Development of five-coordinate zinc mono- and dithiolates as S-donor metalloligands: formation of a Zn-W coordination polymer.
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abstract
The synthesis and isolation of mono- and dithiolate-bridged Zn(mu-SR)(n)W(CO)(m) (where n = 1, m = 5; n = 2, m = 4) species from the dimeric N,N'-bis(2-mercaptoethyl)-1,4-diazacycloheptanezinc(II), [Zn-1'](2), and the monomeric [N-(3-thiabutyl)-N'-(3-thiapentaneoate)-1,5-diazacycloheptane]zinc(II), Zn-1'-Ac, are described. Upon cleavage of the dimeric [Zn-1'](2) with Na(+)[ICH(2)CO(2)](-), the resulting Zn-1'-Ac product is isolated as a monomeric, five-coordinate Zn(N(2)SS'O) complex equipped with one available Zn-bound thiolate for further reactivity. Cleavage of [Zn-1'](2) with [Et(4)N](+)Cl(-) afforded a monomeric intermediate, [Zn-1'-Cl](-), containing two Zn-bound thiolates. The zinc mono- and dithiolato complexes demonstrated reactivity toward labile-ligand tungsten carbonyl species, (THF)W(CO)(5) and (pip)(2)W(CO)(4), to yield respectively [(Zn-1'-Ac)W(CO)(5)](x) and [(Zn-1'-Cl)W(CO)(4)](-) complexes that were isolated and characterized spectroscopically and via X-ray diffraction. Upon binding to W(CO)(5), the five-coordinate Zn(N(2)SS'O) complex becomes six-coordinate within the coordination polymer [(Zn-1'-Ac)W(CO)(5)](x), in which the acetate tether of each molecule provides an O donor to occupy the octahedral axial position of a neighboring moiety. The [(Zn-1'-Cl)W(CO)(4)](-) dithiolate-bridged complex maintains a five-coordinate, square-pyramidal [Zn(N(2)S(2)Cl)](-) center, utilizing a chloride as the apical donor and resulting in an overall anionic complex. The addition of CO(g) to the [(Zn-1'-Cl)W(CO)(4)](-) complex was monitored by IR spectroscopy, which showed the emergence of [(Zn-1'-Cl)W(CO)(5)](-).
