Synthesis and Crystal Structure of a Novel Electron-Rich nido Trimetallocarborane.
CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY
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Reaction of CB5Hg with nickelocene and sodium amalgam has yielded the first trimetallocarborane containing nickel, C5H5Ni3CB5H6. The complex can be formulated as a mixed-valence NiIII-NiIII-NiIV system the near infrared spectrum supports this formulation and indicates a considerable amount of mixed-valence charge transfer. The crystal structure has been determined from three-dimensional X-ray counter data. The complex crystallizes in the orthorhombic system, space group Pnma with a 7.5181 A, b 14.7402 A, c 15.7113 A, and Z 4. Refinement of 1840 independent reflections with Fo 3 sigma Fo has led to a final value of R 3.16. The electron-rich trimetallocarborane was found to adopt a novel nido geometry best described as a distorted monocapped square antiprism. Three nickel atoms and a boron atom compose the four-membered open face the two equivalent Ni-Ni distances are 2.4041 A. Non-bonded distances in the open face are Ni-Ni 3.2501 A, Ni-B 2.9915 A. The geometry is discussed in relation to electron counting rules for polyhedral heteroboranes.
- Physical Chemistry