Ligands nucleophilic attack

This mechanism does not explain what is happening in the rhodium(m) complex, [Rh(bpy)3]3+, where exchange occurs first at the 6-position. Increasing the charge on the metal ion will increase the tendency towards attack by a nucleophile and also the acidity of the pyridine ligand. Nucleophilic attack will always occur at the 4- and 6-positions of... 

In mixed complexes containing carbonyl and thiocarbonyl ligands, nucleophilic attack at co-ordinated carbon could take place either at carbonyl-C or at thiocarbonyl-C. [Fe(A -C5H5)(CO)a(CS)]+ reacts with, for example, azide ion or hydrazine by attack of the nucleophile at the thio-carbonyl-C. On the other hand, methoxide ion attacks [Ir(CO)2(CS)-(PPh3)2]+ at the carbonyl-C. ... 

Addition of amines and phosphines to acyclic (ry -pentadienyOiron cations is reversible in some cases. In a representative example (Scheme 4), kinetically controlled nucleophilic attack by phosphine occurs on the more abundant cisoid cation to generate an ,Z-diene 47. Since significant steric interactions exist between the phosphine nucleophile and substituents present on the pentadienyl ligand, nucleophilic attack in this case is reversible. At higher temperatures and longer reaction times, the thermodynamically more stable , -diene 48 is formed via nucleopilic attack on the less abundant transoid form of the (ry -pentadienyOiron cation. Amine nucleophiles add regioselectively to the unsubstituted terminus of the (ry -pentadienyOiron cation. 

As discussed above, an 18e metal hydride complex can activate CO2 through a direct hydride abstraction (4). During the abstraction process, the hydride ligand nucleophilically attacks the CO2 carbon. We expect that a simultaneous hydrogen bonding interaction of one of the CO2 oxygens with a protic hydrogen would promote the abstraction process. Indeed, it was found that... 

No reaction of soft carbon nucleophiles takes place with propargylic acet-ates[37], but soft carbon nucleophiles, such as / -keto esters and malonates, react with propargylic carbonates under neutral conditions using dppe as a ligand. The carbon nucleophile attacks the central carbon of the cr-allenylpal-ladium complex 81 to form the rr-allylpalladium complex 82, which reacts further with the carbon nucleophile to give the alkene 83. Thus two molecules of the a-monosubstituted /3-keto ester 84, which has one active proton, are... 

We have disclosed that the ligands 4c, 10, and 77, when complexed with a metal ion such as Zn2 +, Ni2+, or Co2+, become highly active toward the hydrolysis of p-nitrophenyl picolinate (7). The catalysis is most likely to occur through formation of a ternary complex in the transition state or in reactive intermediates. The metal ion in such a complex serves to activate the ligand hydroxyl group for nucleophilic attack and to orient the substrate into a favorable position to undergo the reaction. 

The NO ligand is usually regarded as a good a-donor and, therefore, electrophilic, so that the above reaction can be reversed by nucleophilic attack... 

The steric crowding introduced in the latter by the four ethyl substituents inhibits nucleophilic attack at platinum, so that complexes of this type tend to undergo substitution by a dissociative mechanism [89]. The complex of the more rigid ligand, 2,2, 2"-terpyridyl, Pt(terpy)Cl+, is found to be about 103 to 104 times more reactive to substitution than the dien analogue this is ascribed to steric strain [90], which is reflected in the short Pt—N bond to the central nitrogen (Pt-N some 0.03 A shorter than the other two Pt-N bonds) and N—Pt—N bond angles of 80-82°). 

Cleavage of a peptide bond is an example of a nucleophilic attack. The nucleophile in the reaction is either an activated water molecule or part of the side-chain of an amino acid, and peptidases are described as having either a water nucleophile or a protein nucleophile. Peptidases with a water nucleophile either utilize one or two metal ions as ligands for the water molecule, in which case the peptidase generally acts... 

Togni s [38] approach was therefore to test the ability of sparteine to act as an ancillary ligand in Pd(II)-allyl complexes—susceptible to nucleophilic attack by stabihzed anions such as Na[CH(COOMe)2]—which could be employed as catalyst precursors. In addition he speculated that the rather rigid and bulky sparteine would be able to induce significant differentiation between the two diastereotopic sites of 1,3-disubstituted allyl hgand, thus leading to enantioselection upon nucleophilic attack. 

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