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

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)(4)X(2)] (L = aax or bax; X = Cl or Br) and [Mn(bax)(4)Cl(2)] have been obtained. Complexes [Co(bax)(4)Cl(2)], [Co(aax)(4)Cl(2)] and [Co(aax)(4)Br(2)] 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)(4)Cl(2)]. 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.