Tetranuclear mixed-valence Co(II/III) and binuclear Ni(II) complexes incorporating hydroxyl-rich ligand: Syntheses, structures and magnetic properties

Three complexes of composition [(Co2Co2III)-Co-II(H(2)hbhpd)(2)(H(4)hbhpd)(2)(H2O)(2)]Cl-2(CH3OH)(4) (1), [(Co2Co2III)-Co-II (H(2)hbhpd)(2)(H(4)hbhpd)(2)(H2O)(2)](NO3)(2)(CH3OH)(4) (2) and [Ni-2(H(4)hbhpd)(2)(NO3)](NO3)(CH3OH)(1.5) (3) (H(5)hbhpd = 2-(2-hydroxy-benzylamino)-2-hydroxymethyl-propane-1,3-diol) have been synthesized and their structures have been characterized. Complexes 1 and 2 are mixed-valence cobalt clusters and display face-sharing monovacant dicubane structures. In the complexes 1 and 2, one of the three alkyl hydroxyl groups of H(5)hbhpd ligand is deprotonated instead of deprotonation of phenyl hydroxyl group; thus monoanionic H(4)hbhpd ligand displays novel eta(3), eta(1), eta(1), mu(3) coordination mode. Complex 3 is binuclear, and the two metal centers of 3 are bridged by two deprotonated phenyl hydroxyl oxygen atoms and iso-orthogonalized by a nitrato group in eta(1)eta(1)-O,O' coordination fashion. Variable-temperature solid-state dc magnetization studies have been performed in the temperature range 2-300 K for compounds 1 and 3. Antiferromagnetic interactions were determined for 1 and ferromagnetic couplings were found for 3. (C) 2010 Elsevier B.V. All rights reserved.