The tipping point of the inert pair effect: Experimental and computational comparison of In(i) and Sn(ii) bis(imino)pyridine complexes

Abstract

The autoionization reaction of neutral bis(imino)pyridine and SnX 2 led to three compounds [{ArNCPh}2(NC5H 3)]SnX+SnX3- (Ar = 2,6-(2,5- tBu2C6H3), X = Cl, Br; Ar = 2,6-(2,6-Me2C6H3), X = Cl) which display, within the same species, cations and anions possessing Sn(ii) centers. Computational analysis compared the ligated Sn(ii) cations with bis(imino)pyridine In(i) complexes that showed unprecedented weak metal-ligand covalent interactions, consistent with the In(i) 5s2 electrons remaining as an inert nonbonding pair. Analysis of the metal-ligand bonding indicates that the chloride ligand of the Sn(ii) complex induces promotion of the metal 5s2 electron pair to a stereochemically active hybridized orbital, which, in turn, allows strong coordination of the bis(imino)pyridine to Sn. © 2014 The Royal Society of Chemistry.