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Clusters as Ligands. 5. Tricobalt Cluster Alkoxycarboxylates of Titanium and Zirconium Exhibiting Novel Structures and Properties

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journal contribution
posted on 25.11.1997, 00:00 by Xinjian Lei, Maoyu Shang, Thomas P. Fehlner
The protonolysis of group 4 M(IV)(OR)4, M = Ti, Zr, organic alkyl- or aryloxides with the cluster acid (CO)9Co33-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 Zr2(μ-OCH(CH3)2)2(OCH(CH3)2)2{μ-(CO)9Co33-CCO2)}2{(CO)9Co33-CCO2)}2, 1; Ti43-O)4(OR)4{μ-(CO)9Co33-CCO2)}4, 2 (R = CH(CH3)2, 2a; (CH2)3CH3, 2b; C6H5,2c; 2,6-(CH3)2-C6H3, 2d); Ti63-O)4(μ-OCH2CH3)4(OCH2CH3)8{μ-(CO)9Co33-CCO2)}4, 3; and [Ti63-O)2(μ-O)2(μ-OCH(CH3)2)2(OCH(CH3)2)2(1,2-O2C6H4)4{μ-(CO)9Co33-CCO2)}4], 4. Further, the mixed-metal derivatives [Ti2Co2{(OCH2)3CCH3}2(OCH(CH3)2)2{μ-(CO)9Co33-CCO2)}4], 5, and [{Co3Ti(OCH3)6(HOCH3)(THF){μ-(CO)9Co33-CCO2)}3}2(O2CCO2)]·2HOCH3·2THF,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.