Cluster Synthesis. 46. New Mixed-Metal Complexes of the Layer

Richard D. Adams , Thomas S. Barnard , Zhaoyang Li , Lijuan Zhang. Chemische Berichte 1997 130 ... S. Doherty. Annual Reports Section "A" (Inorganic ...
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2664

Organometallics 1996, 15, 2664-2667

Cluster Synthesis. 46. New Mixed-Metal Complexes of the Layer-Segregated Cluster Pt3Ru6(CO)21(µ3-H)(µ-H)3 Richard D. Adams,* Thomas S. Barnard, Jeffrey E. Cortopassi, and Lijuan Zhang Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208 Received February 14, 1996X Summary: The reaction of the dianion [Pt3Ru6(CO)21(µH)2]2-, generated in situ by the deprotonation of [Pt3Ru6(CO)21(µ-H)3(µ3-H)], 1, with [Cp*Ir(NCMe)3]2+ and HgI2, has yielded two new higher nuclearity cluster complexes Pt3Ru6(CO)21(µ3-IrCp*)(µ3-H)2, 5, and [NBu4][Pt3Ru6(CO)21(µ3-HgI)(µ3-H)2], 6, in the yields 15% and 35%, respectively. Both compounds were characterized by single-crystal X-ray diffraction analysis. They both contain layer segregated triangular Pt3 and Ru3 groupings stacked one upon the other with the Pt3 group in the center. The heterometal atom occupies a triply bridging position across one of the Ru2Pt triangles. The hydride ligands have adopted triply bridging positions on the two Ru3 triangles. Introduction We have recently prepared a series of mixed-metal cluster complexes that contain the first examples of layer-segregated triangular stacks of platinum combined with ruthenium1,2 or osmium.3 The platinumruthenium complex Pt3Ru6(CO)21(µ-H)3(µ3-H), 1,has been

found to be a precursor to the alkyne complex Pt3Ru6(CO)21(µ-PhC2Ph)(µ-H)(µ3-H), 2, which has been shown to be a catalyst for the hydrogenation of diphenylacetylene to (Z)-stilbene.4 We have recently shown that 1 can be deprotonated and the resultant anions can be used to prepare the mono- and diaurated layersegregated cluster complexes Pt3Ru6[Au(PEt3)](CO)21(µ-H)3, 3,and Pt3Ru6[Au(PEt3)]2(CO)21(µ3-H)2, 4, by reaction with ClAu(PEt3).5 In further studies we have investigated the reactions of the dianion [Pt3Ru6(CO)21(µ-H)2]2- with [IrCp*(NCMe)3][PF6]2 and HgI2. These Abstract published in Advance ACS Abstracts, May 15, 1996. (1) Adams, R. D.; Barnard, T. S.; Li, Z.; Wu, W.; Yamamoto, J. Organometallics 1994, 13, 2357. (2) Adams, R. D.; Li, Z.; Wu, W. Organometallics 1992, 11, 4001. (3) (a) Adams, R. D.; Lii, J.-C.; Wu, W. Inorg. Chem. 1991, 30, 3613. (b) Adams, R. D.; Lii, J.-C.; Wu, W. Inorg. Chem. 1992, 31, 2556. (c) Adams, R. D.; Lii, J.-C.; Wu, W. Inorg. Chem. 1991, 30, 2257. (4) Adams, R. D.; Barnard, T. S.; Li, Z.; Wu, W.; Yamamoto, J. J. Am. Chem. Soc. 1994, 116, 9103. (5) Adams, R. D.; Barnard, T. S.; Cortopassi, J. E. Organometallics 1995, 14, 2232. X

S0276-7333(96)00116-1 CCC: $12.00

reactions have led to the formation of the new compounds Pt3Ru6(CO)21(µ3-IrCp*)(µ3-H)2, 5, and [NBu4][Pt3Ru6(CO)21(µ3-HgI)(µ3-H)2], 6. The synthesis and characterizations of these new compounds are reported here. Experimental Section General Procedures. All reactions were performed under a nitrogen atmosphere unless specified otherwise. The complexes Pt3Ru6(CO)21(µ3-H)(µ-H)31 and [IrCp*(NCMe)3][PF6]26 were synthesized as described previously. Dichloromethane was dried and distilled from P2O5. NMR solvents were dried over 5 Å molecular sieves. NBu4[OH] (40 weight % in H2O) and HgI2 were purchased from Aldrich and used as received. NMR spectra were recorded at 500 MHz. Spectra above 25 °C were recorded in nitromethane-d3 solvent. Various-temperature spectra were calibrated with methanol or 80% ethylene glycol in DMSO-d6. Chromatographic separations were performed in air on Analtech 0.25 mm silica gel 60 Å F254 plates. Preparation of Pt3Ru6(CO)21(µ3-IrCp*)(µ3-H)2, 5. A 20.0-mg amount of 1 (0.0112 mmol) was dissolved in 20 mL of dichloromethane in a round bottom flask. A 15-µL amount of NBu4[OH] solution (0.0228 mmol) was added via syringe, and the solution was then stirred at room temperature for 15 min. A 16.8-mg amount of [IrCp*(NCMe)3][PF6]2 (0.0227 mmol) was added and the solution stirred at room temperature for 2 h. The solvent was removed in vacuo and the residue separated by TLC using a CH2Cl2/hexane (1/1) mixture. This yielded 3.5 mg of brown Pt3Ru6(CO)21(µ3-IrCp*)(µ3-H)2 (15%). IR (ν(CO), cm-1, in hexane): 2088 (m), 2057 (vs), 2050 (s), 2039 (s), 2013 (m). 1H NMR (δ in CD2Cl2 at -93 °C): 1.89 (s, 15H), -15.47 (s, 1H), -20.72 (s, 1H). Anal. Calcd (found): C, 17.65 (17.52); H, 0.81 (0.74). Preparation of [NBu4][Pt3Ru6(CO)21(µ3-HgI)(µ3-H)2], 6. A 10.1-mg amount of compound 1 (0.0057 mmol) was dissolved in 15 mL of dichloromethane. A 8.2-µL amount of NBu4[OH] solution (0.012 mmol) was added, and the reaction mixture was stirred for 30 min at room temperature. A 12.5-mg amount (0.028 mmol) of HgI2 was then added, and the reaction mixture was stirred for an additional 30 min at room temperature. The volatiles were removed in vacuo, and the residue was dissolved in a minimum amount of methylene chloride. (6) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228.

© 1996 American Chemical Society

Notes

Organometallics, Vol. 15, No. 11, 1996 2665

Table 1. Crystal Data for Compounds 5 and 6 compd

formula fw cryst system lattice params a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) space group Z value Fcalc (g/cm3) µ(Mo KR) (cm-1) temp (°C) 2θmax (deg) no. obs (I > 3σ(I)) goodness of fit (GOF) residuals:a R; Rw max shift/error on final cycle largest peak in final diff map abs corr, max/min

5

6

IrPt3Ru6O21C31H17 2109.37 monoclinic

IHgPt3Ru6O21NC37H38 2351.89 monoclinic

13.581(2) 18.577(5) 17.616(2) 90 97.72(1) 90 4405(6) P21/n (No. 14) 4 3.18 145.4 20 43 3494 1.34 0.031; 0.027 0.00

20.366(3) 10.060(3) 28.738(4) 90 108.64(1) 90 5579(2) P21/c (No. 14) 4 2.80 124.1 20 44 4398 2.40 0.042; 0.042 0.01

1.0

2.2

empirical, 1.00/0.42

empirical, 1.0/0.37

a R ) ∑ 2 hkl(||Fo| - |Fc||/∑hkl|Fo|; Rw ) [∑hklw(|Fo| - |Fc| )/ ∑hklwFo2]1/2, w ) 1/σ2(Fo); GOF ) [∑hkl(|Fo| - |Fc|/σ(Fo)]/ndata - nvari).

This solution was transferred to TLC plates and separated using a 2/1 methylene chloride/hexane solvent mixture as the eluent to yield 4.6 mg of red-brown [NBu4][Pt3Ru6(CO)21(µ3HgI)(µ3-H)2], 6 (0.0020 mmol, 35% yield). Analytical and spectral data for 6 are as follows. IR (ν(CO), in cm-1, in CH2Cl2): 2085 (w), 2045 (vs), 2042 (vs). 1H NMR (δ in CD2Cl2 at 25 °C): 3.08 (t, NCH2, 8 H), 1.61 (m, NCH2CH2, 8 H), 1.44 (m, NCH2CH2CH2, 8 H), 1.04 (t, CH3, 12 H), -18.20 (br s, Ru-H, 2 H). 1H NMR (δ in nitromethane-d3 at 64 °C): 3.27 (t, NCH2, 8 H), 1.95 (m, NCH2CH2, 8 H), 1.44 (m, NCH2CH2CH2, 8 H), 1.13 (t, CH3, 12 H), -17.82 (s, Ru-H, 2 H). Anal. Calcd (found) for 6: C, 18.90 (18.62); H, 1.63 (1.73); N, 0.60 (0.59). Crystallographic Analyses. Crystals of 5 suitable for X-ray diffraction analysis were grown from a solution in a 1/1 dichloromethane/hexane solvent mixture by slow evaporation of the solvent at 25 °C. Crystals of 6 were grown from a solution in a 1/1 CH2Cl2/benzene solvent mixture by slow evaporation of the solvent at 25 °C. The crystals used in intensity measurements were mounted in thin-walled glass capillaries. Diffraction measurements were made on a Rigaku AFC6S automatic diffractometer by using graphite-monochromated Mo KR radiation. The unit cells were determined from 25 randomly selected reflections obtained by using the AFC6 automatic search, center, index, and least-squares routines. Crystal data, data collection parameters, and results of the analyses are listed in Table 1. All data processing was performed on a Digital Equipment Corp. VAXstation 3520 computer by using the TEXSAN structure-solving program library obtained from the Molecular Structure Corp., The Woodlands, TX. Lorentz-Polarization (Lp) and absorption corrections were applied to the data in each analysis. Neutral atom scattering factors were calculated by the standard procedures.7a Anomalous dispersion corrections were applied to all non-hydrogen atoms.7b Both structures were solved by a combination of direct methods (MITHRIL) and difference Fourier syntheses. Full-matrix least-squares refinements minimized the following function: ∑hklw(|Fo| - |Fc|)2, where w ) 1/σ(F)2, σ(F) ) σ(Fo2)/2Fo, and σ(Fo2) ) [σ(Iraw)2+(0.02Inet)2]1/2/ Lp. For both analyses, the positions of the hydrogen atoms on the ligands were calculated by assuming idealized geom(7) International Tables for X-ray Crystallography; Kynoch Press: Birmingham, England, 1975; Vol IV: (a) Table 2.2B, pp 99-101; (b) Table 2.3.1, pp 149-150.

Figure 1. ORTEP diagram of Pt3Ru6(CO)21(µ3-IrCp*)(µ3H)2, 5, showing 40% probability thermal ellipsoids. etry, C-H ) 0.95 Å. Their scattering contributions were added to the structure factor calculations, but their positions were not refined. Compound 5 crystallized in the monoclinic crystal system. The space group P21/n was established on the basis of the patterns of systematic absences observed in the data. All nonhydrogen atoms were refined with anisotropic thermal parameters. The positions of the two hydride ligands were obtained in difference Fourier syntheses, and they were refined with isotropic thermal parameters. Compound 6 crystallized in the monoclinic crystal system. The space group P21/c was established on the basis of the patterns of systematic absences observed in the data. All nonhydrogen atoms were refined with anisotropic thermal parameters. The two hydride ligands could not be located and were ignored in this analysis.

Results and Discussion From the reaction of the dianion [Pt3Ru6(CO)21(µH)2]2-, generated in situ by the deprotonation of 1 by using 2 equiv of [NBu4][OH], with [Cp*Ir(NCMe)3]2+ and HgI2, we have obtained the two new higher nuclearity cluster complexes Pt3Ru6(CO)21(µ3-IrCp*)(µ3-H)2, 5, and [NBu4][Pt3Ru6(CO)21(µ3-HgI)(µ3-H)2], 6, respectively. Both complexes have been characterized by IR, 1H NMR, elemental, and single-crystal X-ray diffraction analyses.

ORTEP diagrams of the molecular structures of 5 and 6 are shown in Figures 1 and 2, respectively. Selected bond distances and angles for both compounds are listed in Tables 2-5. The clusters of both compounds are very similar. Both contain layer-segregated arrangements

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Organometallics, Vol. 15, No. 11, 1996

Notes Table 3. Intramolecular Bond Angles for 5a

Figure 2. ORTEP diagram of [NBu4][Pt3Ru6(CO)21(µ3HgI)(µ3-H)2], 6, showing 40% probability thermal ellipsoids. Table 2. Selected Intramolecular Distances for 5a Pt(1)-Pt(2) Pt(1)-Pt(3) Pt(1)-Ir(1) Pt(1)-Ru(1) Pt(1)-Ru(2) Pt(1)-Ru(4) Pt(1)-Ru(6) Pt(2)-Pt(3) Pt(2)-Ru(1) Pt(2)-Ru(3) Pt(2)-Ru(5) Pt(2)-Ru(6) Pt(3)-Ru(2) Pt(3)-Ru(3) Pt(3)-Ru(4) Pt(3)-Ru(5) Ir(1)-Ru(1) Ir(1)-Ru(2) Ir(1)-C(11) Ir(1)-C(70) Ir(1)-C(71) Ir(1)-C(72) Ir(1)-C(73) Ir(1)-C(74)

2.6762(8) 2.6514(9) 2.8224(9) 2.832(1) 2.803(1) 2.775(2) 2.754(1) 2.6783(9) 2.865(2) 2.845(1) 2.715(2) 2.724(1) 2.823(2) 2.823(1) 2.770(2) 2.709(1) 2.728(1) 2.768(2) 2.43(2) 2.20(1) 2.23(1) 2.20(1) 2.18(2) 2.23(2)

Ru(1)-Ru(2) Ru(1)-Ru(3) Ru(1)-H(2) Ru(2)-Ru(3) Ru(2)-H(2) Ru(3)-H(2) Ru(4)-Ru(5) Ru(4)-Ru(6) Ru(4)-H(1) Ru(5)-Ru(6) Ru(5)-H(1) Ru(6)-H(1) O-C(av) C(70)-C(71) C(70)-C(74) C(70)-C(75) C(71)-C(72) C(71)-C(76) C(72)-C(73) C(72)-C(77) C(73)-C(74) C(73)-C(78) C(74)-C(79)

2.881(2) 2.961(2) 1.9(1) 2.954(2) 1.7(1) 1.9(1) 3.019(2) 2.979(2) 2.2(1) 3.065(2) 1.8(1) 1.7(1) 1.15(2) 1.41(2) 1.43(2) 1.54(2) 1.44(2) 1.48(2) 1.43(2) 1.49(2) 1.41(2) 1.49(2) 1.50(2)

a Distances are in Å. Estimated standard deviations in the least significant figure are given in parentheses.

of the Pt3Ru6 cores with the Pt3 triangle sandwiched between the two Ru3 triangles in a staggered orientation as observed in the compounds 1-4. The heterometal is attached to the Pt3Ru6 cluster as a triple bridging group across one of the six PtRu2 triangles. This contrasts with the structure of 3, where the gold atom bridged a group of three ruthenium atoms, but is similar to that of 4, where both gold atoms bridge PtRu2 triangles. There are some curious differences in the metal-metal bonding in the vicinity of the heterometal atom. For example, the bond between the iridium and platinum atom in 5 is much shorter than the bond between the mercury and platinum atom in 6, 2.8224(9) vs 2.893(1) Å, even though the iridium-ruthenium and mercury-ruthenium distances are nearly the same, 2.728(1) and 2.768(2) Å vs 2.741(2) and 2.774(2) Å. There are very few structurally characterized examples of compounds containing triply bridging Hg-X groups,

Pt(2)-Pt(1)-Pt(3) Pt(2)-Pt(1)-Ru(1) Pt(2)-Pt(1)-Ru(6) Pt(3)-Pt(1)-Ru(2) Pt(3)-Pt(1)-Ru(4) Ir(1)-Pt(1)-Ru(1) Ir(1)-Pt(1)-Ru(2) Ru(1)-Pt(1)-Ru(2) Ru(4)-Pt(1)-Ru(6) Pt(1)-Pt(2)-Pt(3) Pt(1)-Pt(2)-Ru(1) Pt(1)-Pt(2)-Ru(6) Pt(3)-Pt(2)-Ru(3) Pt(3)-Pt(2)-Ru(5) Ru(1)-Pt(2)-Ru(3) Ru(5)-Pt(2)-Ru(6) Pt(1)-Pt(3)-Pt(2) Pt(1)-Pt(3)-Ru(2) Pt(1)-Pt(3)-Ru(4) Pt(2)-Pt(3)-Ru(3) Pt(2)-Pt(3)-Ru(5) Ru(2)-Pt(3)-Ru(3) Ru(4)-Pt(3)-Ru(5) Pt(1)-Ir(1)-Ru(1) Pt(1)-Ir(1)-Ru(2) Ru(1)-Ir(1)-Ru(2) Pt(1)-Ru(1)-Pt(2) Pt(1)-Ru(1)-Ir(1) Pt(1)-Ru(1)-Ru(2) Pt(2)-Ru(1)-Ru(3) Ir(1)-Ru(1)-Ru(2)

60.36(2) 62.61(3) 60.18(3) 62.26(3) 61.35(4) 57.69(3) 58.95(3) 61.50(4) 65.21(4) 59.36(2) 61.35(3) 61.33(3) 61.38(3) 60.29(3) 62.48(4) 68.61(4) 60.28(2) 61.51(3) 61.52(4) 62.22(3) 60.52(4) 63.09(4) 66.85(4) 61.32(3) 60.18(3) 63.23(4) 56.04(3) 60.99(3) 58.76(4) 58.43(4) 59.07(4)

Ru(2)-Ru(1)-Ru(3) Pt(1)-Ru(2)-Pt(3) Pt(1)-Ru(2)-Ir(1) Pt(1)-Ru(2)-Ru(1) Pt(3)-Ru(2)-Ru(3) Ir(1)-Ru(2)-Ru(1) Ru(1)-Ru(2)-Ru(3) Pt(2)-Ru(3)-Pt(3) Pt(2)-Ru(3)-Ru(1) Pt(3)-Ru(3)-Ru(2) Ru(1)-Ru(3)-Ru(2) Pt(1)-Ru(4)-Pt(3) Pt(1)-Ru(4)-Ru(6) Pt(3)-Ru(4)-Ru(5) Ru(5)-Ru(4)-Ru(6) Pt(2)-Ru(5)-Pt(3) Pt(2)-Ru(5)-Ru(6) Pt(3)-Ru(5)-Ru(4) Ru(4)-Ru(5)-Ru(6) Pt(1)-Ru(6)-Pt(2) Pt(1)-Ru(6)-Ru(4) Pt(2)-Ru(6)-Ru(5) Ru(4)-Ru(6)-Ru(5) M-C-O(av) Ir(1)-C(11)-O(11) Ru(1)-C(11)-O(11) Ir(1)-C(70)-C(75) Ir(1)-C(71)-C(76) Ir(1)-C(72)-C(77) Ir(1)-C(73)-C(78) Ir(1)-C(74)-C(79)

60.72(5) 56.23(3) 60.87(3) 59.74(4) 58.45(4) 57.70(4) 60.98(5) 56.40(3) 59.09(4) 58.46(4) 58.30(4) 57.14(3) 57.07(4) 55.60(4) 61.46(5) 59.18(3) 55.83(4) 57.54(4) 58.64(5) 58.49(3) 57.72(4) 55.56(4) 59.90(5) 174(2) 123(1) 159(1) 131(1) 131(1) 133(1) 132(1) 131(1)

a Angles are in deg. Estimated standard deviations in the least significant figure are given in parentheses.

Table 4. Selected Intramolecular Distances for 6a Hg-Pt(1) Hg-I Hg-Ru(1) Hg-Ru(2) Pt(1)-Pt(2) Pt(1)-Pt(3) Pt(1)-Ru(1) Pt(1)-Ru(2) Pt(1)-Ru(4) Pt(1)-Ru(5) Pt(2)-Pt(3) Pt(2)-Ru(1) Pt(2)-Ru(3)

2.893(1) 2.661(1) 2.741(2) 2.774(2) 2.647(1) 2.660(1) 2.989(2) 2.893(2) 2.732(2) 2.726(2) 2.671(1) 2.831(2) 2.842(2)

Pt(2)-Ru(4) Pt(2)-Ru(6) Pt(3)-Ru(2) Pt(3)-Ru(3) Pt(3)-Ru(5) Pt(3)-Ru(6) Ru(1)-Ru(2) Ru(1)-Ru(3) Ru(2)-Ru(3) Ru(4)-Ru(5) Ru(4)-Ru(6) Ru(5)-Ru(6) O-C(av)

2.745(2) 2.702(2) 2.864(2) 2.836(2) 2.724(2) 2.708(2) 3.090(2) 2.952(2) 2.953(2) 2.992(3) 3.021(2) 3.055(3) 1.16(3)

a Distances are in Å. Estimated standard deviations in the least significant figure are given in parentheses.

X ) halide.8 Interestingly, the platinum-ruthenium and ruthenium-ruthenium bond distances that are bridged by the heteroatom are much longer in 6 than in 5, Pt-Ru ) 2.989(2) and 2.893(2) Å vs 2.832(1) and 2.803(2) Å and Ru(1)-Ru(2) ) 3.090(2) and 2.881(2) Å. This latter observation may be attributed to a greater electron-withdrawing power of the Cp*Ir2+ group compared to the HgI+ group. In both products the spacing between the platinum and ruthenium triangles is significantly larger on the side of the molecule that contains the heteroatom, 2.32 vs 2.19 Å in 5 and 2.36 vs 2.17 Å in 6. By contrast in 3 the Pt-Ru interplanar spacing was about 0.23 Å smaller to the Au-bridged ruthenium triangle than to the other triangle. It could be that the interplanar spacings are influenced more by the arrangement of the carbonyl ligands than the presence of the heteroatom. For example, in each of the compounds 3, 5, and 6, three carbonyl ligands on one (8) (a) Gade, L. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 24. (b) Della Pergola, R.; Demartin, F.; Garleschelli, L.; Manassero, M.; Martinengo, S.; Masciocchi, N.; Sansoni, M. Organometallics 1991, 10, 2239.

Notes

Organometallics, Vol. 15, No. 11, 1996 2667

Table 5. Intramolecular Bond Angles for 6a Pt(1)-Hg-I Pt(1)-Hg-Ru(1) Pt(1)-Hg-Ru(2) I-Hg-Ru(1) I-Hg-Ru(2) Ru(1)-Hg-Ru(2) Hg-Pt(1)-Ru(1) Hg-Pt(1)-Ru(2) Pt(2)-Pt(1)-Pt(3) Pt(2)-Pt(1)-Ru(1) Pt(2)-Pt(1)-Ru(4) Pt(3)-Pt(1)-Ru(2) Pt(3)-Pt(1)-Ru(5) Ru(1)-Pt(1)-Ru(2) Ru(4)-Pt(1)-Ru(5) Pt(1)-Pt(2)-Pt(3) Pt(1)-Pt(2)-Ru(1) Pt(1)-Pt(2)-Ru(4) Pt(3)-Pt(2)-Ru(3) Pt(3)-Pt(2)-Ru(6) Ru(1)-Pt(2)-Ru(3) Ru(4)-Pt(2)-Ru(6) Pt(1)-Pt(3)-Pt(2) Pt(1)-Pt(3)-Ru(2) Pt(1)-Pt(3)-Ru(5) Pt(2)-Pt(3)-Ru(3) Pt(2)-Pt(3)-Ru(6) Ru(2)-Pt(3)-Ru(3) Ru(5)-Pt(3)-Ru(6)

131.65(6) 64.03(4) 61.35(4) 141.39(6) 148.83(6) 68.15(5) 55.51(4) 57.31(4) 60.44(3) 59.92(4) 61.34(5) 61.93(4) 60.76(4) 63.35(5) 66.50(6) 60.01(3) 66.05(4) 60.85(5) 61.82(4) 60.53(5) 62.70(5) 67.37(6) 59.55(3) 63.03(4) 60.81(4) 62.05(4) 60.29(5) 62.39(5) 68.43(6)

Hg-Ru(1)-Pt(1) Hg-Ru(1)-Ru(2) Pt(1)-Ru(1)-Pt(2) Pt(1)-Ru(1)-Ru(2) Pt(2)-Ru(1)-Ru(3) Ru(2)-Ru(1)-Ru(3) Hg-Ru(2)-Pt(1) Hg-Ru(2)-Ru(1) Pt(1)-Ru(2)-Pt(3) Pt(1)-Ru(2)-Ru(1) Pt(3)-Ru(2)-Ru(3) Ru(1)-Ru(2)-Ru(3) Pt(2)-Ru(3)-Pt(3) Pt(2)-Ru(3)-Ru(1) Pt(3)-Ru(3)-Ru(2) Ru(1)-Ru(3)-Ru(2) Pt(1)-Ru(4)-Pt(2) Pt(1)-Ru(4)-Ru(5) Pt(2)-Ru(4)-Ru(6) Ru(5)-Ru(4)-Ru(6) Pt(1)-Ru(5)-Pt(3) Pt(1)-Ru(5)-Ru(4) Pt(3)-Ru(5)-Ru(6) Ru(4)-Ru(5)-Ru(6) Pt(2)-Ru(6)-Pt(3) Pt(2)-Ru(6)-Ru(4) Pt(3)-Ru(6)-Ru(5) Ru(4)-Ru(6)-Ru(5) M-C-O(av)

60.46(4) 56.44(4) 54.03(4) 56.80(5) 58.84(5) 58.46(5) 61.35(4) 55.41(4) 55.04(4) 59.85(5) 58.34(5) 58.43(5) 56.13(4) 58.45(5) 59.27(5) 63.12(5) 57.81(5) 56.65(6) 55.64(6) 61.06(6) 58.43(5) 56.86(6) 55.54(6) 59.94(6) 59.17(5) 56.99(6) 56.04(5) 59.00(6) 173(3)

a Angles are in deg. Estimated standard deviations in the least significant figure are given in parentheses.

ruthenium triangle are directed away from the platinum triangle and six carbonyl ligands on the other ruthenium triangle are directed away from the platinum triangle, and in each case the interplanar spacing is larger to the Ru3 triangle that has only three CO ligand directed away from the platinum triangle. Compounds 5 and 6 both contain two hydride ligands. In the structural analysis of 5 both of these ligands were located and refined. Both hydride ligands occupy triply bridging positions across the ruthenium triangles. The hydride ligands in 4 were found in similar positions. The hydride ligands in 6 were not observed crystallographically, but the similar arrangement of the carbonyl ligands between 5 and 6 strongly suggests the hydride ligands in 6 occupy sites analogous to those in 5. The 1H NMR spectrum of 5 shows two broad resonances at approximately δ ) -15.5, -20.7 ppm. At -93 °C these resonances appear as two sharp singlets at δ ) -15.47,

-20.72 ppm. The room-temperature broadening effect is attributed to a dynamical process that produces exchange of the environments of the hydride ligands at room temperature. Hydride ligand exchange was also observed in 1.1 In 6 only a single broad resonance was observed at δ ) -18.20 ppm for the two hydride ligands. This resonance sharpens when the temperature is raised and broadens further when the temperature is lowered, and at -78 °C two very broad resonances were observed at about -17.0 and -19.5 ppm. Accordingly, it is believed that an exchange of the hydride ligands is also occurring in 6, but it is occurring much faster in 6 than in 5. An interesting feature of 6 is that the cluster complex is a monoanion, as confirmed by the solid-state structure which shows the presence of one perfectly normal NBu4 cation. Remarkably, the anion is stable in air and can be isolated by TLC in air and crystallized from solution in the open air with very little decomposition. With 6 being an anion, we suspected that it would react with other cationic reagents to produce neutral molecules. To our great surprise all efforts to produce neutral molecules by allowing cationic metal groupings or precursors to cationic metal groupings to react with 6 have been unsuccessful. We have not even been able to neutralize it by addition of H+. Compound 5 contains a total of 136 valence electrons, which is consistent with the observed structure that can be described as a monocapped face-shared bioctahedron.9 The same count is obtained for 6 if one assumes that the mercury atom brings 12 electrons to the cluster. Acknowledgment. This research was supported by the National Science Foundation. We thank Mr. John Yamamoto for recording the variable-temperature NMR spectra. Supporting Information Available: Tables of positional and B parameters, bond distances and angles, and anisotropic thermal parameters for all of the structural analyses (33 pages). Ordering information is given on any current masthead page. OM960116X (9) Mingos, D. M. P.; May, A. S. In The Chemistry of Metal Cluster Complexes; Shriver, D. F., Kaesz, H. D., Adams, R. D., Eds.; VCH Publishers: New York, 1990; Chapter 2.