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Mono-, Di-, and Tricarboxylic Acids:  Central Building Blocks for the Formation of Multinuclear Transition Metal Complexes

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journal contribution
posted on 30.11.2000, 00:00 by W. Frosch, S. Back, G. Rheinwald, K. Köhler, L. Zsolnai, G. Huttner, H. Lang
The synthesis and characterization of the di-, tetra-, and hexanuclear titanium(IV)−copper(I) carboxylates {[Ti](C⋮CSiMe3)2}CuO2CR2 (3) {3a:  R2 = Me, 3b:  R2 = C6H5, 3c:  R2 = CH2C6H5, 3d:  R2 = CHCMe2; [Ti] = (η5-C5H4SiMe3)2Ti}, {[Ti](C⋮CtBu)2}CuOC(O)−X−C(O)OH [12a:  X = trans-CHCH, 12b:  X = CH2C(CH2)], {[Ti](C⋮CtBu)2}CuOC(O)−X−C(O)OCu{(R1C⋮C)2[Ti]} [R1 = tBu, 13a:  X = trans-CHCH, 13b:  X = cis-CHCH, 13c:  X = 1,4-C6H4, 13d:  X = C⋮C, R1 = SiMe3, 14a:  X = trans-CHCH, 14b:  X = CH2C(CH2)], [{[Ti](C⋮CtBu)2}CuO(O)C]2 (13e) as well as {[Ti](C⋮CtBu)2}CuO(O)C-1-C6H3(CO2H)2-3,5 (16), [{[Ti](C⋮CtBu)2}CuO(O)C]2-1,3-C6H3(CO2H)-5 (17), and [{[Ti](C⋮CtBu)2}CuO(O)C]3C6H3-1,3,5 (18) is described. All of these complexes are easily accessible by the reaction of {[Ti](C⋮CR1)2}CuMe (1a:  R1 = SiMe3, 1b:  R1 = tBu) with the corresponding carboxylic acids in different stoichiometric ratios of the reactants. Furthermore, the preparation and reaction chemistry of the alkyne-stabilized copper(I) percarboxylate {[Ti](C⋮CSiMe3)2}CuO2C(O)C6H4Cl-3 (10) is discussed. As the central organic building block, all complexes contain mono-, di-, or tricarboxylic units. The latter two allow for the subsequent addition of further titanium(IV)−copper(I) assemblies onto these entities. The X-ray structure analyses of 3a and 13a are reported. Within the {[Ti](C⋮CR1)2}CuOC(O)R2 array the copper(I) center is η2-coordinated by both R1C⋮C groups of the organometallic tweezer [Ti](C⋮CR1)2 and η1-bonded by one oxygen atom of the O2CR2 unit. Cyclic voltammetric studies on representative examples are presented and discussed comparatively.