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A room-temperature reaction of cupric acetate dihydrate with 3,5-bis(trifluoromethyl)pyrazole ((CF3)2pzH) in chloroform in the presence of triethylamine gave a complex of the formula [Cu2(μ-(CF3)2pz)2(μ-OH2)(OC(Me)OHNEt3)(OH2)(HCCl3)(OOCMe)(μ-OOCMe)]2 (2). Heating of this complex at 180°C in dibenzyl ether (DBE) in air yielded the tetranuclear pyrazolate-benzoate cluster Cu4(μ4-OH)(μ-(CF3)2pz)4(μ-OOCPh)2(μ-OH)2(OH2)(Et3NH)[O(CH2Ph)2]2. It was suggested that such complexes can be intermediates in the liquid-phase oxidation of DBE with atmospheric oxygen in the presence of copper complexes containing pyrazolate bridges.

Deprotonation reactions of pyrazole and its analogs by aqueous copper acetate in benzene at room temperature in the presence of triethylamine were studied. Unlike 3,5-dimethylpyrazole, more acidic pyrazole, 5-methyl-3-trifluoromethylpyrazole, and 3,5-bis(trifluoromethyl)pyrazoles are deprotonated to give pyrazolate bridges. The structural features of the obtained compounds are discussed based on X-ray diffraction data.

The reaction between Co(Hdmpz)2(OOCPh)2 and cobalt acetate hydrate leads to the deprotonation of coordinated pyrazole and formation of pyrazolate-bridged Co2(μ-dmpz)2(Hdmpz)2(OOCPh)2 binuclear complex. The structure of the complex was determined by X-ray crystallography.

Dissolution of benzoic or pivalic acid in excess triethylamine followed by crystallization was found to yield single crystals of 1: 1 and 1: 2 complexes, respectively. X-ray crystallography have shown that the complex with benzoic acid is an (Et3NH)+(OOCPh)− ion pair, in which the proton is transfered from the acid to the base (N⋯O 2.629(2) A), and the complex with pivalic acid contains, in addition to the ion pair (N⋯O 2.649 A), the homoconjugate anion (ButCOO)(H)(OOCBut)− (O⋯O 2.521 A).

The dissolution of aqueous copper acetate in tetrahydrofuran gives the Cu2(μ-OOCMe)4(thf)2 complex (1), and its reaction with triethylamine in the presence of acetic acid yields “[Cu2(μ-OOCMe)4[μ-OOCMe(HNEt3)]”n polymer (2). Complexes 1 and 2 react with 3,5-dimethylpyrazole to form Cu(Hdmpz)2(OOCMe)2 (3) and Cu2(μ-OOCMe)4(Hdmpz)2 (4), respectively. The structures of complexes 1–4 and that of solvate 4 × 0.5C6H6 (5) are determined by X-ray diffraction.

We discovered that reactions of [Pd(OOCMe)2] n and Pd3(μ-OOCMe) with 3,5-dimethylpyrazole (Hdmpz) yield mononuclear complex [Pd(Hdmpz)4](OOCMe)2, in which acetate anions can exchange for pivalate or benzoate anions in reactions with proper acids. The specifics of intramolecular hydrogen bonding in the complexes prepared are discussed as dependent on the nature of the carboxylate anion using X-ray crystallography data.