Clusters as ligands .5. Tricobalt cluster alkoxycarboxylates of titanium and zirconium exhibiting novel structures and properties

The protonolysis of group 4 M(IV)(OR)(4), M = Ti, Zr, organic alkyl- or aryloxides with the cluster acid (CO)(9)Co-3(mu(3)-CCO2H) leads to a series of novel tricobalt cluster M(IV) alkoxy- or aryloxycarboxylates, most of which contain bridging oxo ligands. The compounds, which are isolated in good yield as crystalline substances and characterized spectroscopically as well as crystallographically, are Zr-2(mu-OCH(CH3)(2))(2)(OCH(CH3)(2))(2){mu-(CO)(9)Co-3(mu(3)-CCO2)}(2){(CO)(9)-Co-3(mu(3)-CCO2)}(2), 1; Ti-4(mu(3)-O)(4)(OR)(4){mu-(CO)(9)Co-3(mu(3)-CCO2)}(4), 2 (R = CH(CH3)(2), 2a; (CH2)(3)CH3, 2b; C6H5, 2c; 2,6-(CH3)(2)-C6H3, 2d); Ti-6(mu(3)-O)(4)(mu-OCH2CH3)(4)(OCH2CH3)(8){mu-(CO)(9)Co-3(mu(3)-CCO2)}(4), 3; and [Ti-6(mu(3)-O)(2)(mu-O)(2)(mu-OCH(CH3)(2))(2)(OCH(CH3)(2))(2)(1,2-O2C6H4)(4){mu-(CO)(9)Co-3(mu(3)-CCO2)}(4)], 4. Further, the mixed-metal derivatives [Ti2Co2{(OCH2)(3)CCH3}(2)(OCH(CH3)(2))(2){mu-(CO)(9)Co-3(mu(3)-CCO2)}(4)], 5, and [{Co3Ti(OCH3)(6)(HOCH3)(THF){mu(CO)(9)Co-3(mu(3)-CCO2)}(3)}(2)(O-2-CCO2)]. 2HOCH(3) . 2THF, 6, in which the Co(II) ions are derived from in situ tricobalt cluster degradation, are characterized in similar fashion. Some of the distinguishing features of an inorganic cluster as a ligand substituent are revealed by a comparison of the observed chemistry with that known for reactions of organic acids with M(IV)(OR)(4).