Hypercarbon species

The manner in which ethyl Grignard reagents (and many other metal alkyls with hydrogen atoms attached to their P-carbon atoms) can function as reducing agents by alkene elimination and P-hydrogen transfer probably also involves hypercarbon species [Eq. (1.5)]. Similar hypercarbon species appear... 

The well-known Arndt-Eistert homologation" of an acyl halide to a carboxylic acid also involves the migration of an R group (with its electron pair) to an electron-deficient acyl carbene (presumably through a hypercarbon species) [Eq. (6.132)]. This rearrangement is also known as the Wolff rearrangement. 

For a monograph on (his type of species, see Olah Prakash Williams Field Wade Hypercarbon Chemistry Wiley New York, 1987. 

To show how hypercarbon compounds are closely related to many classically bonded systems and aromatic systems, and are not exotic species remote from mainstream organic chemistry. 

In the gas phase, Fe+, Co, and NF metal ions react with isobutane with facile C-C bond cleavage. " In fact, in the case of the Co+ ion, C-C bond cleavage appears to be preferred over C-H bond scission.The Co ion reacts with ( L, to Ce cycloalkanes exclusively by C-C bond insertion to provide metallacycles, which themselves decompose largely by C-C bond cleavage pathways. All these reactions must proceed through the intermediacy of hypercarbon-containing species. The reaction pathway for cyclopentane is shown in Equation (6.103)" ... 

First, we survey the major types of compounds that contain hypercarbon. The relationships that link these apparently disparate species are demonstrated by showing how the bonding problems they pose can be solved by the use of three- or multicenter electron-pair bond descriptions or simple MO treatments. We also show the role played by hypercoordinated carbon intermediates in many familiar reactions (carbocationic or otherwise). Our aim here is to demonstrate that carbon atoms in general can increase their coordination numbers in a whole range in reactions. 

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