An Intramolecular Bis(Amino)Phosphine-Stabilised Phosphinidene: Synthesis and CuCl Coordination

Extending the available intramolecularly-stabilised phosphinidene ligands, we report a novel naphthalene supported system derived from readily available starting materials. Specifically, 1,8-bis(diaminophosphino)naphthalene, naphth-1,8-{P(NEt₂)₂}₂ (1), reacts with ethereal HCl to form the mixed diphosphine naphth-1-(PCl₂)-8-{P(NEt₂)₂} 2 as a phosphoranide Zwitterion, which is readily reduced with elemental Mg in forming the target intramolecularly-stabilised phosphinidene 3. The electronic nature of this species is explored through computational DFT, NBO, and TD-DFT analyses, indicating a high electron density at the P^I centre, which delocalizes across the naphthalene ring lending this deep red-purple compound its colour. The coordination capacity of 3 is demonstrated through its reaction with excess CuCl, which surprisingly leads to exclusive formation of the 2 : 1 complex of 3 to Cu, giving initial insights into the coordination chemistry of this novel ligand.