Ductile Metallophilic Interactions and Their Mediation of Magnetic Interactions in [Ni{Pt(SAc)₄}(pyNO₂)]₂ Complexes

Linking paramagnetic centers via metallophilic interactions allows for strong magnetic interactions over long distances. An unprecedented example of genuine isomers of [Ni{Pt(SAc)₄}(pyNO₂)]₂ provides an ideal platform for the experimental assessment of the distance dependence of magnetic interaction across metallophilic bonds. This system can be isolated in two different phases with identical chemical composition but disparate Pt···Pt distances of 3.4207(5) and 3.0992(5) Å, respectively. The pronounced distance difference is linked to a concomitant twisting around the Pt···Pt direction with a long, eclipsed, and short, staggered metallophilic interaction; this provides an extremely rare situation akin to bond-stretch isomerism when the metallophilic interaction is considered to be of σ-symmetry. Phase-pure samples were obtained by optimized synthetic protocols with kinetic control over the resulting phases. Very strong magnetic coupling of J = 95.0 cm^-1 (JS₁·S₂ formalism) in the closer-contact staggered system drastically exceeds the value, 24.5 cm^-1, of the eclipsed system. Supported by spectroscopy and DFT calculations, this suggests a possibility of targeting bond-stretch isomerism for tuning the magnetic functionalities of coordination complexes and functional materials.