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) A, b = 35.428(5) A, c = 15.153(2) A, β = 93.802(3)°, V = 5386(1) A3, Z = 4; [Bu4N][Cu3(μ3-OH)(μ-pz)3Cl3] (1b), triclinic P-1, a = 9.135(2) A, b = 13.631(2) A, c = 14.510(2) A, α = 67.393(2)°, β = 87.979(2)°, γ = 80.268(3)°, V = 1643.2(4) A3, Z = 2; [PPN]2[Cu3(μ3-O)(μ-pz)3Cl3] (2), monoclinic P2/c, a = 12.807(2) A, b = 13.093(2) A, c = 23.139(4) A, β = 105.391(3)°, V = 3741(1) A3, Z = 2; [PPN]2[Cu3(μ3-Cl)2(μ-pz)3Cl3]·0.75H2O·0.5CH2Cl2 (3a), triclinic P-1, a = 14.042(2) A, b = 23.978(4) A, c = 2...