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Structural and magnetic studies of Schiff base complexes of nickel(II) nitrite: change in crystalline state, ligand rearrangement and a very rare μ-nitrito-1κO:2κN:3κO' bridging mode.

Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata-700 009, India.
Dalton Transactions (Impact Factor: 4.1). 02/2011; 40(12):2744-56. DOI: 10.1039/c0dt00978d
Source: PubMed

ABSTRACT Four new nickel(II) complexes, [Ni(2)L(2)(NO(2))(2)]·CH(2)Cl(2)·C(2)H(5)OH, 2H(2)O (1), [Ni(2)L(2)(DMF)(2)(μ-NO(2))]ClO(4)·DMF (2a), [Ni(2)L(2)(DMF)(2)(μ-NO(2))]ClO(4) (2b) and [Ni(3)L'(2)(μ(3)-NO(2))(2)(CH(2)Cl(2))](n)·1.5H(2)O (3) where HL = 2-[(3-amino-propylimino)-methyl]-phenol, H(2)L(') = 2-({3-[(2-hydroxy-benzylidene)-amino]-propylimino}-methyl)-phenol and DMF = N,N-dimethylformamide, have been synthesized starting with the precursor complex [NiL(2)]·2H(2)O, nickel(ii) perchlorate and sodium nitrite and characterized structurally and magnetically. The structural analyses reveal that in all the complexes, Ni(II) ions possess a distorted octahedral geometry. Complex 1 is a dinuclear di-μ(2)-phenoxo bridged species in which nitrite ion acts as chelating co-ligand. Complexes 2a and 2b also consist of dinuclear entities, but in these two compounds a cis-(μ-nitrito-1κO:2κN) bridge is present in addition to the di-μ(2)-phenoxo bridge. The molecular structures of 2a and 2b are equivalent; they differ only in that 2a contains an additional solvated DMF molecule. Complex 3 is formed by ligand rearrangement and is a one-dimensional polymer in which double phenoxo as well as μ-nitrito-1κO:2κN bridged trinuclear units are linked through a very rare μ(3)-nitrito-1κO:2κN:3κO' bridge. Analysis of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the nickel(ii) ions in four complexes, with exchange parameters J of -5.26, -11.45, -10.66 and -5.99 cm(-1) for 1, 2a, 2b and 3, respectively.

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