A study of ionic and radical reactivities of bridging sulfido ligands in dimeric cyclopentadienyl complexes of molybdenum

Abstract

Reaction of (CpMo-..mu..-S)/sub 2/S/sub 2/CH/sub 2/ (I, Cp = C/sub 5/H/sub 4/CH/sub 3/) with methyl iodide or methyl fluorosulfate leads to the formation of the cationic dimer ((CpMo)/sub 2/(..mu..-S)(..mu..-SCH/sub 3/)S/sub 2/CH/sub 2/)/sup +/ (II). The bisulfate salt of II has been characterized by an X-ray diffraction study which confirms that a bridging sulfido ligand in I is the site of electrophilic attack. The salt crystallizes in space group P2/sub 1//n with a = 10.155 (2) A, b = 17.478 (9) A, c = 22.201 (7) A, ..beta.. = 97.89 (2)/sup 0/, and V = 3903 (2) A/sup 3/. The electrochemical characteristics of II are compared to those of related molybdenum dimers. II undergoes two reversible one-electron reductions in acetonitrile at -0.34 and -1.24 V vs. SCE to form a neutral mixed valence Mo(III)/Mo(IV) dimer, V, and an anionic Mo(III)/Mo(III) derivative, VII, respectively. The reactivity of each member of this redox series has been characterized. The bridging sulfido ligand in II reacts readily with carbanions and alkyl-substituted borohydride reagents. In contrast, the sulfido ligand in VII is strongly nucleophilic. For example, VII reacts with acetylene to form, upon protonation, the ethenyl thiolate bridged derivative (CpMo)/sub 2/(..mu..-SC/sub 2/H/sub 3/)(..mu..-SCH/sub 3/)S/sub 2/CH/sub 2/more » (IV). The reactivity of the unsaturated ligand in IV toward further reduction has been investigated. 38 references, 3 figures, 3 tables.« less