupled and assignment offrequency is ambiguousHowever atM06def2-TZVPMo=Ostretch and OndashO stretch remain decoupled

Systematic error in calculated IR frequencies calculatedby theoretical methods such as ab initio and DFT is welldocumented Scaling factor has been determined for HF

Journal of Chemistry 3

Table 2 Key vibration modes and their respective frequencies calculated at M06 with various basis sets

Vibration mode Expt[a] M06def2-SVP M06def2-SVPD M06def2-TZVP M06def2-TZVPD]Mo=O 951 104241 102976 102821 102707]OndashO 877 103681 103837 104097 104026OOP bending CndashH of Cp NA 81394 82131 83087 82603

]MondashO 565 63730 62628 63575 6343762086 60996 61686 61579

[a]Based on assignment based on the work of Al-Ajlouni et al [30]

H

H

H H

H

HH

H H H

HH

HHH

H H

H

H

HH

H H

HH

H

H

HHH

CC

CC C

C

CC

CC

CCC

CC

CCC

C C C C

C

O

O

O OO

O

O

O

O

O

O

O

Mo Mo Mo Mo

61686 cmminus163575 cmminus1 102821 cmminus1 104097 cmminus1

MondashO stretch Mo=O stretch OndashO stretch

C

H

Figure 2 Normal modes associated with MoO(1205782-O2) of 1-C2

H

H H

H

H H

H

HH

H H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

HH

H

HH H

H

CC

C CC

CC

C CC C

C CC

CC

CC

C C

CCCCO

O

OO

O

O

O

O

O

O

O

O

Mo Mo Mo Mo

82180 cmminus1 83087 cmminus1 103912 cmminus184710 cmminus1

OOP CndashH bending of Cp + IP CndashH bending of Cp IP CndashH bending of CpOOP

Figure 3 800ndash850 cmminus1 bending modes that are associated with the Cp ring for 1-C2

MP2 and various DFT functionals with many different basissets [32ndash35] The order of frequencies is important as scalingcould improve agreement with experimental frequencies butit does not change the order of frequencies

In order to ascertain that the reversed order of OndashO stretch and Mo=O stretch frequencies when the M06functional was used is not sensitive to the choice of basis set(other than theWeigend andAldrich ones used) calculationswere performed with the two variants of the LANL2 basis setfor Molybdenum and the 6-311+G(dp) or ACCT basis set forcarbon hydrogen and oxygen atoms As can be seen fromTable 3 the order of ]OndashO and ]Mo=O is not affected by thechange of basis set

Nevertheless the problem could lie in the functional andcould be largely independent of the basis set Therefore we

optimized the geometry of 1 with various DFT functionalsand also MP2 The basis set is restricted to def2-TZVP forDFT and MP2 (def2-SVP and def2-SVP are included forcomparison purpose as ab initio results are known to improvewith increasing basis set size) The results are tabulated inTable 4M06 is the outlier amongst all themethods employedin Table 4 as it predicts that ]OndashO is higher in wavenumberthan ]Mo=O in 1

It is likely that the assignment made byM06 is erroneoustherefore it is not recommended for assignment of Molybde-num complexes which contain bothMo=O andOndashO groups

311 Discrepancy between Calculated and XRD OndashO BondLength From Table 4 there is a large discrepancy betweenOndashO bond lengths derived from XRD and calculations It is


Table 3 Results at M06 with various basis sets as indicated in the table

Basis set ]Mo=Ocmminus1 ]OndashOcm

minus1 ]Mo=O minus ]OndashO Mo=OAMo Non-Mo

LANL2TZ(f) 6-311 + G(dp) 100002 102754 minus2752 1669ACCT 101106 104092 minus2986 1669

LANL2DZmod 6-311 + G(dp) 98763 102278 minus3515 1695ACCT[a] 101059 104099 minus304 1684

[a]Invoked via the keyword ldquoaug-cc-pVTZrdquo in Gaussian 09

Table 4 Mo=O and OndashO stretching and Cprsquos CndashH OOP bending frequencies for 1

]Mo=Ocmminus1 ]OndashOcm

minus1 ]Mo=O minus ]OndashOcmminus1 ]OOPbendingCndashHcm

minus1 Mo=OA OndashOAM06L 98021 96392 +1629 82880 1685 1430M06 102821 104097 minus1276 83087 1670 1408M06-2X 107674 106031 +1643 84772 1658 1412PBE0 104341 103192 +1149 84294 1669 1414B3LYP 101740 97741 +3999 84090 1681 1437B3PW91 103009 100912 +2097 83989 1675 1422MP2def2-SVP 95202 89469 +5733 81675 1708 1457MP2def2-SVPD 93688 87131 +6557 82009 1714 1469MP2def2-TZVP 95483 92028 +3455 82625 1711 1459Expt 951a 877a +74 1728 1271aBased on assignment based on the work of Al-Ajlouni et al [30]

Table 5 Mo=O and OndashO stretching and Cprsquos CndashH OOP bending frequencies for 1-CF3


minus1 ]Mo=O minus ]OndashOcmminus1 Mo=O[a]A OndashO[a]A

M06L 97699 96787 912 1685 1427M06 102887 104462 minus1575 1669 1404M06-2X 108430 106557 1873 1656 1409Expt 9527[b] 1689 1440[a]Bond lengths are taken from the work of Hauser et al [38] [b]From the work of Hauser et al [39] no assignment was made by themWe believe that Mo=Oand OndashO band may not be resolved as the next strong band is at 891 cmminus1

Table 6 Mo=O and OndashO stretching and Cprsquos CndashH OOP bending frequencies for 1-Cl


minus1 ]Mo=O minus ]OndashOcmminus1 Mo=OA OndashOA

M06L 98110 96324 1786 1678 1430M06 103238 104076 minus838 1662 1406M06-2X 108537 106620 1917 1649 1410Expt 881 842 39 1771 1352Bond lengths and IR frequencies are taken from the work of Galakhov et al [40]

unlikely that modern computational methods would give anerror of such magnitude Al-Ajlouni et al have indicated thatthe crystal used for XRD is twinned and technical difficultieswere encountered in solving the X-ray structure (supportinginformation of [30])

Two other peroxo complexes were calculated they are 1-CF3 and 1-Cl The XRD solution for 1-CF3 is of better qualitythan both 1 and 1-Cl This is indicated by multiple warningwhen the CIF files of 1 and 1-Cl were subjected to checkingby checkCIF [36] Therefore it would be more prudent tocompare calculated bond lengths of 1-CF3 with those derived

from XRD The results for this comparison are tabulated inTable 5

From Table 5 the trend is similar to that of 1 M06functional predicted that OndashO stretch would be of higherfrequency than Mo=O stretch The calculated OndashO andMo=O bond lengths are of much better agreement with XRDdetermined bond length

Calculated frequencies for complex 1-Cl gave the sametrend as 1 and 1-CF3 (Table 6) Similar to 1 checkCIFdisplayed several warnings for the CIF file of 1-Cl Thediscrepancy between XRD and calculated Mo=O and OndashO


Table 7 Mo=O stretching and Cprsquos CndashH OOP bending frequencies for 2

]Mo=O asymcmminus1 ]Mo=O symcm

minus1 ]Mo=O sym minus ]Mo=O asymcmminus1

M06Ldef2-TZVP 94629 97392 2763M06def2-TZVP 98201 101378 3177M06-2Xdef2-TZVP 101738[a] 105988[a] 425PBE0def2-TZVP 99675 102754 3079B3LYPdef2-TZVP 97530 100435 2905CAM-B3LYPdef2-TZVP 100655 104296 3641B3PW91def2-TZVP 98568 101536 2968wB97xDdef2-TZVP 100662 104462 38MP2def2-SVP 92880 89936 minus2864MP2def2-SVPD 90311 88442 minus1869MP2def2-TZVP 92348 90353 minus1995Experimental[b] 918 887 minus31[a]Tight convergence criteria and ultrafine integration grid were used due to a low imaginary frequency when optimized with default setting [b]Assignmentbased on the work of Legzdins et al see [29]

Table 8 Results of asymmetric and symmetric Mo=O stretches for MoO4

2minus at various levels of theory See Figure 5

Methods ]Mo=O asymcmminus1 ]Mo=O symcm

minus1 ]Mo=O sym minus ]Mo=O asym

MP2def2-SVP 82852 80883 1969MP2def2-SVPD 77278 76895 383MP2def2-TZVP 81013 79953 106MP2def2-TZVPD 78631 78921 minus29MP2def2-QZVPD 78353 78982 minus629CCSD(T)def2-SVP[a] 83960 84017 84027 87213 minus32 (840ndash872)M06Ldef2-SVP 84369 87491 minus3122M06Ldef2-SVPD 81843 86074 minus4231M06Ldef2-TZVP 81771 86485 minus4714M06Ldef2-TZVPD 80775 86315 minus554[a]The optimized geometry does not have a 119879119889 symmetry

bond lengths is large as in the case of 1 We concluded thatin the case of 1 and 1-Cl the XRD derived OndashO and Mo=Obond length is unlikely to be as reliable as the calculated oneThis is similar to the conclusion made by Costa et al [7]

32 Vibrational Modes of CpMoO2CH3 Geometries and

vibrational frequencies of CpMoO2CH32 were initially

calculated with the same set of methods as in Table 4 Wewould focus on the Mo=O stretching frequencies (Table 7)The higher wavenumber band is assigned to the asymmetricM=O stretch and the lower one to the symmetric stretchby Legzdins and coworkers [31] However calculations withvarious DFT functionals indicate that the assignment shouldbe reversed In this case there is no discrepancy amongstall the DFT functionals employed Interestingly and alsorather disturbingly MP2 results are in stark contrast withDFT resultsTherefore two additional functionals long rangecorrected CAM-B3LYP and wB97xD were tested Howeverthe assignments remain unchanged

In this case we believe that MP2 does not give reliableassignment even with the def2-TZVP basis set The reasonsare discussed in the following paragraphs

Firstly the work of Butcher et al on Molybdenum(VI)dihalide dioxide complexes assigned the lower 905 cmminus1 tothe asymmetricMo=O stretch and the higher 940 cmminus1 to thesymmetric Mo=O stretch [37] Consistent with the results ofButcher et al calculation atM06Ldef2-TZVP shows that theasymmetricM=O is at 100350 cmminus1 and the symmetricM=Ostretch is at 104263 cmminus1

Secondly when testing MP2 with def2-SVP def2-SVPDdef2-TZVP and def2-TZVPD on MoO4

2minus we found thatthe symmetric Mo=O stretch (IR inactive) becomes higherin wavenumber than the asymmetric Mo=O stretches atdef2-TZVPD (Table 8) When diffuse function is addedthe difference between asymmetric and symmetric Mo=Ostretches decreases for MP2 but increases for M06L Theaccuracy of MP2 is dependent on the size of basis set thusthe results at def2-QZVPD should be the most accuratetherefore the asymmetric Mo=O stretch should be of lowerwavenumber than the symmetric one This indicates thatfor MP2 a very large basis set augmented with diffusefunctions is required for accurate assignment of Mo=Ostretches However this is computationally very expensive formost molecules that are relevant to Molybdenum catalysis


Table 9 Results of asymmetric and symmetric Mo=O stretches for variuos Molydbenum and Tungsten complexes See Figure 6

Complex Label ]Mo=O sym ]Mo=O asym

Expt Calc[a] Expt Calc[a]

CpMo(1205782-O2)OCH3 1 951[b] 97392 NA NACpMo(O)2CH3 2 926[b] 97392 902[b] 94629CpMo(O)2Cl 3 920[d] 97316 887[d] 94471CplowastMo(1205782-O2)OCl 4 934[e] 95754[i] NA NACpMo(1205782-O2)OCequivC-Ph 5 953[f] 97482 NA NACplowastW(1205782-O2)OCH3 6 949[b] 96145 NA NACpW(O)2CH3 7 943[b] 98120 899[b] 94129CplowastW(1205782-O2)OCH2Si(CH3)3 8 941[b] 95874 NA NA9 9 963[g] 97934 NA NAMoO2Cl2(DMF)2+ 10 940[h] 98768 905 95731[a]Calculated at M06Ldef2-TZVP [b]Al-Ajlouni et al see [30] [c]Legzdins et al see [31] [d]Cousin and Green see [41] [e]Trost and Bergman see [42][f]Chandra et al see [43] [g]Thiels and Eppinger see [44] [h]Butcher et al see [37] [i]strongly coupled to OndashO stretch

Table 10 Results of OndashO stretches for variuos Molybdenum and Tungsten complexes

Complex[a] Label OndashO Scaled (cmminus1) byExpt Calculated Linear model[b] 09613 09595[c]

CpMo(1205782-O2)OCH3 1 877[d] 96392 92612 92662 92527CplowastMo(1205782-O2)OCl 4 884[e] 95384 91414 91693 91559CpMo(1205782-O2)OCequivC-Ph 5 930ndash950[f] 95805 91914 92097 91963CplowastW(1205782-O2)OCH3 6 860[g] 92613 88120 89029 88899CplowastW(1205782-O2)OCH2Si(CH3)3 8 868[g] 92374 87836 88799 88670

9 9 870[h] 94032 89807 90393 9026195149 91135 91467 91334

[a]Refer to Table 9 formolecular structure [b]Linear equation is 119910 = 11887119909minus21969with a1198772 of 05801 [c]From the work of Kesharwani et al forM06Ldef2-TZVP [35] [d]Al-Ajlouni et al see [30] [e]Trost and Bergman see [42] [f]Chandra et al see [43] [g]Legzdins et al see [31] [h]Thiels and Eppinger see [44]

The local DFT functional M06L offers reliable assignment inthis case even with medium size basis set such as def2-SVPThe more accurate CCSD(T) was also tested with def2-SVPbasis set The results are similar to that obtained fromM06Lthus lending credence to the validity of M06L

33 Scaling for Calculated Harmonic Frequency to Fun-damental Frequency We then examined the Mo=O andOndashO stretching frequencies in ten complexes containingMolybdenum or Tungsten by restricting the level of theoryto M06Ldef2-TZVP based on the results presented in theprevious section on 1 and 2 and also because of the lowercomputational cost of a local DFT functional such as M06L[22] The results are tabulated in Table 9 and Figure 6 forMo=O stretch and Table 10 for OndashO stretch

We attempted to perform mode specific scaling for theMo=O of complexes listed in Table 9 and Figure 6 by usinglinear regression to model the experimental fundamentalfrequencies as a function of the calculated harmonic frequen-cies A linear model 119910 = 11887119909 minus 21969 with a 1198772 of 05801was obtained (119910 is the experimental frequency and 119909 is thecalculated frequency at M06Ldef2-TZVP) A scaling factorwas also obtained by setting the intercept of the linear modelto zero (119910 = 09613119909 1198772 = 05588)

Attempt to perform linear regression on the data inTable 10 gave a very poor 1198772 of 01581 when a linear model(119910 = 119898119909 + 119888) is used A negative 1198772 is obtained when theintercept 119888 is set to zero Given the smaller dataset for OndashOstretching and the poor correlation when attempting to fit thedata to a linear model we decided to exclude these data fromfitting and instead used the linear model or scaling factordetermined from Table 9 and Figure 6 to scale the calculatedharmonic frequencies of Table 10

Kesharwani et al reported a scaling factor for fundamen-tals of 09595 at M06Ldef2-TZVP [35] The optimal scalingfactor for Mo=O stretch fundamental determined from theset of data in Table 9 and Figure 6 is 09613 which is veryclose to that of Kesharwani et al Alternatively we havealso determined a linear equation to fit the calculated har-monic frequencies to the observed fundamental frequencies(Table 11 footnote a) The unscaled RMSD for Mo=O stretchfor results in Table 9 and Figure 6 is 404 cmminus1 and scalingby all three methods improved the RMSD to about 15 cmminus1(Table 11) which is smaller than the 2665 cmminus1 reported byKesharwani et al

The agreement between experimental OndashO stretchingfrequencies and calculated ones is not as good as thoseof Mo=O The unscaled RMSD is larger at 8072 cmminus1


Table 11 RMSD of predicted fundamental frequency of Mo=O andOndashO stretch

Mo=O OndashORMSD (cmminus1) atM06Ldef2-TZVP 4045 8072

RMSD (cmminus1) scaled with linearmodel[a] 1505 4175

RMSD (cmminus1) scaled with afactor of 09613 1543 4466


[a]Linear equation is 119910 = 11887119909 minus 21969 with a 1198772 of 05801

The RMSD is reduced by about 50 after scaling to about thesamemagnitude as the unscaled RMSD for Mo=O stretchingand is larger than those reported by Kesharwani et al

At this point it would be prudent to discuss the validity ofassigning IR bands that is in the range of 860ndash880 cmminus1 Fromthe work of Al-Ajlouni et al CpMo(1205782-O

2)OCH

31 shows

strong IR bands at 575 831 849 and 931 cmminus1 beside those inTable 2 [30] The authors have not attempted to assign thesebands Given the poor correlation when we attempt to fit theexperimental OndashO stretch in Table 10 and the large RMSDof calculated OndashO after scaling (Table 11) reassignment ofOndashO stretch might be needed Specifically the scaled OndashOstretch at M06Ldef2-TZVP is about 922 cmminus1 therefore thestrong band at 931 cmminus1 could be a better candidate for theOndashO stretch of 1 It should be noted that our claim remains tobe testedwith further experiments (such isotopic substitutionwith 17O)

Work of Postel et al demonstrated through isotopicsubstitution with 17O that 16Ondash16O stretching of a Molybde-num complex is 898 cmminus1 while the Mo=O is 914 cmminus1 [45]Although this is a different complex from 1 it is interestinglyand potentially helpful to know that the difference betweenMo=O and OndashO frequencies is 16 cmminus1 This is much smallerthan the 74 cmminus1 for 1 according to the assignment by Al-Ajlouni et al [30] and is generally closer to the differencepredicted by most of the DFT functionals in Table 4 Finallywe noted that Chandra et al assign peak in the range of 930ndash950 cmminus1 to OndashO stretch of peroxo in Mo complexes [43]

34 Correlation between Calculated OndashOBond Length andOndashO Stretching Frequencies Cramer and coworkers observed afairly linear relationship betweenOndashO stretching frequenciesand OndashO bond length in a diverse of molecules [46] Inour case the linear correlation between calculated OndashOstretching frequencies and OndashO bond length is excellent (1198772Figure 4)

35 Solvent Effects on Calculated IR Frequencies With 1-CF3as amodel we investigated the effect of solvents on the peroxostretching and Mo=O stretch frequencies Two solvents areinvestigated they are water and acetonitrile Although inpractice 1-CF3might have limited solubility in these solventsthe effect of hydrogen bonding between water and oxygen

920925930935940945950955960965970975

1425 143 1435 144 1445 145 1455 146 1465

y = minus12817x + 27942

R2 = 09762

OndashO bond length (Aring)

OndashO

stre

tchi

ng fr

eque

ncy

(cm

minus1 )

Figure 4 Plot of OndashO stretching frequencies against OndashO bondlength for complexes reported in this work

in 1-CF3 on OndashO and M=O stretching frequencies could beinteresting

The results are tabulated in Table 12 Generally bothexplicit and implicit solvation models predict a decreasein ]Mo=O and ]OndashO Given the limited data and lack ofexperimental data for validation it is premature to drawfurther conclusion The results presented in this section areintended to serve as preliminary guide to further study

4 Conclusion

In this work we have demonstrated the unsuitability of M06functional for assignment of OndashO and Mo=O frequency in1 We have also demonstrated that MP2 requires a largebasis set with diffuse function to produce accurate orderof asymmetric and symmetric Mo=O stretch A series ofcomplexes that calculated M06Ldef2-TZVP indicates thatsymmetric M=O stretch (M=Mo or W) is generally higherin frequency than asymmetric M=O stretch We foundgood agreement between experimental M=O stretches andcalculated ones at M06Ldef2-TZVP after scaling Howeverperoxo stretching frequency remains problematic As accu-rate assignment of IR bands to normal modes is crucial forkinetic study which employed in situ IR techniques morework (both experimental and computational) on the assign-ment of peroxo stretching frequency in metal complexes isimportant

Abbreviations

Cp Cyclopentadienyl ligand C5H5

Cp1015840 Cp and its derivative C5R5 where R could

be any groups such as CH3in Cplowast

DFT Density functional theoryIR InfraredIP In planeOOP Out of planePCM Polarizable continuum modelRMSD Root mean square deviation


Table 12 Calculated Mo=O and OndashO stretching frequencies in gas phase with explicit solvation and with implicit solvation via PCM

Level of theory Solvent ]Mo=Ocmminus1 ]OndashOcm

minus1

M06Ldef2-TZVP

No 97699 96787Acetonitrile PCM[a] 94448 95934Acetonitrile explicit[b] 95275 96173

Water PCM[a][c] 96028[d]

Water explicit[b][c] 95920 96815[a]Default implicit solvent of Gaussian 09 A02 was used [b]Three molecules of solvents were added [c]Tight convergence criteria and ultrafine integrationgrid were used due to low imaginary frequency with default setting [d]Mo=O stretch and OndashO stretch are strongly coupled and assignment is ambiguous andtherefore not attempted

O

O

O

O

O

O

O

OMo

Mo

Asymmetric Mo=O stretch Symmetric Mo=O stretch

Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

Choon Wee Kee acknowledged C-H Tan and NTU forfunding and NUSHPC for generously providing free compu-tational resources

References

[1] F E Kuhn A M Santos and M Abrantes ldquoMononuclearorganomolybdenum(VI) dioxo complexes synthesis reactivityand catalytic applicationsrdquoChemical Reviews vol 106 no 6 pp2455ndash2475 2006

[2] N Grover and F E Kuhn ldquoCatalytic olefin epoxidation with1205785-cyclopentadienylmolybdenum complexesrdquoCurrent OrganicChemistry vol 16 no 1 pp 16ndash32 2012

[3] S A Hauser M Cokoja and F E Kuhn ldquoEpoxidation of olefinswith homogeneous catalystsmdashquo vadisrdquo Catalysis Science ampTechnology vol 3 no 3 pp 552ndash561 2013


[4] Z Wang S W B Ng L Jiang W J Leong J Zhaoand T S A Hor ldquoCyclopentadienyl molybdenum(II) NC-chelating benzothiazole-carbene complexes synthesis struc-ture and application in cyclooctene epoxidation catalysisrdquoOrganometallics vol 33 no 10 pp 2457ndash2466 2014

[5] S Li C W Kee K-W Huang T S A Hor and J ZhaoldquoCyclopentadienylmolybdenum(IIVI)N-heterocyclic carbenecomplexes synthesis structure and reactivity under oxidativeconditionsrdquo Organometallics vol 29 no 8 pp 1924ndash1933 2010

[6] Z Wang C W Kee S Li T S A Hor and J Zhao ldquoAqueousphenol oxidation catalysed by molybdenum and tungsten car-bonyl complexesrdquoApplied Catalysis A General vol 393 no 1-2pp 269ndash274 2011

[7] P J Costa M J Calhorda and F E Kuhn ldquoOlefin epoxidationcatalyzed by 1205785-cyclopentadienyl molybdenum compounds acomputational studyrdquo Organometallics vol 29 no 2 pp 303ndash311 2010

[8] MDrees S AHauserM Cokoja and F E Kuhn ldquoDFT studieson the reaction pathway of the catalytic olefin epoxidationwith CpMoCF3 dioxo and oxondashperoxo complexesrdquo Journal ofOrganometallic Chemistry vol 748 pp 36ndash45 2013

[9] A Comas-Vives A Lledos and R Poli ldquoA computational studyof the olefin epoxidation mechanism catalyzed by cyclopenta-dienyloxidomolybdenum(VI) complexesrdquo Chemistry A Euro-pean Journal vol 16 no 7 pp 2147ndash2158 2010

[10] S F Sousa P A Fernandes and M J Ramos ldquoGeneralperformance of density functionalsrdquo The Journal of PhysicalChemistry A vol 111 no 42 pp 10439ndash10452 2007

[11] Y Zhao andDG Truhlar ldquoTheM06 suite of density functionalsfor main group thermochemistry thermochemical kineticsnoncovalent interactions excited states and transition ele-ments two new functionals and systematic testing of fourM06-class functionals and 12 other functionalsrdquo TheoreticalChemistry Accounts vol 120 no 1ndash3 pp 215ndash241 2008

[12] H Kruse L Goerigk and S Grimme ldquoWhy the standardB3LYP6-31G model chemistry should not be used in DFTcalculations ofmolecular thermochemistry understanding andcorrecting the problemrdquo Journal of Organic Chemistry vol 77no 23 pp 10824ndash10834 2012

[13] M P Waller H Kruse C Muck-Lichtenfeld and S GrimmeldquoInvestigating inclusion complexes using quantum chemicalmethodsrdquoChemical Society Reviews vol 41 no 8 pp 3119ndash31282012

[14] P Hobza J Sponer and T Reschel ldquoDensity functional theoryand molecular clustersrdquo Journal of Computational Chemistryvol 16 no 11 pp 1315ndash1325 1995

[15] L F Holroyd and T van Mourik ldquoInsufficient description ofdispersion in B3LYP and large basis set superposition errorsin MP2 calculations can hide peptide conformersrdquo ChemicalPhysics Letters vol 442 no 1ndash3 pp 42ndash46 2007

[16] S T Schneebeli A D Bochevarov and R A Friesner ldquoParam-eterization of a B3LYP specific correction for noncovalentinteractions and basis set superposition error on a giganticdata set of CCSD(T) quality noncovalent interaction energiesrdquoJournal of Chemical Theory and Computation vol 7 no 3 pp658ndash668 2011

[17] Y Zhao and D G Truhlar ldquoApplications and validations of theMinnesota density functionalsrdquo Chemical Physics Letters vol502 no 1ndash3 pp 1ndash13 2011

[18] M J Frisch Gaussian 09 Revision C01 Gaussian WallingfordConn USA 2009

[19] FWeigend andR Ahlrichs ldquoBalanced basis sets of split valencetriple zeta valence and quadruple zeta valence quality for Hto Rn design and assessment of accuracyrdquo Physical ChemistryChemical Physics vol 7 no 18 pp 3297ndash3305 2005

[20] D Feller ldquoThe role of databases in support of computationalchemistry calculationsrdquo Journal of Computational Chemistryvol 17 no 13 pp 1571ndash1586 1996

[21] K L Schuchardt B T Didier T Elsethagen et al ldquoBasis setexchange a community database for computational sciencesrdquoJournal of Chemical Information andModeling vol 47 no 3 pp1045ndash1052 2007

[22] Y Zhao and D G Truhlar ldquoA new local density functionalfor main-group thermochemistry transition metal bondingthermochemical kinetics and noncovalent interactionsrdquo TheJournal of Chemical Physics vol 125 no 19 Article ID 1941012006

[23] C Adamo and V Barone ldquoToward reliable density functionalmethods without adjustable parameters the PBE0 modelrdquo TheJournal of Chemical Physics vol 110 no 13 pp 6158ndash6170 1999

[24] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[25] T Yanai D P Tew and N C Handy ldquoA new hybrid exchange-correlation functional using the Coulomb-attenuating method(CAM-B3LYP)rdquo Chemical Physics Letters vol 393 no 1ndash3 pp51ndash57 2004

[26] J P Perdew K Burke and Y Wang ldquoGeneralized gradientapproximation for the exchange-correlation hole of a many-electron systemrdquo Physical Review B vol 54 no 23 pp 16533ndash16539 1996

[27] J-D Chai andM Head-Gordon ldquoLong-range corrected hybriddensity functionals with damped atom-atom dispersion correc-tionsrdquo Physical Chemistry Chemical Physics vol 10 no 44 pp6615ndash6620 2008

[28] C Y Legault CYLview Universite de Sherbrooke 2012[29] P Legzdins E C Phillips S J Rettig L Sanchez J Trotter and

V C Yee ldquoRemarkably inert metal-alkyl linkages in alkyl dioxocomplexes of molybdenum and tungstenrdquoOrganometallics vol7 no 8 pp 1877ndash1878 1988

[30] AMAl-Ajlouni DVeljanovski A Capape et al ldquoKinetic stud-ies on the oxidation of 1205785 cyclopentadienyl methyl tricarbonylmolybdenum(II) and the use of its oxidation products as olefinepoxidation catalystsrdquo Organometallics vol 28 no 2 pp 639ndash645 2009

[31] P Legzdins E C Phillips and L Sanchez ldquoNew types oforganometallic oxo complexes containing molybdenum andtungstenrdquo Organometallics vol 8 no 4 pp 940ndash949 1989

[32] M W Wong ldquoVibrational frequency prediction using densityfunctional theoryrdquo Chemical Physics Letters vol 256 no 4-5pp 391ndash399 1996

[33] I M Alecu J Zheng Y Zhao and D G Truhlar ldquoComputa-tional thermochemistry scale factor databases and scale factorsfor vibrational frequencies obtained from electronic modelchemistriesrdquo Journal of Chemical Theory and Computation vol6 no 9 pp 2872ndash2887 2010

[34] P Sinha S E Boesch C Gu R A Wheeler and A KWilson ldquoHarmonic vibrational frequencies scaling factors forHF B3LYP and MP2 methods in combination with correlationconsistent basis setsrdquo The Journal of Physical Chemistry A vol108 no 42 pp 9213ndash9217 2004


[35] M K Kesharwani B Brauer and J M Martin ldquoFrequencyand zero-point vibrational energy scale factors for double-hybrid density functionals (and other selected methods) cananharmonic force fields be avoidedrdquo The Journal of PhysicalChemistry A vol 119 no 9 pp 1701ndash1714 2015

[36] checkCIF 2015 httpcheckcifiucrorg[37] R J ButcherH P Gunz RGA RMaclaganH K J Powell C

J Wilkins and Y S Hian ldquoInfrared spectra and configurationsof somemolybdenum(VI) dihalide dioxide complexesrdquo Journalof the Chemical Society Dalton Transactions no 12 pp 1223ndash1227 1975

[38] S A Hauser R M Reich J Mink A Pothig M Cokoja andF E Kuhn ldquoInfluence of structural and electronic properties oforganomolybdenum(II) complexes of the type [CpMo(CO)

3R]

and [CpMo(O2)(O)R] (R = Cl CH

3 CF3) on the catalytic olefin

epoxidationrdquo Catalysis Science amp Technology vol 5 no 4 pp2282ndash2289 2015

[39] S A Hauser M Cokoja M Drees and F E Kuhn ldquoCatalyticolefin epoxidation with a fluorinated organomolybdenum com-plexrdquo Journal of Molecular Catalysis A Chemical vol 363-364pp 237ndash244 2012

[40] M V Galakhov P Gomez-Sal T Pedraz et al ldquoCyclopenta-dienyl dithiocarbamate and dithiophosphate molybdenum andtungsten complexesrdquo Journal of Organometallic Chemistry vol579 no 1-2 pp 190ndash197 1999

[41] M Cousins and M L H Green ldquo311 Some oxo- andoxochloro-cyclopentadienylmolybdenum complexesrdquo Journalof the Chemical Society (Resumed) pp 1567ndash1572 1964

[42] M K Trost and R G Bergman ldquoCpMoO2Cl-catalyzed epoxi-dation of olefins by alkyl hydroperoxidesrdquoOrganometallics vol10 no 4 pp 1172ndash1178 1991

[43] P Chandra S L Pandhare S B Umbarkar M K Dongare andK Vanka ldquoMechanistic studies on the roles of the oxidant andhydrogen bonding in determining the selectivity in alkene oxi-dation in the presence ofmolybdenum catalystsrdquoChemistrymdashAEuropean Journal vol 19 no 6 pp 2030ndash2040 2013

[44] W R Thiel and J Eppinger ldquoMolybdenum-catalyzed olefinepoxidation ligand effectsrdquoChemistry A European Journal vol3 no 5 pp 696ndash705 1997

[45] M Postel C Brevard H Arzoumanian and J G RiessldquoOxygen-17 NMR as a tool for studying oxygenated transition-metal derivatives first direct oxygen-17 NMR observationsof transition-metal-bonded peroxidic oxygen atoms Evidencefor the absence of oxo-peroxo oxygen exchange in molyb-denum(VI) compoundsrdquo Journal of the American ChemicalSociety vol 105 no 15 pp 4922ndash4926 1983

[46] C J Cramer W B Tolman K H Theopold and A LRheingold ldquoVariable character of OndashO and MndashO bonding inside-on (1205782) 11 metal complexes of O

2rdquo Proceedings of the

National Academy of Sciences of the United States of Americavol 100 no 7 pp 3635ndash3640 2003

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


B3LYP [24] CAM-B3LYP [25] B3PW91 [26] and wB97xD[27] More detailed references to theoretical methods couldbe found in theDFT andMP2 section of Gaussian 09 website

Frequency calculations were performed at the defaultatmosphere and temperature as implemented in GaussianDefault convergence criteria and integration grid were usedunless otherwise stated For tighter convergence criteriaand larger integration grid the keywords ldquoopt=tightrdquo andldquoint=ultrafinerdquo were used in Gaussian 09

For the study of solvent effect two approaches wereadopted For explicit solvation three solvent molecules(acetonitrile or water) were added For implicit solvationmodel the PCM model implemented in Gaussian 09 wasused Geometries optimization and frequencies calculationsfor explicit solvation are the same as in the gas phasecalculations For implicit solvation model optimization andfrequencies calculations are performed with PCM via thekeywords ldquoscrf=(solvent=acetonitrile)rdquo Note that for watertighter convergence criteria and larger integration grid werespecified via ldquoopt=tightrdquo and ldquoint=ultrafinerdquo in addition toldquoscrf=(solvent=water)rdquo

The isotopes used for frequency calculations are thedefault in Gaussian 09 unless otherwise stated

Geometries for 1-CF3 (see Table 5) 1-Cl (see Table 6) 8(see Table 9 and Figure 6) 9 (see Table 9 and Figure 6) and10 (see Table 9 and Figure 6) were obtained from XRD

Anharmonic correction is generally neglected in thisstudy We attempted to fit the calculated harmonic frequen-cies to the fundamental frequencies observed experimentally

3D images of optimized geometries are created withCYLview v10562 beta [28] which generates the script forPOYRAY Images showing normal modes are generated withGaussView 509

3 Results and Discussion

31 Vibrational Modes of CpMo(1205782-O2)OCH

3 Synthesis and

characterization of CpMo(1205782-O2)OCH

31 were reported by

Legzdins et al [29] and Al-Ajlouni et al [30] Relevant IRbands and their assignment by Al-Ajlouni et al are tabulatedin Table 2 Legzdins and coworkers assignment was similar

During the course of our study we explored the useof M06 functional as recommended by Zhao and Truhlarfor transition metal [11] We found that with the M06functional IR frequencies of Mo=O stretch and OndashO stretchfor 1 obtained do not agree with assignments made in theliterature [30 31] More specifically we found that the OndashOstretching frequency is higher than that of Mo=O in termsof wavenumber which contradicts the generally acceptedassignment that M=O stretch is higher in wavenumber thanOndashO stretch for Molybdenum complexes of the generalformula Cp1015840Mo(1205782-O

2)OR

In our calculations the geometry optimization and sub-sequent frequency analysis were performed with M06 func-tional and the family of basis sets defined by Weigend andAhlrichs [19] The optimized geometries of 1 at def2-TZVPare depicted in Figure 1 Two distinct conformations could belocated They are very close in energy with 1-C2 being morestable at M06def2-TZVP (Δ119867C1-C2 = +004 kcalmol and

1-C1 1-C2

ΔG = +038kcalmol ΔG = +00 kcalmol

Figure 1 Illustrating the conformation differences

Table 1 Key vibrational modes and their calculated frequencies

1-C1 1-C2]MondashO 64035 62581 63575 61686

OOP CndashH bending of Cp 8498882984 81868

84710 83087821

]Mo=O 103234 102821In-plane CndashH bending of Cp 103802 103912]OndashO 104144 104097

Δ119866C1-C2 = +038 kcalmol)The effect of the Cp conformationon the vibrational frequencies is generally small (Table 1)

Thenormalmodes of various key vibrationalmodes listedin Table 1 are depicted in Figures 2 and 3 In general MondashOMo=O and OndashO stretches are strongly coupled to vibrationmodes of the Cp ring (Figure 2) but the bendingmodes of Cpring are not strongly coupled to theMo(1205782-O

2)OCH

3portion

of 1The normalmodes associatedwith the bending of Cp ring

are shown in Figure 3 The IP CndashH bending was predicted tohave a relative high intensity

The various isotopes of Molybdenum have negligibleeffect on the frequencies The difference is generally less than10 cmminus1 therefore we would not be considering the effect ofisotope in the calculations

The effects of size of basis sets on the vibrational modesof interest and their frequencies are tabulated in Table 2 TheOndashO stretch is in all cases higher than the M=O stretchexcept in the case of the smallest basis set def2-SVPHoweverthe result at M06def2-SVP is unlikely to be accurate as theaddition of diffuse function reversed the order (M06def2-SVPD) Larger basis sets def2-TZVP and def2-TZVPD gavethe same order as def2-SVPD

When the numerical accuracy is increased by employinga larger integration grid and tighter convergence criteriaas implemented in Gaussian 09 the Mo=O stretch andOndashO stretch become strongly coupled and assignment offrequency is ambiguousHowever atM06def2-TZVPMo=Ostretch and OndashO stretch remain decoupled

Systematic error in calculated IR frequencies calculatedby theoretical methods such as ab initio and DFT is welldocumented Scaling factor has been determined for HF




]MondashO 565 63730 62628 63575 6343762086 60996 61686 61579


H

H

H H

H

HH

H H H

HH

HHH

H H

H

H

HH

H H

HH

H

H

HHH

CC

CC C

C

CC

CC

CCC

CC

CCC

C C C C

C

O

O

O OO

O

O

O

O

O

O

O

Mo Mo Mo Mo



C

H


H

H H

H

H H

H

HH

H H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

HH

H

HH H

H

CC

C CC

CC

C CC C

C CC

CC

CC

C C

CCCCO

O

OO

O

O

O

O

O

O

O

O

Mo Mo Mo Mo




























































9 9 870[h] 94032 89807 90393 9026195149 91135 91467 91334

















2)OCH

31 shows





920925930935940945950955960965970975

1425 143 1435 144 1445 145 1455 146 1465

y = minus12817x + 27942

R2 = 09762


OndashO

stre

tchi

ng fr

eque

ncy

(cm

minus1 )




4 Conclusion


Abbreviations








minus1

M06Ldef2-TZVP




O

O

O

O

O

O

O

OMo

Mo


Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6



Acknowledgments


References









































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




]MondashO 565 63730 62628 63575 6343762086 60996 61686 61579


H

H

H H

H

HH

H H H

HH

HHH

H H

H

H

HH

H H

HH

H

H

HHH

CC

CC C

C

CC

CC

CCC

CC

CCC

C C C C

C

O

O

O OO

O

O

O

O

O

O

O

Mo Mo Mo Mo



C

H


H

H H

H

H H

H

HH

H H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

HH

H

HH H

H

CC

C CC

CC

C CC C

C CC

CC

CC

C C

CCCCO

O

OO

O

O

O

O

O

O

O

O

Mo Mo Mo Mo




























































9 9 870[h] 94032 89807 90393 9026195149 91135 91467 91334

















2)OCH

31 shows





920925930935940945950955960965970975

1425 143 1435 144 1445 145 1455 146 1465

y = minus12817x + 27942

R2 = 09762


OndashO

stre

tchi

ng fr

eque

ncy

(cm

minus1 )




4 Conclusion


Abbreviations








minus1

M06Ldef2-TZVP




O

O

O

O

O

O

O

OMo

Mo


Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6



Acknowledgments


References









































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



















































9 9 870[h] 94032 89807 90393 9026195149 91135 91467 91334

















2)OCH

31 shows





920925930935940945950955960965970975

1425 143 1435 144 1445 145 1455 146 1465

y = minus12817x + 27942

R2 = 09762


OndashO

stre

tchi

ng fr

eque

ncy

(cm

minus1 )




4 Conclusion


Abbreviations








minus1

M06Ldef2-TZVP




O

O

O

O

O

O

O

OMo

Mo


Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6



Acknowledgments


References









































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










2)OCH

31 shows





920925930935940945950955960965970975

1425 143 1435 144 1445 145 1455 146 1465

y = minus12817x + 27942

R2 = 09762


OndashO

stre

tchi

ng fr

eque

ncy

(cm

minus1 )




4 Conclusion


Abbreviations








minus1

M06Ldef2-TZVP




O

O

O

O

O

O

O

OMo

Mo


Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6



Acknowledgments


References









































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




minus1

M06Ldef2-TZVP




O

O

O

O

O

O

O

OMo

Mo


Figure 5

MoMo

Mo

Mo

OO

Cl

Cl

Cl

O

OOO

OOO

Ph

OO

MoMoMoCl O

O

WO

OO

WO

O WO

OO

1 2 3 4 5

6 7 8TMS

O

OO

O ON

NN

9

DMF

DMF

O

O

10

H2C

H3C

H3C

H3C

H3C

H3C

H3C H3C

H3CH3C

H3C

CH3CH3

CH3

CH3CH3

CH3

CH3

CH3

CH3

C8H17

F3C

Figure 6



Acknowledgments


References









































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






































3R]























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Assignment of O O and Mo=O Stretching ...Molybdenum and Tungsten complexes studied...

Documents

Transcript of Research Article Assignment of O O and Mo=O Stretching ...Molybdenum and Tungsten complexes studied...