Addition of the iminium salt [Me2N=CMe2][BF4] to the reductively activated benzene in [Cr(eta(4)-C6H6)(CO)(3)](2-)

Abstract

The iminium salt [Me2N=CMe2][BF4] (4BF(4)) adds to the reductively activated eta(4)-benzene ligand in [Cr(eta(4)-C6H6)(CO)(3)](2-) (2(2-)) to give the aminoalkyl-substituted eta(5)-cyclohexadienide Cr(0) complex [Cr(eta(5)-C6H6)(CMe2NMe2)(CO)(3)](-) (5(-)). The unusual upfield chemical shift in NMR spectra of the methyl protons and carbons, which are positioned right above the cyclohexadienide ligand by an exo-addition, suggests a magnetic shielding effect indicative of a modest ring current despite the open conjugation of the cyclohexadienyl ligand. The analogous Mn(I) complex [Mn(eta(5)-C6H6)(CMe2NMe2)(CO)(3)] (6) has been crystallographically characterized.