Organometallics 1996, 14, 245-250 245

Size-Selective Reactions of ~~~-MO(CO)~{P~~P(CH~CH~O),CH~CH~PP~~-P,P) (n = 4,5)

Metallacrown Ethers with Mercury(I1) Salts. Crystal Structure of cis-Mo(C0)4-

an Unusual Bimetallic Complex Containing a Molecular Cleft

Gary M. Gray* and Christina H. Duffey Department of Chemistry, The University of Alabama at Birmingham, UAB Station,

Birmingham, Alabama 35294

Received May 31, 1994@

{ - P h 2 P ( CH2CH20) &H2CH2PPh2-P,P90,0’,0”,0”’, O””}*HgCl2,

The reactions of mercury(I1) salts with cis-Mo(CO)4{ P~zP(CHZCHZO),CH~CHZPP~Z-P,P} (n = 5 (l), 4 (2)) metallacrown ethers are surprisingly complex, and the product depends upon the size of the metallacrown ether ring and the anion in the mercury(I1) salt. The reaction of HgC12 and 1 gives the bimetallic metallacrown ether complex, cis-Mo(CO)4@- Ph~P(CH~CH~O)~CH~CH~PPh~-~,P,0,0’ ,0”,0,0””}*HgC1~, 3, because the metallacrown ether ring is sufficiently large to accommodate the Hg2+. “he X-ray crystal structure of 3 (triclinic space group Pi, a = 10.387(2) A, b = 13.0359(7) A, c = 17.710(3) A, a = 69.401(7)”, /3 = 81.32(1)”, y = 87.15(1)”; V = 2218.8 A3; Z = 2; R = 5.82; R, = 7.19; GOF = 1.996 for 497 parameters and 7737 out of 9505 unique reflections) has been determined. The coordination environment of the Hg2+ is a hexagonal bipyramid with one missing equatorial ligand, axial chlorides, and equatorial ether oxygens. The open coordination site points toward the molybdenum, and the Mo-Hg distance is 6.8854(6) A. In contrast, the reaction of HgClz and 2 results in the isomerization of 2 to trans-Mo(CO)4{ P~zP(CHZCHZO)~CHZCHZPP~Z- P,P’}, 4. The Hg2+, which is too large to fit in the metallacrown ether ring in 2, catalyzes this isomerization, perhaps via coordination to the metallacrown ether and a lone pair on one of the carbonyl oxygens. Finally, the reaction of Hg(NO&H20 and 1 results in the oxidation of the molybdenum carbonyl complex and the formation of a Hg2+ complex of Ph2P( CH&H20)&H&H2PPh2. This mercury complex is not formed when Hg(N03)2*H20 is stirred with PhzP(CHzCH20)5CHzCHzPPhz indicating that the metallacrown ether is required for the reaction to occur.

Introduction

Metallacrown ethers are formed when RzPX(CH2- CHZO),CHZCH~XPRZ (R = Ph, O-alkyl; X = -, 0; n L 3) ligands chelate transition meta l~ . l -~ These complexes are of interest because they contain both a transition metal complex, which may catalyze a variety of organic reactions, and a crown ether, which may act as a phase- transfer catalyst. Studies of these metallacrown ethers have shown that they, like the crown ethers, are capable

* Abstract published in Advance ACS Abstracts, November 15,1994. (1) (a) Powell, J.; Kuksis, A.; May, C. J.; Nyberg, S. C.; Smith, S. J.

J. Am. Chem. SOC. 1981,103,5941. (b) Powell, J.; Nyberg, S. C.; Smith, S. J. Znorg. Chim. Acta 1983, 76, L75. (c) Powell, J.; Ng, K. S.; Ng, W. W.; Nyberg, S. C. J. Organomet. Chem. 1983,243, C1. (d) Powell, J.; Gregg, M.; Kuskis, A.; Meindl, P. J. Am. Chem. SOC. 1983,105, 1064. (e) Powell, J.; Gregg, M. R.; Kuksis, A.; May, C. J.; Smith, S. J. Organometallics 1989, 8, 2918. (0 Powell, J.; Kuskis, A.; May, C. J.; Meindl, P. E.; Smith, S. J. Organometallics 1989,8, 2933. (g) Powell, J.; Gregg, M. R.; Meindl, P. E. Organometallics 1989, 8, 2942. (h) Powell, J.; Lough, A.; Wang, F. Organometallics 1992, 11, 2289.

(2) (a) Alcock, N. W.; Brown, J. M.; Jeffery, J. C. J. Chem. SOC., Chem. Commun. 1974, 829. (b) Alcock, N. W.; Brown, J. M.; Jeffery, J. C. J. Chem. Soc., Dalton Trans. 1976,583. (c) Thewissen, D. H. W.; Timmer, K.; Noltes, J. G.; Marsman, J. W.; Laine, R. M. Znorg. Chim. Acta 1985,97,143. (d) Timmer, K.; Thewissen, D. H. W. Znorg. Chim. Acta 1985,100, 235. (e) Timmer, K., Thewissen, H. M. D.; Marsman, J. W. Recl. Trav. Chim. Pays-Bas 1988, 107, 248. (3) (a) Varshney, A.; Gray, G. M. Znorg. Chem. 1991, 30, 1748. (b)

Varshney, A.; Webster, M. L.; Gray, G. M. Znorg. Chem. 1992,31,2580. (4) Gray, G. M.; Duffey, C. H. Organometallics, in press.

0276-7333/95/2314-0245$09.00fO

of coordinating alkali metal cations and that the stabili- ties of the resulting complexes depend upon the relative sizes of the cation and the metallacrown ether cavity.’~~ These studies have also shown that carbonyl ligands in metallacrown ether complexes are activated toward nucleophilic attack by organolithium reagents when the cavity is of the appropriate size to bind the Li+.l

Little is known about the conformational changes that occur when these metallacrown ethers bind hard metal cations because no X-ray crystal structures of such complexes have been reported. In addition, nothing is known about the abilities of the metallacrown ether complexes to bind heavy metal cations such as Hg2+. In this paper, we report the results of a synthetic and NMR spectroscopic study of the reactions of Hg2+ salts with metallacrown ethers of the type cis-Mo(COk- (Ph2P(CH2CH20),CH2CH2PPh2-P$”} (n = 5 (1) or n = 4 (2)). We also report the X-ray crystal structure of cis-

O , O , O , O } ~ H g C l ~ , 3, and discuss the significance of this structure.

Mo(CO)~{ Ph2P( CH2CH20)5CH2CH2PPh2-P,P’,O,

Experimental Section

All manipulations were carried out under a atmosphere of nitrogen. The solvents were of reagent grade and were used

0 1995 American Chemical Society

246 Organometallics, Vol. 14, No. 1, 1995 Gray and Duffey

Table 1. NMR Data for the Metallacrown Ethers and their HgClz Complexes

1 2 3 4 5 5 4 3 2 1 A A A A A

P h 2 P 0 0 0 0 P P h 2

1 2 3 4 5 6 6 5 4 3 2 1 nnnnnn

P h 2 P 0 0 0 0 0 P P h p

c 1 c 2 C3-C6 P

compd &31P) (ppm) I'J(HgP)I (Hz) W3C) (ppm) IJ(W (Hz) W3C) (ppm) IJ(PC)I (Hz) W3C) (ppm) 1" 20.44 s 32.87 aq 2w 66.94 bs 69.96 s, 70.34 s, 70.47 s, 70.47 s 2" 20.11 s 31.32 aq 67.71 bs 70.16 s, 70.25 s, 70.65 s 36 21.20 s 32.28 aq 13c 67.33 bs 69.91 s, 69.91 s, 70.02 s, 70.07 s 46 32.54 s 56 27.83 sd 9861 27.37 d 37d 64.53 bs 70.00 s, 70.07 s , 70.07 s, 70.30 s 6" 20.11 s 31.22 aq 15c 67.57 aq 9' 69.81 s, 69.99 s, 69.99 s, 69.99 s

Data from ref 3a. Data from this work. IIJ(PC) + 3J(P'C)I. IIJ(PC)I. I2J(PC) + 4J(P'C)I.

as received. Literature procedures were used to prepare cis- MO(CO)~{P~~P(CH~CH~O)~CH~CH~PP~~-P,P'} (n = 5 (l), 4 (2)).3a

The 31P{1H}, 13C{'H}, and 'H NMR spectra were recorded on a GE NT-300, wide-bore, multinuclear NMR spectrometer. The 31P NMR spectra were referenced to external 85% phos- phoric acid, and the I3C and 'H NMR spectra were referenced to internal tetramethylsilane. Chemical shifts that are down- field from those of the reference compounds are reported as positive. The 31P and aliphatic 13C NMR data for the com- plexes are given in Table 1. Infrared spectra of dilute dichloromethane solutions of the carbonyl complexes in a 0.2 mm KBr solution cell were run on a Nicolet IR44 FTIR spectrometer. The background for these measurements was pure dichloromethane in the same cell. Elemental analyses of the compounds were performed by Atlantic Microlab, Inc., Norcross, GA.

0 , 0 , 0 , 0 , 0 } ~ H g C 1 ~ , 3. A mixture of 0.176 g (0.213 mmol) of 1 and 0.301 g (1.11 mmol) of HgCl2 in 3 mL of chloroform- dl was stirred at ambient temperature for 4 h and then filtered through diatomaceous earth. The filtrate was allowed to stand in the dark for 2 days and then refiltered. This filtrate was evaporated to dryness to give a quantitative yield of crude 3. Recrystallization from a dichloromethane-methanol mix- ture yielded analytically pure 3. Anal. Calc (found) for

(CDC13): 6 7.507 and 7.352 (Ph, m, 5H); 6 3.652 (C5 and C6 methylenes; m, 4H), 3.578 (C4 methylene; m, 2H), 3.405 (C3 methylene; m, 2), 3.274 (C2 methylene, t, I3J(HH)l = 7.6 Hz, 2H), 2.805 (C1 methylene, t, I3J(HH)l = 7.6 Hz, 2H). IR [v(CO)l (CH2C12): 2022 m, 1919 sh, 1909 s, 1886 sh cm-'.

Reaction of C ~ ~ - M O ( C ~ ) ~ { P ~ S ( C H ~ C H Z O ) ~ C H Z C H ~ P ~ Z - Pr}, 2, and HgClz. A mixture of 0.098 g (0.129 mmol) of 2 and 0.170 g (0.626 mmol) of HgCl2 in 2.0 mL of chloroform-dl was stirred in the dark at ambient temperature for 70 h. The mixture was then filtered through a 0.2 pm syringe filter. The residue was washed with two, 0.50 mL portions of chloroform- dl, and these were also filtered through the syringe filter and combined with the reaction mixture. A quantitative 31P NMR spectrum was taken of the filtrate. This spectrum contained a singlet at 20.19 ppm due to 1 and a singlet at 32.54 ppm due to truns-Mo(CO)r{ P~~P(CHZCH~O)&H~CHZPP~~-P,P'}, 4, in a 46.3 to 53.7 ratio (from integration).

Reaction of cis-Mo(CO)r(PhzPMe)z and HgC12. The reaction of 0.078 g (0.129 mmol) of ci~-Mo(CO)4(PhzPMe)z and 0.170 g (0.626 mmol) of HgCl2 in 2.0 mL of chloroform-dl was carried out using the procedure described for the reaction of 2 and HgC12. A quantitative 31P NMR spectrum of the filtrate contained a singlet at 15.44 ppm due to &-Mo(CO)*(Ph2PMe)2 and a singlet at 28.49 ppm due to trans-Mo(C0)4(PhzPMe)z in a 79.2 to 20.8 ratio (from integration).

Reaction of cis-Mo(CO)r{ PhS(CH&H2O)~CHZCHPPhr Pp}, 2, and Hg(NOs)z.HzO. A mixture 0.20 g (0.24 mmol) of 1 and 0.425 g (1.24 mmol) of Hg(N03)2*H20 in 25 mL of dichloromethane was stirred at ambient temperature for 24 h. During this time, the color of the solution changed from

C ~ S - M O ( C O ) ~ { ~ - P ~ ~ P ( C H Z C H Z O ) ~ C H ~ C H Z P P ~ ~ - P , ~ ,

C ~ ~ H U C ~ ~ H ~ O Q M O P ~ : C, 58.11 (58.26); H, 5.36 (5.42). 'H NMR

colorless to yellow to dark brown to beige and a beige solid precipitated. The reaction mixture was then filtered, and the filtrate evaporated to dryness to yield 0.126 g of a foamy white solid, 5, which appeared to be a Hg(N03)~ complex of the P ~ ~ P ( C H ~ C H ~ O ) & H ~ C H Z . P P ~ ~ ligand on the basis of its 31P and NMR spectra.

X-ray Structure Determination of 3. A colorless, needle- like crystal of 3 was grown by slowly diffusing hexanes into a THF solution of the complex. The crystal was mounted on a glass fiber with epoxy cement, and the cell constants were obtained from least-squares refinement of 25 reflections with 25 5 8 5 35". All measurements were carried out at 23 "C on an Enraf-Nonius CAD4 diffractometer using graphite mono- chromated Cu Ka radiation (1 = 1.5418 A).

Data were collected by 0-28 scans. The crystal decayed 12.3% during the data collection, and a linear decay correction was applied. An analytical absorption correction (using the Crystal and Abscor programs) was also applied to the data. Of the 9505 independent reflections measured, 7737 had Z > 3 d n and were used for structure solution and refinement.

The structure was solved by heavy-atom methods and refined by a full-matrix least squares procedure that mini- mized w(lFol - IFc1)2, where w = l/u2(Fo), using the MolEN package of programs. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were placed in calculated positions (C-H = 0.96 A, UISO(H) = 1.3U1so(C)) and were not refined. Data were weighted using a non-Poisson scheme. A secondary extinction correction was applied to the data,5 and the extinction coefficient was refined. In the last stage of the refinement no parameter varied by more than 0.01 of its standard deviation, and the final difference Fourier map had no interpretable peaks. Atomic scattering factors were taken from the compilations of Cromer and Weber: and those for H were taken from the ref 7. Corrections for anomalous disper- sion were taken from the compilations of Cromer and Lieber- mans and applied to chlorine, mercury, molybdenum, and phosphorus. Data for the X-ray structure analyses are given in Table 2. Positional parameters are given in Table 3. Values of selected bond lengths and angles and torsion angles are given in Tables 4-6. Tables of hydrogen atomic positional and thermal parameters, thermal parameters, torsion angles, and least squares planes are available as supplementary material. An ORTEPQ drawing of the molecule is given in Figure 1.

Results and Discussion

Previous studies of cis-Mo(C0)4{Ph2P(CH2CH20)n- CH~CHZPP~~-P,F"} (n = 5 (1),4 (2)) metallacrown ethers have shown that 1 weakly coordinates to Li+ and

( 5 ) Zachariasen, W. H. Acta Crystallogr. 196.3, 16, 1139. (6) Cromer, D. T.; Waber, D. T. Acta Crystallogr. 1966,18, 104. (7) International Tables for Crystallography; Hahn, T., Ed.; The

(8) Cromer, D. T.; Lieberman, D. J. J. Chem. Phys. 1970,53, 1891. (9) Johnson, C. K. ORTEPZZ. Report ORNL-5138; Oak Ridge Na-

Kynoch Press: Birmingham, U.K., 1974; Vol. IV, p 72.

tional Laboratory: Oak Ridge, TN, 1976.

Reactions of Metallacrown Ethers with Hg(II) Salts

Table 2. Data Collection and Structure Solution and Refinement Parameters for 3

Organometallics, Vol. 14, No. 1, 1995 247

Table 3. Positional Parameters and Isotropic Thermal Factors (Az) for J

formula Mw

:p:G b (A) c (A) a (de@ B (deg) Y (deg) v (A31 Z dCdc (dcm3) cyst diamens (mm) h m u , hmjn k m u , kmin

kdMn temp (“C) abs coeff (cm-’) 8 limits (deg) decay corr decay (%) abs corr Tmu. Trmn (%) reflns measd scan width (deg) reflns with I ?. 3u(Z) no. of variables function minimized weighting scheme instrumental uncertainty factor secondary extinction corr type minimized extinction coeff R (%)

GOF‘ max, min resid electron density (e/A3) max shifuerror

Rw (%)

C&&12HgMOOgPz

P1 10.387(2) 13.0359(7) 17.710(3) 69.401(7) 81.32( 1) 87.15(1) 2218.8 2 1.644 0.13 x 0.17 x 0.70 12, 0 -16, 16 -21,21 1.541 84 23 111.825 0.1-74 linear 12.3

38.46, 5.83 9505 1.34 7737 497 W(lF0 - I F C V non-Poisson (w = l/u2(Fo)) 0.03 Zachariesen 1.995 x 5.82 7.19 1.996 3.109, -0.175 0.01

1098.18

analytical

strongly coordinates to Na+ but that 2 strongly coordi- nates to Li+ and weakly coordinates to Na+.3a Because Na+ and Hg2+ have similar ionic radii (for coordination number 6: Na+, 1.16 A, and Hg2+, 1.16 &,lo we expected that 1 would strongly bind Hg2+ but that 2 would not. This picture, however, is much too simplistic. Reaction of C ~ S - M O ( C O ) ~ ( P ~ ~ P ( C H ~ C H ~ O ) & H ~ -

CH2PPh2-PQ’}, 1, and HgC12. The reaction of 1 with HgC12 in dichloromethane, shown in eq 1, yields only

I

3

the bimetallic complex, C ~ ~ - M O ( C O ) ~ C ~ - P ~ ~ P ( C H ~ C H ~ O ) ~ - CH~CH~PPh~-P,P’,O,O,O,O,O}~HgCl2,3. This com- plex is quite stable in solution and can be recrystallized.

atom X Y Z B

Hg Mo c12 P1 P2 01 02 03 04 05 06 07 0 8 09 c1 c2 c3 c4 c5 c7 C8 c9 c10 c11 c12 C13 C14 C15 C16 C17 C18 c19 c20 c2 1 c22 C23 C24 C25 C26 C27 C28 C29 C30 C3 1 C32 c33 c34 c35 C36 c37 C38 c39 C40

0.33142(3) 0.06877(5) 0.1926(3) 0.2349(2)

-0.0437(2) -0.1089(7) 0.2031(6) 0.2650(8)

-0.1272(6) 0.4733(5) 0.5579(6) 0.4390(6) 0.1972(6) 0.0908(5)

-0.0459(8) 0.1559(8) 0.1965(8)

-0.0586(7) 0.3048(6) 0.5720(7) 0.6408(8) 0.620(1) 0.524(1) 0.347( 1) 0.285( 1) 0.144(1) 0.0356(9)

-0.0070(7) 0.0604(7) 0.3782(6) 0.4751(7) 0.5794(7) 0.5911(8) 0.4929(9) 0.3868(8) 0.1971(6) 0.2902(7) 0.2567(9) 0.1272(9) 0.0344(8) 0.067 l(7)

-0.1229(7) -0.0794(8) -0.13 14(9) -0.232( 1) -0.2784(9) -0.2265(7) -0.1699(6) -0.2795(7) -0.3655(7) -0.3459(8) -0.2363(8) -0.1481(7)

0.58858(2) 1.02894(4) 0.5003(2) 0.8943( 1) 0.8863( 1) 1.2231(5) 1.2104(4) 1.0859(7) 1.008 l(5) 0.6686(4) 0.4760(4) 0.4195(4) 0.5082(4) 0.6996(4) 1.1481(6) 1.1436(6) 1.0624(6) 1.0103(6) 0.7905(5) 0.5960(6) 0.5518(6) 0.4190(7) 0.3504(7) 0.3626(6) 0.4404(7) 0.5944(7) 0.6459(7) 0.7501(6) 0.8144(6) 0.9720(5) 0.999 l(6) 1.0632(6) 1.1027(6) 1.0796(6) 1.0159(6) 0.8094(5) 0.7704(6) 0.7040(7) 0.6773(7) 0.7121(6) 0.7771(6) 0.7764(5) 0.6706(6) 0.5952(7) 0.6245(8) 0.7294(7) 0.8065(6) 0.9352(5) 0.8745(6) 0.9109(7) 1.0109(7) 1.0691(7) 1.0338(6)

0.67593(2) 0.77377(3) 0.7910(1) 0.84785(9) 0.73701(9) 0.6893(4) 0.8132(4) 0.6 102(4) 0.9345(4) 0.7860(3) 0.7473(3) 0.6315(3) 0.574 l(3) 0.5990(3) 0.7190(5) 0.7994(4) 0.6689(5) 0.8778(4) 0.8039(4) 0.8189(4) 0.7565(5) 0.6959(5) 0.6834(5) 0.6077(5) 0.5420(5) 0.5139(5) 0.5544(5) 0.6389(4) 0.6780(4) 0.8445(4) 0.7775(4) 0.77 12(5) 0.8320(6) 0.8980(4) 0.9052(4) 0.9555(4) 1.0073(4) 1.0877(4) 1.1186(5) 1.0688(5) 0.9876(4) 0.8255(4) 0.8522(5) 0.9262(5) 0.9754(5) 0.9490(5) 0.8753(4) 0.6700(4) 0.6776(4) 0.6205(4) 0.5570(5) 0.5493(4) 0.6052(4)

3.733(6) 2.576(9) 6.05(6) 2.62(3) 2.78(3) 7.0(2) 5.9(1) 8.3(2) 5.7(1) 3.5(1) 4.4(1) 4.8(1) 4.9(1) 3.8(1) 4.2(2) 3.9(2) 4.3(2) 3.6(1) 3.2(1) 3.8(1) 4.2(2) 5.4(2) 5.9(2) 5.3(2) 5.1(2) 5.1(2) 5.6(2) 4.1(2) 3.6(1) 2.9(1) 3.7(1) 4.5(2) 4.8(2) 4.7(2) 4.1(2) 3.0(1) 3.7(1) 4.4(2) 4.8(2) 4.5(2) 3.5(1) 3.2(1) 4.2(2) 5.5(2) 5.6(2) 4.9(2) 3.7(2) 3.1(1) 3.4(1) 4.3(2) 4.8(2) 4.5(2) 3.7(1)

Anisotropically refined atoms are given in the form of the isotropic equivalent displacement parameter defined as (4/3)[a2B(l,l) + b2B(2,2) + c2B(3,3) -t ab(cos y)B(1,2) + ac(cos /3)B(1,3) + bc(cos a)B(2,3)].

The shift in the 31P NMR resonance of 1 upon coordina- tion of the HgClz is in the opposite direction and approximately twice as large as the shift that occurs upon coordination of NaBPh, to 1 to form cis-Mo(CO)&-

O}*NaBPh,, 6.3a The shifts in the methylene 13C NMR resonances of 1 upon coordination of the HgCl2 are in the same directions as those observed upon coordination of NaBPh, to 1 but are of somewhat different magni- tudes. These differences are not surprising given the different coordination geometries preferred by Hg2+ and Na+ and the flexibility of the metallacrown ether ring in 1.

P h ~ P ~ C H ~ ” ~ 0 ) ~ C H ~ C H ~ P P h ~ - P , P ’ , O , O ’ , O ’ ’ , O ” ’ ,

(10) (a) Shannon, R.; Prewitt, C. T. Acta Crystallogr. 1966, B25,925. (b) Shannon, R. Acta Crystallogr. 1976, A32, 751.

248 Organometallics, Vol. 14, No. 1, 1995

Table 4. Selected Bond Lengths (A) for 3 Hg-Cl1 2.281(2) 02-c2 1.13( 1)

Hg-05 3.085(6) 04-C4 1.132(9) Hg-06 2.921(6) 05-C6 1.434(9) Hg-07 2.727(6) 05-C7 1.408(8) Hg-08 2.921(7) 06-C8 1.41(1) Hg-09 3.078(5) 06-C9 1.43(1) Mo-P1 2.558(2) 07-C10 1.42(1) Mo-P2 2.557(2) 07-Cll 1.43( 1) Mo-C1 1.969(8) 08-C12 1.43(1) Mo-C2 1.999(9) 08-C13 1.405(9) M o - C ~ 2.036(7) 09-C14 1.42(1) Mo-C4 2.046(7) 09-C15 1.417(9) P1-C5 1.854(7) C5-C6 1.484(9) P1-C17 1.823(7) C7-C8 1.49(1) Pl-C23 1.830(6) C9-C10 1.46(2) P2-Cl6 1.842(8) Cll-c12 1.46(1) P2-C29 1.826(5) C13-Cl4 1.50(1) P2-C35 1.84 l(7) C15-Cl6 1.5 1( 1) 01-c1 1.16( 1)

Hg-C12 2.276(2) 03-C3 1.12( 1)

Table 5. Selected Bond Angles (deg) for 3

Gray and Duffey

Cll-Hg-C12 169.41(9) M0-Pl-U 118.0(3) C11 -Hg-05 88.5( 1) Mo-Pl-Cl7 102.6(3) C11 -Hg-06 92.4(1) Mo-Pl-C23 103.6(3) C11-Hg-07 88.2(1) Mo-P2-C16 102.6(3) C11-Hg-08 92.4(1) Mo-P2-C29 100.8(3) Cll-Hg-09 88.2( 1) Mo-P2-C35 103.6(3) C12-Hg-05 86.1(1) C6-05-C7 112.0(5) C12-Hg-06 92.3(1) C8-06-C9 1 13.1(6) C12-Hg-07 102.4(1) C10-07-Cll 114.6(6) C12-Hg-08 93.1(1) C12-08-C13 113.7(6) C12-Hg-09 87.4(1) C14-09-C15 110.9(6) 05-Hg-06 57.4( 1) Pl-C5-C6 117.9(5) 06-Hg-07 60.8(2) 05-C6-C5 108.4(6) 07-Hg-08 61.4(2) 05-C7-C8 109.8(6) 08-Hg-09 56.2(2) 06-C8-C7 108.4(6) P1-M0-n 94.57(5) 06-C9-C10 109.4(8) P1-Mo-C1 172.2(3) 07-ClO-C9 108.4(6) Pl-Mo-C2 86.7(2) 07-Cll-C12 109.3(7) Pl-Mo-C3 88.5(2) 08-C12-Cll 109.5(7) P1 -Mo-C4 94.1(2) 08-Cl3-Cl4 108.9(6) P2-Mo-C 1 93.2(3) 09-Cl4-Cl3 108.1(7) P2-Mo-C2 178.4(2) 09-Cl5-Cl6 107.6(6) P2-Mo-C3 89.9(3) P2-Cl6-Cl5 117.2(5) P2-Mo-C4 94.5(2)

Table 6. Selected Torsional Angles (deg) for 3 and Hg( CH~C~~0(C~~~H~0)&H~CH~-O,O’,O”,O”’,O’’’,O”’’)Cl~, 9

3 9”

C7-05-C6-C5 -176.2(6) C3-01-C2-C1 -170 C6-05-C7-C8 -174.3(6) C2-01-C3-C4 171 C9-06-C8-C7 -173.2(5) C5-02-C4-C3 170 C8-06-C9-C10 -174.6(6) C4-02-C5-C6 - 174 Cl1-07-ClO-C9 174.4(7) C7-03-C6-C5 -176 C10-07-Cll-C12 -168.1(7) C6-03-C7-C8 - 179 C13-08-Cl2-Cll 172.9(8) C9-04-C8-C7 178 C12-08-Cl3-Cl4 169.3(7) C8-04-C9-C10 177 C15-09-Cl4-Cl3 180.0(6) Cll-05-ClO-C9 -178 Cl4-09-Cl5-Cl6 -174.6(6) C10-05-Cll-Cl2 -80 05-C7-C8-06 -73.1(7) Ol-C3-C4-02 -77 06-C9-C10-07 7 1.9(8) 02-C5-C6-03 72 07-C11-C12-08 -72.2(9) 03-C7-C8-04 -71 0 8 -C 13 -C 14-09 68.2(8) 04-C9-C10-05 73

Data from ref 14b.

The X-ray crystal structure of 3 is shown in Figure 1 and contains a number of interesting features. The coordination geometry of the molybdenum is a distorted octahedron similar to that observed in other cis-Mo- (CO)1(P-donor 1igand)z complexes. The Pl-Mo-P2 angle (94.57(5)”) is similar to those in cis-Mo(CO)r-

and c~s-P~C~~{P~~P(CH~CH~O)~CH~CH~PP~~-P,P}, 8 (99.03(6)0).3b This suggests that the metallacrown ether

{Ph2P(CH2CH20)3CH2CH2PPh2-P,P}, 7 (93.78(2)0),3a

c20

c21 c19

c22

C36 c37-49c38 Figure 1. ORTEP drawing of the molecular structure of 3. Thermal ellipsoids are drawn at the 50% probability level, and hydrogens are omitted for clarity.

ring in 2 is sufficiently flexible that coordination of HgC12 does not greatly perturb the coordination envi- ronment of the molybdenum.

The coordination environment of the Hg2+ ion is unusual. The Hg2+ is coordinated to all five oxygens in the metallacrown ether and to both chlorides. The oxygens are in a nearly planar arrangement (largest deviations from the least squares plane through the five oxygens are 0.141(6) A for 0 7 and -0.107(6) A for 08). The chlorides are trans to each other, and the mercury- chloride bonds are perpendicular to the least squares plane through the five ether oxygens. Because the 0-Hg-0 angles are all close to 60” and not 72”, the coordination environment of the Hg2+ is better described as a hexagonal bipyramid with a missing equatorial ligand than as the more common pentagonal bipyramid.

The open coordination site in the hexagonal bipyra- mid is pointed toward the molybdenum. This, together with the Mo-Hg bond distance of 6.8854(6) A, suggests that it might be possible to bridge a ligand between the metals in bimetallic, metallacrown ether complexes. One difficulty with this is that the protons on C5 and C16 are pointed into the cavity between the Mo and the Hg (distances (A): H5-Hl6, 2.719; H5-Hl6, 3.178; H5’- H16, 2.184; H5’-H16‘, 3.322) and would interfer with a ligand bridging between the two metals. However, it seems likely that this could be avoided by rotation about the Mo-P bonds. This occurs rapidly in solution as indicated by the equivalence of the phenyl groups on the phosphines and thus should not introduce a great deal of strain into the molecule.

The asymmetric coordination environment of the Hg2+ ion in 3 is unlike that observed for Hg2+ coordinated to crown ethers and azacrown ethers. With larger crown ethers such as 1,4,10,13-tetraoxa-7,16-diazacycloocta- decane and 18-crown-6, the Hg2+ coordinates in the center of the crown with the ether oxygens sym- metrically arranged around the Hg2+ and with trans monodentate anionic 1igands.ll With smaller crown ethers such as 15-crown-5, the Hg2+ is too small to fit

(11) (a) Malmsten, L.-A. Acta Crystallogr. 1979, B35,1702. (b) Paige, C. R.; Richardson, M. F. Can. J. Chem. 1984,62,332. (c) Drew, M. G. B.; Lee, K. C.; Mok, K. F. Znorg. Chim. Acta 1989,155, 39.

Reactions of Metallacrown Ethers with Hg(II) Salts

into the crown and coordinates above the crown with cis monodentate anionic ligands.12 Very similar behav- ior is also observed in Pb2+ crown ethers ~omp1exes.l~

The Hg2+ coordination environment in 3 closely resembles that in complexes with linear ethylene oxide 01igomers.l~ This resemblance is seen in the similarity of the torsion angles for equivalent bonds in 3 and in

Cl2, 9, shown in Table 6. The only major difference in these angles is between that for C14-09-Cl5-Cl6 in 3 and that for C10-05-Cll-C12 in 9, and this is to be expected because the polyether is cyclic in 3 and acyclic in 9. This striking similarity in torsion angles suggests that presence of the large transition metal complex in the ring allows metallacrown ethers to adopt a larger variety of coordination modes than can the crown ethers and therefore resemble the open chain polyethers in this regard.

Reaction of c~s-Mo(CO)~(P~~P(CH~CH~O)~CH~- CH2PPh2-PQ’}, 2, and HgCl2. In contrast to the above results, when a chloroform-dl solution of 2 is stirred with excess HgC12 in the dark at ambient temperature, truns-Mo(C0)4{ P ~ ~ P ( C H ~ C H ~ O ~ C H Z C H Z -

Hg(CH~CH~0(CH~CH~0)~CH~CH~-O,O,O’,0,0”’’)-

PPhz-PQ’}, 4, is

2

formed, as shown in eq 2. This

P O ?

4

isomerization is 53.7% complete after 70 h in the presence of HgClz but does not occur to any appreciable extent during this time if HgC12 is not present. We recently reported that this reaction occurs very slowly in the dark (15% isomerization after 24 days at 5 “C) and rapidly when 1 is irradiated with W light (12 min at 21 “ 0 . 4

In order to better understand the mechanism of this isomerization, we carried out a similar isomerization of cis-Mo(CO)4(Ph2PMe)~ to trans-Mo(C0)4(PhzPMe)~ in chloroform-dl solution in the presence of HgC12. This isomerization also occurs but at a much lower rate than the isomerization of 2 t o 4. This suggests that the Hgz+ facilitates the loss of the carbonyl by binding to the lone pair on the oxygen and weakening the metal carbon bonds as demonstrated by Shriver with a variety of Lewis acids and metal carbonyl ~omp1exes.l~ The increased rate of the isomerization of 2 to 4 by HgClz could result from initial binding of the HgC12 to the metallacrown ether in 2 followed by coordination of a carbonyl oxygen to the Hg2+. The crystal structure of cis-Mo(CO)4(pu-Ph2P(CHzCHzO)sCHzCHzPPhz-P,P’, 0,O,0”,0”’,O}.HgC1~, 3, discussed above, suggests that bridging of a carbonyl between the Mo and the Hg2+ in these complexes is possible. The proposed mecha-

(12) Byriel, K. A.; Dunster, K. R.; Gahan, L. R.; Kennard, C. H. L.; Latten, J. L. Inorg. Chim. Acta 1992, 196, 35. (13) Byriel, K. A.; Dunster, K. R.; Gahan, L. R.; Kennard, C. H. L.;

Latten, J. L. Swann, I. L. Polyhedron 1992, 10, 1205. (14) (a) Iwamoto, R. Bull. Chem. Soc. Jpn. 1973, 46, 1115. (b)

Iwamoto, R. Bull. Chem. Soc. Jpn. 1973,46,1115. (c) Iwamoto, R. Bull. Chem. SOC. Jpn. 1973,46, 1123. (15) Shriver, D. F. J. Orgunomet. Chem. 1975,94,25 and references

therein.

Organometallics, Vol. 14, No. 1, 1995 249

nism is similar, in many respects, to the mechanism suggested by Powell for the activation of carbonyls to attack by alkyl- and aryllithiums in related metalla- crown ethers.‘

Reaction of c~s-Mo(CO)~{P~~P(CH~CH~O)&H~- CHzPPh2-PQ’), 2, and Hg(NOs)a*HaO. In an attempt to synthesize a Hg2+ complex with less strongly coor- dinating anions, Hg(N03)2-H20 was added to a dichlo- romethane solution of 1. This caused the color of the solution to change from colorless to deep brown and finally to beige and a beige solid to precipitate from the solution. A 31P NMR spectrum of the methylene chlo- ride soluble portion of the reaction mixture contained a single resonance that was a superimposed singlet and doublet. The relative intensities of the singlet and doublet and magnitude of the coupling constant indi- cated that the diphenylphosphino groups in the PhzP(CH&H20)5CH&H2PPhz ligand were coordinated to mercury. This suggests that the nitrate oxidized the molybdenum, hence the color change, allowing the diphenylphosphino groups of the PhzP(CHzCH20)5CHz- CH2PPh2 ligand to cooordinate to the mercury, as shown in eq 3. The formulation for the product is supported

by the presence of resonances for all the ligand carbons and the absence of carbonyl resonances in its 13C NMR spectrum and by the absence of CEO stretches in its IR spectrum. This formulation is also supported by the fact that no reaction is observed when the PhzP(CH2- CH20)5CH2CH2PPh2 ligand is stirred with Hg(N03)2.H20 in dichloromethane, indicating that the metallacrown ether is needed as a template for this reaction to occur. The only problem with this explanation is that all of the 13C NMR resonances of the Ph2P(CH2CH20)5CH2- CH2PPh2 ligand appear to be doublets, suggesting that only one phosphorus is coordinated to each Hg2+. However, these doublets could also result if lZJ(PP)l is small, which would be the case if the complex is fluxional. Unfortunately, we have been unable to either purify or crystallize this material to prove the exact nature of the product.

Conclusions

The reactions of Hg2+ salts with the cis-Mo(C0)4- {P~~P(CHZCH~O),CH~CH~PP~~-PJ”} (n = 4,5) metal- lacrown ethers are surprisingly complex. The nature of the product depends on the the size of the metalla- crown ether and the reactivity of the anions. The size- selective reactions of the metallacrown ethers with Hg2+ are particularly fascinating because it might be possible to employ them in sensors for Hg2+ and related anions.

The coordination environment of the Hg2+ in cis-

0 , O , O , O , O } ~ H g C l ~ is a hexagonal bipyramid with M o ( C ~ ) ~ { ~ - P ~ ~ P ( C H ~ C H ~ O ) ~ C H ~ C H ~ P P ~ ~ - P , P ’ ,

250 Organometallics, Vol. 14, No. 1, 1995

an empty equatorial site pointing toward the molybde- num. This is quite interesting because it suggests that is should be possible to bridge a bifunctional ligand, such as carbon monoxide or carbon dioxide, between the two metals in these complexes. This type of bridging may be the reason that HgC12 catalyzes the isomerization of

much more rapidly than it does the isomerization of cis- Mo(CO)r(PhzPMe)z. In bimetallic metallacrown ethers containing Pt-group metal complexes, such bridging

c~s-Mo(CO)~{ Ph2P(CH2CH20)4CH2CH2PPh2P,P'}

Gray and Duffey

could give rise to catalytic activities and selectivities that are quite different from those of monometallic Pt- group metal complex catalysts.

Supplementary Material Available: Tables listing po- sitional and thermal parameters for hydrogens, temperature factors, bond lengths, bond angles, torsion angles, and least squares planes for 3 (10 pages). Ordering information is given on any current masthead page.

OM940409V