The structures of ring-expanded NHC supported copper(I) triphenylstannyls and their phenyl transfer reactivity towards heterocumulenes.

Three ring-expanded N-heterocyclic carbene-supported copper(I) triphenylstannyls have been synthesised by the reaction of (RE-NHC)CuOtBu with triphenylstannane (RE-NHC = 6-Mes, 6-Dipp, 7-Dipp). The compounds were characterised by NMR spectroscopy and X-ray crystallography. Reaction of (6-Mes)CuSnPh3 with di-p-tolyl carbodiimide, phenyl isocyanate and phenylisothiocyanate gives access to a copper(I) benzamidinate, benzamide and benzothiamide respectively via phenyl transfer from the triphenylstannyl anion with concomitant formation of (Ph2Sn)n. Attempts to exploit this reactivity under a catalytic regime were hindered by rapid copper(I)-catalysed dismutation of Ph3SnH to Ph4Sn, various perphenylated tin oligomers, H2 and a metallic material thought to be Sn(0). Mechanistic insight was provided by reaction monitoring via NMR spectroscopy and mass spectrometry.