Synthesis and structure of a trinuclear manganese(II) complex containing low-spin metal

Abstract

The reaction of α-phenylazobenzaldehyde oxime, HL, with manganese(II) salts has afforded the first known mixed-spin trinuclear complex [Mn^II₃L₆]. The structure of the benzene solvate [Mn₃L₆]·2C₆H₆ has been determined by X-ray crystallography. The Mn₃ fragment is exactly linear with the terminal low-spin (S=½) metal(II) atoms tris-chelated by azo- and oxime-nitrogen functions into facial pseudo-octahedral MnN₆ dispositions. Two such [MnL₃]^– moieties sequester the central high-spin (S=5//₂) manganese(II) atom into an O₆ environment using oximato oxygen donors. The average Mn ⋯ Mn, Mn–N, and Mn–O distances are 3.577(7), 1.956(18), and 2.146(15)Å respectively. It is proposed that oximato nitrogen co-ordination is primarily responsible for the low-spin configuration of the terminal manganese(II) atoms.