The hare and the hedgehog – Similar thermal expansion of argento- and aurophilic contacts for different reasons

Abstract This study investigates the thermal expansion properties of argentophilic and aurophilic contacts in coordination complexes of the form [( i Pr NHC) 2 Ag]ClO 4 and [( i Pr NHC) 2 Au]ClO 4 . Using X-ray crystallography distinct structural changes and phase transitions at varying temperatures are revealed. Both complexes exhibit a similar strong temperature dependence of the metallophilic distances. Analysis shows that the shallower, more anharmonic aurophilic interaction is counterbalanced by the smaller vibrational amplitude of the heavier gold atoms, resulting in comparable thermal elongation despite differing atomic dynamics.