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 SnX2 led to three compounds [{ArNCPh}2(NC5H3)]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.