Magneto−Structural Relationships in a Series of Dinuclear Oxalato-Bridged (Diphenyldipyrazolylmethane)copper(II) Complexes

A series of oxalato-bridged dinuclear copper(II) complexes of the general formula [Cu2(Pz2CPh2)2(X)2(μ-C2O4)]
(X = Cl- (1), NO3- (2), ClO4- (3); Pz2CPh2 = diphenyldipyrazolylmethane) or [Cu2(Pz3m2CPh2)2(H2O)2(μ-C2O4)](NO3)2·H2O (4) (Pz3m2CPh2 = diphenylbis(3-methylpyrazolyl)methane) was synthesized where the axial ligand was
systematically varied to study its effect on structure and magnetic coupling. The structures of compounds 1, 2, and
4 have been elucidated by single-crystal X-ray diffraction. [Cu2(Pz2CPh2)2(Cl)2(μ-C2O4)] and [Cu2(Pz2CPh2)2(NO3)2(μ-C2O4)] are isostructural and crystallize in the triclinic system, space group P1̄, Z = 2, with a = 8.6155(8) Å, b
= 10.1435(9) Å, c = 11.3612(11) Å, α = 95.535(2)°, β = 110.303(2)°, and γ = 106.111(2)° for 1 and with a
= 8.863(7) Å, b = 10.241(9) Å, c = 11.425(10) Å, α = 98.985(14)°, β = 110.449(13)°, and γ = 103.664(14)°
for 2. [Cu2(Pz3m2CPh2)2(H2O)2(μ-C2O4)]·NO3·H2O crystallizes in the monoclinic system, space group C2/c, Z = 4,
with a = 23.4588(14) Å, b = 8.8568(5) Å, c = 21.7818(13) Å, α = γ = 90°, and β = 100.8890(10)°. Variable-temperature magnetic susceptibility studies indicate that all four compounds are strongly antiferromagnetically coupled
(2J/k = −364, −344 cm-1 (2), −424 cm-1 (3), and −378 cm-1 (4)). Magnetic and EPR results are discussed with
respect to structural parameters to explore possible magneto−structural correlations.