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

Abstract

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 {<b>L</b>Zn^II(OH₂)}₂(ClO₄)₂ (<b>1a</b>) as a hydrolase model, we illustrate in this report that complex <b>1a</b> readily hydrolyses CS₂ in the presence of Et₃N to afford H₂S. In contrast, penta-coordinated [Zn^II] sites in dinuclear {(<b>L</b>Zn^II)₂(μ-X)}(ClO₄) complexes (<b>7</b>, X = OAc; <b>8</b>, 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 {(<b>L</b>Zn^II)₂(μ-OH)}₂(ClO₄)₂ (<b>4</b>) 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 <b>1a</b>/Et₃N and CS₂ suggest the involvement of zinc(II)-thiocarbonate (<b>3a</b>) and COS species, thereby providing mechanistic insights into CS₂ hydrolysis mediated by the dinuclear [Zn^II] hydrolase model complex <b>1a</b>.