SYNTHESIS AND CHARACTERIZATION OF THE SERIES OF D(0) ARENE COMPLEXES [CP-ASTERISK-MME(2)(ETA(6)-ARENE)] [MEB(C6F5)(3)] (M=TI, ZR, HF)

Treatment of the neutral trimethyl compounds CpMMe(3) (M = Ti, Zr, Hf ) with the highly electrophilic borane B(C6F5)(3) in methylene chlorid e in the presence of various arenes results in methyl carbanion abstra ction and coordination of the arene to form complexes of the type [Cp MMe(2)(eta(6)-arene)][MeB(C6F5)(3)] (M = Ti, Zr, Hf; arene = benzene, toluene, m- and p-xylene, anisole, styrene, mesitylene). Indications o f relative metal-arene affinities have been gleaned from a variety of low-temperature H-1 NMR experiments, and it seems that both steric and electronic factors play significant roles in determining stabilities. The crystal and molecular structures of [CpHfMe(2)(eta(6)-toluene)][ MeB(C6F5)(3)] have been determined; as anticipated, there are no signi ficant contacts between anion and cation, and the latter assumes a ben t-metallocene type of structure.