Platinum(II) and Palladium(II) Dichalcogenolene Complexes Containing the Ligand Tri(1-cyclohepta-2,4,6-trienyl)phosphane. Molecular Structure, Intramolecular Dynamics in Solution, and the Absolute Signs of Coupling Constants

Tri(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3 (1), serves as a bidentate chelating ligand [P] in platinum(II) and palladium(II) complexes. Here the synthesis of the four dichalcogenolene complexes [P]M[E2C2(CO2Me)2] (4) (M = Pt) and 5 (M = Pd) with E = S (a) and Se (b) from the reaction of the respective dicyclopentadienyltitanium dichalcogenolenes, Cp2Ti[E2C2(CO2Me)2], and [P]MCl2 with M = Pt (2) and Pd (3) is reported. At room temperature, the complexes 4 and 5 are fluxional with respect to the NMR time scale, and the nature of the dynamic process is discussed. The complexes have been characterised by H, C, P, Se and Pt NMR spectroscopy. The signs of the coupling constants J(Pt, Se) (< 0) and J(Se, P) (> 0) were obtained by selective PfPtg and PfSeg spin tickling experiments. The crystal structure of 4b was determined by X-ray analysis.