Oxazoles revisited: On the nature of binding of benzoxazole and 2-methylbenzoxazole with the zinc and palladium halides

Abstract

A synthetic and structural (X-ray) investigation into the bonding modes of benzoxazole (box) and 2-methylbenzoxazole (Mebox) ligands with halide precursors of Zn and Pd has been undertaken to clarify earlier discrepancies concerning the nature of the bonding mode(s) of the two azoles. In four structurally characterised examples, all contain the title ligands in a κ¹N bonding motif. Calculations at the density functional level (DFT) of theory (B3LYP) confirm the ground state stability of this class of coordination for several hypothetical Pd and Zn (gas phase) compounds. The attempt to obtain suitable crystalline material of PdCl₂(box)₂ (i.e., 5) leads to substantial complex degradation. One minor product of this process has been identified (X-ray) as the diarylformamidinato complex C₂₆H₂₂N₄O₄Pd, presumably formed via a complex combination of the decomposition products of both free box and 5.