Reactions of bimetallic group VI (6) complexes. 3. Synthesis, characterization and reactivity of dimeric molybdenum(III) and tungsten(III) compounds with bridging thiolate ligands. A molybdenum-95 NMR study on dinuclear molybdenum complexes. Crystal structure of [Mo2III(.eta.5-C5H5)2(SMe)3(CO)2]Br.c