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

A new binuclear Zn(II) complex, [Zn₂(PhBIMP)(DMF)₂]³⁺ (1) (where PhBIMP¹ 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, [Zn₂(PhBIMP)(μ-SH)(DMF)]²⁺ (2), which has been thoroughly characterized in comparison with the corresponding chloride complex, [Zn₂(PhBIMP)(Cl)(DMF)]²⁺ (3), as a control. The binuclear Zn(II)-thiolate complexes [Zn₂(PhBIMP)(μ-SR)]²⁺ (R = Ph, 4a; 3-Br-C₆H₄, 4b) have also 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 [Zn₂(PhBIMP)(μ-SR)(OH)]¹⁺ has been proposed to be the active intermediate that precedes the C-S bond cleavage of thiolates. The complex [Zn₂(PhBIMP)(μ-SCOPh)(DMF)]²⁺ (5) also demonstrates the hydrolysis of the coordinated thiobenzoate to produce [Zn₂(PhBIMP)(μ-O₂CPh)(MeCN)]²⁺ (6). However, unlike 4a and 5, the benzeneselenolate-bridged complex, [Zn₂(PhBIMP)(μ-SePh)]²⁺ (7), does not generate the species, [Zn₂(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.