Carbon O-bonding

Compounds containing lanthanide-carbon o-bonds have recently been reviewed. ... 

Iridium(I) complexes with metal-carbon o-bonds are markedly more stable than those of Rh(I). In contrast to Rh(I), both EtCOIr(CO)2(PPh3)2... 

Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of w-Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, 5, 225 Insertion Reactions of Transition Metal-Carbon o-Bonded Compounds I Carbon Monoxide Insertion, 11, 88... 

Ionic dissociation of the carbon-carbon o- bond in hydrocarbons... 

The cleavage of carbon-carbon o- bonds is the main reaction in thermal cracking of naphtha, one of the commonest processes in the hydrocarbon conversion industry. Thus, radical dissociation or cleavage of carbon-carbon cr bonds has been quite familiar to synthetic and physical organic chemists. 

Lenhert and Hodgkin (15) revealed with X-ray diffraction techniques that 5 -deoxyadenosylcobalamin (Bi2-coenzyme) contained a cobalt-carbon o-bond (Fig. 3). The discovery of this stable Co—C-tr-bond interested coordination chemists, and the search for methods of synthesizing coen-zyme-Bi2 together with analogous alkyl-cobalt corrinoids from Vitamin B12 was started. In short order the partial chemical synthesis of 5 -de-oxyadenosylcobalamin was worked out in Smith s laboratory (22), and the chemical synthesis of methylcobalamin provided a second B 12-coenzyme which was found to be active in methyl-transfer enzymes (23). A general reaction for the synthesis of alkylcorrinoids is shown in Fig. 4. 

It contains a palladium-carbon o-bond (alkyl or aryl)... 

Insertion Reactions of Transition Metal-Carbon o--Bonded Compounds II. Sulfur Dioxide and Other Molecules, 12, 31... 

A change in the allyl hapticity (q3 to p1 slippage) leading to the less substituted titanium-carbon o bond accounts for the observed y-regioselectivity. The anti diastereoselectivity stems from a pseudo-equatorial orientation of the aldehyde group. The diastereoselectivity of the reaction can be reversed through the use of a more coordinating cosolvent such as HMPA (Scheme 13.7) [14]. This reversal of anti to syn diastereoselectivity can be rationalized in terms of an open transition state. 

The electrosynthesis of metalloporphyrins which contain a metal-carbon a-bond is reviewed in this paper. The electron transfer mechanisms of a-bonded rhodium, cobalt, germanium, and silicon porphyrin complexes were also determined on the basis of voltammetric measurements and controlled-potential electrooxidation/reduction. The four described electrochemical systems demonstrate the versatility and selectivity of electrochemical methods for the synthesis and characterization of metal-carbon o-bonded metalloporphyrins. The reactions between rhodium and cobalt metalloporphyrins and the commonly used CH2CI2 is also discussed. 

KADISHETAL. Metalloporphyrins Containing Metal-Carbon o-Bonds 453... 

Oxidation of alkanes involves the removal of an electron from either a carbon-hydrogen or a carbon-carbon o-bond. These are dissociative processes where the radical-cation cannot be detected as an intermediate in either fluorosulphuric acid or acetonitrile. 

It has dso proved possible in the metal-olefin systems formed to isolate intermediates which have short lives in simpler systems for example, the complex PtBr4 (vp) can be seen as analogous to the unstable yellow oils sometimes reported in the oxidation of Zeise s salt to PtCU and 1,2 dichloroethane. Even weak interactions which affect the course of a reaction can be noted. Neither of the vinyl groups in PtBr2 (oS)2 is co-ordinated to the platinum atom, but bromine oxidation yields a Pt-carbon o-bond, indicating some interaction in the transition state at least. 

Fig. 18. Platinum(II)-carbon o-bond formation from an acetylene...

Scheme 10. Moss s convergent construction of organometallic dendrimers containing ruthenium-carbon o-bonds.

It is evident from the trends pertaining to the ionization of the metal-carbon o bonds of r2 symmetry that the IEs are less for the Me3XCH2-substituted compounds than for the methylated compounds. On the basis of Koopmans theorem this would imply that the metal-carbon bonding is weaker in the Me3XCH2 derivatives. 

The insertion of CS2 into transition metal -carbon o bonds also has been reported (408). The complexes (LCS2)M(CO)4 (L = Ph, p-CH3Ph, Me M = Mn, Re) are obtained by the reaction of CS2 and the LM(C0)4 complexes in CS2. The structure and bonding of these new dithiocarboxylate complexes are discussed on the basis of their mass, PMR, and IR spectra (408). 

With this representation two reaction routes are possible one through the metal-carbon o-bond and the other through the 7r-bond. 

This chapter introduces complexes with metal-carbon o-bonds. i.c. 

In spite of the presence of metal-carbon o-bonds and carbon-carbon triple bonds in the backbone, the metal-poly-yne polymers are fairly stable to air in the solid state and show considerably good thermal stability (Table 6). The platinum-containing... 

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