Trinuclear hydridobis-μ3-sulphido complexes of Rh(I); Synthesis and structures of Rh3(COD)3(μ3-S)2(μ-H), Rh3(COD)2(t-Bu2PH)2(μ3-S)2(μ-H), (COD = 1,5-cyclooctadiene) and Rh3(CO)4(t-Bu2PH)2(μ-S)2(μ-H)

Abstract

Reaction of [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene) with two equivalents of NaSH in methanol at −78°C gives bright red crystalline Rh3(COD)3(μ3-S)2(μ-H)(1)(83%), H2S is also formed. The overall molecular geometry of (1) consists of a Rh3 triangle capped on each face by a μ3-S atom. Each Rh atom bears a COD ligand in the boat configuration. The centroids of the carbon-carbon double bonds of each COD and the μ3-S atoms give each Rh a roughly planar coordination geometry. One RhRh bond is notably longer than the other two: (2.814(1), 2.962(1) and 3.210(3) Å). The overall molecular geometry suggests that the μ-H atom bridges the longest RhRh bond, although this could not be confirmed by X-ray data. Reaction of (1) with excess t-Bu2PH in THF gives Rh3(COD)2(t-Bu2PH)2(μ3-S)2(μ-H), (2), in which the unique COD ligand bonded to the Rh atom opposite the long Rh(μ-H)Rh bond is replaced by two cist-Bu2PH ligands. (2) reacts with CO (1 atm., 25°C) in toluene to give Rh3(CO)4(t-Bu2PH)2(μ3-S)2(μ-H), (3). Both (2) and (3) are formed quantitatively. In (3), two terminal CO ligands replace each of the COD ligands. Crystal data for (l): C24H37Rh3S2, M = 698.40, monoclinic, C2/c (No. 15), a = 27.808(5), b = 9.060(1), c = 19.248(3) Å, β = 97.52(2)dg, U = 4807.6(5) Å3, Dc = 1.930 g cm−3, Z = 8, λ(Mo-Kα) = 0.71073 Å (graphite monochromator), μ(Mo-Kα,) = 21.83 cm−1. Methods: MULTAN, difference Fourier, full matrix least-squares. Refinement of 2432 reflections (I > 3σ(I)) out of 4123 unique observed reflections (3° < 2θ < 50°) gave R and Rw values of 0.048 and 0.062, respectively. Data/parameter ratio = 9.28, highest peak in final difference Fourier = 1.051 e Å−3. Crystal data (2): C39H69P2Rh3S2,M = 972.78, triclinic, P1, (No. 2), a = 10.738(1), b = 19.503(2), c = 20.353(4) Å, α = 90.36(1), β = 105.47(2), γ = 92.77(1)°, U = 4102.3(5) Å3, Dc = 1.58 g cm−3, Z = 4, μ(Mo-Kα) = 13.76 cm−1. Refinement of 4205 reflections (I > 3σ(I)) out of 5674 unique observed (3° < 2θ < 48°) gave R and Rw values of 0.0559 and 0.0632, respectively. Data/parameter ratio = 10.23, highest peak in final difference Fourier = 0.751 e Å−3. Crystal data (3): C20H38P2O4Rh3S2, M= 777.31, monoclinic, C2/c (No. 15), a = 21.727(1), b = 19.457(2), c = 17.809(2) Å, β = 116.87(2)°, U = 6716.4(5) Å3 , Dc = 1.537 g cm−3, Z = 8, μ(Mo-Kα) = 16.69 cm−1. Refinement of 1084 reflections (I > 3σ > (I)) out of 4649 unique observed (3° < 2θ < 46°) gave R and Rw valuesof 0.0750 and 0.0870, respectively. Data/parameter ratio = 6.302, highest peak in the difference Fourier = 1.023 e Å−3.