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

Heteroleptic zinc and cadmium complexes of the type [{Me2N^E^OR2}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^OR2}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.