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

摘要

The synthesis and structural characterization of four multinuclear, halide-bridged iron(ii) and cobalt(ii) diamidosilylether complexes of the form{Fe_2Br_2[~(tBu)NON]}_2 (1), {Co _2Br_2[~(tBu)NON]}_2 (2), {Fe _2Cl_2[~(tBu)NON]}_n (3) and {Co _2Cl_2[~(tBu)NON](LiCl)·2THF}_2 (4) ([~(tBu)NON]~(2-) = [Me_3CN(SiMe_2)] _2O~(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_2X_2[~(tBu)NON] units which dimerize via bromide bridges to form tetranuclear {Fe_2Br _2[~(tBu)NON]}_2 (1) and {Co_2Br _2[~(tBu)NON]}_2 (2) or form an infinite 1D chain of chloride-bridged dinuclear clusters {Fe_2Cl_2[ ~(tBu)NON]}_n (3). Replacing bromide for chloride in 2 results in a tetranuclear "ate" complex {Co_2Cl_2[ ~(tBu)NON](LiCl)·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_2SiMe_3 with 4 generated the high-spin cobalt(ii) alkyl complex {Co_2(CH_2SiMe _3)_2[~(tBu)NON]} (5), in which each amide in [ ~(tBu)NON]~(2-) bridges two Co(ii) centres, but the silylether donor only binds to one metal; each Co(ii) centre has a terminal -CH _2SiMe_3 unit bonded as well. Variable temperature (1.8-300 K) magnetic susceptibility data for 1-5 showed significant antiferromagnetic coupling between metal centres.