Synthesis and crystal structure of the 16 e(-) cationic tungsten(IV) complex [WCp*(4,4 '-Me(2)bipy)Cl-2]+BPh4-

A general synthetic route to electron rich half-sandwich tungsten(IV) compl exes with a series of 4,4'-disubstituted 2,2'-bipyridyl (R(2)bipy) donor li gands of the type [(WCp)-Cp-IV*(R(2)bipy)Cl-3] has been elaborated. The cry stal structure and conductivity measurements of the R=methyl derivative evi denced quite weak bonding of the chloride ligands in these complexes. This propensity has been utilized to prepare the novel square pyramidal, 16e(-) Lewis acid [WCp*(Me(2)bipy)Cl-2]+BPh4- through halide abstraction from [WCp *(Me(2)bipy)Cl-3] with NaBPh4. The crystal structures of the cationic compl ex and its 18e(-) CO adduct [WCp*(Me(2)bipy)(CO)Cl-2]+BPh4- obtained throug h carbon monoxide addition to the former have been determined.