Organometallic chemistry of arsenic, phosphorus and other systems

Abstract

Arsenic hydride and antimony hydride reactions with iron carbonyls were investigated and compared to analogous reactions using germanium hydrides. The reaction between arsane and Fe(CO)₅ is a new, higher yielding synthesis of [(μ₃-As)₂Fe₃(CO)₉]. The reaction between arsane and Fe₂(CO)₉ led to the new cluster [Fe₂(CO)₈(μ₄-As)]₂[Fe₂(CO)₆]. Characterisation was by an X-ray crystal structure determination. [Fe₂(CO)₈(μ₄-As)]₂[Fe₂(CO)₆] crystallises in the orthorhombic space group Pbca, with unit cell parameters a = 22.908(7), b = 17.521(9), c = 16.071(7) Å and Z = 8. This cluster consists of four AsFe₂ triangles linked by arsenic vertices and an iron-iron edge. In an attempt to prepare similar antimony clusters, stibane was reacted with Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂, but no analogues were isolated. The β-ketophosphane (2-acetylphenyl)diphenylphosphane, Ph₂P[C₆H₄COMe], was prepared in a multi-step synthesis that involved; (i) coupling chlorodiphenylphosphane and 2-bromoethylbenzene, (ii) oxidation of the phosphorus with H₂O₂, (iii) oxidation of the ethyl group with CrO₃, and (iv) reduction at the phosphorus atom. Attempts to prepare the similar disubstituted phosphane PhP[C₆H₄COMe]₂, by an analogous route, instead afforded PhP[C₆H₄C(O)O]₂ at the CrO₃ oxidation step. The potential use of Ph₂P[C₆H₄COMe] as a ligand on metal centres was demonstrated by its electron-transfer catalysed reaction with Ru₃(CO)₁₂, which gave the expected product Ru₃(CO)₁₁[PPh₂(C₆H₄COMe)]. Gentle heating of Ru₃(CO)₁₁[PPh₂(C₆H₄COMe)] in heptane led to the cyclo-metallated cluster Ru₃(CO)₉(μ-PPh₂)(η²-C₆H₄COMe) through P-C bond cleavage. A single crystal X-ray diffraction study on Ru₃(CO)₉(μ-PPh₂)(η²-C₆H₄COMe) showed that it crystallises in the triclinic space group Pī with a = 10.200(11), b = 12.084(12) and c = 14.422(13) Å, a= 81.06(7), β = 77.18(8) and γ = 76.98(8)° and Z = 2. The cluster is derived from Ru₃(CO)₁₂ with three carbonyl ligands replaced by a μ-PPh₂ moiety and an η²-2-acetylphenyl group. The reactions between ortho-manganated acetophenone derivatives and various halides were investigated and compared to the analogous aryl-transfer reactions using mercury chloride. From the reaction between RC(O) C₆H₃R"Mn(CO)₄, ( R=Me, OMe, Ph; R"=H, OMe ), R'OH ( R'=Me, Et and Ph ) and CuCl₂ the following products were isolated [Figures x 4] These can be explained in terms of competition between Mn-Cₐᵣᵧₗ bond cleavage ( the first two products ), or in terms of CO insertion into the Mn-Cₐᵣᵧₗ bond, with subsequent attack by the solvent ( the last two products). The reaction between 2-MeC(O) C₆H₄Mn(CO)₄, and PPh₂Cl involves CO replacement to give fac-[2-MeC(O)C₆H₄Mn(CO)₃(PPh₂Cl)] in essentially quantitative yield. Prolonged refluxing of fac-[2-MeC(O)C₆H₄Mn(CO)₃(PPh₂Cl)] yields Mn₂(μ-η¹-η¹-PhPPPh)-(μ-Cl)₂(CO)₆ in which the newly formed diphosphane ligand bridges two non-bonded manganese atoms; this compound was characterised by an X-ray structure analysis; Pī with a = 10.980(4), b = 11.756(3) and c = 12.186(3) Å, α = 96.20(2), β = 99.51(2) and γ = 96.56(2)° and Z = 2. The probable products from the reaction between SnCl₂ and 2-RC(O)C₆H₄HgCl ( R = Ph, Me) and from the reaction between RₙSnCl₄₋ₙ and 2-MeC(O)C₆H₄HgX ( R = Buⁿ, n = 1, X = Cl; R = Ph, n = 2, X = I) are the acylaryltin derivatives 2-RC(O)C₆H₄SnX₂Cl ( R = Ph, X = Cl; R = Me, X = Cl, Ph) and [2-MeC(O)C₆H₄]₂Sn(Buⁿ)Cl shown below [Figures x 2] These assignments were based on ¹¹⁹Sn and ¹³C nmr spectroscopy.