4-(hydroxymethyl)pyridine and pyrimidine in manganese benzoate chemistry: Preparation and characterization of hexanuclear clusters featuring the {(Mn4Mn2III)-Mn-II(mu(4)-O)(2)}(10+) core

摘要

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) center dot 2H(2)O 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 Mn-4 tetrahedra at the center of each of which is a mu(4)-O2- ion. Peripheral ligation to the octahedrally coordinated Mn centres is provided by 10 bridging PhCO2- ligands, three N-monodentate ligands and one terminal MeCN group. The complex is mixed-valence ((Mn4Mn2III)-Mn-II) and the Mn-III 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 S-T = 0 ground state is explained in terms of the strong antiferromagnetic coupling within the central (Mn2O2)-O-III unit. (C) 2005 Elsevier Ltd. All rights reserved.