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