A Stable Bis(methylene)-λ4-selane with a >C=Se=C< bond containing Se(IV)

Bis(methylene)-λ4-selane 1, a new class of heteroallenes, was synthesized and isolated as a stable purple crystalline solid. An X-ray crystallographic analysis revealed a bent allene-type structure with pseudo C2v symmetry and a bent C=Se=C moiety that contains a 3-center-4-electron π-bond. The NMR spectrum of 1 shows compelling evidence for a slow rotation of the Se=C moieties at room temperature. The 77Se NMR spectrum of 1 contains one signal in the region characteristic for Se(IV) compounds.