Crystal structure and magnetic behavior of two new dinuclear carbonate-bridged copper(II) compounds. Superexchange pathway for the different coordination modes of the carbonate bridge in polynuclear copper(II) compounds

Four new mu-CO32- copper(II) complexes with different coordination modes for the carbonate bridge have been obtained by fixation of atmospheric CO2: {(mu(3)-CO3)[Cu-3(ClO4)(3)(Et(3)dien)(3)]}(ClO4) (1), Et(3)dien = N,N',N "-triethylbis(2-aminoethane)amine; {(mu-CO3)[Cu-2(H2O)(Et(4)dien)(2)]}(ClO4)(2). H2O (2), Et(4)dien = N,N,N ",N "-tetraethylbis(2-aminoethane)amine; {(mu-CO3)[Cu-2(H2O)(2)(EtMe(4)dien)(2)]} (ClO4)(2). 2H(2)O (3), EtMe(4)dien = N'-ethyl-N,N,N ",N "-tetramethylbis(2-aminoethane)amine; and {(mu-CO3)[Cu-2(H2O)(Me(5)dien)(2)]}(ClO4)(2). H2O (4), Me(5)dien = N,N,N',N ",N "-pentamethylbis(2-aminoethane)amine. The crystal structures have been solved for 2, monoclinic system, space group P2(1)/n, formula [C25H62Cl2Cu2N6O13] With a = 12.763(6) Angstrom, b = 25.125(8) Angstrom, c = 13.261(4) Angstrom, beta = 111.85(3)degrees Z = 4, and for 3, triclinic system, space group P (1) over bar, formula [C21H58Cl2Cu2N6O15] With a 8.412(3) Angstrom, b = 14.667(4) Angstrom, 16.555(5) Angstrom, alpha = 99.66(2)degrees, beta = 102.14(2)degrees, gamma = 104.72(2)degrees, Z = 2. Susceptibility measurements show ferromagnetic behavior (J = +6.7(6) cm(-1)) for the trinuclear compound 1 whereas 2-4 are antiferromagnetically coupled with J = -17.8(8), -125.5(9), and -21.2(3) cm(-1) respectively. Certain synthetic aspects that may be related to the nuclearity of the copper(II) mu-CO32- compounds and the superexchange pathway for the different coordination modes of the carbonate bridge are discussed.