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Reactions of copper(II) carboxylates with dibenzyl ether (DBE) gave binuclear complexes of the formula Cu 2 (µ OOCR) 4 (DBE) 2 (R = Bu t , Ph, and CF 3 ). The complexes were characterized by X ray dif fraction. The axial positions in the lantern type dimer are occupied by the coordinated DBE molecules. The complexes seem to be analogs of intermediate catalysts for the oxidation of DBE with atmospheric oxygen in the presence of transition metal complexes. When stored in air, the complex Cu 2 (µ OOCPh) 4 (DBE) 2 under went oxidation into Cu 2 (µ OOCPh) 4 (HOOCPh) 2 , which was characterized by X ray diffraction. The geom etry of its framework is similar; the structure is stabilized by intramolecular H bonds between the axially ori ented benzoic acid molecules and the adjacent bridging benzoate anions.

The liquid-phase oxidation of cyclohexene (CH) by atmospheric oxygen is of considerable practical interest in connection with the broad synthetic possibilities of its oxidation products -the epoxide (OCH), 3-hydroperoxide (HP), cyclohexen-3-ol (CHol), cyclohexen-3-one (CHone), etc. [1,2]. At the same time CH is a convenient (model) compound for investigation of the main pathways and the selectivity in both direct and conjugate oxidation of compounds with an activated CH bond in relation to composition of the catalytic system and the structure of the metal-complex catalyst.In a continuation of our researches on the catalytic characteristics of the polynuclear pivalates of 3d metals [3, 4] we examined the oxidation of CH in the presence of a series of homo-and heteronuclear complexes with the CoM 2 O core (M = Co, Cr, Fe), viz.: [Co 3 OPiv 6 (g-Pic) 3 ]Piv (I), CoCr 2 OPiv 6 ·3Ppy (II), and CoFe 2 OPiv 6 ·3Ppy (III). For comparison the pivalate NiCr 2 OPiv 6 ·3Ppy (IV), which exhibited catalytic characteristics close to its cobalt analog in the decomposition of the hydroperoxide of dibenzyl ether [5] (II), was included in this series. The synthesis and structure of the investigated pivalates were described in [6,7]. 900040-5760/07/4302-0090

The main products of the reaction in the presence of homo-and heteroligand pivalate and 3,5-dimethylpyrazolate mono-, bi-, and trinuclear complexes of Co, Cu, Ni, and Zn are the hydroperoxide, benzaldehyde, and benzoic acid. The effect of the composition and structure of the complexes on the conversion of the substrate, the selectivity of the process, and the possibility of alternative routes to the oxidation of dibenzyl ether is discussed.Metal carboxylates are some of the best known and most widespread classes of coordination compounds, the variety of which is due to the broad possibilities of the structural function of the polydentate ligand RCOO - [1]. It is this specific characteristic that makes it possible to vary the composition and structure of carboxylate complexes, leading on the one hand to the unusual characteristics (catalytic, magnetic, etc.) of such compounds (e.g., see [2,3]) and on the other to the possibility of using them as "platforms" for the production of the metal complexes regarded as synthetic analogs of the active part of metalloenzymes [4][5][6].Thus, the authors of [7-11] developed approaches to the synthesis of a similar series of pivalate complexes of zinc, copper, nickel, and cobalt containing coordinated 3,5-dimethylpyrazole (Hdmpz), which models the histidine fragment in the enzyme part of metalloenzymes.In a continuation of our investigations into the catalytic properties of the polynuclear carboxylates of 3d metals in the liquid-phase oxidation of compounds with activated CH bonds [e.g., dibenzyl ether (DBE) [12]] by atmospheric oxygen (and then by air) in the present article features of the oxidation of DBE in the presence of complexes (mainly bi-and trinuclear complexes) of cobalt, copper, nickel, and zinc, in which the metal cores are formed by pivalate (ì-Piv) or 3,5-pyrazolate (ì-dmpz) bridging ligands, are discussed. As seen from Table 1, the terminal ligands in these complexes are either neutral 0040-5760/09/4506-0355

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