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 PhBIMP 1 is the 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-S bond cleavage of a series of aliphatic and aromatic thiolates to yield the corresponding alcohols/phenols along with the formation of a hydrosulfide-bridged complex, [Zn 2 (PhBIMP)(μ-SH)(DMF)] 2+ ( 2 ), which has been thoroughly characterized in comparison with the corresponding chloride complex, [Zn 2 (PhBIMP)(Cl)(DMF)] 2+ ( 3 ), as a control. The binuclear Zn(II)-thiolate complexes [Zn 2 (PhBIMP)(μ-SR)] 2+ (R = Ph, 4a ; 3-Br-C 6 H 4 , 4b ) have also been synthesized by avoiding the C-S bond cleavage reaction. Based on the experimental results for the effects of H 2 O and Et 3 N on 1 , 4a , and 4b , the complex [Zn 2 (PhBIMP)(μ-SR)(OH)] 1+ has been proposed to be the active intermediate that precedes the C-S bond cleavage of thiolates. The complex [Zn 2 (PhBIMP)(μ-SCOPh)(DMF)] 2+ ( 5 ) also demonstrates the hydrolysis of the coordinated thiobenzoate to produce [Zn 2 (PhBIMP)(μ-O 2 CPh)(MeCN)] 2+ ( 6 ). However, unlike 4a and 5 , the benzeneselenolate-bridged complex, [Zn 2 (PhBIMP)(μ-SePh)] 2+ ( 7 ), does not generate the species, [Zn 2 (PhBIMP)(μ-SePh)(OH)] 1+ , in solution, and in 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 ligands in 2 , 4a , 5 , and 7 , respectively, toward selected organic substrates has been performed to reveal the distinct differences in the reactivity of these bridging ligands.