Crystal Structure of a Mixed-valent Hexanuclear Manganese Complex Made-up from Two Oxido-centered Triangular MnIIMnIII2 Cores

Abstract

A hexanuclear Mn II2 Mn III4 complex with 2-(5-nitro-2-hydroxyphenyl)-1,3-bis(2-(5-nitro-2-hydroxybenzylideneamino)-ethyl)imidazolidine (H 3 L NO2 ) and its hydrolyzed ligand, 1,10-bis(5-nitrosalicylideneamino)-4,7-azadecane (H 2 L NO2 ′ ), was isolated. The crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. The complex crystallized as [{Mn 3 ( μ 3 -O)( μ -CH 3 COO) 2 ( μ -L NO2 )} 2 (L NO2 ′ )]·2.5THF·CH 3 OH in the monoclinic space group C 2/ c with a = 21.253(3), b = 16.630(2), c = 29.508(4)Å, β = 93.147(2) ° , V = 10413(2)Å 3 , D calcd = 1.551 g/cm 3 , Z = 4. The R 1 [ I > 2 σ ( I )] and wR 2 (all data) values are 0.0836 and 0.2500, respectively, for all 11924 independent reflections. The complex is a hexanuclear manganese molecule which has a crystallographic inversion center at the midpoint of the ethylenediamine backbone of L NO2 ′ 2– ligand. In the asymmetric unit, three manganese atoms (Mn1, Mn2, and Mn3) are arranged in a μ 3 -oxido-centered triangle, and the Mn1 and Mn2 atoms are further bridged by a phenolato-oxygen atom of L NO23– , and both of the Mn1 and Mn3 atoms and the Mn2 and Mn3 atoms are further bridged by an acetato ligand in a syn - syn mode. The charge balance and a bond valence sum calculation supported the mixed-valent Mn II2 Mn III4 state with the Mn II state for the Mn1 atom and the Mn III state for the Mn2 and Mn3 atoms, respectively.