Hexacoppergermsesquioxanes as complexes with N-ligands: Synthesis, structure and catalytic properties
Résumé
A simple and versatile strategy of synthesis of cage metallagermaniumsesquioxanes is demonstrated for isolation of Cu 6-based phenylgermsesquioxanes 1e6. Structure of newly synthesized coppergermsesquioxanes was established by single-crystal X-ray diffraction analysis. General principle of these cages' topology implies the presence of two linear Cu 3 fragments, coordinated by three pairs of ligands. These are: (i) cyclic germsesquioxanes [PhGeO 1,5 ] 5 , products 1e6, (ii) 1,10-phenanthrolines, (1, 3e5) or 2,2'bipyridines, (2, 6), (or and (iii) OX species (X ¼ H, 1e2, CH 3 , 3, H and C 2 H 5 O, 4, HCO, 5, CH 3 CO, 6). Appearance of non-expected species (formiate for 5, acetate for 6), resulted from corresponding alcohols used as reaction media, points at easyness of oxidation processes in the conditions of such selfassembling reactions. Catalytic tests showed high activity of complexes 1 and 2 as precatalysts in homogeneous oxidations of alkanes (cyclohexane, methylcyclohexane, n-heptane, cis-1,2dimethylcyclohexane with hydrogen peroxide in acetonitrile solution. Hydroxyl radicals take part in the reaction. The same complexes catalyze oxidation of alcohols (cyclohexanol, 2-heptanol, 1phenylethanol) to corresponding ketones with tert-butyl hydroperoxide in almost 100% yield. With the addition of various alkyl ammonium salts, complex 2 could also furnish corresponding amides in high yield.
Domaines
Chimie
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