Annie L. Colebatch

We present four proton‐responsive palladium and platinum complexes, [MCl 2 ( R PONNHO)] (M=Pd, Pt; R= i Pr, t Bu) synthesised by complexation of PdCl 2 or PtCl 2 (COD) with the 1,8‐naphthyridine ligand R PONNHO. Deprotonation of [MCl 2 ( tBu PONNHO)] switches ligand coordination from mono‐ to dinucleating, offering a synthetic pathway to bimetallic Pd II and Pt II complexes [M 2 Cl 2 ( tBu PONNO) 2 ]. Two‐electron reduction gives planar M I −M I complexes [M 2 ( tBu PONNO) 2 ] (M=Pd, Pt) containing a metal‐metal bond. In contrast to the related nickel system that forms a metallophosphorane [Ni 2 ( tBu PONNOPONNO)], an unusual phosphinite binding mode is observed in [M 2 ( tBu PONNO) 2 ] containing close phosphinite‐naphthyridinone P⋅⋅⋅O interactions, which is investigated spectroscopically, crystallographically and computationally. The presented proton‐responsive and structurally‐responsive R PONNHO and bimetallic R PONNO complexes offer a novel platform for future explorations of metal‐ligand and metal‐metal cooperativity with palladium and platinum.