Tellurium-Centered Bent Allenes: Synthesis, Characterization, and Reactivity.

Compounds with multiple bonds between elements of the second and fifth periods are extremely unstable, and systematic investigations into their properties remain elusive. Herein, we report a tellurium-centered heteroallene that contains multiple bonds between carbon and tellurium. This compound is the first example of bis(methylene)-λ 4 -tellane, which was synthesized and fully characterized using multinuclear NMR spectroscopy and X-ray crystallography. In the solid state, this λ 4 -tellane exhibits a bent allene structure for the C═Te═C moiety and unsaturated Te-C bonds. Interestingly, the allene-type structure is retained in the solution, which is reflected in an absorption band due to the π-π* transition at 610 nm. This λ 4 -tellane also exhibits unique reactivity toward dihalogermylenes, which yielded rare cyclic telluragermetanes.