Effects of Non-leaving Groups

Effects of Non-leaving Groups.— There have been a number of reports of the kinetics of the first step in the stepwise aquation of chloride ions from complex ions of the type cis-[Cr(LL)2Cl2] [LL = en, iso-bn (bn = butylenediamine), meso-hn, dl-hn, or 1,2-diaminobenzene] in acidic solution. The results are collected in Table 15. There is no marked effect of changing the nature of LL, and the reactions generally proceed with retention of configuration. 

The complex ions c/5 -[Cr(en)2(CN)a]+ and cw-[Cr(en)2(OH2)CN] + have recently been prepared and kinetic studies are underway.  

Mutarotation is reported to proceed for reaction (12) without complications from racemization, cis-trans-isomerimtion, or chelate ring-opening.  

A series of complex ions of the type [Cr(tren)XY]+ has been prepared. Stepwise aquation of the dichloro-complex (X = Y = Cl) occurs with loss of Cl- (first step) and with Cr—N bond fission (second step) to give a complex in which tren is acting as a protonated terdentate ligand (trenH)  

Ratio of values of k to those for the aquation of the ions cis-[M(en)2Cl2]+ ond a-cis-[M(trien)Cl2l  

142 Udovenko, L. E. Reiter, and I. Reran, Zftur. neorg. Khim., 1977, 22, 1154. 

An /a mechanism is also favoured for the aquation of a,6c, ( -[Cr(dien)(LL)Cl]-ZnCl4,H20 [LL=en, 1,2-diaminopropane (1,2-pn), or 1,3-diaminopropane (1,3-pn)]. The results (itaq) are collected in Table 18 together with those for the Hg -catalysed (A hk) and base-catalysed (/ oh) reactions.  

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Catalysis.—Acid- and base-catalysed reactions have already been mentioned [equation (27)] and will not be dealt with further in this section. c -Activation by coordinated oxoanions has also been discussed in the section dealing with the effects of non-leaving groups. Addition of sulphite, acetate, and nitrate ions to [Cr(H20)5X] + complexes (X = F, N3, or AcO) is also reported to accelerate the rate of aquation by the facile formation of oxoanion complexes. Rate data are reported for sulphite labilizations of the acetato- and azido-complexes and the nitrate labilizations of acetato- and fluoro-complexes. The catalysed reactions are characterized by a rate law of the type... 

On Main Group Metal Ions by Al3+ Effect of Non-leaving Ligands on the Rate Constants and Activation Parameters for Solvent Exchange on Al3+... 

This proposal rests on a combination of 3 chief experimental findings. (1) The order of the reactions (5-9 ) is never less than one with respect to the concentration of the phosphazene and the amine requiring that both of these be involved in the rate-determining, or a prior, step. (2) The existence of a second-order term in the concentration of amine in non-polar solvents arising from base catalysis by amine (7). (3) The effect of the leaving group, the... 

Effects of non-leaving ligands, and of chelating ligands in particular, on reactivities have been reviewed. The cis and trans influences, i.e. initial-state effects as far as kinetic phenomena are concerned, of some groups in platinum(ii) complexes have been assessed by CNDO-MO calculations. The cis influences were found to be comparable in magnitude to trans influences, but the ligand orders in the two series of influences were not identieal. ... 

Effects of Non-leaving Ligands.—[Co(en)aXY] + Complexes. A number of different groups have reported rate data for the aquation of cobalt(iii) complexes of the type cis- and /ra/7 -[Co(en)aXY] + (X and Y are unidentate ligands with X the leaving group). The results are collected in Table 5. When X = Cl, the ratio of the rate... 

Figure 11,45 (a) dependence of the rates of spontaneous hydrolysis of 4-nitrophenyl triesters and one diester on the sum of the pK/s of the non-leaving groups ROH. (b) Effects of leaving group capability on the energy surface for the reaction of phosphate triesters with nucleophiles according to Kirby and Nome. ... 

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