Organometallics 1996, 15, 2619-2623
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Synthesis, Characterization, and Molecular Structure of the First closo-Hydrido Complexes of Osmium with Carborane Ligands: closo-3,3-(PPh3)2-3-H-3-Cl-3,1,2-OsC2B9H11 and closo-3,3-(PPh3)2-3,3-H2-1,2-Me2-3,1,2-OsC2B9H9 Igor T. Chizhevsky,* Pavel V. Petrovskii, Pavel V. Sorokin, Vladimir I. Bregadze, Fedor M. Dolgushin, Aleksandr I. Yanovsky, and Yuri T. Struchkov† A. N. Nesmeyanov Institute of Organoelement Compounds, 28 Vavilov Str., 117813 Moscow, Russian Federation
Albert Demonceau and Alfred F. Noels Institute of Chemistry, B6, University of Liege, B-4000 Sart Tilman, Belgium Received December 18, 1995X
Novel 12-vertex closo-hydridometallacarboranes 3,1,2-[(PPh3)2OsHXC2B9H11] (1a,b: X ) Cl, H) and 3,1,2-[(PPh3)2OsH2-1,2-Me2C2B9H9] (1c) have been synthesized via oxidative addition of K+ salts of the nido-carborane anions [nido-7,8-R2-7,8-C2B9H10]- (R ) H, Me), respectively, to OsCl2(PPh3)3 and characterized by spectroscopic (NMR and IR) as well as by single-crystal X-ray diffraction studies of 1a,c. Hydridometallacarborane clusters of closo and exonido types have played an important role in the development of metallacarborane chemistry1 and since the discovery of their catalytic activity2 have found widespread use as catalyst precursors in numerous organic processes.3,4 Although now the variety of closo-hydridometallacarboranes of platinum group metals derived from nido-C2B9H122- is very extensive,5-8 examples of closo-hydridoosmacarboranes are still lacking. This is particularly surprising taking into account the known ability of osmium to form stable closo-osmaborane clusters9 and also in view of well-documented chemistry of related closo-hydridoruthenacarboranes.6-8 A successful synthesis of the latter by the oxidative addition of 7,8- and 7,9-C2B9H12- to coordinatively unsaturated †
Deceased on August 16, 1995. Abstract published in Advance ACS Abstracts, April 15, 1996. (1) (a) Kelb, W. C.; Demidowich, Z.; Speckman, D. M.; Knobler, C. B.; Teller, R. G.; Hawthorne, M. F. Inorg. Chem. 1982, 21, 4027. (b) Zheng, L.; Baker, R. T.; Knobler, C. B.; Walker, J. A.; Hawthorne, M. F. Inorg. Chem. 1983, 22, 3350. (c) Behnken, P. E.; Marder, T. B.; Baker, R. T.; Knobler, C. B.; Thompson, M. R.; Hawthorne, M. F. J. Am. Chem. Soc. 1985, 107, 932. (d) Walker, J. A.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1985, 24, 2688. (e) Walker, J. A.; Zheng, L.; Knobler, C. B.; Soto, J.; Hawthorne, M. F. Inorg. Chem. 1987, 26, 1608. (f) Zakharkin, L. I.; Chizhevsky, I. T.; Zhigareva, G. G.; Petrovskii, P. V.; Polyakov, A. V.; Yanovsky, A. I.; Struchkov, Yu. T. J. Organomet. Chem. 1988, 358, 449. (g) Chizhevsky, I. T.; Lobanova, I. A.; Pisareva, I. V.; Zinevich, T. V.; Bregadze, V. I.; Yanovsky, A. I.; Struchkov, Yu. T.; Knobler, C. B.; Hawthorne, M. F. In Current Topics in the Chemistry of Boron; Kabalka, G. W., Ed.; Royal Society of Chemistry: Cambridge, U.K., 1994; p 301. For the latest review see: Grimes, R. N. In Comprehensive Organometallic Chemistry II; Abel, E. F., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon Press: Oxford, U.K., 1995; Vol. 1, Chapter 9, p 373. (2) Paxon, T. E.; Hawthorne, M. F. J. Am. Chem. Soc. 1974, 96, 4674. (3) See for examples: (a) Delaney, M. S.; Knobler, C. B.; Hawthorne, M. F. J. Chem. Soc., Chem. Commun. 1980, 849. (b) Belmont, J. A.; Soto, J.; King, R. E., III; Donaldson, A. J.; Hewes, J. D.; Hawthorne, M. F. J. Am. Chem. Soc. 1989, 111, 7475 and references therein. (c) Kang, H. C.; Hawthorne, M. F. Organometallics 1990, 9, 2327. (d) Zakharkin, L. I.; Zhigareva, G. G. Izv. Akad. Nauk SSSR, Ser. Khim. 1992, 41, 1284 (English translation). (4) Demonceau, A.; Saive, E.; de Froidmont, Y.; Noels, A. F.; Hubert, A. J.; Chizhevsky, I. T.; Lobanova, I. A.; Bregadze, V. I. Tetrahedron Lett. 1992, 33, 2009. X
S0276-7333(95)00967-8 CCC: $12.00
Ru(II) species6,7 or by thermal rearrangement of some exo-nido-ruthenacarboranes8 prompted us to examine these possible routes for the preparation of 12-vertex osmium congeners. We now report the synthesis of closo-3,3-(PPh3)2-3-H-3-X-1,2-R2-3,1,2-OsC2B9H9 (1a, R ) H, X ) Cl; 1b, R ) X ) H; 1c, R ) Me, X ) H) and X-ray structural characterization of two of them, namely 1a,c. Complexes 1a-c proved to be readily obtained by gentle reflux of a suspension of freshly prepared OsCl2(PPh3)3 (2)10 with a slight excess of corresponding carborane monoanions in the form of their potassium salts [nido-7,8-R2-7,8-C2B9H10]-K+ (3a, R ) H; 3b, R ) Me) in a deoxygenated ethanol for 6-8 h (Schemes 1 and 2). The reaction of 2 with unsubstituted carborane salt 3a produced a mixture of two hydrido complexes 1a,b in an approximately 1:1 ratio, along with a byproduct which was identified as Os(CO)ClH(PPh3)3 (4) by comparison of its NMR spectra with those of an authentic sample.10 This crude mixture of complexes was (5) (a) Knobler, C. B.; Marder, T. B.; Mizusawa, E. A.; Teller, R. G.; Long, J. A.; Behnken, P. E.; Hawthorne, M. F. J. Am. Chem. Soc. 1984, 106, 2990 and references therein. (b) Hewes, J. D.; Thompson, M.; Hawthorne, M. F. Organometallics 1985, 4, 13. (c) Doi, J. A.; Teller, R. G.; Hawthorne, M. F. J. Chem. Soc., Chem. Commun. 1980, 80. (d) Delaney, M. S.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem. 1981, 20, 1341. (e) Delaney, M. S.; Teller, R. G.; Hawthorne, M. F. J. Chem. Soc., Chem. Commun. 1981, 235. (f) Busby, D. C.; Hawthorne, M. F. Inorg. Chem. 1982, 21, 4101. (6) Wong, E. H. S.; Hawthorne, M. F. J. Chem. Soc., Chem. Commun. 1976, 257. (7) Wong, E. H. S.; Hawthorne, M. F. Inorg. Chem. 1978, 17, 2863. (8) Chizhevsky, I. T.; Lobanova, I. A.; Bregadze, V. I.; Petrovskii, P. V.; Polyakov, A. V.; Yanovsky, A. I.; Struckhov, Yu. T. Organomet. Chem. U.S.S.R. 1991, 4, 469 (English translation). (9) (a) Bould, J.; Greenwood, N. N.; Kennedy, J. D. J. Organomet. Chem. 1983, 249, 11. (b) Bould, J.; Crook, J. K.; Greenwood, N. N.; Kennedy, J. D. J. Chem. Soc., Chem. Commun. 1983, 951. (c) Elrington, M.; Greenwood, N. N.; Kennedy, J. D.; Thornton-Pett, M. J. Chem. Soc., Chem. Commun. 1984, 1398. (d) Elrington, M.; Greenwood, N. N.; Kennedy, J. D.; Thornton-Pett, M. J. Chem. Soc., Dalton Trans. 1986, 2277. (e) Bown, M.; Greenwood, N. N.; Kennedy, J. D. J. Organomet. Chem. 1986, 309, C67. (10) Oudeman, A.; Van Rantwijk, F.; Van Bekkum, H. J. Coord. Chem. 1974, 4, 1.
© 1996 American Chemical Society
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Organometallics, Vol. 15, No. 11, 1996 Scheme 1
Scheme 2
successfully separated by fractional crystallization into yellow 1a (36% yield) and white-grayish 1b (42% yield) crystalline solids whose structures were assigned by spectroscopic and, for 1a, crystallographic means. Thus, the 400.13 MHz 1H and 161.98 MHz 31P{1H} NMR spectra of 1a,b in CD2Cl2 in each case showed high-field proton triplets with characteristic coupling constants JH-P ) 36 and 33 Hz and single phosphorous resonances at -11.3 and 17.5 ppm, respectively, as expected for the presence of terminal monodentate hydrido ligands and equivalent PPh3 groups at the metal centers. The IR spectra of 1a,b revealed strong bands at 2450-2575 cm-1 and moderate singlets or doublets located near 2150 cm-1 which were assigned to νBH and νOsH absorptions, respectively. By contrast, the reaction of 2 with dimethyl-substituted monoanion 3b under exactly the same conditions gave an osmacarborane complex of the closo type, 1c, besides the byproduct 4. The former was isolated as pure white-grayish crystals after recrystallization of the crude solid from a CH2Cl2/n-hexane mixture in 68% yield. No traces of closo-3,3-(PPh3)2-3-H-3-Cl-1,2-Me23,1,2-OsC2B9H9 were detected by 1H NMR among with the reaction products either in the crude solid precipitate or in the mother liquor, as would be expected by the analogy with the reaction discussed above. Higher steric requirements of a Cl ligand relative to the C2B3 face conflicting in this case with the generally overcrowded environment due to the presence of two substituents at the cage carbon atoms may account for the instability of the latter chloro complex. However, the 1H NMR spectra of the crude solid precipitate in CD 2 Cl2 solution indicated the formation of one more carbaborane-containing osmium species in an approximately 1:5 ratio relative to 1c. On the basis of the 1H and 31P{1H} NMR data {[CD Cl , δ (ppm)]: 1H NMR 7.20 2 2 (overlapped m), 1.11 (s, 6H, Me), -0.82 (m br, 1H, B10H), -6.3 (m br, 2H, BH), -16.1 [m br, 1H, BH]; 31P{1H} NMR -0.21 (s br)}, this species can be tentatively
Chizhevsky et al.
formulated as symmetrical exo-nido-[Cl(PPh)3)2Os]-7,8Me2C2B9H9 (5) wherein three two-electron, three-center B-H‚‚‚Os bonds are present;11 the exo-nido-ruthenacarboranes with three, one, or two analogous B-H‚‚‚Ru bonds have been previously reported by us12 and others.13 Remarkably, in view of these results, our attempt to prepare the ruthenium congener of 1c, closo-3,3-(PPh3)23,3-H2-1,2-Me2-3,1,2-RuC2B9H9, by the reaction of RuCl2(PPh3)3 with 3b in boiling ethanol solution failed and the known exo-nido-5,6,10-[Cl(PPh3)2Ru]-5,6,10-µ-(H)310-H-7,8-Me2C2B9H612 (72% yield) was obtained as the sole product. As shown previously,12 this complex exists in solution as an equilibrium mixture of symmetrical and nonsymmetrical exo-nido isomers and, by contrast with the unsubstituted analog, could not be converted into the corresponding closo isomer even upon heating to 110 °C in toluene.8 All of these findings, taken together, reveal rather unexpected differences in the stability and solution behavior of closo and exo-nido complexes within the family of the apparently closely related ruthena- and osmacarboranes of this type. Since little attention has been given in literature to closo-osmacarborane clusters14 and, in particular, no osmium closo complexes derived from the extensively studied C2B9H112- ligand have been so far structurally characterized, we have determined the structure of the two complexes 1a,c by X-ray diffraction study. The high quality of single crystals grown from both samples allowed us to locate objectively and reliably refine all hydrogen atoms including hydride atoms. The structures of 1a,c are shown in Figures 1 and 2, respectively. The compounds 1a,c should be formulated as 18 electron closo-osmacarboranes with formally sevencoordinate osmium(IV) atoms. The overall geometry of 1a and the orientation of P2OsHCl moiety relative to the pentagonal plane of the carborane cage proved to be very similar to those found in closo-3,3-(PPh3)2-3-H3-Cl-3,1,2-RuC2B9H11 (6).8,15 The P(1)‚‚‚P(2) vector in 1a is approximately parallel to the C(1)‚‚‚C(2) vector of the coordinating five-membered carborane open face (the angle formed by the two vectors being equal to 13.2°), whereas the Cl-Os-H plane bisects the C(1)C(2) bond and the Cl(1) ligand occupies a nearly trans position to the B(8) atom (Figure 3a). Bonding of the osmium atom to the C2B3 carborane open face in 1a is essentially symmetric, with Os-B and Os-C distances in the range 2.217(3)-2.314(4) Å. (11) Further investigations in order to elucidate the exact geometry of 5 and to establish whether 5 exists in solution solely as exo-nido isomer or is involved in a slow interconverting equilibrium with 1c are in progress. (12) Chizhevsky, I. T.; Lobanova, I. A.; Bregadze, V. I.; Petrovskii, P. V.; Antonovich, V. A.; Polyakov, A. V.; Yanovsky, A. I.; Struckhov, Yu. T. Mendeleev Commun. 1991, 47. (13) (a) Teixidor, F.; Ayllo´n, J. A.; Vin˜as, C.; Kiveka¨s, R.; Sillanpa¨a¨, R.; Casabo´, J. J. Chem. Soc., Chem. Commun. 1992, 1281. (b) Teixidor, F.; Ayllo´n, J. A.; Vin˜as, C.; Kiveka¨s, R.; Sillanpa¨a¨, R.; Casabo´, J. Organometallics 1994, 13, 2751. (c) Teixidor, F.; Vin˜as, C.; Casabo´, J.; Romerosa, A. M.; Rius, J.; Miravitlles, C. Organometallics 1994, 13, 914. (d) Vin˜as, C.; Nun˜ez, R.; Flores, M. A.; Teixidor, F.; Kiveka¨s, R.; Sillanpa¨a¨, R. Organometallics 1995, 14, 3952. (14) (a) Hanusa, T. P.; Huffman, J. C.; Curtis, T. L.; Todd, L. J. Inorg. Chem. 1985, 24, 787. (b) Davis, J. H.; Sinn, E., Jr.; Grimes, R. N. J. Am. Chem. Soc. 1989, 111, 4776. (c) Hosmane, N. S.; Sirmokadam, N. N. Organometallics 1984, 3, 1119. (d) Bown, M.; Fontaine, X. L. R.; Greenwood, N. N.; Kennedy, J. D.; Thornton-Pett, M. J. Chem. Soc., Chem. Commun. 1987, 1650.
closo-Hydrido Complexes of Osmium
Figure 1. Molecular structure of complex 1a. Thermal ellipsoids of non-hydrogen atoms are drawn at the 50% probability level. All hydrogen atoms except H(3) have been omitted for clarity. Selected interatomic distances (Å) and angles (deg): Os(3)-B(4) ) 2.314(4), Os(3)-B(8) ) 2.313(4), Os(3)-B(7) ) 2.253(3), Os(3)-C(1) ) 2.254(3), Os(3)-C(2) ) 2.217(3), Os(3)-P(1) ) 2.3834(12), Os(3)-P(2) ) 2.372(2), Os(3)-Cl ) 2.432(2), Os(3)-H(3) ) 1.39(4), B(8)-H‚‚‚H-Os(3) ) 2.42(7); P(2)-Os(3)-Cl(1) ) 83.26(5), P(1)-Os(3)-Cl(1) ) 82.87(5), P(2)-Os(3)-P(1) ) 109.45(4), Cl(1)-Os(3)-H(3) ) 131(2), P(1)-Os(3)-H(3) ) P(2)Os(3)-H(3) ) 70(2).
The metal atom in 1c, by contrast, is markedly shifted parallel to the open face in the direction of its boron atoms so that the cage carbon atoms are about 0.12 Å further than in 1a and atom B(8) is 0.05 Å closer to the Os center. This difference is apparently due to the sterically overcrowded solid-state conformation of the (PPh3)2OsH2 moiety relative to the cage open face of 1c wherein one of the two PPh3 groups is disposed not as far away as possible from the cage substituents as one might have expected. Thus the Os-P(1) bond projects over the midpoint of the B(7)-B(8) bond of the coordinating C2B3 open face while Os-P(2) almost eclipses the C(1)-Me bond. Consequently, the hydride ligands are located approximately trans to C(2) and B(4) atoms of the open carborane face (Figure 3b). The observed difference in the relative orientations of the P2OsHX moieties with respect to the C2B3 open face in 1a,c seems to be rather unexpected. The extended Hu¨ckel molecular orbital studies of closometallacarboranes of the [3,1,2-L2MC2B9H11]16 and [3,1,2HL2MC2B9H11]17 types showed that the orientation of ML2 and ML2H moieties with respect to the coordinating C2B3 planes of the carborane cage is primarily deter(15) In spite of the similarity of the solid-state structural geometry of 1a and 6, comparison of their 1H NMR spectra reveals one striking difference. The hydride resonance in the 1H NMR spectra of 6 is observed as a doublet of triplets (Jt ) 28.9 Hz, Jd ) 10.3 Hz), by contrast to a triplet in the spectra of 1a. On the basis of the proton decoupling NMR experiment an additional splitting of the former signal was proved to result from the unique HB(8)‚‚‚HRu through-space spinspin interaction. Indeed, according to the X-ray data the B(8)-H‚‚‚HOs distance in 1a [2.42(7) Å] is significantly longer than the corresponding B(8)-H‚‚‚H-Ru distance found in 6 [2.11(8) Å].8 There are also noticeable differences in the corresponding angles between M-H bonds and the coordinating C2B3 planes in 1a and 6 which are equal 19.2 and 9.3°, respectively. These are apparently consistent with the above phenomena observed for the 1H NMR spectra of 6. (16) Mingos, D. M. P. J. Chem. Soc., Dalton Trans. 1977, 602.
Organometallics, Vol. 15, No. 11, 1996 2621
Figure 2. Molecular structure of complex 1c. Thermal ellipsoids of non-hydrogen atoms are drawn at the 50% probability level. All hydrogen atoms except H(3A) and H(3B) have been omitted for clarity. Selected interatomic distances (Å) and angles (deg): Os(3)-B(4) ) 2.310(3), Os(3)-B(8) ) 2.259(3), Os(3)-B(7) ) 2.249(3), Os(3)-C(1) ) 2.375(3), Os(3)-C(2) ) 2.338(3), C(1)-C(13) ) 1.519(3), C(2)-C(14) ) 1.531(3), Os(3)-P(1) ) 2.3275(14), Os(3)P(2) ) 2.373(2), Os(3)-H(3A) ) 1.55(4), Os(3)-H(3B) ) 1.52(4); P(1)-Os(3)-H(3A) ) 72(2), P(2)-Os(3)-H(3A) ) 73(2), P(1)-Os(3)-H(3B) ) 75.9(14), P(2)-Os(3)-H(3B) ) 70.2(14), P(1)-Os(3)-P(2) ) 100.46(5).
Figure 3. View of the P2OsHCl and P2OsH2 moieties and the C2B3 face coordinated to osmium in 1a,c, respectively.
mined by geometrically optimal conditions of the overlap of the HOMO-LUMO nodal planes of the metalcontaining and π-dicarbollyl ligands, respectively. Therefore, the differences in the solid-state conformations of 1a,c may reflect possible differences in the geometry of the HOMO-LUMO interaction between the corresponding orbitals of the π-dicarbollyl ligand and P2OsHCl and P2OsH2 moieties. In order to understand this phenomena in more detail, extended Hu¨ckel or more profound quantum chemical calculations on these complexes or their hypothetical model compounds closo3,3-(PH3)2-3-H-3-X-1,2-R2-3,1,2-OsC2B9H9 (7a, R ) H, X ) Cl; 7b, R ) Me, X ) H) are required. In conclusion, the first fully characterized closohydridoosmacarborane complexes 1a-c were prepared by simple oxidative addition reactions. The reaction provides a simple route to useful new starting materials (17) Mingos, D. M. P.; Minshall, P. C.; Hursthouse, M. B.; Malik, K. M. A.; Willoughby, S. D. J. Organomet. Chem. 1979, 181, 169.
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Table 1. Crystal Data and Details of the X-ray Experiments for 1a,c compd formula mol wt cryst color, habit cryst size, mm cryst system space group cell constants a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z Dcalcd, g cm-3 diffractometer temp, K radiation (Å) scan mode 2θmax, deg tot. unique refls collcd abs coeff, µ(Mo KR), cm-1 R1 (on F for refls with I > 2σ(I)) wR2 (on F2 for all refls)
1a
1c
C38H42B9ClP2Os‚1.5C6H6 1000.76 pale yellow prisms 0.15 × 0.20 × 0.25 triclinic P1 h
C40H47B9P2Os 877.21 white-grayish prisms 0.15 × 0.20 × 0.20 triclinic P1 h
12.177(3) 13.362(5) 16.353(9) 102.26(4) 110.78(4) 100.31(3) 2335(2) 2 1.423 CAD4 Enraf Nonius 296 Mo KR (λ ) 0.710 73) θ-5/3θ 52 9156 28.9 0.0275 (8219 refls) 0.0786 (9106 refls)
11.311(8) 11.322(6) 16.099(11) 83.98(5) 80.63(6) 71.78(5) 1929(2) 2 1.510 Siemens P3/PC 146 Mo KR (λ ) 0.710 73) θ-2θ 64 13 319 34.2 0.0260 (11 686 refls) 0.0694 (13 268 refls)
for the development of chemistry of these rare osmacarborane clusters. Experimental Section General Procedures. All reactions were performed under argon atmosphere using standard Schlenk techniques. Solvents for reactions and purification procedures were dried with an appropriate drying agents and distilled under argon prior to use. The 1H and 31P NMR spectra were recorded on a Bruker AMX-400 spectrometer using TMS as an internal reference and 85% H3PO4 as an external reference. All IR spectra were obtained on a Specord M-82 in KBr pellets. Microanalyses were performed at the Analytical Laboratory of the Institute of Organoelement Compounds of the Russian Academy of Sciences. Preparation of closo-3,3-(PPh3)2-3-H-3-Cl-3,1,2-OsC2B9H11 (1a) and closo-3,3-(PPh3)2-3,3-H2-3,1,2-OsC2B9H11 (1b). To a stirred suspension of freshly prepared OsCl2(PPh3)3 (0.55 g, 0.53 mmol) in deoxygenated absolute ethanol (40 mL) was added [nido-7,8-C2B9H12]-K+ (0.1 g, 0.58 mmol) as a solid, and the mixture was heated at reflux temperature under an argon atmosphere for ca. 8 h. After the mixture was cooled to room temperature, the resulting light yellow precipitate was separated under pressure of argon using an internal frit of medium porosity. The residue was extracted by hot benzene (10 mL), and the yellow solution obtained was transferred into a 25 mL round-bottom flask, layered in half with hot n-hexane, and slowly cooled to 0 °C, yielding 0.17 g (36%) of pure 1a as pale yellow crystals. Anal. Calcd for C38H42B9ClP2Os‚0.5C6H6: C, 53.37; H, 4.88; B, 10.54; Cl, 3.85; P, 6.73; Os, 20.63. Found: C, 53.31; H, 5.01; B, 10.66; Cl, 3.52; P, 6.78; Os, 20.63. 1H NMR [25 °C, CD2Cl2, J (Hz)]: δ 7.20-7.62 (m, ∼30H, PPh3), 3.94 (s, 2H, CH), -11.60 (t, 1H, JH-P ) 36, Os-H). 31P{1H} NMR (25 °C, CD2Cl2): δ -11.3 (s). IR (KBr): νBH 2568 cm-1, νOsH 2178 cm-1, νOsCl 310 cm-1. The combined solid residue from benzene extraction was treated by CH2Cl2 (8 mL) followed by addition of n-hexane (2-3 mL), and after refrigerating of the solution overnight 0.19 g (42%) of analytically pure whitegrayish crystals of 1b were filtered off. Anal. Calcd for C38H43B9P2Os: C, 53.75; H, 5.07; B, 11.46; P, 7.31; Os, 22.42. Found: C, 53.60; H, 5.31; B, 11.60; P, 7.26; Os, 22.43. 1H NMR [25 °C, CD2Cl2, J (Hz)]: δ 7.24-7.65 (m, 30H, PPh3), 2.78 (s, 2H, CH), -10.58 (t, 2H, JH-P ) 33, Os-H). 31P{1H} NMR (25 °C, CD2Cl2): δ 17.5 (s). IR (KBr): νBH 2574 cm-1, νOsH 2163,
2132 cm-1. The examination of the NMR spectra of the crude product taken before benzene extraction in CD2Cl2 solution revealed the existence of the byproduct 4 in ratio of 1:4 to 1a. 1H NMR [25 °C, CD Cl , J (Hz)]: δ 7.14-7.60 (m, 45H, PPh ), 2 2 3 -6.90 (dt, Jd ) 86.2, Jt ) 24.7). 31P{1H} NMR [25 °C, CD2Cl2, J (Hz)]: δ -9.1 (t, 1P, Jt ) 11.2), 7.9 (d, 2P, Jd ) 11.2). Preparation of closo-3,3-(PPh3)2-3,3-H2-1,2-Me2-3,1,2OsC2B9H9 (1c). Using a procedure similar to those for 1a,b, a mixture of OsCl2(PPh3)3 (0.40 g, 0.38 mmol) and [nido-7,8Me2-7,8-C2B9H10]-K+ (0.09 g, 0.45 mmol) in 40 mL of deoxygenated absolute ethanol was stirred at reflux temperature for 6 h. After the mixture was cooled to room temperature, the precipitate formed was separated by filtration, dissolved in 8 mL of CH2Cl2, and layered approximately in half with n-hexane. From the solution which was cooled overnight at 0 °C white-grayish microcrystals of 1c (0.23 g, 68%) were obtained. Anal. Calcd for C40H47B9P2Os: C, 54.77; H, 5.36; B, 11.09; P, 7.07; Os, 21.70. Found: C, 54.96; H, 5.56; B, 11.27; P, 7.06; Os, 21.72. 1H NMR [25 °C, CD2Cl2, J (Hz)]: δ 7.207.65 (m, 30H, PPh3), 1.57 (s, 6H, Me), -10.42 (t, 2H, JH-P ) 34, Os-H). 31P{1H} NMR (25 °C, CH2Cl2): δ 11.7 (s). 11B{1H} NMR (128.33 MHz, CH2Cl2, BF3‚Et2O as external standard): 1.2 (2B), -6.0 (2B), -8.3 (1B), -9.2 (2B), -14.0 (2B). IR (KBr): νBH 2542 cm-1, νOsH 2175, 2107 cm-1. X-ray Data Collection, Structure Determination, and Refinement for 1a,c. Single crystals of 1a,c were slowly grown from the diluted solutions in benzene-n-hexane (1a)18 and methylene chloride-n-hexane (1c) mixtures at approximately 10 °C. Accurate unit cell parameters and orientation matrices were obtained by least-squares refinement of carefully centered 24 reflections in the 26 e 2θ e 27° ranges. Three standard reflections were monitored every 1 h for 1a and every 97 reflections for 1c and showed no significant variations in either case. Data were corrected for Lorentz and polarization effects. Carefully chosen rather small well formed and essentially isometric single-crystal samples, the quality (18) The crystals suitable for X-ray diffraction experiment were grown from the benzene-n-hexane mixture enriched in benzene (5:1, respectively) as compared with that used for the synthetic procedures (see above). Therefore, the sample of 1a which was employed for elemental analyses turned out to be the benzene semisolvate, whereas the specimen subjected to the diffraction experiment was proved to contain 1.5 benzene molecules per molecule of the complex.
closo-Hydrido Complexes of Osmium of the obtained results, and the relatively low absorption coefficient values justified no necessity for absorption corrections. The structures were solved by direct methods and subsequent difference Fourier maps. All H atoms of both molecules including the hydride ligands were located in the difference syntheses and refined in the isotropic approximation. All calculations were carried out on an IBM PC with the SHELXTL PLUS 5 (gamma-version) programs. Crystal data and details of the X-ray experiments are given in Table 1.
Acknowledgment. This research has been supported in part by INTAS 94-541. I.T.C., P.V.P., V.I.B., F.M.D., and A.I.Y. also gratefully acknowledge the financial support of the Russian Foundation for Basic Research (Grant No. 94-03-08838) and International
Organometallics, Vol. 15, No. 11, 1996 2623
Science Foundation (Grant. Nos. M4P000, SAU000, and M04000). We are also grateful to Dr. I. G. Barakovskaya for performing special research in order to obtain full analytical data for the osmium clusters prepared. Supporting Information Available: Tables of crystal data collection parameters, atom coordinates and U values, bond distances and angles, and anisotropic parameters, a thermal ellipsoid plot, and the full and high-field region of the 1H NMR spectrum of complex 1c with the hydride signals of the exo-nido-osmacarbaborane 5 (12 pages). Ordering information is given on any current masthead page. OM950967P
