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

Abstract

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. Mössbauer 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.