C-Metalated Diazoalkane Complexes of Platinum Based on PCP- and PCN-Type Ligands

A series of the first C-metalated diazoalkane complexes of Pt, based on pincer-type PCN
and PCP ligands (PCP = C6H3[CH2P(iPr)2]2; PCN = C6H3[CH2P(tBu)2](CH2)2N(CH3)2), with
the general formula (PCX)Pt[C(N2)R] (2, X = N, R = Ph; 3, X = N, R = SiMe3; 5, X = P, R
= Ph) were prepared via direct nucleophilic attack of RCN2-Li+ at the metal center. These
remarkably stable complexes were characterized by 1H, 31P{1H}, and 13C NMR and IR
spectroscopy. Complex 2 was also characterized by single-crystal X-ray crystallography.
Reactions of the C-metalated diazoalkane Pt complexes with Cu(I) (reported to catalyze
decomposition of diazoalkanes) were strongly influenced by the nature of the pincer ligand.
Bimolecular coupling to generate diphenylacetylene and (PCP)Pt−OTf (6) was observed in
the case of the rigid PCP-based complex 5, while the hemilabile PCN-based complex 2 was
converted to an ylide-bridged dimeric structure, the formation of which was promoted by
the decoordination of the ligand amine arm. In addition, formation of the stable metal-substituted azine-type binuclear complex 10, generated by reaction of 2 with Rh2(OAc)4, is
described.