DERIVATIVE CHEMISTRY OF NINE-BORON CLUSTERS
Abstract
The synthesis of perhalogenated nonahydrononaboratesB(,9)X(,9)('2-) (X = Cl,Br,I) from B(,9)H(,9)('2-) is described. Oxidations of theperchloro, perbromo, and periodo dianions gave the correspondingnovel and highly colored borane radicals. Further oxidations gavethe corresponding neutral clusters B(,9)X(,9). The redox sequenceB(,9)X(,9)('2-) (DBLHARR) B(,9)X(,9)('-) (DBLHARR) B(,9)X(,9) has been established. The stability of theoxidation products has been ascribed to the extensive involvementof the halogen substituents in the cage. The Synthesis of B(,9)H(,8)S(Me)(,2)('-) and B(,9)H(,7)(S(Me)(,2))(,2) from B(,9)H(,9)('2-) and DMSO/acetic anhydride is also described. Variable temperature ('1)H nmr and ('13)C nmr studies revealed the first intramolecular rearrangement of a nine-boron cluster. The disubstituted product exists as the 1,5- isomer in the solid state and in low temperature solutions (0(DEGREES)C). The nmr results suggested that above ambient temperature the 1,5- isomer is in equilibrium with the 1,7(8)- and 4,5- isomers. Coalescence occurs at 130(DEGREES)C indicating rapid cage rearrangement. The structural nonrigidity of the nine boron cluster is discussed in the light of known dynamic processes in boron cluster chemistry. X-ray structure analysis of B(,9)H(,7)(SMe(,2))(,2) showed that thiscompound crystallizes in the orthorhombic space group P2(,1)2(,1)2(,1).Unit cell parameters are a = 7.879(2), b = 9.014(2), c = 19.436(4) (ANGSTROM),V = 1379.4 (ANGSTROM)('3), Z = 4, and D(,x) = 1.101 g/cm('3). The structure was solved by conventional heavy atom methods, resulting in a final R factor of 7.9% for 1538 independent reflections. Substitution occurs at two different boron sites yielding the 1,5-isomer. Bonds joining capping boron atoms (a) to prismatic boron atoms (e) are shorter than those joining two prismatic boron atoms as is expected. The long bond distances of the B(2)-B(3) and B(8)-B(9) support the fact that these are involved in the pairwise interconversion of the five- and six-coordinate vertices.
Subject Area
Inorganic chemistry|Chemistry
Recommended Citation
KABBANI, RAIFAH MAHMOOD, "DERIVATIVE CHEMISTRY OF NINE-BORON CLUSTERS" (1981). ETD Collection for Fordham University. AAI8123549.
https://research.library.fordham.edu/dissertations/AAI8123549
