Stannaacetylene (RSn⋮CR‘) Showing Carbene-like Reaction Mode

Photolysis of diazomethylstannylene 2 (ArSn−C(N2)Si(i-Pr)3, Ar = C6H3-2,6-Tip2 (Tip = C6H2-2,4,6-(i-Pr)3)) generated formal stannaacetylene 1 as a reactive intermediate, which was evidenced by the formation of cyclic arylalkylstannylene 4 via an intramolecular carbene insertion to a CH bond of isopropyl groups. The structures of the compounds 2 and 4 were fully characterized by X-ray crystallography. Stannaacetylene 1 was directly observed by laser flash photolysis of 2; λmax = 355 nm, τ = 50 ms at room temperature. No triplet ESR signals were observed during the photolysis of 2 in 3-methylpentane glass matrix at 77 K, indicating the singlet nature of 1. Theoretical calculations for the parent stannaacetylene suggest that the stannaacetylene is characterized as a Sn⋮C triple-bonded compound with a significant contribution of stannylene−(doubly excited)carbene structure.