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The mononuclear 7-vertex closo-ferracarborane cluster (C 5 Me 5 )Fe II H(Et 2 C 2 B 4 H 4 ) (1) and (C 5 Me 5 )Fe III (Et 2 C 2 B 4 H 4 ) (2) and the phenylene-linked diiron species (Et 2 C 2 B 4 H 4 )M(C 5 Me 4 -C 6 H 4 -C 5 Me 4 )M'(Et 2 C 2 B 4 H 4 ) (3, M=M'=Fe II H ; 4, M=Fe II H, M'=Fe III ; and 5, M=M'=Fe III ) were prepared and isolated via column and/or plate chromatography on silica or Al 2 O 3 . Their chemical interconversion was examined, and the air-stable products were characterized from their 1 H, 13 C, and 11 B NMR, infrared, UV-visible, mass spectra, and elemental analysis and an X-ray diffraction study of 3. The crystallographic data established the location of the Fe-H hydrogen atom in each of the two equivalent ferracarborane clusters ; this hydrogen is coordinated both to iron and to the neighboring atoms in the carborane ligand and be described as capping an Fe-B-B triangular face

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The preparation and characterization of the compounds [HFe 4 (CO) 12 C] BXY (X=Y=H, Cl, Br; X=H, Y=Cl, Br, OH) are described. Geometric, spectroscopic, and Fenske-Hall quantum-chemical parameters demonstrate that these compounds are usefully described as tricoordinate boron compounds substituted with a carbido cluster. The carbido cluster [HFe 4 (CO) 12 C], as a substituent, is shown to be both a sterically demanding ligand and a strong π donor to the boron center. The unanticipated differences in the reactivity of these compounds with AlX 3 , NEt 3 , H 2 O, and THF as X and Y are varied reflect the unusual properties of this compound type. Single-crystal X-ray diffraction studies of [HFe 4 (CO) 12 C]BHX (X=Cl, Br) are reported

A mechanistic hypothesis of metallaborane cluster build-up by the condensation of metal and boron containing fragments, which is supported by circumstantial evidence from previous work, suggests improved routes to the synthesis of ferraboranes. This work describes two new approaches consisting of the examination of two precursors with properties consistent with such a hypothesis. The first precursor, a neutral mononuclear dimethyl sulfide substituted iron tetracarbonyl, Fe(CO) 4 SMe 2 , is a new compound and the high yield synthesis and structural characterization of it are reported. This compound provides a better route to the ferraborane Fe 2 (CO) 6 B 2 H 6 than those presently known and is an isolatable, alternate source of the Fe(CO) 4 fragment. The second precursor, Fe(CO) 3 (cco) 2 , where cco is η 2 - cis -cyclooctene, is a known, ready source of the Fe(CO) 3 fragment. The reaction of Fe(CO) 3 (cco) 2 with BH 3 sources at low temperatures results in good yields of known ferraboranes and a product distribution that depends primarily on the ratio of boron to iron in the reactants. Both of these results support a mechanism for metallaborane cluster formation involving rapid metal carbonyl fragment condensation as a principal mechanistic component.

The synthesis and structural characterization of the first example of a boracyclopropene ring coordinated to a trimetal fragment, Fe 3 (CO) 9 [C 3 -B(H)C(H)C(Me)], are described. The compound constitutes an example of a cluster containing three transition metals that can only be reasonably considered as a six-atom cluster containing three iron, two carbon, and one boron atoms. This particular derivative of the cluster core also constitutes an example of a chiral cluster

Etude de la conversion de (μ-H) 3 Fe 3 (CO) 9 (μ 3 -CCH 3 ) en (μ-H)Fe 3 (CO) 9 (μ-CO)CCH 3 et de la reaction inverse