67
Organometallics 1986, 5, 67-71
do-d8 Heterobimetallic Complexes as Catalysts: Molecular and Crystal Structure of a Zirconium-Dirhodium Complex, Robert Choukroun,'a Danible Gervais, * la Joel Jaud,Ib Philippe Kalck,
IC and
Franqois Senocq"
Laboratoire de Chimie de Coordination du CNRS, Unit6 No. 824 1 li6e par convention 5 I'Universit6 Paul Sabatier, 3 1400 Toulouse, France, GITER, CNRS, 3 1400 Toulouse, France, and Laboratoire de Chimie Minerale et de Cristallochimie, Ecole Nationale Sup6rieure de Chimie, 3 1077 Toulouse Cedex, France Received April 1, 1985
Addition of the zirconium(1V) diphosphine (q5-C5H5)zZr(CHzPPhz)z to the (p-thiolato)dirhodium(I) complex Rhz(t-BuS)z(CO)4 results in the hydroformylation-active bimetallic species Rhz(p-t-BuS)z[(pPhzPCH2)zZr(q5-C5H5)2](C0)2, the crystal and molecular structures of which were studied by 'H, 13C,and 31PNMR spectroscopy and by X-ray diffraction. The compound crystallizes in the monoclinic space group R J c , with four molecules in a cell having dimensions a = 16.020 (4) A, b = 16.237 (7) A, c = 18.304 (8) A, and 0 = 112.61 (3)". The zirconium diphosphine bridges the two rhodium atoms in a cis arrangement toward the bent (1-thio1ato)dirhodiumcore. One of the sulfur atoms interacts with the zirconium giving a pentacoordinated 18-electron configuration. This unprecedented geometry explained the inequivalences shown in IH and 13C spectra and is related to the stoichiometric and catalytic reactivity. Introduction We have recently shown2 that hydroformylation of 1hexene is catalyzed at low pressure and low temperature (5 bar, 80 "C) by addition of the zirconium(1V) diphosphine ( T - C ~ H ~ ) ~ Z ~ ( Cto H ~the P Pinactive ~ ~ ) ~ (pthiolato)dirhodium(I) species Rh,(p-S-t-Bu),(CO),. Comparison with the catalytic activity obtained when 1,4-bis(dipheny1phosphino)butaneis used instead of the zirconium diphosphine demonstrated the important role of the zirconium atom. We have investigated the structure of the bimetallic (CO), complex Rh,(p-t-BuS),[ (p-(Ph2PCH2)2Zr(s-C5H,)2] (l),readily obtained in the catalytic mixture as well as by mixing the two reactants in 1:l stoichiometry in toluene at room temperature. Spectroscopic Data Experimental Data. All preparations were carried out under argon using Schlenk techniques. All solvents were dried and distilled under argon and degassed before use. C P , Z ~ ( C H ~ P may P ~ ~be ) ~prepared either as previously reported by Schore3 or by the procedure used for Cp2Ti(CH2PPh2).4 R ~ , ( ~ - ~ - B u S ) ~ was ( C Oprepared )~ as previously r e p ~ r t e d . ~ 'H, 31P,and 13CNMR spectra were recorded on Bruker WH90 and WM 250 spectrometers. Values of 31Pchemical shifts are positive downfield from external 85% H3P04in DzO. Microanalyses were performed by the Service Central de Microanalyses du CNRS. Preparation of Rh2(r-S-t-Bu)2[(r-Ph2PCH2)2Zr(vC5H5),](C0),. A solution of the dinuclear rhodium complex Rh2(p-t-BuS),(CO), (0.383 g, 0.77 mmol) in 15 mL of toluene was added slowly at room temperature to a 15-mL toluene solution of Cp2Zr(CH2PPh&(0.478 g, 0.77 mmol). (1) (a) Laboratoire de Chimie de Coordination. (b) GITER. (c) Laboratoire de Chimie Minerale et Cristallochimie. (2) Senocq, F.; Randrianalimanana, C.; Thorez, A,; Kalck, P.; Choukroun, R.; Gervais, D. J. Chem. Soc., Chem. Commun. 1984, 1376. (3) Schore, N. E.; Young, S. J.; Olmstead, M. M.; Hofmann, P. Organometollics 1983, 2, 1769. (4) Etienne, M.; Choukroun, R.; Basso-Bert, M.; Dahan, F.; Gervais, D. Nouu. J . Chim. 1984,8,531. (5) Kalck, P.; Poilblanc, R. Inorg. Chem. 1976, 14, 2779.
0276-7333/86/2305-0067$01.50/0
The resulting solution was stirred for 30 min and evaporated to 5 mL. Pentane (20 mL) was added to give a yellow precipitate which was filtered, washed with pentane, and dried under vacuum: yield 85%; IR u(C0) 1930,1945cm-'; 31P(1H)NMR 6 53.1 (d, 'JRh+ 140 Hz). Recrystallization from a saturated CH2C12solution by slow evaporation of the solvent gave crystals suitable for X-ray analysis. Anal. Calcd for C48H52Rh2Zr02P2S2: C, 52.1; H, 4.9; P, 5.9; Zr, 8.6. Found: C, 52.3; H, 5.1; P. 6.2; Zr, 8.8. Results and Discussion. From analytical data and IR and 31PNMR spectra a structure could be proposed with one CO ligand per rhodium atom and two equivalent phosphorus nuclei each bonded to one rhodium atom giving a cis arrangement as seen in I. t-Bu
CH,
CH,
I
In the l3C(lH]spectrum (see Table I) the equivalent carbonyl groups give a doublet of doublets resulting from coupling to one rhodium and one phosphorus. The quaternary carbons and the methyl carbons of the tert-butyl groups give two sets of peaks due t o the magnetic inequivalence of the thiolato-bridging groups (endo and exo positions) as previously reported for various complexes of general formula [M(SR)(CO)L], with M = Rh5 or Ir.6 The bridging diphosphine with the Rh-S-Rh sequence gives an eight-membered ring, and we observed that the four phenyl groups give two separate sets of peaks of equal (6) de Montauzon, D.; Kalck, P.; Poilblanc, R. J. Organomet. Chem. 1980,186, 121.
0 1986 American Chemical Society
68 Organometallics, Vol. 5, No. 1, 1986
Choukroun et al.
Table I. 13C{'H}NMR Data for [ Rh,(p-t-Bus), { (Ph,PCH2),Zr(q-C5HS),}(CO),] and Related Derivatives t-BuS
6co
compoundn Rh,(p-t-Bus), [(Ph,PCH,),ZrCp,] (CO), Rh( PPh, ), ( CO)Clc
193.0 187.4
Ir,( p -t-Bus),( PMe,),( CO), Rh,(p-t-BuS),(CO),e
179.67
lJRhC,
'44, H Z
HZ
76.3 73
12.2 16
6 S C C
6SCc
33.9 {45.4
35.2 37.7
{
9.3
{
46.37 53.29 46.90 44.33 49.97
G88:328
i
Rh,(p-t-BuS ) 2 [ph,P(CH,),PPh, ](CO),
33.48 39.66 34.55
Cp = q-C,H,. In CD2Cl,. Other resonance peaks: C,H,, 109.7 and 112.2 ppm; phenyl C ' , 144.9 ( ' J p c = 30.5 Hz) and 139.6 ppm ('Jpc = 42.7 Hz); C 2 , 134.2 ('JPc = 1 2 . 1 Hz) and 131.6 ppm ('JPc = 12.2 Hz); C3-C4,multiplet 129.7F r o m ref 6 in CD,Cl,. e Measured in C,D, . In CDCl, (Kalck, P.; 128.1 ppm. From ref 7 in CDCI, . Randrianalimanana, C.; Thorez, A., unpublished results). Table 11. IR and 'H NMR Data for Rh,(p-t-BuS),[(Ph2PCH,),Zr(q-CjHj),](CO), and Related Derivatives compoundn
"CO;
cm
6(t-BuS)f 6 (C,H, )f 1.43 2.19
1972 1985 1942 1956
1.58 1.92 5.76 5.30 6.10
4 , Cp,Zr(CH,PPh,), 5, Cp,Zr(CH,PPh,)2Cr(CO),d 6, Cp,Zr(CH,PPh,),Rh(CO)Cle a Cp = q-C,H,. In toluene-d, .
From ref 6. In CH,Cl, .
From ref 7.
5.45 6.16
From ref 3
e
From ref 8.
f
JP-H,
JRh-H9
Hz
Hz
1.27 2.17 1.29 1.58'
17.5 11.4 9.6 9.6
1.9 0 1.2 1.2
1.39f
9.7
0.97 1.50f 2.16f
3 6 3.4
6 (PCH)g
I n C,D, ( o r C,H,).
g
0.9
PCH, or PCH,
.
intensity. This is indicative of two nonequivalent kinds Table 111. Crystallographic Experimental Details of phenyl bonded to the phosphorus nuclei. The cycloA. Crystal Data pentadienyl groups v5-bondedto zirconium also clearly are formula: C46H52Rh2Zr02P2S2 a = 16.020 (4) 8, nonequivalent (Table I). fw: 1056.00 b = 16.237 (7) 8, In the 'H spectrum, these inequivalences are confirmed c = 18.304 (8) 8, f(OO0) = 2128 (see Table 11) and the corresponding chemical shift sepa/3 = 112.61 (3) cryst dimens: 0.25 X 0.05 X 0.05 mm ration depends on the nature of the solvent (for instance, v = 4395.3 A3 Mo Ka radiatn: X = 0.71073 i\ temp: 20 "C f 1" 2 = 4 &Bus, 2.19 and 1.43 ppm in C6D6,2.27 and 1.52 ppm in p = 1.60 g/cm3 monoclinic space group P2,/c toluene-& 1.76 and 1.17 ppm in CD2C1;cyclopentadienyl, p = 11.6 cm-' 6.16 and 5.45 ppm in C6D6, 6.26 and 5.76 ppm in toluene& 6.04 and 5.99 ppm in CD2C12).The spectrum is B. Intensity Measurements instrument Enraf-Nonius CAD4 diffractometer unaffected when the temperature is lowered to -80 "C or monochromator graphite crystal, incident beam raised to 100 O C (in toluene-d,). Moreover, while in the attenuator Zr foil, factor 19.4 13C spectrum the methylene resonance (Zr-CH2-P) could takeoff angle 3.2' not be clearly distinguished, in the lH spectrum we can detector aperture 4.0 mm horizontal see a complex pattern appearing as two sets of peaks of 4.0 mm vertical equal intensity: a pseudotriplet and two doublets of cryst detector dist 21 cm scan type 8-28 doublets. This reveals the nonequivalence of the hydrogen scan rate l-lO"/min (in w ) nuclei of each methylene group. By irradiation techniques Scan width, deg 0.9 + 0.350 tan 0 and 31Pdecoupling the pseudotriplet could be attributed maximum 28 55.0' to HA with bA 2.17 (2JH-H = 11.5 Hz, 2JH = 11.4 Hz, 3JH-Rh no of reflctn measd 8748 total, 5208 unique = 0) and the octet to HB with bB 1.27 (2JH-H = 11.5 Hz, 2 J ~ correctns Lorentz-polarization = 17.5 Hz, 3JH = 1.94 Hz) (in toluene-d8). linear decay (from 0.964 to 1.177 on I ) empirical absorptn As the proposed structure is unprecedented and the strong magnetic inequivalences observed by NMR specC. Structure Solution and Refinement troscopy have not been described previously and lack ready solution direct methods explanation, it seemed necessary to investigate the crystal included as fixed contribution to hydrogen atoms the structure factor structure of complex 1. X-ray Structure Experimental Data. A green-yellow needle-shaped crystal of C4,H52Rh2Zr02P2Sz having approximate dimensions of 0.25 x 0.05 x 0.05 mm was mounted in a glass capillary, on a CAD4 Enraf-Nonius PDP 11/23 computer-controlled single-crystal diffractometer. The unit cell was refined by optimizing the setting of 25 reflections (Mo K a radiation). The results are shown in Table I11 as well as the schedule for the measurement of the intensity of
minimization functn least-squares weights anomalous dispersn reflections included parameters refined unweighted agreement factor weighted agreement factor high peak in final diff map
C W ( l F 0 l - lFd2 4F,2/a2(F,2) all non-hydrogen atoms 5080 with I > 2 u ( n 497
0.034 0.038 0.14 (19) e / k 3
the reflections which were corrected for Lorentz-polarization factors; empirical absorption corrections were applied.
Organometallics, Vol. 5, No. I , 1986 69
Heterobimetallic Complexes as Catalysts
c5\?c6
atom 1
c3
Rh(1) Rh(1) Rh(1) Rh(1) Rh(2) Rh(2) Rh(2) Rh(2)
o(1)
O(2) Rh(1)
Table V. Selected Bond Distances (A)n atom 2 dist atom 1 atom 2 dist
P(1) S(1) S(2) C(1) P(2)
S(1) S(2) C(2)
c(l) C(2) Rh(2)
2.264 (1) 2.376 (1) 2.412 (1) 1.814 (4) 2.294 (1) 2.394 (1) 2.398 (1) 1.806 (4) 1.141 (5) 1.152 (5) 3.391 (1)
P(1)
C(l1)
P(1) P(1)
C(13) C(19) C(12) C(25) C(31) C(11) C(12) S(1) S(2) Cp(l)b CP(~
P(2) P(2) P(2) Zr(1) Zr(1) Zr(1) Zr(1) Zr(1) Zr(1)
1.809 (3) 1.827 (4) 1.830 (4) 1.808 (4) 1.839 (4) 1.829 (4) 2.423 (3) 2.413 (4) 5.701 (1) 2.995 (1) 2.242 (4) )~ 2.271 (4)
Figure 1. An ORTEP drawing of Rhz(S-t-Bu)z[(PhzPCHz)zZr(~- Numbers in parentheses are estimated standard deviations in
C,H5),](CO), (1) with 50% thermal ellipsoids. C p l and Cp2 contain the atoms C(37)-C(41) and C(42)-C(46). P h l , Ph2, Ph3, and Ph4 contain C(13)-C(18), C(19)-C(24), C(25)-C(30), and C (31)-C (36), respectively. Table IV. Selected Positional and Thermal Parameters for
Rhz(~-~-BuS)z[(PhzPCHz)zZ~(~-C,H,),I(Co)z (1) atom
X
Y
2
B , AZ
Rh(1) Rh(2) Zr(1) P(1) P(2)
0.13203 (3) 0.34976 (3) 0.28107 (4) 0.0634 (1) 0.4617 (1) 0.2272 (1) 0.2752 (1) -0.0499 (4) 0.4343 (4) 0.0218 (4) 0.4015 (5) 0.1845 (4) 0.3082 (4) 0.1413 (4) 0.4293 (4) -0.0193 (4) -0.0102 (4) 0.5628 (4) 0.5155 (4) 0.2018 (4) 0.2918 (4) 0.3129 (5) 0.2340 (5) 0.1649 (4) 0.2565 (5) 0.2543 (5) 0.3390 (6) 0.3950 (5) 0.3470 (7)
0.20525 (3) 0.19150 (3) 0.43773 (4) 0.3197 (1) 0.2884 (1) 0.0968 (1) 0.2556 (1) 0.1487 (4) 0.1090 (4) 0.1692 (5) 0.1426 (4) 0.0412 (4) 0.2040 (4) 0.3965 (4) 0.3768 (4) 0.2973 (4) 0.3777 (4) 0.2470 (4) 0.3299 (4) 0.3957 (4) 0.4073 (5) 0.4912 (5) 0.5314 (5) 0.4732 (4) 0.5192 (5) 0.5738 (5) 0.5793 (5) 0.5296 (5) 0.4883 (5)
0.23440 (3) 0.25077 (3) 0.30387 (3) 0.25514 (9) 0.30011 (9) 0.22525 (9) 0.32719 (9) 0.1299 (4) 0.1524 (3) 0.1679 (4) 0.1901 (4) 0.1287 (4) 0.4284 (3) 0.3154 (3) 0.3433 (4) 0.2988 (3) 0.1686 (3) 0.3797 (3) 0.2361 (3) 0.1598 (3) 0.1712 (3) 0.1876 (4) 0.1836 (4) 0.1674 (4) 0.4149 (4) 0.3573 (4) 0.3552 (4) 0.4101 (5) 0.4499 (4)
2.501 (9) 2.558 (9) 2.34 (1) 2.44 (3) 2.63 (3) 2.74 (3) 2.53 (3) 7.1 (2) 7.7 (2) 3.9 (2) 4.0 (2) 3.1 (1) 3.1 (1) 2.4 (1) 3.1 (1) 2.5 (1) 2.8 (1) 2.8 (1) 2.7 (1) 3.1 (1) 3.3 (2) 3.8 (2) 3.7 (2) 3.3 (2) 4.7 (2) 4.8 (2) 4.8 (2) 5.1 (2) 5.7 (3)
S(1) S(2) O(1) O(2) C(1) C(2) C(3) C(7) C(l1) C(12) C(13) C(19) C(25) C(31) C(37) C(38) C(39) C(40) C(41) C(42) C(43) C(44) C(45) C(46)
The structure was solved by direct methods. With 250 reflections (minimum E of 1.40) and 2000 relationships, a total of nine phase sets were produced. A total of 29 atoms were located from an E map prepared from the phase set. The remaining atoms were located in succeeding difference Fourier syntheses. Hydrogen atoms were located and added to the structure factor calculations but their positions were not refined. Scattering factors were taken from Cromer and Waber? and Anomalous dispersion effects were included in FC,lo their values were those of Cromer and Liberman." A total (7) Bresler, L. S.; Buzina, N. A.; Vashavsky, Yu. S.; Kiseleva,y. V.; Cherkasova, T. G. J. Organomet. Chem. 1979, 171, 229. (8) Choukroun, R.; Gervais, D. J. Organomet. Chem. 1984,266,C37. (9) Cromer, D. T.; Waber, J. T. "International Tables for X-Ray Crystallography";Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.2.B. (10) Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781. (11) Cromer, D. T.; Liberman, D. 'International Tables for X-Ray Crystallography";Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.3.1.
the least significant digits. *Centroid of the C5H5ring.
Ysz c&cgg
Figure 2. An ORTEP drawing showing pentacoordination around the zirconium atom in 1. C(98) and C(99) are the centroids of the ?-C,H, rings.
i"
51
Figure 3. A view of 1 looking approximately down the Rh(1)Rh(2) axis showing the conformation of the eight-membered ring Zr(1)-C(l1)-P(1)-Rh(1)-S( l)-Rh(2)-P(2)-C( 12). Phenyl rings are omitted for clarity.
of 5080 reflections having intensities I > 2 were used in the refinements. The final cycle of refinement included 497 variable parameters and converged with unweighted and weighted agreement factors of R1 = 0.034 and R2 = 0.038. The highest peak in the final difference Fourier had a height of 0.14 e/A-3. All calculations were performed on a VAX-11 computer using SDP.PLUS.12 Results and Discussion. An ORTEP diagram of the molecular structure of compound 1 is shown in Figure 1 and does not differ greatly from the proposed arrangement shown in I. Final positional and thermal parameters are given in Table IV. Tables V and VI list selected interatomic distances and angles. The molecule has a quasimirror plane containing the zirconium and the two sulfur (12) Frenz, B. A. "The Enraf-Nonius CAD4 SDP (crystal determination package)" In 'Computing in Crystallography";Schenk, H., OlthofHazelkamp, R., Vankonigsveld, H., Bassi, G. C., Eds.; Delft University Press: Delft, Holland, 1978; pp 64-71.
70 Organometallics, Vol. 5, No. 1, 1986
Dlane no. 1
A -0.9937
Choukroun et al.
Table VII. Equation of Planes and Distances (A) from the Planes" B C D atom X Y 0.0756
-0.0828
-2.2375 2.0542 2.1067 2.3645 0.4657 3.8385 -0.7805 5.2846 0.0444 4.4625 -0.8325 5.0948 -1.7144 5.8850 2.0495 1.9231 2.1089 3.4702 3.6931 2.4569 1.4645 1.1899 1.5606 2.9309 3.4423 2.3927
0.0606
-0.4660
-0.8827
-7.7011 2.3645 0.0444 4.4625
0.0680
0.9974
-0.0242
3.2597 0.4657 3.8385 1.9231 2.1067 2.3645
Atoms in Plane 1.5724 4.1500 7.1073 Other Atoms 3.3325 3.1093 5.1903 4.6828 6.4372 6.1183 2.7479 2.3158 2.4148 1.7703 0.6685 3.3126 6.4241 6.6138 7.9748 8.6281 7.6832 8.4299 9.3173 9.4059 8.5993 7.9284 Atoms in Plane 7.1073 6.4372 6.1183 Atoms in Plane 3.3325 3.1093 3.3126 Other Atoms 4.1500 7.1073
dist
esd
3.8062 5.5288 5.1346
0.000 0.000 0.000
0.002 0.002 0.001
3.9608 4.2374 4.3112 5.0711 5.3292 5.8006 2.8375 3.2115 2.1954 2.5749 2.1748 7.2386 2.7004 2.8926 3.1700 3.1021 2.8285 7.0114 6.0367 6.0019 6.9300 7.6025
1.699 -1.693 3.048 -3.080 2.239 -2.215 3.038 -2.916 3.942 -3.690 0.071 -0.022 0.404 -0.950 -1.092 0.191 1.129 1.112 0.891 -0.461 -1.107 -0.170
0.001 0.001 0.002 0.002 0.006 0.007 0.008 0.008 0.007 0.007 0.007 0.007 0.007 0.007 0.008 0.008 0.007 0.008 0.009 0.009 0.009 0.012
5.1346 5.3292 5.8006
0.000 0.000 0.000
0.001 0.006 0.006
3.9608 4.2374 7.2386
0.000 0.000 0.000
0.001 0.001 0.007
5.5288 5.1346
0.889 3.866
0.002 0.001
Z
Dihedral Angle between Planes 1 and 2: 91.3' "The equation of the plane is of the form Ax coordinates.
+ By + Cz - D = 0 where A , B , C, and D are constants and x , y , and z are orthogonalized
atoms as well as the two centroids of the C5H5rings; the quaternary carbons of the tert-butyl groups are nearly in the same plane since the maximum displacements are only 0.071 ( 7 ) %, for C(3) and -0.022 ( 7 ) for C(7) (Table VII). This plane is perpendicular to the plane defined by the zirconium atom and carbons C(l1) and C(12) of the methylene groups of CHzPPh2. The dirhodium core Rhz(t-BuS)z(CO)zPz is roughly comparable to the bent geometry of previously reported Rhz or Irz systems such as Rhz(SPh)z(CO)z(PMe3)z13 (2) and Irz(t-BuS)z(CO)2[P(OMe)3]214(3): the tert-butyl groups are in an anti con(13)Bonnet, J. J.;Kalck, P.; Poilblanc, R. Inorg. Chem. 1977,16,1514.
figuration with respect to the RhzS2arrangement, with the t-Bu in the exo position lying between the phosphine ligands. The intramolecular rhodium-rhodium distance is 3.391 (1)%, (to be compared to 3.061 (1) %, in 2). The structural arrangement of the zirconium diphosphine part of the molecule roughly resembles those (4) or the cis of the uncomplexed (~-C5H,)zZr(CHzPPhz)z complex (V - C ~ H , )(CHzPPh2) ~Z~ (CO) ( 5 ) previously described by S ~ h o r e .The ~ more striking discrepancy is observed for the C(ll)-Zr-C(12) angle which is 134.2' (1) (14)Bonnet, J. J.; Thorez, A.; Maisonnat, A,; Galy, J.; Poilblanc, R. J. Am. Chem. SOC.1979,101, 5940.
Heterobimetallic Complexes as Catalysts in (l),a much larger value than those in 4 (100.2O) and 5 (93.5O). Pentacoordination around the zirconium atom may then be presumed by comparison to the recently re(7) or the ported cationic species15 [ (q-C5H,)zZr(HzO)3]2+ thiocarbamate complex16 (rl-C5H5)zZrC1(S2CNEt2)(8) where the corresponding angles X(l)ZrX(3) (11)are 145.2O
I1 (2) and 137.5' (l),respectively. This is supported by the distance Zr-S(2) (2.995 (1) A), much shorter than expected for noninteracting atoms, although significantly longer than the two Zr-S distances in the thiocarbamato complex 8:16 2.635 (2) and 2.723 (2) A. Moreover, the lone pair of S(2) directly faces zirconium as demonstrated by comparing the Zr(l)-S(2) distance (2.995 A) to the difference (2.977 A) between the distance of Zr(1) (3.866 A) and S(2) (0.889 A) to the plane Rh(l)Rh(2)C(7) (Table VII) containing the three other atoms directly bonded to S(2)which is then brought to tetracoordination. The pentacoordinated arrangement around zirconium is shown in Figure 2. The characteristic structural features of complex 1 can be seen in Figure 3 where the geometric arrangement of the eight-membered ring formed by the zirconium diphosphine bridging the Rh-S-Rh sequence is clearly visible. Magnetic inequivalences shown in 'H and 13C NMR spectra are now explainable on account of axial and equatorial positions with respect to the ring. This holds for the phenyls bonded to each phosphorus and for the hydrogens of each methylene group as well as for the two cyclopentadienyl groups bonded to the zirconium atom. The coordination of the sulfur atom S(2) to zirconium is certainly responsible for the stereorigidity of complex 1 even in solution up to 100 "C in toluene. It also explained the unusual chemical shift of one of the quaternary carbons (found at 33.9 ppm) due very probably to the influence of the tetracoordination of the sulfur S(2)on the C(7) carbon nucleus. (15)Thewalt, U.;Lasser, W. J. Organomet. Chem. 1984,276, 341. (16)Silver, M.E.; Eisenstein,0.;Fay, R. C. Znorg. Chem. 1983,22,759.
Organometallics, Vol. 5, No. 1, 1986 71 Conclusions By reacting the zirconium diphosphine (q-C5H5)2Zr(CHZPPh2)z with Rhz(t-BuS)2(C0)4, we obtained a novel bimetallic zirconium-dirhodium species, Rh,(p-S-t-Bu),[ (~-Ph2PCHz)zZr(o-CSHS)z](CO)z (l),with the zirconium diphosphine bridging the two rhodium in a cis arrangement toward the retained bent dirhodium dicarbonyl bis(pthiolato) core. A strong interaction between one of the sulfur atoms and the zirconium is responsible for the unprecedented inequivalences shown in the lH and 13C spectra. It also can explain the unexpected stability of the zirconium-alkyl bond which is not cleaved by dihydrogen, carbon monoxide, olefins, or aldehydes, due probably to the saturation of the pentacoordinated 18-electron configuration of the zirconium. In contrast to most of the previous work on bimetallic complexes, the bimetallic frame of 1 can be maintained under catalytic conditions (e.g., for hydroformylation),and this is quite unique for bimetallic species involving such an oxophilic metal as zirconium. On the other hand, the reason why the catalytic performance is improved by using the zirconium diphosphine ligand instead of the more classical 1,4-bis(phenylphosphino)butaneis not completely understood. The ( V - C ~ H ~moiety ) ~ Z ~probably plays the role of an electron buffer which is able to push or pull the electron density toward or from the rhodium atoms following the successive steps of the catalytic cycle such as oxidative addition of dihydrogen, coordination of hexene, and insertion of carbon monoxide.
Acknowledgment. We wish to thank the Centre National de la Recherche Scientifique for support of this research through Greco-Oxydes de Carbone and Dr. Jean Galy for useful discussions. We also greatly acknowledge Mr. Gerard Commenges for his assitance 'with NMR investigations. Registry No. Rhz(r-t-BuS)z(CO)4, 54032-58-5; Cp,Zr(CHZPPhJ2, 74395-16-7; R ~ ~ ( ~ - S - ~ - B U ) ~ [ ( ~ P ~ ~ P C H ~ ) C5H&] (CO),, 95029-92-8; Rhz(p-t-BuS)z[PhZP(CHJ,PPh2] (C0)2, 95029-17-7. Supplementary Material Available: Listings of anisotropic and isotropic general temperature factors, refined temperature factors, root mean square amplitudes of thermal vibration, bond angles, bond distances, positional parameters, and observed and calculated structure factor (51 pages). Ordering information is given on any current masthead page.
