Exchange reactions involving transition-metal–mercury bonds

Abstract

π-Cyclopentadienyl complexes of the type π-C₅H₅M(CO)_nHgX (M = Mo or W, n= 3; M = Fe, n= 2; X = Cl, Br, l, or SCN) are immediately formed by exchange reactions between [π-C₅H₅M(CO)_n]₂Hg and HgX₂ in acetone or methanol solution at room temperature. Polymetallic complexes of the type π-C₅H₅M(CO)_nHgCo(CO)₄ have also been prepared by similar reactions between [π-C₅H₅M(CO)_n]₂Hg and [Co(CO)₄]₂Hg. All these new complexes have been isolated as air-stable crystalline solids, and their infrared, ultraviolet, and nuclear magnetic resonance spectra are reported. In solution, reactants and products are in labile equilibrium although equilibrium constants usually strongly favour the products. The preparative scope of the reaction is discussed.