Remote attack

M s-, outer-sphere reduction by Co(CN) -. Remote attack. Adjacent attack. J. H. ... 

Table I summarizes kinetic parameters for the reaction of Cr+2 with car-boxylatopentaamminecobalt(III) complexes of ligands which favor neither chelation of the reducing agent nor reaction by remote attack.

The neutral carboxyl group is not very effective in increasing the reduction rate of the complex. However, when the proton is removed from the carboxyl, the effect can increase and is greatest when the carboxyl ion is in a configuration favorable to chelation. Thus, the inverse (H+) path is not even observable for acid succinate in the same acidity range as that for which this path is important in the acid malonato reaction. The acid dissociation constants are known well enough so that the behavior difference between acid malonato and acid succinato can not be entirely ascribed to different acidities of the complexes. The results obtained with the acid malonate complexes, as reported in Table II, incidentally provide no support for the hypothesis (22) that electron transfer takes place by remote attack across hydrogen bonds. 

In only a few cases is there direct proof that remote attack takes place when complexes containing conjugated bond systems extending from a remote polar group (for example... 

Invoking the reducibility of the ligand in certain instances helps explain some other comparisons. Thus, it has been a matter of concern that electron transfer by remote attack through an esterified carboxyl group is accompained by such drastic effects as hydrolysis of the ester, while electron transfer through a carbonyl, when this is part of a ketonic or aldehydic function, takes place easily. This occurs even though there are no opportunities here for the kind of chemistry which accompanies... 

The case for remote attack, however, does not rest solely on these experiments, and I will outline some others which suggest that remote attack does take place in certain systems. D. LaFollette has re-examined the chemistry of the reaction of... 

On the other hand, the reverse trends exhibited by Eu+2 and Fe+2 as reductants imply in part that we are gaining more from the increasing stability of the bond being formed as we go from Br to F than we are losing from the stability of the bond being broken. I think this is also pertinent to the question of comparison of azido and thiocyanato complexes. With Co(CN)fz as reductant, the stable form of the product complex is sulfur-bonded, so that the orientation of the ligand in the oxidant is favorable for remote attack on the sulfur end, whereas the situation is unfavorable for Cr+2 and Fe+2 as reductants. 

If the bridging ligand contains only one atom (e.g.. Cl ). both metal atoms of the complex must be bound to it. However. If the bridging ligand contains more than one atom (e.g.. SCN ). the two metal atoms may or may not be bound to the same bridging-ligand atom (see Problem 13.30). Hie two conditions are called adjacent and remote attack, respectively. A remote attack may lead to both linkage isomers ... 

A related example of inner-sphere reaction is shown in reaction (5), where an additional mechanistic subtlety appears.10 As shown by the products, inner-sphere electron transfer also occurs but now by remote attack in which the sites of bridging ligand binding to the reductant and oxidant are at different atoms on the bridging ligand. 

Two separate but somewhat interwoven themes have emerged from the study of inner-sphere reactions. The first is the use of product and rate studies to establish the existence of inner-sphere pathways and then the exploitation of appropriate systems to demonstrate such special features as remote attack . In the second theme the goal has been to assemble the reactants through a chemical bridge and then to study intramolecular electron transfer directly following oxidation or reduction of the resulting dimer (note equation 7). It is convenient to turn first to chemically prepared, intramolecular systems since many of the theoretical ideas and experimental results for outer-sphere reactions can be carried over directly as an initial basis for understanding the experimental observations. 

The proposed method is universal to different attack types, and it enables to detect the status of remote attacking computer in the real time. The software module allows to promote the efficiency of corporate networks defense systems functioning, using its aggregation with the program complexes of the Intrusion Detection System. 

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