On the halogenonium derivatives of molybdenum and tungsten cyclopentadienylcarbonyls

A study has been made of a possibility of synthesis of halogenonium derivatives of molybdenum and tungsten cyclopentadienylcarbonyls. Interaction of BF3 etherate with Cp(CO)3WI followed by treatment with NaBF4 results in formation with a 47% yield of an iodonium salt, ([Cp(CO)3W]2I)BF4, with composition C16H10BF4106W2 characterized by elemental analysis, IR and PMR spectra. Similar procedure in the case of Cp(CO)3WBr and Cp(CO)2Ph3PWI leads to small yields of corresponding halogenonium derivatives identified by IR spectra. Cp(CO)3MoI with BF3 etherate forms ([Cp(CO)3Mo]2I)BF4, which rapidly decomposes to form the starting iodide. Reaction of Cp(CO)3WI with AgBF4 yields ([Cp(CO)3WI]4Ag)BF4, whose composition s C C32H20AgBF4I4O12W4 and melting point 183-4 deg. This is the first tetrahedral complex in which the Ag+ ion is coordinated with four neutral iodine atoms. Under similar conditions Cp(CO)2FeI with AgBF4 forms only an iodonium salt, ([Cp(CO)2Fe]2I)BF4