Utilising a Proton‐Responsive 1,8‐Naphthyridine Ligand for the Synthesis of Bimetallic Palladium and Platinum Complexes

Abstract

We present four proton‐responsive palladium and platinum complexes, [MCl2(RPONNHO)] (M = Pd, Pt; R = iPr, tBu) synthesised by complexation of PdCl2 or PtCl2(COD) with the 1,8‐naphthyridine ligand RPONNHO. Deprotonation of [MCl2(tBuPONNHO)] switches the ligand coordination from mono‐ to dinucleating, offering a synthetic pathway to bimetallic PdII and PtII complexes [M2Cl2(tBuPONNO)2]. Two‐electron reduction gives planar MI–MI complexes [M2(tBuPONNO)2] (M = Pd, Pt) containing a metal‐metal bond. In contrast to the related nickel system that forms a metallophosphorane [Ni2(tBuPONNOPONNO)], an unusual phosphinite binding mode is observed in [M2(tBuPONNO)2] containing close phosphinite‐naphthyridinone P···O interactions, which is investigated spectroscopically, crystallographically and computationally. The presented proton‐responsive and structurally‐responsive RPONNHO and bimetallic RPONNO complexes offer a novel platform for future explorations of metal‐ligand and metal‐metal cooperativity with palladium and platinum.