Cyclometalated platinum(II) complexes derived from a chiral pyridine ligand: Synthesis, structure, and catalytic activity

Abstract

A direct cyclometalation of a chiral pyridine derivative, (5R,7R)-5,6,7,8-tetrahydro-6,6-dimethyl-2-phenyl5,7-methanoquinoline (L), with K2PtCl4 in acetic acid is described. A chiral mononuclear cyclometalated platinum(II) complex (6) was obtained, in which second L was simply coordinated by nitrogen. This new platinum(II) complex was characterized by H-1 and C-13 NMR spectroscopy, and further by X-ray crystallography. Both the solution and solid structures show C-H... Cl hydrogen bonding, which explains a distorted square-planar geometry in the solid state. A reactive cationic platinum(II) species (8) was generated from the chloro complex by treatment with silver triflate, whose catalytic efficiency was evaluated in asymmetric aldol and silylcyanation reactions of aldehydes.