Reactions of acetylenes with noble metal carbonyl halides. 9. Preparation, chemical characterization and x-ray structural analysis of [cyclic] [Pt{C(O)CPr:CPrCPr:CPrCl}Cl]2 and the cyclocarbene derivative [Pt{CCPr:CPrCPr:CPrO}(PBu3)2Cl][PF6]

The cyclopentadienone compound [Pt{η4-C(=O)C(Pr)=C(Pr)C(Pr)=C(Pr))Cl2] (1a) and the octadienoyl complex [Pt{-C(=O)C(Pr)=C(Pr)C(Pr)=C(Pr)Cl}Cl]2 (2a) were isolated during the reaction of Pt(CO)2Cl2 with 4-octyne. The reactions of compounds 1a and 2a with nitrogen and phosphorus ligands have also been studied. Compound 2a reacts with excess of phosphines to give the complex [Pt{CC(Pr)=C(Pr)-C(Pr)=C(Pr)O}L2Cl2] [L = PPh3 (8a), PBu3 (9a)], containing a six-membered carbenic ring bonded to platinum, which is easily transformed into the ionic [Pt{CC(Pr)=C(Pr)C(Pr)=C(Pr)O}(PBu3)2Cl][PF6] complex (11a). The analogous products obtained in the reaction of 2-butyne and 3-hexyne with Pt(CO)2Cl2 have been reformulated. A 13C NMR study on a series of derivatives is reported. The crystal structures of complexes 2a and 11a have been determined by X-ray diffraction. Crystals of 2a are triclinic of space group P1 with Z = 1, a = 8.256 (2) Å, b = 10.293 (3) Å, c = 12.632 (3) Å, α = 73.50 (2)°, β = 76.50 (1)°, and γ = 81.62 (2)°. A total of 2762 reflections were used in the refinement, resulting in a final R of 0.034. The dimeric compound 2a lies on a crystallographic inversion center; the coordination around each platinum is distorted square-planar, with the olefinic double bond approximately perpendicular to the coordination plane. Crystals of 11a are orthorhombic of space group P212121 with Z = 4, a = 25.394 (6) Å, b = 14.897 (4) Å, and c = 13.858 (3) Å. The final agreement factor is R = 0.057 for 2198 independent observed reflections. The coordination around platinum is, as expected, square-planar with a Pt-C distance of 1.94 (2) Å.