The structures and reactivity of NHC-supported copper(i) triphenylgermyls.

Deprotonation of triphenyl germane with NHC-supported copper alkoxides afforded four novel (NHC)CuGePh 3 complexes. Of these, (IPr)CuGePh 3 (IPr = :C{N(2,6-iPr 2 C 6 H 3 )CH} 2 ) was selected for further investigation. Analysis by EDA-NOCV indicates it to be a germyl nucleophile and its σ-bond metathesis reaction with a range of p-block halides confirmed it to be a convenient source of [Ph 3 Ge] - . The Cu-Ge bond of (IPr)CuGePh 3 underwent π-bond insertions with t BuNCS, CS 2 , and PhNCO to furnish a series of germyl substituted carboxylate derivatives, (IPr)CuXC(Y)GePh 3 (X = S, NPh; Y = S, N t Bu, O), which were structurally characterised. (IPr)CuGePh 3 inserted phenyl acetylene, providing both the Markovnikov and anti-Markovnikov products. The (NHC)CuGePh 3 compounds were validated as catalytic intermediates; addition of 10 mol% of NHC-copper(i) alkoxide to a mixture of triphenyl germane and a tin(iv) alkoxide resulted in a tin/germanium cross coupling with concomitant formation of alcohol. Moreover, a catalytic hydrogermylation of Michael acceptors was developed with Ph 3 GeH adding to 7 activated alkenes in good conversions and yields in the presence of 10 mol% of NHC-copper(i) alkoxide. In all cases, this reaction provided the β-germylated substrate implicating nucleophilicity at germanium.