Hydrolysis and Transfer Reactivity of the Coordinated Thiolate, Thiocarboxylate, and Selenolate in Binuclear Zinc(II) Complexes

A new binuclear Zn(II) complex, [Zn-2(PhBIMP)(DMF)(2)](3+) (1) (where PhBIMP1 isthe anion of 2,6-bis[bis[(N-1-methyl-4,5-diphenylimidazoylmethyl)amino]methyl]-4-methylphenol),has been shown for the first time to mediate the hydrolytic C-Sbond cleavage of a series of aliphatic and aromatic thiolates to yieldthe corresponding alcohols/phenols along with the formation of a hydrosulfide-bridgedcomplex, [Zn-2(PhBIMP)(& mu;-SH)(DMF)](2+) (2), which has been thoroughly characterized in comparisonwith the corresponding chloride complex, [Zn-2(PhBIMP)(Cl)(DMF)](2+) (3), as a control. The binuclear Zn(II)-thiolatecomplexes [Zn-2(PhBIMP)(& mu;-SR)](2+) (R = Ph, 4a; 3-Br-C6H4, 4b) havealso been synthesized by avoiding the C-S bond cleavage reaction.Based on the experimental results for the effects of H2O and Et3N on 1, 4a, and 4b, the complex [Zn-2(PhBIMP)(& mu;-SR)(OH)](1+) has been proposed to be the active intermediate that precedesthe C-S bond cleavage of thiolates. The complex [Zn-2(PhBIMP)(& mu;-SCOPh)(DMF)](2+) (5) alsodemonstrates the hydrolysis of the coordinated thiobenzoate to produce[Zn-2(PhBIMP)(& mu;-O2CPh)(MeCN)](2+) (6). However, unlike 4a and 5, the benzeneselenolate-bridged complex, [Zn-2(PhBIMP)(& mu;-SePh)](2+) (7), does not generate the species, [Zn-2(PhBIMP)(& mu;-SePh)(OH)](1+), in solution, andin line with that, the coordinated benzeneselenolate in 7 does not undergo hydrolysis to generate hydroselenide and phenol.Finally, a comparative study for the transfer reactivity of the bridging-SH, -SPh, -SC(O)Ph, and -SePh ligandsin 2, 4a, 5, and 7, respectively, toward selected organic substrates has been performedto reveal the distinct differences in the reactivity of these bridgingligands. A comparative study for the synthesisof binuclear Zn(II)complexes featuring thiolates, thiobenzoate, and selenolate, hydrolysisof the coordinated thiolate to generate hydrosulfide, identificationof the intermediate species, and transfer of the coordinated thiolate,selenolate, thiobenzoate, and hydrosulfide to selected organic compoundsis presented.