Leaving group effect platinum complexes

Lanthanide shift reagents silver complexes, 806 Leaving group effect platinum complexes substitution reactions, 494 Leucine aminopeptidase zinc, 1005 Ligases zinc, 1002... 

We certainly do not intend these rules to restrict future research, but only to encompass a large amount of past experience with platinum(II) complexes. Obviously exceptions will, and have already, occurred. For example, the high activity of bidentate leaving groups such as oxalate and malo-nate (see structures of Fig. 4) first synthesized by M. Cleare and J. Hoe-schele in this laboratory are not encompassed nor is the effect of cyclic amines, developed by Tobe, which decrease the solubility of the complexes, but markedly enhance the antitumor activity. Here, studies of the rela-... 

A very recent report moves forward significantly understanding the mechanism of reductive elimination reactions to form carbon-carbon bonds from platinum(IV) complexes.245 This report described the kinetics of reductive elimination from a cationic platinum(IV) complex as a function of solvent, of substituent character in a leaving group, of the potential effect of different spectator ligands and addressed whether there was a kinetic isotope effect. The reactions were studied also as a... 

The Russian School, particularly Chernyaev, did much of the early research on platinum(ii) chemistry. This arose from the large platinum resources in some of their natural minerals. So important was the availability of platinum to them that they had an Institute devoted in large part to the chemistry of platinum. Most of their research dealt with the syntheses and reactions of platinum complexes. Their primary goal seemed to have been to enhance the extraction of platinum from its mineral source. As early as 1926, Chernyaev" reported that certain ligands in the position trans to the leaving group of square-planar platinum(ii) complexes have a marked effect on its replacement substitution. He used this with considerable success in the preparation of desired platinum(ii) complexes. For example, he was able to prepare cis- [PtCl2(N02)(NH3)]"bythe reactions shown in (1). 

For reactions with proteins in vivo we are not in a position to say anything about the incoming group except that it is likely to be the same protein (or proteins) and site (or sites) which are involved in each case. Thus we must concentrate on the leaving groups in each platinum complex. The kinetic effect of these ligands is not completely clear as yet, but certain general conclusions can be drawn. Three important sets of data are presented in Table 1. 

Table 5.4. Effect of the leaving group on the rate of ligand substitution of a platinum coordination complex.

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. ... 

---