Di- and trinuclear phosphido-bridged platinum complexes. Crystal structures of [Pt{CH2=CHC(O)OMe}(PPh3)2], trans-[Pt2(μ-PPh2)2I2(PPh3)2] and cis,cis,cis-[Pt3(μ-I)2(μ-PPh2)2Cl0.5I1.5(PPh3)2]

Abstract

The readily available Pt(0) methyl acrylate complex [Pt{CH₂CHC(O)OMe}(PPh₃)₂] (2) allows access to the known, mixed-valence trinuclear cluster [Pt₃(μ-PPh₂)₃Ph(PPh₃)₂] (3) in 64% yield. Oxidation of 3 with 2 equivalents of I₂ afforded the new trinuclear complex [Pt₃(μ-I)₂(μ-PPh₂)₂I₂(PPh₃)₂] (4) whose molecular structure is similar to that of the related compound of empirical formula [Pt₃(μ-I)₂(μ-PPh₂)₂Cl_0.5I_1.5(PPh₃)₂] (5) which has been generated by oxidation of 3 with successively 1 equivalent of I₂ and 1 equivalent of C₆H₅ICl₂. In these complexes, the four halogen atoms lie on the same side of the almost aligned platinum atoms and the nearly square-planar coordination planes of the metal atoms adopt a “japanese screen”, chair-like conformation. The reaction of the dinuclear, metal–metal bonded Pt(I)–Pt(I) complex [Pt₂(μ-PPh₂)₂(PPh₃)₂] with one equivalent of I₂ afforded the Pt(II) complex [Pt₂(μ-PPh₂)₂I₂(PPh₃)₂] (6). The molecular structures of complexes 2·CH₂Cl₂, [Pt₃(μ-I)₂(μ-PPh₂)₂(I_1.3Cl_0.7)(PPh₃)₂][Pt₃(μ-I)₂(μ-PPh₂)₂(I_1.7Cl_0.3)(PPh₃)₂]·C₆H₅Cl·3CH₂Cl₂ (5A·5B·C₆H₅Cl·3CH₂Cl₂) and 6 have been established by single crystal X-ray diffraction studies.