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 [MnII3L6]. 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 = 1/2) 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.