Electrochemical Synthesis of Triphenylphosphine Coinage Metal Complexes stabilized by closo-Dodecaborates [B12X12]2− (X=H, F, Cl, Br, I)

Abstract

The synthesis of salts of reactive cations and weakly coordinating anions is of great interest to the development of catalysts, because the weak electrostatic interaction between the two may greatly increase catalytic activity and solubility in nonpolar solvents. However, the synthesis of these salts is in many cases difficult and requires elaborate, sometimes multi-step procedures. Here, we describe the synthesis of a library of monocationic group 11 metal-triphenylphosphine complexes of dodecaborates generated by means of electrochemistry. The complexes of the general formula [M(PPh3)y(CH3CN)z]2[B12X12] (M=Cu, Ag, Au; X=H, F, Cl, Br, I; y=2–4; z=0–2) were synthesized from the free acid of the respective dodecaborate and the elemental metal in acetonitrile in the presence of triphenylphosphine. The reactions were performed in an electrochemical cell under ambient conditions in polypropylene containers in all cases. A total of 13 different crystal structures in the [M(PPh3)y(CH3CN)z]2[B12X12] system were obtained. As a by-product in some reactions single crystals of [(H3O)(OPPh3)3]2[B12X12] (X=Cl, Br, I) were found.