Selective Carbanion-Pyridine Coordination of a Reactive P,N Ligand to RhI

Ligands with reactive carbon sites in the periphery of a metal center have emerged as a powerful approach for metal-ligand bond activation. These reactive carbon sites are commonly generated by deprotonation strategies. Carbon-silicon bond cleavage is a potential alternative to access such constructs. Herein, the monodesilylation of bis-silyl-substituted P,N scaffold PNSi2 in the coordination sphere of [Rh-I(Cl)(CO)(PNSi2)] (1) with sodium azide is disclosed. This affords a unique dinucleating anionic kappa(2)-C,N-kappa(1)-P ligand with a carbanionic methine carbon atom directly bound to rhodium as part of a four-membered Rh-N-C-C rhodacycle. This dimer undergoes meta-pyridine C-H activation facilitated by weak bases, which leads to a desymmetrization of the system and provides a sigma,pi-bridging 3-pyridyl fragment bound to Rh-I. The facile Si-C cleavage strategy may pave the way to studying the reactivity and functionalization of a variety of kappa(2)-C,N-coordinated pyridine scaffolds for selective transformations.