A carbene–stannylene adduct with a long tin–carbon double bond?

Abstract
Bis(2,4,6-triisopropylphenyl)stannylene, formed by thermolysis of the cyclotristannane 4, reacts with 4,5-dimethyl-1,3-diisopropylimidazol-2-ylidene to furnish the adduct 8; an X-ray structural analysis of this compound reveals the presence of a long tin–carbon ‘double bond’ with a length of 237. 9(5) pm and a distinctly pyramidal tin centre.