STRUCTURAL STUDIES ON RUTHENIUM CARBONYL HYDRIDES .15. X-RAY STRUCTURAL-ANALYSES OF SYMMETRICALLY AND UNSYMMETRICALLY SUBSTITUTED MU-3-ETA-3-C3R3 COMPLEXES OF RUTHENIUM - (MU-H)RU3(MU-3-ETA-3-CMECMECME) (CO)9, (MU-H)RU3(MU-3-ETA-3-CMECMECOME)(CO)9, AND (MU-H)RU3(MU-3-ETA-3-CMECMECSET)(CO)9 - INFLUENCE OF PI-DONOR SUBSTITUENTS UPON NIDO-ARACHNO POLYHEDRAL DISTORTION

Single-crystal X-ray diffraction studies of the title commpounds have been performed. Comparison of these structures with that of (μ-H)Ru3(μ3-η3-CMeCHCNEt2)(CO)9, previously reported, provide evidence that π-donor substituents on the C3 unit cause distortion of the Ru3C3 polyhedron from a nido toward an arachno structure, based upon a pentagonal-bipyramidal skeleton. The μ3-η3-CMeCMeCMe complex crystallizes in space group Pnma (No. 62) with a = 17.483 (11) Å, b = 16.033 (9) Å, c = 7.105 (3) Å, V = 1992 (2) Å3, and Z = 4. The structure was refined to RF = 3.9% for 1348 data (Mo Kα, 2θ = 4.0-45.0°, |Fo| > 0) and RF = 2.7% for 1111 data with |Fo| > 6σ (|Fo|). The μ3-η3-CMeCMeCOMe complex crystallizes in space group P21/n (No. 14) with a = 9.581 (2) Å, b = 20.470 (3) Å, c = 10.7003 (15) Å, β = 106.400 (13)°, V = 2013.5 (5) Å3, and Z = 4; refinement converged with RF = 3.5% for 3356 data (2θ = 4.5-50.0°, |Fo| > 0) and RF = 2.4% for 2739 data with |Fo| > 6σ (|Fo|). The μ3-η3-CMeCMeCSEt complex crystallizes in space group P21/n (No. 14) with a = 10.0275 (13) Å, b = 16.430 (3) Å, c = 13.812 (2) Å, β = 107.976 (11)°, V = 2164.4 (6) Å3, and Z = 4; refinement converged with RF = 5.1% for 2736 data (2θ = 4.0-45.0°, |Fo| > 0) and RF = 4.2% for those 2308 data with |Fo| > 6σ(|Fo|). The three complexes each contain two Ru(CO)3 groups bridged by a hydride ligand and linked to a further Ru(CO)3 group; the μ3-CMeCMeCX ligand is linked by σ-bonds to the two hydrido-bridged Ru atoms and via an η3-allyl linkage to the third Ru atom. The principal effect of changing X is to cause asymmetry in the (η3-allyl)→Ru linkage such that the Ru–(X-bonded carbon) distance is 2.230 (9) Å for X = SEt, 2.251 (9) Å for X = Me, and 2.433 (5) Å for X = OMe; the literature value for X = NMe2 is 2.689 (6) Å. © 1990, American Chemical Society. All rights reserved.