Rh-Rh Bonds of Order 0, 1, and 2 in Dinuclear Rhodium(I) Phosphido and Arsenido Complexes: X-ray Crystal Structures of [Rh(CO)(t-Bu2PH)]2(μ-t-Bu2P)(μ-H) (Rh-Rh), [Rh(COD)]2(μ-t-Bu2P)(μ-Cl) (COD = 1,5-Cyclooctadiene), and [Rh(μ-t-Bu2As)(CO)2]2

Atta M. Arif, Richard A. Jones, Mark H. Seeberger, Bruce R. Whittlesey, Thomas C. Wrirght

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Abstract

Reaction of t-Bu2PH with Rh4(CO)12in toluene under reflux yields [Rh(CO)(t-Bu2PH)]2(μ-t-Bu2P)(μ-H) (1) (61%). 1 has one t-Bu2P unit, which bridges two virtually planar Rh(I) atoms. The hydride could not be located in the crystal structure, but the overall geometry indicates that it probably occupies a bridging site. There is a relatively long single Rh-Rh bond (2.906 (2) A), and the phosphine (t-Bu2PH) ligands are cis with respect to it. Reaction of Li(t-Bu2P) with [Rh(COD)Cl]2(1:1) (COD = 1,5-cyclooctadiene) in THF yields [Rh(COD)]2(μ-t-Bu2P)(M-Cl) (2) (55%). 2 has one t-Bu2P group bridging two planar Rh(I) atoms. The chlorine atom is also bridging. There is no Rh-Rh bond in 2 (Rh-Rh - 3.395 A (average)). Reaction of Li(t-Bu)2As with [Rh(CO)2Cl]2(2:1) in THF at -78 °C yields [Rh(μ-t-Bu2As)(CO)2]2(3) (25%) as well as Rh3(CO)11(μ-t-Bu2As)24-BuAs) (4) (35%). 4 has been described elsewhere. The structure of 3 consists of two t-Bu2As groups, which bridge two planar Rh(I) atoms with no Rh-Rh bond (Rh-Rh = 3.884 (1) A). The structures of 1–3 have been determined by single-crystal X-ray diffraction studies. 1 crystal data: C38H85O2P3Rh2, MT = 872.83, monoclinic, P21/c (No. 14), a = 12,335 (1) A, b = 15.142 (2) A, c - 22.304 (2) A, 0 = 91.35 (2)°, U = 4164.9 (5) A3, Dc= 1.392 g cm”3, Z = 4, (Mo Ka) = 0.71069 A (graphite monochromator), M(MoKa) = 9.229 cm-1. Methods: Multan, difference Fourier, full-matrix least squares. Refinement of 3605 reflections (/ > 3ff(/)) out of 7250 unique observed reflections (2° < 2$ < 50°) gives R and /?wvalues of 0.070 and 0.075, respectively. The data/parameter ratio = 10.92. Hydrogen atoms were not located. 2 crystal data: C24H38ClPRh2, MT= 598.81, orthorhombic, Pbcn (No. 60), a = 13.379 (1) A, b = 29.020 (2) A, c = 25.621 (1) A, V = 9947.5 (7) A3, Dc= 1.599 g cm”3, Z = 16, (Mo Ka) = 0.71069 A (graphite monochromator), M - 14.87 cm-1. Refinement of 3342 reflections (/ > 3<r(/)) out of 9559 measured (2° <2$ < 50°) gave R and Rw values of 0.0502 and 0.0554, respectively. The data/parameter ratio = 6.62. All non-hydrogen atoms were anisotropic; hydrogen atoms were not located. 3 crystal data: C2oH36As204Rh2, Afr= 696.16, monoclinic, I2/m (a nonstandard setting ofC2/m,No. 12), A = 11.102 (2)A, b = 11.201 (2) A, c = 11.575 (1) A, 0 = 115.44 (1)°, £/= 1299.8 (5) A3, Dq= 1,779 g cm-3, Z = 2, (Mo Ka) = 0.71069 A (graphite monochromator), M(Mo Ka) = 37.92 cm-1. Refinement of 1612 reflections (/ > 3o-(/)) out of 1672 unique observed reflections (2° < 26 < 60°) gave R and R„ values of 0.033 and 0.040, respectively. The data/parameter ratio = 22.39. All non-hydrogen atoms were anisotropic; hydrogen atoms were not located. Reaction of the dilithio diphosphide LiP(f-Bu)(CH2)4(?-Bu)PLi with [Rh(COD)Cl]2in THF at -78 °C gives dark red, crystalline [Rh(COD)]2(M-P(*-Bu)(CH2)4(r-Bu)P) (5) in 60% yield. NMR data indicate pseudotetrahedral Rh atoms with a Rh-Rh double bond. X-ray quality crystals of 5 could not be obtained.

Original languageEnglish
Pages (from-to)3943-3949
Number of pages7
JournalInorganic Chemistry
Volume25
Issue number22
DOIs
StatePublished - 1986

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