Cobalt(II) aldoxime complexes stabilised by halide hydrogen bonding: crystal structures of [Co{HONC(H)(Me)}4X2] (X = Cl or Br) and [Co{HONC(H)(Pr)}4Cl2]

Abstract

Starting from the metal halide hydrates and the simple monoximes butyraldoxime (bax) and acetaldoxime (aax), under dehydrating conditions by the use of trimethyl orthoformate, complexes of general formula [Co(L)₄X₂] (L = aax or bax; X = Cl or Br) and [Mn(bax)₄Cl₂] have been obtained. Complexes [Co(bax)₄Cl₂], [Co(aax)₄Cl₂] and [Co(aax)₄Br₂] have been structurally characterised using single crystal X-ray diffraction. All three contain mononuclear octahedral cobalt ions which are stabilised by intramolecular hydrogen-bonding interactions. Strong intermolecular hydrogen-bonding interactions are present only in [Co(aax)₄Cl₂]. Spectroscopic studies indicate that the manganese aax and bax complexes obtained are similar to the cobalt analogues. The manganese compounds, however, are much less stable thereby thwarting the isolation of crystals for structure determination. The isolated coordination complexes are all highly reactive towards atmospheric water and readily decompose to yield the metal hydrates.

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