CRYSTAL AND MOLECULAR-STRUCTURE OF AN IRON DIHYDROGEN METALLOCARBORANE, [2,3-(CH3)2C2B4H4]2FEH2 - STERIC ASPECTS OF THE OXIDATIVE FUSION PROCESS

A single-crystal X-ray diffraction investigation of the title compound established the structure as a sandwich composed of two pentagonal-pyramidal carborane ligands face bonded to iron, in accord with the geometry proposed earlier from NMR data. The “extra” hydrogen atoms were not directly located, but strong evidence that they occupy bridging locations on the FeB2 polyhedral faces is given by the orientation of the C2B3 bonding faces on the ligands. The C2B3 planes are inclined at an angle of 7.80° such that the methyl groups are forced close together, an effect attributed to the presence of the FeH2 hydrogens wedged between the polyhedra on the side of the complex opposite the methyl groups. The relationship of this structure to that of (CH3)4C4BgH8, which is produced from the title compound by oxidative fusion of the [(CH3)2C2B4H4]2- ligands, is discussed. Crystal data: space group Aba2; a = 12.861 (4) Å, b = 10.144 (4) Å, c = 11.257 (5) Å;V= 1469 (2) Å3; m(Mo Kα) = 10.2 cm-1; p(calcd) = 1.178 g cm-3 for Z = 4. The structure was refined by full-matrix least-squares methods to a final R value of 0.039 for the 662 reflections for which Fo2 > 3σ(Fo2). © 1979, American Chemical Society. All rights reserved.