Small Metallacarboranes with Metal-metal Bonds. Crystal and Molecular Structures of 2,3-(CH₃)₂-1,2,4,5-(η⁵-C₅H₅)₂Co₂C₂B₃H₃ and 2,3-(CH₃)₂-1,2,4,5-(η⁵-C₅H₅)₂CoFe(H)C₂B₃H₃


The structures of the title compounds were determined by single-crystal X-ray diffraction and in both cases were found to contain 7-vertex pentagonal-bipyramidal M2C2B3 cages (M = Fe or Co) with cobalt in an equatorial vertex and cobalt or iron in an apical vertex. In both cases, the framework carbon atoms occupy adjacent positions in the equator. Both structures are in agreement with those proposed earlier from NMR data, except that the presumed face-bridging proton in the iron-cobalt cluster was not directly observed. The parent 1,2,4,5-(η5-C5H5)2Co 2C2B3H5 isomer is an isolable intermediate in the previously studied thermal rearrangement of the triple-decked complex 1,7,2,3-(η5-C5H5)2Co 2C2B3H5 to the 1,7,2,4 isomer via the 1,2,3,5 and 1,2,4,5 species. The present structures provide the first structural confirmation of equatorial metal atoms in pentagonal-bipyramidal metallaboron cages and are the smallest metallacarboranes containing metal-metal bonds to be crystallographically established. Crystal data for 2,3-(CH3)2-1,2,4,5-(η5-C5H 5)2Co2C2B3H3: mol wt 338, space group P21/c, Z = 4; a = 9.240 (3), b = 12.314(7), c = 13.933 (4) Å; β = 108.94 (4)°; V = 1499 Å3; R = 0.057 for 1230 independent reflections having Fo 2 > 3σ(Fo 2). Crystal data for 2,3-(CH3)2-1,2,4,5-(η5-C5H 5)2CoFe(H)C2B3H3: mol wt 338, space group P21/c, Z = 8 (two molecules per asymmetric unit); a = 9.385 (3), b = 22.431 (7), c = 14.133 (4) Å; β = 90.86 (4)°; V = 2975 Å3; R = 0.056 for 3548 independent reflections for which Fo 2 > 3σ(Fo 2). © 1980 American Chemical Society.



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© 1980 American Chemical Society (ACS), All rights reserved.

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01 Jan 1980