Carbonyl complexes oxygen-bonded

On treatment with a potassium fluoridc-orown ether complex, alkyl 1,2,2,2-tetrachloroethyl carbonates are cleaved at the carbonyl group-oxygen bond to give high yields of alkyl fluoioformates [ 15] (equation 25)... 

Table 8. Correlation of oxygen 1 s binding energies of carbonyl complexes with back-bonding...

Fig. 7.4. Conformations of (a) free valinomycin and (b) of its potassium complex. The carbonyl oxygen atoms, P, P, M and M are in especially exposed positions, so that they can initiate complexation of potassium ion. During complexation, hydrogen bonds 1 and 2 are broken, so that oxygen atoms R and R can take part in the co-ordination of the cation. Further smaller conformation changes allow oxygen atoms Q and Q to partake in formation of new hydrogen bonds, the molecule thus attaining the final round shape (see [44a ]). (By permission of the American Association for Advancement of Science.)...

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

It was discovered by Roelen in 1938 and is the oldest and largest volume catalytic reaction of alkenes, with the conversion of propylene to butyraldehyde being the mosi important. About 5 million tons of aldehydes and aldehyde derivatives (mostly alcohols) are produced annually making the process the most important industrial synthesis using a metal carbonyl complex as a catalyst. The name hydroformylation arises from the fact that in a formal sense a hydrogen atom and. formyl group are added across a double bond. The net result of the process is extension of (he carbon chain by one and introduction of oxygen into the molecule. 

It is, of course, not correct to treat the wave function of a polyatomic molecule as localized in the chromophoric group considered responsible for the optical absorption. The carbonyl group in aldehydes and ketones gives rise to absorption which extends from about 3430 A to about 2200 A (as well as to absorption at shorter wavelengths). Nevertheless the carbon-oxygen bond is never broken by absorption at these wavelengths. Frequently an adjacent bond is broken but often more complex processes occur. It is sometimes possible to describe these processes in terms of quantum mechanics but some of them should not be treated as direct dissociations. 

Platinum nanoparticles, preparation, 12, 78 Platinum-nitrogen bonds, in platinacycles, 8, 508 Platinum-osmium carbonyl clusters, characteristics, 8, 420 Platinum-oxygen bonds, in platinacycles, 8, 505 Platinum particles, surface reactivity, 12, 542 Platinum-phosphorus bonds, in platinacycles, 8, 508 Platinum-rhenium carbonyl clusters, characteristics, 8, 420 Platinum(II)-ruthenium(II) binary complexes, preparation,... 

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