Reactions of acetylenes with noble metal carbonyl halides. Part 11. Synthesis of [Pt{CMeC(H)COOMe}(CO)Cl]via polynuclear platinum carbonyls. X-Ray crystal structure determination of the σ-alkenyl platinum complex [N(PPh3)2][Pt{CMeC(H)CO2Me}(CO)Cl2]

Abstract

The polynuclear derivative [{Pt(CO)₂}_n] reacts, in chloroform solution, with H[Pt(CO)Cl₃] and MeCCCO₂Me to give [Cl(CO)[graphic omitted]t(CO)Cl](2) and [[graphic omitted]OMe}(CO)Cl](3). Compound (3) reacts with PPh₃ to give [Pt{CMeC(H)CO₂Me}(PPh₃)₂Cl](7a), while with chloride ions it is transformed into the anionic complex [Pt{CMeC(H)CO₂Me}(CO)Cl₂]^–(4). A multinuclear n.m.r. study on a series of derivatives is reported. The crystal and molecular structure of [N(PPh₃)₂][Pt{CMeC(H)CO₂Me}(CO)Cl₂](4a) has been determined from three-dimensional X-ray data. The complex crystallizes in the monoclinic space group Pc, with two formula units in a unit cell of dimensions a= 9.378(2), b= 14.362(3), c= 14.760(4)Å, and β= 100.10(5)°. The structure was determined by Patterson and Fourier methods and refined by least-squares methods to R= 0.0268 from 3 212 independent reflections with I > 3σ(I). The platinum atom has the expected square-planar co-ordination; relevant bond lengths are Pt–C(sp²) 2.016(7), Pt–C(sp) 1.836(9), Pt–Cl (trans to the alkene) 2.404(2), and Pt–Cl (trans to CO) 2.313(2), while the CC bond distance is 1.32(1)Å. The plane of the olefinic moiety is rotated by 65.6(2)° with respect to the co-ordination plane of the metal atom giving a short intramolecular separation of 3.163(7)Å between Pt and the oxygen of the carboxylate carbonyl group.