Naphthyl-Based PCP Platinum Complexes. Nucleophilic Activation of Coordinated CO and Synthesis of a Pt(II) Formyl Complex

A series of naphthyl-based PCP Pt(II) complexes was synthesized and characterized. A single-crystal X-ray study of (PCP)PtCl (2) reveals stacking of the aromatic units between each pair of molecules of 2. Chloride abstraction from 2 under nitrogen atmosphere leads to formation of the unsaturated cationic complex [(PCP)Pt]+BF4- (3), with the metal center being stabilized by the counteranion (3a) or by the solvent (3b). Abstraction of the chloride ligand from 2 under CO atmosphere leads to formation of the cationic carbonyl complex [(PCP)Pt(CO)]+BF4- (4), containing an electrophilic carbonyl ligand. The latter is attacked by nucleophiles (MeO- and H-) to give the platinum carbomethoxy complex 5 and a rare platinum formyl complex, 6. Stabilized by the bulky bis-chelating tridentate pincer-type system, the formyl complex 6 was isolated and characterized. Complex 6 is more stable than the previously reported platinum formyls. At room temperature complex 6 is slowly converted (during days) into a hydride complex, 7.