4-(Hydroxymethyl)pyridine and pyrimidine in manganese benzoate chemistry: Preparation and characterization of hexanuclear clusters featuring the { Mn4II Mn2III ( μ4 - O )2 }10 + core

Abstract

The use of 4-(hydroxymethyl)pyridine (4hmpH) and pyrimidine (pym) in manganese benzoate chemistry has been investigated. The reactions of 4hmpH and pym with Mn(O2CPh)2 · 2H2O in MeCN affords the complexes [Mn6O2(O2CPh)10(4hmpH) 3 (MeCN)] (1) and [Mn6O2(O2CPh)10(pym) 2(MeCN)2] (2), respectively. Complex 1 contains a {Mn6O2}10+ core that can be conveniently described as two edge-sharing Mn4 tetrahedra at the center of each of which is a μ4-O2- ion. Peripheral ligation to the octahedrally coordinated Mn centres is provided by 10 bridging multiscripts(PhCO, 2, mml:none(), mml:none(), -) ligands, three N-monodentate ligands and one terminal MeCN group. The complex is mixed-valence ( Mn4II Mn2III ) and the MnIII ions are assigned as the two central metal centres bridged by two O2- ions. The molecular structure of 2 is very similar to that of 1, except that the terminal ligands are two monodentate pym molecules and two MeCN groups. IR data are discussed in terms of the nature of bonding and the known structures. Complexes 1 and 2 were characterized by variable-temperature ac and dc magnetic susceptibility data and found to possess a total spin ground state of 0. The ST = 0 ground state is explained in terms of the strong antiferromagnetic coupling within the central Mn2III O2 unit. © 2005 Elsevier Ltd. All rights reserved.