Cationic half-sandwich complexes, [CpM{P(C7H7)2(η2-C7H7)}]BF4 (M=Ni, Pd, Pt), containing a bidentate tri(1-cyclohepta-2,4,6-trienyl)phosphane ligand

Displacement of η4-cycloocta-1,5-diene (cod) from [CpM(cod)]BF4 by the olefinic phosphane P(C7H7)3 (1) leads to complexes [CpM{P(C7H7)2(η2-C7H7)}]BF4 (M=Ni (4), Pd (5)) in which one of the cyclohepta-2,4,6-trienyl substituents is symmetrically η2-coordinated to the metal in addition to phosphorus. The platinum analogue (M=Pt (6)) was obtained from [PtCl2(cod)] by consecutive reactions with 1, TlCp and AgBF4. The homologous series 4–6 was studied by multinuclear (1H, 13C, 31P and 195Pt) NMR spectroscopy, and related tetrafluoroborates such as the pentaphenyl-cyclopentadienyl analogue of 5 and the tert-butylisocyanide adduct of 4, [CpNi(CNtBu){P(C7H7)3}]BF4 (11), were considered for comparison. An X-ray crystallographic structure determination of 4 has been carried out.