Platinum(II) Complexes with 1‐Cyclohepta‐2,4,6‐trienyl‐diphenylphosphane, Ph 2 P(C 7 H 7 ), and Alkyn‐1‐yl Ligands

[1‐Cyclohepta‐2,4,6‐trienyl‐diphenylphosphane]platinum(II) dichloride ( 4 ) was prepared by the 1:1 reaction of (cod)PtCl 2 (cod = η 4 ‐cycloocta‐1,5‐diene) with the phosphane. The reaction of 4 with di(alkyn‐1‐yl)dimethylstannanes, Me 2 Sn(C≡C‐R) 2 [R = H ( a ), Me ( b ), Ph ( c ), SiMe 3 ( d )], in boiling THF gave selectively in high yield the monoalkynyl complexes [Ph 2 P(C 7 H 7 )]Pt(Cl)C≡C‐R ( 6b,c,d ), in which the alkyn‐1‐yl group is arranged in cis position with respect to the phosphorus atom, and the C 7 H 7 ring is η 2 ‐coordinated to platinum through the central C=C bond. The same reaction at room temperature afforded, again selectively and in high yield, the dialkynyl complexes [Ph 2 P(C 7 H 7 )]Pt(C≡C‐R) 2 ( 7a ‐ d ). The new complexes were characterised in solution by 1 H, 13 C, 29 Si, 31 P and 195 Pt NMR spectroscopy, and the molecular structures of 4 and 7d were determined by X‐ray crystallography.