Copper(I) Chemistry of Bis(pyrazolyl)diphenylborate Ligands: Formation of a Heterocycle by Cu-Mediated Acetonitrile Addition

Cycloaddition of CH3CN to a Ph2B(pz) fragment was discovered during explorations of the reactions of the new ligands Ph2B(pzR,R‘)2- (pz = 3,5-R,R‘-pyrazolyl; R = Ph, R‘ = H and R and R‘ = CH3) with [Cu(CH3CN)4]SbF6. Thus, while treatment of Na[Ph2B(pzPh,H)2] with [Cu(CH3CN)4]SbF6 afforded [Ph2B(pzPh,H)2]Cu(HpzPh,H) that exhibited the expected bidentate coordination of the bis(pyrazolyl)borate ligand in its X-ray crystal structure, the analogous reaction with Na[Ph2B(pzCH3CH3)2] led to the product shown in the figure.