Reaction co-ordinate

Ziegler processes are based on co-ordination reactions catalysed by metal alkyl systems. Such reactions were discovered by Karl Ziegler in Germany and developed by G. Natta at Milan in the early 1950s. 

Carbenes, addition to multiple bonds, 61 addition to olefins, 59, 60 analogy with carbonium ions, 60 co-ordination reactions of, 61 dibromo-, see dihalocarbenes dichloro-, see dihalocarbenes dihalo-, addition to olefins, 59, 61 dihalo-, deoxygenation of aromatic N-oxides by, 77... 

PtCla(C2H4)]2 reacts with various mono-, di-, and tri-alkyl substituted cyclopropanes via insertion into the least substituted carbon-carbon bond to yield platinacyclobutanes such as (13). At low temperature, reaction with pyridine yields the bis-pyridine adduct, but on warming, the j -compIex (14) is formed. Arylcyclopropanes react with [PtCla(CaH4)]a in a similar fashion, and a kinetic study indicates an initial cyclopropane-Pt co-ordination. " Reaction of (diphos)PdCl2 with 1,4-dilithiobutane yields the palladocyclopentane (diphos)-... 

Nickel, Platinum, and Palladium.— Reaction of (cod)2Pt or (CaHJaPt with acetylenes yields various (RCaROgPt complexes the crystal structure of the PhCjPh complex reveals an essentially tetrahedral co-ordination. Reaction with (cod>2Pt is stepwise, and in some cases e.g., CeHjCaCsFs) only the (jy -alkyne)-Pt(cod) derivative is formed. Reaction of Pt(cod>2 with Pt (codXjj -CFaCaCFa)... 

The factor analysis revealed that the tests covered six major areas attention. involuntary control of motor functions, stability of behavior, co-ordination, reaction time, and intelligence. The factor with the highest loading on the accident criterion was the attention factor, followed by involuntary control of motor functions, stability and adaptability of behavior. Negative aspects associated with the accidents were insecurity, tension, and neuroticism. 

The reactions of carbenes, which are apparently unique in displaying electrophilic character in strongly basic solutions, include substitution, addition to multiple bonds, and co-ordination with lone pairs of electrons to form unstable ylides. This last reaction is of obvious relevance to a consideration of the reactions of heterocyclic compounds with carbenes and will be summarized. 

Complex ions used for electroplating are anions. The cathode tends to repel them, and their transport is entirely by diffusion. Conversely, the field near the cathode assists cation transport. Complex cyanides deserve some elaboration in view of their commercial importance. It is improbable that those used are covalent co-ordination compounds, and the covalent bond breaks too slowly to accommodate the speed of electrode reactions. The electronic structure of the cyanide ion is ... 

Recent study of these complexes has focused on the reactions of trimethyls and trihydrides (Figure 2.92) as on protonation they generate reactive co-ordinatively unsaturated species... 

Significantly, the pre-exponential factors decrease with increasing reactivity, and this suggests that the Wheland intermediate is more nearly formed in the transition state, the more reactive the compound. Or, considered another way, the position along the reaction co-ordinate at which a given amount of carbon-halogen bond formation occurs is nearer to the ground state the more reactive the compound. 

Although the most important chain reactions are those involving free radicals, they are not the only ones that are possible. The reactive centre at the growing end of a polymer molecule may alternatively be ionic in character or involve co-ordination to metal complexes. 

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