Probing Cyanocuprates by Electrospray Ionization Mass Spectrometry
Organometallics, 2010, 29, 3593-3601 published on 25.05.2010
Solutions of CuCN/(RLi)n (n=0.5, 0.8, 1.0, and 2.0 and R=Me, Et,nBu,sBu,tBu, and Ph) intetrahydrofuran are analyzed by electrospray ionization mass spectrometry. In all cases, organo-cuprate anions are observed, whose exact nature depends on the reagent stoichiometry. While cyanide-free Lin-1CunR2n- anions completely predominate for CuCN/(RLi)2 solutions, cyanide-containing Lin-1CunRn(CN)n- complexes prevail for CuCN/(RLi)n reagents with n <1. Mixing studies with CuCN/MeLi/RLi as well as gas-phase fragmentation experiments of the mass-selected anions provide further insight into the relative stability and the likely structural composition of polynuclear cuprates. The thus obtained information not only agrees quite well with previous results from spectroscopic and crystallographic work but moreover reveals clear trends of how different organyl substituents influence the aggregation and ion-pairing behavior of cyanocuprates. Inaddition, the observation of Cu(+2)-containing cyanocuprate complexes for CuCN/(RLi)n solutions, with n <1 and R=nBu and sBu, indicates the intrinsic stability of these unprecedented species in the diluted gas phase.