ChemInform Abstract: Organotransition-Metal Metallacarboranes. Part 11. Chromium Tricarbonyl η6-Complexes of nido-2,3-(PhCH2)2C2B4H6: Metal Complexation and Oxidative Fusion.

ChemInform Abstract

The consequences of η6-phenyl coordination of Cr(CO)₃ groups on the chemistry of the carborane (I) are investigated. The monochromium species (III) undergoes B-H-B-bridge deprotonation by NaH, and the resulting anion on treatment with FeCl₂ forms the derivatives (VI) and (VII), which are not isolated. Subsequent oxidation with O₂ gives the two isomers (VIII) and (IX), which are characterized spectroscopically (IR, ¹¹B NMR, mass). Reaction of the tetracarbon carborane (XI), obtained from (I) in the same fusion sequence, with Cr(CO)₆ (II) yields dichromium products identical with (VIII) and (IX), but no other isomers. An attempted analogous sequence with (IV) proceeds only as far as bridge deprotonation with KH; the resulting anion on treatment with FeCl2/O2 does not undergo fusion, noris fusion observed with other transition metals. An attempted mixed ligand fusion of the anions of (I) and (IV) gives only (XI). The resistance of (IV) to oxidative fusion is discussed in terms of steric and electronic effects.