Ligands trans

The wer-isomer does not react under these conditions. The properties of coordinated anions (e.g. Cl-) in these complexes depend on the trans-ligand in various ways. Thus in wer-IrCl3(PR3)3, the chloride trans to phosphine is more labile and thus readily removed by aqueous AgN03 (unlike the other two chlorides). Likewise i/(Ir—Cl) in the IR spectra of these complexes depends on the ligand trans to chloride. 

Table 3.13 Comparison of the effect of the trans-ligand on substitution of Cl by py in rrans-PtClX(PEt3)2 at 25°C...

Study of a series of complexes trans-Pt(PEt3)2HX shows a pronounced dependence of i/(Pt-H) upon the trans-ligand (Table 3.18). 

Table 3.18 shows how the position of the low-frequency hydride resonance is affected by the trans-ligand, while study of a series of complexes trans-[Pt(PMe2Ph)2(Me)L]+ and neutral trans-Pt(PMe2Ph)2(Me)X shows the trans-influence of the ligand on 2/(195Pt- H) with better donors tending to reduce the value of J (Table 3.20) [152],... 

The structures of the cis- and trans-isomers of Pt(PEt3)2Cl4 have been determined [176]. Table 3.26 shows the bond lengths depend slightly on the trans-ligand. 

Now consider a molecular stretching vibration that alternately elongates and compresses axial (parallel to z, let s say) and equatorial bonds as outlined in Fig. 7-3. Imagine an extreme vibration of this kind that eventually distorts an octahedral molecule so as to gradually remove two trans ligands (again, let this direction be... 

The above results show that the reactions of all organocobalt(III) complexes with Hg(II) ions so far reported share several features in common. The reaction proceeds by an Se2 mechanism and the rate is reduced [compared to that of the simple aquated Hg(II) ion with the methyl complex] by (1) complexing of the Hg(II), e.g., with chloride, (2) increased substitution on the a-carbon, and (3) reduced electron donation from the cis and/or trans ligands. 

These results indicate that the form in HX solution is most likely [TcN(OH2)X4], with the trans ligand readily lost or exchanged, and the form precipitated de-... 

A good indicator of the presence of the Tc =0 group in the complex is its stretching vibration, observed in the ir spectra as a sharp, intensive band. Its values range from 890 to about 1020 cm-1 and are related to the electronegativities of the ligands in the equatorial plane as well as of the presence and nature of a trans ligand. 

Theoretical explanation of the trans-effect (and /ram-influence) has centred on two theories, one based on cr-bonding the other on tr-bonding. The cr-bonding argument considers two trans-ligands sharing a metal p orbital (Figure 3.83). 

In the imido systems the n n transition is shifted to lower energy (518 nm) and markedly decreases in intensity. On the other hand, upon substitution of the anionic trans-ligands by acetonitrile the n->-n transition is found at 450 nm, shifting to 525 nm upon protonation. Moreover, the metal-N(nitrido) stretching frequency increases to 1016 cm From a chemical viewpoint it is important that the nitrido-nitrile complex can be... 

Table 4.31. Computed Pt—H, Pt—X, and Pt—PIT bond lengths for cis and trans isomers o/PtHX (PH3)2 (X = H, F, Cl, Br, I), showing marked variations depending on the trans ligand (in parentheses)...

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