Indian Journal of Chemistry Vol. 44A, March 2005, pp. 516-520

Ruthenium (I) complexes with

4-ethoxy-phenyl tellurol : X-ray

crys tal structure of complex

[Ru2(C0)4(!-l-TeC6H 40CH2CHr4)2 (/-l-dppm)]

( dppm=Ph2PCH2PPh2)

Noorj ahan Bcgum 1; Md Iqbal Hyder1

, Shahidull slam 1,

Shariff E Kabir 1, Kalipada Kundu 1* & K M Abdul Mali k2*

1Department of Chemi stry, Jahangi rnagar University, Savar, Dhaka 1342, Bangladesh

Email: skabirj u@yahoo .com

2Department of Chemi stry, Cardiff Unive rsity, P.O. 13ox 912 , Park Place, Cardiff CF I 0 3TI3 , United Kingdom

Receil'ed 15 March 2004; reFised 13 January 2005

The reaction of [R uJ(C0) 10(~t-dppm)] (dppm=Ph2PCH 2PPh2)

with two molar equ ivalents o f Te2Ar2 (A r = C6H~OCH 2CH1-4) in relluxing THF for 6 h gave the known co mplex [Ru 2(C0)~ (~t -TeArh(~t -dppm )] 11 together with two new complexes [Ru2(COl6(}1-TeAr)2] 2 and cis-[Ru(COM111-TeAr)2] 3. Complex I has been struct urall y charac teri zed by X-ray crystall ography. Both Ru atoms are in highly di storted octahedral geo met ry. For each Ru , two CO groups in cis posit ions, the other bo nded Ru atom and the Te atom of a bridging TeA r li ga nd occupy equatorial sites, and the Tc atom of the other bridging TeAr ligand and a P atom of the bridging dppm li gand are in trans pos iti ons. Thus, in complex 1, the Te ato m of one TeA r gr.Jup lies in the Ru 21'2 plane wh ile that o f the second TeA r group at a po int nearly perpendicul ar to thi s plane, mak ing the two TeAr groups non­equivale nt but keep ing the two P atoms of the bridgi ng dppm li gand in eq uival ent positions.

IJ>C Code: Int. Cl. 7 C07 15/00; GO IN'23/00

The coordinat ion behaviour of sulphur and selenium li gands with transition metals has been extensively ex plorecl2.15, but that of tellurium analogues has so fa r received little attention. Khandelwal and

k 16 17 I d I . . b I . cowor ers · , 1ave reporte t 1e mterestmg e 1avtour of the diary I ditelluricles Te2Ar2 (Ar=C6H5, C6H40Me-4, C6H40Et-4) in their reactions with Pt(ll ) and Pcl(ll). Keeping the Te-Te bond intact, these ligands coordinate with Pt(II ) using only one Te atom acting as a monodentate li gand and with Pd(fl ) using both of the two Te atoms giv ing a two-centre bridge structure. However, in most of their reactions with transition metal complexes, the Te-Te bond of the Te2Ar2

compounds breaks to give two TeAr groups which coordinate to metal centres by oxidative addition either as monodentate terminal grou ps or as two or three-centre bridging ligands18. Recent ly, we reported 1

that the cluster complex [Ru 3(C0) 10(~-dppm)] reacts with Te2Ar2 (A r=C6H40CH2CH3-4) in refluxii1g toluene over a period of 2 h to form the complexes [Ru2(COM~-TeArh(~-dppm)] , [Ru4(CO)s(~-CO)

(~-Te)2 (~-dppm)] , [Ruz(CO)o{ ~-CH2PPh (C6H-1) PPh}] and [Ru2(C0)6 {~-C6H4 PPh(CH2) PPh}] . Since the nature of products in reacti ons of transi tion metal complexes with chalconido ligands depends on reaction conditi ons (so lvent, temperature, reaction time, etc.) we have repeated the same reaction in refluxin g THF with a reaction time of 6 h. The results are reported in thi s note.

Experimental Reactions and manipul alions were carri ed out

under an atmosphere of dry oxygen-free nitrogen by the conventional Schlenk techniques. Solvents were dried by standard methods and di sti lied before use. All reagents were Aldrich or BDH reagent grade chemicals and used as obtained. [Ru3(C0 )10

(~-clppm) ] 1 1) and Te2A rz (A r=C6H40 CHzCH3-4i0

were prepared by publi shed methods. lR spectra were recorded in CH1CI? on a Shimadzu FT lR 810 I spectrophotomet~r, -and 1H and 31 P{ 1H} NMR in CDCI3 on a Bruker DPX 400 spectrometer. Chemical shifts in the 1H and 31P{ 1H} NMR spectra are relative to SiMe4 and 85 % H3P04, respectively. The mass spectra were recorded with a Vari an MAT CH 7 instrument from the Department of Chemistry, University of Bayreuth, Germany.

Synthesis of complexes [Ru2(CO)~ ().l-TeArh{).l-dppm) ] 1, [Ru2(CO)r.().l-TeAr)z]2 and cis-[Ru(C0)~(11 1 -TeAr)z]3

A mi xture of [Ru3(C0) 10(~t-dppm)] (0.350 g, 0.362 mmol) and Te2Ar2 (0.360 g, 0.724 mmol) in I :2 molar ratio was dissolved in THF (50 mL) and the solution thus obtained was heated under reflu x for 6 h. A deep reel so lution was formed from whi ch the solvent was removed under reduced pressure and the residue thus obtained was redissolved in CH2CI2 and chromato­graphed on sili ca plates by preparative TLC [eluant: hexane (b.p. 40-60°)-CH2Cl2, 3: I , vlv]. This gave

NOTES 517

three bands which after recrystallization from CH2Cb/ hexane at 0°C afforded the following three complexes:

[RulCCOM~-t-TeArhC~-t-dppm)] 1, orange crystals (0.142 g, 22%) [Found: C, 44.86; H, 3.42; Reqd. for C4sH4o06P2Te2Ru2: C, 45.19; H, 3.35%]. Spectral data: IR: v(CO) 2019 (vs), 2010 (s), 1967 (br), 1956 (sh) cm-1; 1H NMR: 8 3.92 (q, J = 6.9, 13 .8 Hz, 2H, OCH2), 3.98 (q, J = 6.9, 13.9 Hz, 2H, OCH2), 1.33 (t, J = 7.0 Hz, 3H, CH3), 1.37 (t, J = 7.0 Hz, 3H, CH3), 6.58 (d, J = 8.5 Hz, 2H, C6H4), 6.62 (d, J = 8.5 Hz, 2H, C6H4), 7.66 (br, 4H, C6H4), 4.24-4.40 (m, 2H, PCH2P), 6.99-7.44 (m, 20H, Ph); 31P{ 1H} NMR: 8 13.56; mass: m/z 1195 (M+).

[Ru2(COM~-t-TeArh] 2, light orange crystals (0.06 g, 13%) [Found: C, 30.82; H, 2.16; Reqd. for C22H, 80 sTe2Ru2: C, 30.44; H, 2.07%]. Spectral data: IR: v(CO) 1998 (br), 1975 (br), 1933 (br) cm-1; 1H NMR: 8 7.78 (d, J = 7.5 Hz, 4H, C6H4), 6.94 (d, J = 7.6 Hz, 4H, C6H4), 4.12 (q, J = 6.6, 13.4 Hz, 4H, OCH2), 1.46 (t, J = 6.7 Hz, 6H, CH3); mass: m/z 867 (M+).

cis-[Ru(COMr( TeAr)2] 3, yellow crystals (0.14 g, 18%) [Found: C, 33.92; H, 2.48; Reqd. for C2oH1 s06Te2Ru: C, 33 .79; H, 2 .53 %]. Spectral data: IR: v(CO) 2021 (vs), 2002 (s), 1969 (s, br), 1944 (br) cm-1; 1H NMR: 8 7.56 (d, J = 7.4 Hz, 2H, C6H4), 6.62 (d, J = 7.4 Hz, 2H, C6H4), 3.97 (q, J = 5.6, 9.2 Hz, 2H, OCH2), 1.31 (t, J = 7.7 Hz, 3H, CH3); mass: mlz 710 (M+).

X-ray crystal structure determination of [Ru2(CO)~ (J.l· TeArh(J.t-dppm)] 1

Single crystals of 1 suitable for X-ray diffraction were obtained by slow diffusion of hexane into a CH2Cb solution of the complex at 0°C. Crystallographic data were collected at 293(2) K using a FAST TV area detector diffractometer positioned at the window of rotating anode generator, using Mo-Ka radiation (A=0.71073 A) by following previously described procedure21. The data were corrected for Lorentz and polarization factors and also for absorption effects (DIFABS)22

. The structure was solved by direct methods (SHELXS-97)23 and refined on F2 by full-matrix-least-squares (SHELXL-97)24 , using all unique data with intensities greater than zero. All non-hydrogen atoms were refined anisotropically, with the phenyl rings treated as idealized hexagon (C-C= 1.390A, C-C-C= 120.0°). The hydrogen atoms were included in calculated positions

Table I -Crystal data and structure refinement for 1

Compound

Chemical formula

Formula weight

Temperature, K

Radiation, wavelength, A Crystal system

Space group

Unit cell dimensions

a= 10.00100(10) A b = 12.2200 (2) A c = 18.8920 (4) A Volume, A' z Density (calculated), g/cm3

Absorption coefficient, mm· '

F(OOO)

Crystal size, mm3

0 range for data collection

Reflections collected

Independent reflections

Refinement method

Data/restraints/parameters

Goodness-of-fit on F2

Final R indices[/> 2a (I)]

R indices (all data)

Largest diff. peak and hole, e A-3

[Ru2(COM~t-TeArh(J.t-dppm)]

C4sH3s06P2Ru2 Te2 1194.03

293(2)

Mo, 0.71073

Triclinic

P-1

a=79.7030 (6t

13=83.4800 (6) 0

y=87 .3330 ( I W 2256.14 (6)

2

1.758

2.053

1156

0. I Ox0.08x0.08

2.94-27.49°

41593

10266 [Rirn=0.0508)

Full-matrix least-squares on F2

1 0266/26/516

0 .967

R /=0.0373, wR2=0.0872

R 1=0.0521, wR2=0.0948

1.878 and -0.942

(riding model ). The crystal data and refinement details are summarized in Table 1. The largest peak in the final difference Fourier map ( 1.878 e A3) was located in the vicinity of C44 atom; the map had no other significant features . A final analysis of variance between observed and calculated structure factors showed no dependence on amplitude or resolution and the hydrogen atoms on the C44 atom were refined with 26 restraints . The goodness of fit is 0.967 and the restrained goodness of fit is 0.982 for 26 restraints .

Results and discussion [Ru3(C0) 10(~-t-dppm)] reacted with two molar

equivalents of Te2Ar2 (Ar=C6H40CH2CH3-4) in refluxing THF over a period of 6 h to form the complexes [Ru2(COM~-t-TeArM~-t-dppm)] 1, [Ru2(COM~-t-TeAr)2] 2 and cis-[Ru(C0)4(r( TeArh ] 3 which were characterized by spectroscopic methods (spectral data included in the experimental section). Previously, we reported 1 the result of the same reaction carried out in refluxing toluene over a period of 2 h where the complex 1 together with three other known complexes [Ru4(CO)s(~-t-CO)(~-t4 -Teh(~-t-

518 INDIAN J CHEM, SEC A, MARCH 2005

l (A)

Ar

oc"'- / T~ /co

o~ryr'co Ph2 P~ /PPh2

CH2

l (B)

Fig. I - Strucwrc of 1 in accordance with its crystal structure 1(A) and the previously proposed st ructure 1(B) (Ar = C6H40CH 2CHr 4).

Fig. 2---0RTEP drawing of the X-ray structure of 1

dppm)]25, [Ruz(C0)6 { )..l-CHzPPh(CGH4)PPh} f 6 and

[Ruz(C0)6{ )..l-C6H4PPh(CH2)PPh} ]26 were obtained. This clearly es tablished the idea that the nature of products formed in reactions of a transition metal complex with another reagent depends much on reaction conditions (solvent, temperature, reaction time, etc.) .

A careful examination of the t H NMR of 1 shows that two sets of sharp peaks of equal intensity for the TeC6H40CH2CH3-4 group are present in the spectrum [8 3.92 (q, J = 6.9, 13.8 Hz, 2H, OCH2), 3.98 (q, J = 6.9, 13.9 Hz, 2H, OCH2), 1.33 (t, J = 7.0 Hz, 3H, CH3), 1.37 (t, J = 7.0 Hz, 3H, CH3), 6.58 (d, J = 8.5 Hz, 2H, Cr,H4), 6.62 ' (d, J = 8.5 Hz, 2H, C6H4), 7.66

(br, 4H, C6H~)]. This cannot be explained by the proposed structure previously reported 1 or by the existence of two isomers of 1 in solu tion because the intensity of the two sets of peaks are exactl y eq ual. Hence, the actu al structure of 1 was determined by X­ray diffraction of its crystal. A simple drawing in accordance with the X-ray structure 1 (A) along with the previously proposed structure 1 (B) is shown in Fig. I and an ORTEP diagram of the X-ray structure is shown in Fig. 2. Selected bond lengths and angles in 1 are given in Table 2.

From the X-ray structure, we find that with the two bonded Ru atoms, the bridging dppm ligand forms a pentagon, a bridging TeAr group forms a triangle slightl y inclined towards the pentagonal plane [P(l)Ru(l)Te(2)= 156.56(3), P(2)Ru(2)Te(2)= 150.65(3)] and the other bridging TeAr group forms another triangle almost perpendicular to thi s plane [P(l )Ru( 1 )Te( I )=88.0 I (3), P(2)Ru(2)Te(l )=85.80(3)]. Both Te atoms are almost eq uidi stant from the two bonded Ru atoms [Te(l )Ru(l)=2 .7018 (4), Te( I )Ru(2)=2.7180( 4 ), Te(2)Ru(l )=2.6720( 4) , Te(2)Ru(2)=2.6709(4)A] but the Te( I )Ru ( I), Te(l)Ru(2) di stances are slightly larger than the Te(2) Ru ( I), Te(2)Ru(2) distances. Each of the two Ru atoms is also bonded to two terminal CO groups in cis positions. Both Ru are thus in highly di storted octahedral geometry with two cis CO groups, the other bonded Ru atom and a bonded Te atom of one bridged TeAr group at the equatorial sites , and the Te atom of the other bridging TeAr group and a P atom of the bonded dppm li gand in axial posi tions. The structure clearly shows that the TeAr group perpendicul ar to the pentagonal plane is closer to the dppm li gand compared to the in plane TeAr group but their distances fro m the metal centers vary in the reverse order.

The two TeAr groups are, therefore, non-equivalent and show two sets of sharp signals of equal intensity in the 1 H NMR spectrum. It is also clear from the structure that the two P atoms in the complex are almost equi valent [Ru( I )P(l )=2.3 199(1 1 ), Ru(2)P(2) =2.3361 (11 )A, P( I )Ru(l )Ru(2)""97°, P(2)Ru(2)Ru( 1) ""92°] and hence only one sharp signal for P (8 13.6) is found in the 31P{ 1H} NMR of 1. From Table 2, we find that the Ru-Ru distance in 1 [2.7457(4) A] is significantly lower than that in the starting complex [Ru3(CO)I!J()..l-dppm)] [2.834( I) A] in which the two Ru atoms considered are also bridged by the dppm ligand27

. This may be exp lained by the presence of

NOTES 519

Table 2 - Bond lengths (A) and angles (deg) for 1

Bond lengths

Ru( I )-C( l ) 1. 87 1(4)

Ru ( l )-P( l ) 2.3 199( 11 )

Ru(l )-Tc( l ) 2.70 18(4)

Ru(2)-C(4) 1.87 1(4)

Ru (2)-P(2) 2.336 1( 11 )

Ru(2)-Te( I ) 2.7 180(4)

Te(2)-C(38) 2. 139(4)

Bond angles

C( I )-Ru( I )-C(2) I 0 1.65( 19)

C(2)-Ru( I )-P( I ) 101.96( 15)

P( l )-Ru(I )-Te( l ) 88.0 1 (3)

P( I )-Ru( I )-Ru(2) 97.50(3)

Te( I )-Ru ( I )-Ru(2) 59.855(10)

C(4)-Ru(2)-P(2) 95.74(13)

P(2)-Ru(2)-Te(2) 150.65(3)

Te(2)-Ru(2)-Te( I ) 80.6 16( 12)

Te(2)-Ru(2)-Ru( I ) 59.096( 11 )

Ru( I )-Te(l )-Ru (2) 60.874( I 0)

two extra bridges by TeAr groups in 1 since these bridging bring the two Ru atoms closer. Table 2 also shows that Te(2) is significantly closer to the metal centres compared to Te( I). The basic structure of 1 is si milar to that of the recently reported selenium analog Ru2(COM!l-SePhM!l-dppm), synthesized by the reaction of [Ru3(C0 )10(!l-dppm)] with PhSeSePh in refluxing THF28

.

Complexes 2 and 3 were characterized by spectroscopic methods. 2 showed three JR bands in the region for terminal carbonyl groups but none in the bridging region , 1H NMR displayed only one set . of sharp signal s for C6H40CH2CH3-4 group but no signal for the P-CHrP or phenyl groups of dppm, and 3 1P{ 1H} NMR did not give any signal for P atom. All these pieces of information indicated that complex 2 contains only terminal carbonyls and equivalent TeAr groups but no dppm ligand. The mass spectrum showed the molecular ion peak at m/z 867 and other peaks for successive removal of six CO groups. The proposed structure shown in Fig. 3 is thus consistent with all spectral investigations.

IR spectrum of 3 showed four absorption frequencies v(CO) only for terminal carbonyl groups and 1H NMR displayed one set of sharp signals for TeA r groups and none for dppm ligand . The mass spectrum showed the molecular ion peak (111/z=71 0)

Ru( I )-C(2) 1.904(4)

Ru( I )-Te(2) 2.6720 (4)

Ru ( I )-Ru(2) 2.7457(4)

Ru(2)-C(3) 1.889(4)

Ru(2)-Te(2) 2.6709(4)

Te( I )-C(30) 2.134(4)

C( I )-Ru( I )-P(I ) 89. 12( 13)

P(l )-Ru( I)-Te(2 ) 156.54(3)

Te(2)-Ru( I )-Te( I ) 80.894( 12)

Te(2)-Ru( I )-Ru(2) 59.058( II)

C(4)-Ru(2)-C(3) 92.17(19)

C(3)-Ru(2)-P(2) 101.43( 14)

P(2)-Ru(2)-Te( I ) 85.80(3)

P(2)-Ru(2)-Ru(l ) 91.61(3)

Te( I )-Ru(2)-Ru( I ) 59.27 1( 10)

Ru(2)-Te(2)-Ru( I) 6 1.846( II )

Ar

0\/Te~/o OC-Ru / Ru--co

oc! ~ 'co e

Ar

2

OC~~~TeAr / Ru

OC I ~TeAr co 3

Fig. 3--Suggested structures for complexes 2 and 3

and peaks for success ive elimination of four vCO groups consistent with the formulation [Ru(COM11 1

-

TeAr)2] . The occurrence of four IR bands for CO groups suggested a cis structure with C2v sy mmetry for the complex. From these spectroscopic results, an octahedral structure of C2v symmetry with two cis TeAr groups is proposed for 3 which is shown in Fig. 3. The proposed structures of both 2 and 3 also obey the 18-electron rule for metal carbony I complexes.

Acknowledgement We thank Prof. (Dr) H G Alt of the Department of

Chemistry, Bayreuth University, Germany, fo r recording the mass spectra and National University, Gazipur, Bangladesh, for financial support for the work.

520 INDIAN J CHEM, SEC A, MARCH 2005

Supplementary material Crystal lographic data have been deposited with the

Cambridge Crystallographic Data Center, CCDC No. 259332 for compound 1. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road Cambridge, CB2 I EZ, UK (Fax: +44-1223-336033; Email: deposit@ccdc.cam.ac.uk http://www.ccdc.ac.uk)

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