Chloride trans effect

In the case of the trans-complex, only the two chloride ions are substituted, the trans-effect of ammonia being too low to give substitution with the result that white needle crystals of trans-[Pt(NH3)2(tu)2]Cl2 are formed [73],... 

Because Cl- has a stronger trans-effect than NH3, a group opposite to Cl-is replaced in the second substitution. Similarly, in the synthesis of the transisomer by heating Pt(NH3)4+ with Cl-(Figure 3.86), it is the ligand trans to chloride that is again replaced in the second step. 

The cis- and trans-isomers of [Pt(NH3)(N02)Cl2]- have been synthesized from PtCl - merely by choice of the order of ligand substitution (Figure 3.87). (In the second step, chloride trans to chloride is more labile.) The second substitution is dictated by N02 having a higher position in the trans-effect series than chloride [144],... 

The trans-effect can be used synthetically. In the reaction of Br- with Au(NH3)4+, the introduction of the first bromine weakens the Au—N bond trans to it so that the introduction of a second bromine is both sterospecifically trans and rapid. (A similar effect occurs in the corresponding chloride.) The third and fourth ammonia molecules are replaced with difficulty, permitting the isolation of AuBr2(NH3)2 (second-order rate constants at 25°C are k] = 3.40, k2 = 6.5, k2 = 9.3 x 10-5 and k4 — 2.68 x 10 2lmor s l at 25°C) [141]. 

Elder, R. C., and Trkula, M. (1974). Structural trans effect in sulfur bound sulfitopen-taamminecobalt(Ill) chloride./. Am. Chem. Soc. 96, 2635. 

It appears that one of these rate constants (kc or kt) is 10 times as large as the other and anyone who has worked in platinum chemistry will say, of course, that chloride has a greater trans effect than ammonia. These are both weak trans directors, but one would expect the fast reaction site to be the cw-chlorides in other words, the chloride which is trans to a chloride, the cis-diaquo isomer, is the one which should be formed rapidly. 

Two types of three-coordinate selenium(II) complexes, isolated as the triselenocyanate and the triselenourea salts, and which have essentially similar structures, have been identified.66 Several three-coordinate tellurium(II) complexes have also been obtained67 when one of the ligands has a very strong trans effect, for example a phenyl group, as in phenylbis(thiourea)tellurium(II) chloride.68... 

VC13 treated with Bu NC produces mer-[VCl3(CNBu,)3]. The structure was determined by X-ray diffraction.182 The HNMR spectra in CDC13 showed that the free ligand exchanges more rapidly with the isocyanide tram to chloride than with the trans isocyanide groups. Therefore, the kinetic trans effect of chloride ion is larger than that of isocyanide. 

With strong trans effect ligands, the high lability of the substrates requires that the kinetics are followed by relaxation techniques and ligands much more tightly bound than chloride have to be used in order to ensure effective competition with the solvent.245 The bulk of the strong trans effect data relates to the dissociation rate constant for the solvento species (these processes having a D... 

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