Structural and spectroscopic characterisation of bis-ligand complexes of iron(II), nickel(II) and nickel(III) with the hydrotris(methimazolyl)borate anion: soft S6 donor sets generating a weak ligand field

Reaction of iron(II) and nickel(II) halides with sodium hydrotris(methimazolyl)borate (NaTm) results in the formation of 2 1 complexes [M(Tm)2]. Crystallographic characterisation reveals in both cases trigonally distorted octahedral geometry in an S6 donor set. Spectroscopic properties indicate that the Tm ligand generates a weak ligand field, with Dq between that of H2O and Cl– and this is confirmed by the high-spin configuration of the iron(II) complex. Both complexes display classical paramagnetic behaviour. Mossbauer spectroscopy of the iron complex is also consistent with a high-spin complex. Reaction of NiCl2·6H2O with [Tl (Tm)] results in a small quantity of a material which is crystallographically demonstrated to be [Ni(Tm)2]Br.