A theoretical study of M-M' polar-covalent bonding in heterobimetallic multinuclear organometallic complexes of monovalent group 11 metal centres.

Complexes with closed-shell (d-d) interactions have been studied for their interesting luminescence properties in organic light-emitting diode (OLED) devices. The present computational study aims at understanding the chemical bonding/interactions in a series of molecules with unusually short metal-metal bond distances between monovalent coinage-metal (d-d) centres. The investigated molecules include pentanuclear complexes with M or M' = Cu(I), Ag(I), or Au(I) and Mes = 2,4,6-MeCH. In such complexes, the M-M' distances are up to 50-100 pm shorter than typical metallophilic bonds in homometallic analogues. Characterization and analysis of the chemical bond strength was performed using methods, density functional theory methods including a semi-empirical treatment of dispersion interactions (DFT-D3) and semi-empirical calculations at the extended Hückel theory (EHT) level. Population analysis suggests that hybridization occurs by mixing the ( + 1)s and ( + 1)p orbitals of M with the (d) orbitals of M'. The orbital mixing plays a pivotal role in the polydentated polar-covalency/dative M-M' bonds that distinguish this bonding from the weaker metallophilic interactions.