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

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)2Cu(dcdmp)2 crystallises in the triclinic system, space group P1¯, Z = 1, with unit cell parameters a = 9.9512(6) Å, b = 10.541(1) Å, c = 13.221(1) Å, α = 69.756(9)°, β = 88.112(6)° and γ = 79.658(7)°. 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 μB/f.u. n-Bu4NCu(dcdmp)2 crystallises in the monoclinic space group C2/c, Z = 8, with unit cell parameters a = 35.281(4) Å, b =  9.501(1) Å, c =  21.885(2) Å and β = 109.842(9)°, 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) Å, b = 10.5133(7) Å, c = 30.264(3) Å and β = 91.105(2)°. Its crystal structure consists of out-of-registry columns, parallel to b, of alternated dianions and side-by-side pairs of cations, … A2−(D+D+)A2−(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*)2cations.

Cu(dcdmp)2 was obtained in both dianionic and monoanionic states. The [Fe(Cp*)2]2[Cu(dcdmp)2] salt presents paramagnetic contributions from both cations and dianions with a large anisotropy and no magnetic ordering down to 1.7 K.Figure optionsDownload as PowerPoint slide