Reactions of Di- and Polynuclear Complexes. 14. Synthesis of Permethylated-Cyclopentadienyl Chalcogeno-Bridged Compounds: A Route to the Stable Thiolatosulfidocarbonyldimolybdenum(III) Complex [Cp*2Mo2(CO)2(.mu.-SMe)2(.mu.-S)]. Crystal Structure Determination of [Cp*2Mo2(CO)2(.mu.-SMe)2(.mu.-SH)][BF4]