Portal de Periódicos da CAPES

Coordination Modes of the 1,3-Dithiosquarate (1,3-dtsq) Ligand. Syntheses, Crystal Structures, and Magnetic Properties of [Ni(tren)(1,3-dtsq)(H 2 O)] and [Ni 2 (tren) 2 (1,3-dtsq)](ClO 4 ) 2 [tren = Tris(2-aminoethyl)amine]

1996; American Chemical Society; Volume: 35; Issue: 10 Linguagem: Inglês

10.1021/ic951393j

1520-510X

M. Luisa Calatayud, Isabel Castro, Jorunn Sletten, Joan Cano, Francesc Lloret, Juan Faus, Miguel Julve, G. SEITZ, Klaus Mann,

Metal complexes synthesis and properties

The first X-ray crystallographic stucture determinations of metal complexes of the 1,3-dithiosquarate (1,3-dtsq, dianion of 3-hydroxy-4-mercapto-2-thioxo-3-cyclobuten-1-one) are reported herein. Compounds [Ni(tren)(1,3-dtsq)(H2O)] (C10H20N4NiO3S) (1) and [Ni2(tren)2(1,3-dtsq)](ClO4)2 (C16H36Cl2N8Ni2O10S2) (2) (where tren is tris(2-aminoethyl)amine) both crystallize in the monoclinic system, space group P21/c, with a = 8.519(1) Å, b = 13.931(1) Å, c = 13.587(3) Å, β = 106.705(8)°, and Z = 4 for 1 and a = 8.663(1) Å, b = 14.496(2) Å, c = 11.617(2) Å, β = 98.135(9)°, and Z = 2 for 2. The structure of 1 consists of mononuclear, neutral [Ni(tren)(1,3-dtsq)(H2O)] complex units, whereas that of 2 is made up of dinuclear dithiosquarate-bridged cations, [Ni2(tren)2(1,3-dtsq)]2+, and uncoordinated perchlorate anions. The nickel environment is distorted octahedral in both cases, the tren group acting as a tetradentate ligand through its four nitrogen atoms and the dithiosquarate being monodentately coordinated through one of the sulfur atoms in 1 and bridging bis-bidentate in 2. A water molecule which is hydrogen bonded to the neighboring carbonyl-oxygen atom of the dithiosquarate completes the octahedron around the metal atom in 1. The intradimer metal−metal separation in 2 is 7.096(1) Å. Variable-temperature magnetic susceptibility measurements of complex 2 reveal the occurrence of a weak intramolecular antiferromagnetic coupling. The ability of the 1,3-dithiosquarate ligand to transmit electronic effects between metal ions has been analyzed through extended Hückel calculations. The theoretical influence of the position (1,2-dithiosquarate versus 1,3-dithiosquarate) and the number of sulfur (1,2,3,4-tetrathiosquarate) atoms on the exchange coupling through bis-bidentate thiosquarates is also considered.