Hydrocarbon metal-carbon single bond

In connection with the activation of saturated hydrocarbons via homogeneous catalysis, we have examined transition metal catalyzed reactions of various strained hydrocarbon systems that have unique steric and electronic properties. Strained carbon-to-carbon single bonds have considerable TT-bonding character. The chemistry of these substrates should be intermediate between well-documented transition metal chemistry of alkenes and rather unclarified alkane chemistry (1, 2, 3). Our attention has been focused particularly on the stereoselectivity, regioselectivity, and periselec-tivity of the Ni(0)-catalyzed reactions (4-14). 

It seems beyond debate that when an exchange reaction of a hydrocarbon (HC) with D2 is observed and the initial product distributions are binomial (random distribution of D atoms), single c-metal-carbon bonds are being formed. Nevertheless, this conclusion was puzzling in the period when virtually no homogeneous alkyl-metal complexes were known and the stability of alkyl-metal complexes was doubted for principal reasons (see, e.g., 169). However, it appeared that these complexes can be rather stable when one blocks a very fast and easy elimination of one of the H atoms in the jS-position, which step decomposes the alkyl-metal bond into an olefin and a bound hydrogen atom (170,171). On the other hand, this means that the transition... 

The anionic complex M2 [IrCl6] (M = Na and K) are commercially available and have been used as outer-sphere single-electron oxidants in mechanistic studies of the cleavage of metal-carbon bonds [218]. The isostructural oxidant [PtCle] is also known, especially its ability to oxidize saturated hydrocarbon by electrophilic C-H activation (inner-sphere two-electron oxidant) [219]. 

Two of the parameters which are required for surface thermodynamic and kinetic constants in metal catalysis are the strength of atomic hydrogen bonded to the surface of a metal, and the strength of carbon-metal single bonds between hydrocarbon fragments and the surface, c- These parameters can be estimated from heats of adsorption of H2 and CO, respectively (226). The values of E can be obtained directly from the heat of hydrogen adsorption, since the adsorption of one molecule of Hj involves the rupture of the H—H bond and the formation of two hydrogen-metal bonds. To estimate we may use the bond order conservation theory of Shustorovich (235). 

In contrast, the Anderson-Avery mechanism does not discriminate among the various isomerization reactions. Moreover, for hydrogenolysis, it forecasts the rupture, in the 1,1,3-triadsorbed precursor, of the C2-C3 bond next to the single metal-carbon bond. However, in a recent investigation of the hydrogenolysis of a number of hydrocarbons on platinum catalysts, Leclercq, Leclercq, and Maurel (82) showed that the C-C bonds in the P position to a tertiary carbon atom are preferentially ruptured. As pointed out by these... 

One of the most important methods for specific incorporation of single deuterium atoms into both aliphatic and aromatic hydrocarbons employs compounds containing a carbon-metal bond. Most such substances are extremely sensitive to hydrolysis and it is thus a simple matter to label them by treatment with heavy water. 

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