Synthesis and characterization of a series of halide-bridged, multinuclear iron(II) and cobalt(II) diamido complexes and a dinuclear, high-spin cobalt(II) alkyl derivative.

The synthesis and structural characterization of four multinuclear, halide-bridged iron(ii) and cobalt(ii) diamidosilylether complexes of the form{Fe(2)Br(2)[(tBu)NON]}(2) (1), {Co(2)Br(2)[(tBu)NON]}(2) (2), {Fe(2)Cl(2)[(tBu)NON]}(n) (3) and {Co(2)Cl(2)(tBu)NON·2THF}(2) (4) ((tBu)NON = Me(3)CN(SiMe(2))O(2-)) are reported. Thus, reaction of one equivalent of Li(2)[(tBu)NON] with two equivalents of MX(2) (X = Cl or Br; M = Co or Fe) form 1-4, which structurally contain one diamido ligand bridging two metal centres. Each amido group interacts with both metal centres to yield binuclear M(2)X(2)[(tBu)NON] units which dimerize via bromide bridges to form tetranuclear {Fe(2)Br(2)[(tBu)NON]}(2) (1) and {Co(2)Br(2)[(tBu)NON]}(2) (2) or form an infinite 1D chain of chloride-bridged dinuclear clusters {Fe(2)Cl(2)[(tBu)NON]}(n) (3). Replacing bromide for chloride in 2 results in a tetranuclear "ate" complex {Co(2)Cl(2)(tBu)NON·2THF}(2) (4) in which the tetranuclear core is capped with one LiCl and two THF molecules on each side. The reaction of four equivalents of LiCH(2)SiMe(3) with 4 generated the high-spin cobalt(ii) alkyl complex {Co(2)(CH(2)SiMe(3))(2)[(tBu)NON]} (5), in which each amide in (tBu)NON bridges two Co(ii) centres, but the silylether donor only binds to one metal; each Co(ii) centre has a terminal -CH(2)SiMe(3) unit bonded as well. Variable temperature (1.8-300 K) magnetic susceptibility data for 1-5 showed significant antiferromagnetic coupling between metal centres.