Dicationic tellurium analogues of the classic N-heterocyclic carbene.

The synthesis and comprehensive characterization of the first dicationic tellurium analogues of N-heterocyclic carbenes (NHCs) has been reported, in both the +2 and +4 oxidation states. For the +2 oxidation state, a base-stabilized form of TeCl(2) is used as the starting material. The dications are isolated by means of halide metathesis and the solid-state structures confirm the previously calculated diimine bonding arrangement. For Te(IV), a diamine is used in a high-yielding dehydrohalogen coupling reaction from TeCl(4). The dicationic NHC analogue is isolated in a base-stabilized form through halide abstraction and subsequent coordination by pyridine.