Search

This study investigates the thermal expansion properties of argentophilic and aurophilic contacts in coordination complexes of the form [(iPrNHC)2Ag]ClO4 and [(iPrNHC)2Au]ClO4. 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. [ABSTRACT FROM AUTHOR]

Iron is of interest as a catalyst because of its established use in the Haber-Bosch process and because of its high abundance and low toxicity. Nitrogen-heterocyclic carbenes (NHC) are important ligands in homogeneous catalysis and iron-NHC complexes have attracted increasing attention in recent years but still face problems in terms of stability under oxidative conditions. The structure of the iron(II) complex [1,1′-bis(pyridin-2-yl)-2,2-bi(1 H-imidazole)-κ N3][3,3′-bis(pyridin-2-yl-κ N)-1,1′-methanediylbi(1 H-imidazol-2-yl-κ C2)](trimethylphosphane-κ P)iron(II) bis(hexafluoridophosphate), [Fe(C17H14N6)(C16H12N6)(C3H9P)](PF6)2, features coordination by an organic decomposition product of a tetradentate NHC ligand in an axial position. The decomposition product, a C-C-coupled biimidazole, is trapped by coordination to still-intact iron(II) complexes. Insights into the structural features of the organic decomposition products might help to improve the stability of oxidation catalysts under harsh conditions. [ABSTRACT FROM AUTHOR]