Synthesis and characterization of copper complexes with the 2,3-dicyano-5,6-dimercaptopyrazine ligand: Magnetic properties of a ferrocenium salt

摘要

Copper complexes with the 2,3-dicyano-5,6-dimercaptopyrazine ligand (dcdmp), Cu(dcdmp)(2), were obtained in both monoanionic and dianionic forms as the tetrabutylammonium salts and were characterised, as well as a decamethylferrocenium salt of the dianion. (n-Bu4N)(2)Cu(dcdmp)(2) crystallises in the triclinic system, space group P1, Z = 1, with unit cell parameters a = 9.9512(6) angstrom, b = 10.541 (1) angstrom, c = 13.221 (1) angstrom, alpha = 69.756(9)degrees, beta = 88.112(6)degrees and gamma = 79.658(7)degrees. Its crystal structure consists of layers of well isolated square planar Cu(dcdmp)(2)(-) anions alternating with layers of n-Bu4N+ cations along b + c, and the magnetic properties in the range 2-300 K are close to those of an ideal paramagnet with an effective magnetic moment of 1.7 mu B/f.u. n-Bu4NCu(dcdmp)(2) crystallises in the monoclinic space group C2/c, Z = 8, with unit cell parameters a = 35.281(4) angstrom, b = 9.501 (1) angstrom, c = 21.885(2) angstrom and beta = 109.842(9)degrees, being isostructural with the Au analogue previously described. The salt [Fe(Cp*)(2)](2)-[Cu(dcdmp)(2)] crystallises in the monoclinic system, space group C2/c, Z = 4, with unit cell parameters a = 15.891 (1) angstrom, b = 10.5133(7) angstrom, c = 30.264(3) angstrom and beta = 91.105(2)degrees. Its crystal structure consists of out-of-registry columns, parallel to b, of alternated dianions and side-by-side pairs of cations, ... A(2-)(D+D+)A (2-)(D+D+)... This compound behaves as a paramagnet with weak AF interactions and no ordering down to 1.7 K. The magnetic properties, due to both cation and anion S = 1/2 contributions, show a large anisotropy, ascribed essentially to the g-factor anisotropy of the Fe(Cp*)(2) cations. (c) 2005 Elsevier Ltd. All rights reserved.