Antiferromagnetically and ferromagnetically coupled nickel(II) dimers with and without interdimer coupling. Solvent effects in the preparation of nickel(II) dimers

Article abstract of DOI:10.1021/ic50224a066

The structural and magnetic properties are reported for a group of chemically similar nickel(II) dimers with salicylaldimine ligands. Three general categories of compounds may be prepared for a variety of bidentate Schiff base (sb) nickel(II) complexes that have the same general formula [Ni(sb)(NO₃)L]₂ and differ only in structural details and the type of Lewis acid solvent molecule (L) that is present during crystallization. Antiferromagnetic interactions are observed when the central Ni₂O₂ bridging group is approximately coplanar with the principal sb ligand plane. Ferromagnetic interactions are observed when these planes are approximately orthogonal. When L = C₂H₅OH, hydrogen bonding between L and the NO₃ groups of neighboring molecules forms an antiferromagnetic pathway along infinite chains of ferromagnetic dimers. The three categories are represented by the following complexes. [Ni(ps)(NO₃)(2-pic)]₂·CH₂Cl₂ (ps = phenylsalicylaldimine): crystal data space group P1, Z = 1, a = 9.424 (2) A?, b = 11.327 (3) A?, c = 11.468 (3) A?, α = 117.96 (2)°, β = 90.29 (3)°, γ = 91.62 (2)°, V = 1081 A?³, R = 4.5% for 2342 reflections; magnetic data g = 2.12, J = 8.7 cm^-1, D ≈ 13 cm^-1 (zJ′ = 0.07). [Ni₂(ips)₂(NO₃)₂(EtOH) ₂]_∞ (ips = isopropylsalicylaldimine): crystal data space group P1, Z = 1, a = 9.161 (5) A?, b = 9.183 (2) A?, c= 13.353 (7) A?, α = 128.25 (3)°, β = 93.72 (4)°, γ = 110.44 (3)°, V = 764 A?³, R = 3.1% for 1851 reflections; magnetic data g = 2.15, J = 16.0 cm^-1, D ≈ 15 cm^-1 (zJ′, = 0.14). [Ni(ips)(NO₃)DMF]₂: crystal data space group P1, Z = 1, a = 9.506 (2) A?, b = 10.095 (4) A?, c = 10.588 (3) A?, α = 94.80 (2)°, β = 126.59 (2)°, γ = 92.70 (2)°, V = 807 A?³, R = 5.5% for 2039 reflections; magnetic data g = 2.32, J = -9.2 cm^-1, D ≈ 12 cm^-1. The magnetic behavior is correlated with differences in exchange pathways as obtained from the crystal structures. Although it is demonstrated that D and zJ′ cannot be estimated accurately from the magnetic data, the values of the intradimer interaction, J, are reliable.