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

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 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. The proton responsive behaviour of the 1,8‐naphthyridine PONNHO ligands can be harnessed to provide nuclearity control, where deprotonation results in a switch from mono‐ to dinucleating coordination. Reduction provides access to planar palladium and platinum bimetallic complexes containing close phosphinite‐naphthyridinone P⋅⋅⋅O interactions.