Cadmium complexes bearing Me2N^E^O− (E = S, Se) organochalcogenoalkoxides and their zinc and mercury analogues

Abstract

Heteroleptic zinc and cadmium complexes of the type [{^Me₂N^E^O^R₂}M-Nu]_n (M = Zn, Cd; E = S, Se; R = CH₃, CF₃; Nu = N(SiMe₃)₂, I, Cl; n = 1–2) were prepared by reacting the alcohol proteo-ligands {^Me₂N^E^O^R₂}H with [M(N(SiMe₃)₂)₂] (M = Zn, Cd) or [XMN(SiMe₃)₂] (M = Zn, X = Cl; M = Cd, X = I) in an equimolar ratio. These group 12 metal complexes were characterised in solution by multinuclear NMR spectroscopy and their solid-state structures were determined by X-ray diffractometry. The ligands {^Me₂N^E^O^(CH₃)₂}⁻ bearing CH₃ groups in α position to the alkoxide behave as κ²-O,E-bidentate moieties (E = S, Se) and form centro-symmetric dinuclear O-bridged heteroleptic alkoxo–amido complexes both with zinc and cadmium, with four-coordinate metal centres resting in tetrahedral environments. By contrast, complexes supported by the CF₃-substituted {^Me₂N^E^O^(CF₃)₂}⁻ crystallise as tetrahedral mononuclear species, with tridentate κ³-N,O,E-coordinated ligands. These structural differences resulting from changes in the ligand skeleton and in the electron-donating properties of the alkoxide were also observed in solution. Attempts to prepare congeneric heteroleptic mercury complexes from [Hg(N(SiMe₃)₂)₂] unexpectedly only afforded homoleptic bis(alkoxide)s such as [{^Me₂N^S^O^(CF₃)₂}₂Hg]. Owing to the strong Hg–C bond, treatment of [PhHgN(SiMe₃)₂] with {^Me₂N^S^O^(CF₃)₂}H afforded the heteroleptic, T-shaped [{^Me₂N^S^O^(CF₃)₂}HgPh] mercuric alkoxide upon elimination of hexamethyldisilazane. [{^Me₂N^S^O^(CF₃)₂}₂Hg] and [{^Me₂N^S^O^(CF₃)₂}HgPh] constitute very rare examples of structurally characterised mercuric alkoxides.