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

Article abstract of DOI:10.1021/om00120a020

Reaction of (CpMo-μ-S)₂S₂CH₂ (I, Cp = C₅H₄CH₃) with methyl iodide or methyl fluorosulfate leads to the formation of the cationic dimer [(CpMo)₂(μ-S)(μ-SCH₃)S₂CH ₂]⁺ (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 P2₁/n with a = 10.155 (2) A?, b = 17.478 (9) A?, c = 22.201 (7) A?, β = 97.89 (2)°, and V = 3903 (2) A?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)₂(μ-SC₂H₃)(μ-SCH₃)S ₂CH₂ (IV). The reactivity of the unsaturated ligand in IV toward further reduction has been investigated.