Synthesis and Structural Characterization of Trinuclear CuII−Pyrazolato Complexes Containing μ3-OH, μ3-O, and μ3-Cl Ligands. Magnetic Susceptibility Study of [PPN]2[(μ3-O)Cu3(μ-pz)3Cl3]

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Abstract
The nine-membered [−CuII−N−N−]3 ring of trimeric copper−pyrazolato complexes provides a sturdy framework on which water is twice deprotonated in consecutive steps, forming μ3-OH and μ3-O species. In the presence of excess chlorides the μ3-O(H) ligand is replaced by two μ3-Cl ions. The interconversion of μ3-OH and μ3-O and the exchange of μ3-O(H) and μ3-Cl are reversible, and the three species involved have been structurally characterized: [PPN][Cu3(μ3-OH)(μ-pz)3Cl3(thf)]·CH2Cl2 (1a), monoclinic P21/n, a = 10.055(2) Å, b = 35.428(5) Å, c = 15.153(2) Å, β = 93.802(3)°, V = 5386(1) Å3, Z = 4; [Bu4N][Cu3(μ3-OH)(μ-pz)3Cl3] (1b), triclinic P-1, a = 9.135(2) Å, b = 13.631(2) Å, c = 14.510(2) Å, α = 67.393(2)°, β = 87.979(2)°, γ = 80.268(3)°, V = 1643.2(4) Å3, Z = 2; [PPN]2[Cu3(μ3-O)(μ-pz)3Cl3] (2), monoclinic P2/c, a = 12.807(2) Å, b = 13.093(2) Å, c = 23.139(4) Å, β = 105.391(3)°, V = 3741(1) Å3, Z = 2; [PPN]2[Cu3(μ3-Cl)2(μ-pz)3Cl3]·0.75H2O·0.5CH2Cl2 (3a), triclinic P-1, a = 14.042(2) Å, b = 23.978(4) Å, c = 25.195(4) Å, α = 76.796(3)°, β = 79.506(3)°, γ = 77.629(3)°, V = 7988(2) Å3, Z = 4; [Bu4N]2[Cu3(μ3-Cl)2(μ-pz)3Cl3] (3b), monoclinic C2/c, a = 17.220(2) Å, b = 15.606(2) Å, c = 20.133(2) Å, β = 103.057(2)°, V = 5270(1) Å3, Z = 4; [Et3NH][Cu3(μ3-OH)(μ-pz)3Cl3(pzH)] (4), triclinic P-1, a = 11.498(2) Å, b = 11.499(2) Å, c = 12.186(2) Å, α = 66.475(3)°, β = 64.279(3)°, γ = 80.183(3)°, V = 1331.0(5) Å3, Z = 2. Magnetic susceptibility measurements show that the three copper centers of 2 are strongly antiferromagnetically coupled with JCu-Cu = −500 cm-1.

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