H2S Generation from CS2 Hydrolysis at a Dinuclear Zinc(II) Site

The controlled generation of hydrogen sulfide (H2S) under biologically relevant conditions is of paramount importance due to therapeutic interests. Via exploring the reactivity of a structurally characterized phenolate-bridged dinuclear zinc(II)-aqua complex {LZnII(OH2)}(2)(ClO4)(2) (1a) as a hydrolase model, we illustrate in this report that complex 1a readily hydrolyses CS2 in the presence of Et3N to afford H2S. In contrast, penta-coordinated [Zn-II] sites in dinuclear {(LZnII)(2)(mu-X)}(ClO4) complexes (7, X = OAc; 8, X = dimethylpyrazolyl) do not mediate CS2 hydrolysis in the presence of externally added water and Et3N presumably due to the unavailability of a coordination site for water at the [Zn-II] centers. Moreover, [Zn-II]-OH sites present in the isolated tetranuclear zinc(II) complex {(LZnII)(2)(mu-OH)}(2)(ClO4)(2) (4) react with CS2, thereby suggesting that the [Zn-II]-OH site serves as the active nucleophile. Furthermore, mass spectrometric analyses on the reaction mixture consisting of 1a/Et3N and CS2 suggest the involvement of zinc(II)-thiocarbonate (3a) and COS species, thereby providing mechanistic insights into CS2 hydrolysis mediated by the dinuclear [Zn-II] hydrolase model complex 1a.