Studies on the relative stabilities of Mn(II) and Mn(III) in complexes with N 4O 2 donor environments: crystal structures of [Mn(pybzhz) 2] and [Mn(Ophsal)(imzH) 2] ClO 4 (pybzhz = N-(benzoyl)- N′-(picolinylidene) hydrazine, Ophsal = N,N′- o-phenylenebis(salicylideneimine), imzH = imidazole)

Abstract

Manganese(II) complexes of four aroyl hydrazone ligands were prepared and characterized by different physicochemical techniques. The complexes are of the type Mn(L) 2, where L stands for the deprotonated hydrazone ligand. One of the compounds, Mn(pybzhz) 2, was also characterized by single crystal structure determination. In all these complexes, the Mn(II) is in an N 4O 2 donor environment and the Mn(II) center cannot be oxidized either chemically or electrochemically. However, when another ligand Ophsal is used to give the compound [Mn(Ophsal)(imzH) 2]ClO 4, which was also characterized by X-ray crystal structure determination, manganese can easily avail the +3 oxidation state. The relative stabilities of the +2 and +3 oxidation states of manganese were analyzed and it was concluded that the extent of distortion from the perfect octahedral geometry is the main controlling factor in these cases.