Stability and Reactivity of Cyclometallated Naphthylamine Complexes in Pd–C Bond Insertion Reactions with Coordinated Alkynylphosphanes

Abstract

AbstractPhenylbis(phenylethynyl)phosphane PhP(C≡CPh)2 coordinates regiospecifically to the α‐methyl‐chiral ortho‐platinated and ‐palladated naphthylamine units at the positions trans to the nitrogen donors. The P→Pt coordination bond is kinetically inert, whereas the P→Pd bond is labile. Upon heating of these phosphane complexes at 70 °C, one of the C≡C bonds in the coordinated PhP(C≡CPh)2 was activated towards an intermolecular Pd–C bond insertion reaction with an external ortho‐palladated naphthylamine ring. No intramolecular insertion reaction occurred. In contrast to its palladium analogue, the ortho‐platinated ring is not reactive towards coordinated PhP(C≡CPh)2, although it can promote the Pd–C bond insertion reaction. However, despite the high kinetic stability of the P→Pt coordination, the organoplatinum unit is a noticeably weaker activator than its organopalladium counterpart. The chirality of the reacting ortho‐metallated naphthylamine ligand exhibited high stereochemical influence on the formation of the new stereogenic phosphorus center during the course of these C–C bond‐formation reactions. The coordination chemistry and the absolute stereochemistry of the dimetallic products were determined by single‐crystal X‐ray crystallographic analysis.