Alkyl and aryl complexes of platinum(II) and palladium(II) containing the tri(1-cyclohepta-2,4,6-trienyl)phosphane ligand. Intramolecular dynamics and signs of coupling constants

Abstract

Tri(1-cyclohepta-2,4,6-trienyl)phosphane, P(C 7H 7) 3 ([P] when coordinated to the metal centre), behaves as a bidentate chelating ligand in platinum(II) and palladium(II) complexes, [P]MR 2 [M=Pt, R=Me ( 3a), Et ( 3b), Pr ( 3c), Bu ( 3d), CH 2Ph ( 3e), Ph ( 3f), C 6H 4–4-F ( 3g), C 6F 5 ( 3h), Fc ( 3i); M=Pd, R=Me ( 4a), C 6F 5 ( 4h)], which were synthesized by the reaction of [P]MCl 2 with either LiR or RMgBr. The molecular structure of 3g was determined by X-ray analysis, confirming the PtP bond and the η 2-coordination of one of the C 7H 7 rings by its central CC bond. In solution at room temperature, all complexes are fluxional with respect to the NMR time scale, due to intramolecular exchange of the C 7H 7 rings in η 2-CC coordination to the metal centre. The products were characterised by 1H, 13C, 31P and 195Pt NMR spectroscopy, and signs of various coupling constants were determined by application of appropriate 1D spin tickling experiments and 2D heteronuclear shift correlations.