Trans-effect, in metal complexes

Basolo, Fred and Pearson, Ralph G., The Trans Effect in Metal Complexes. . 4 381... 

Basolo, F., Pearson, R. G., Progr. Inorg. Chem. (F. A. Cotton, ed., Interscience, New York) 3, 381 (1962) (trans-effect in metal complexes). 

F. Basolo and R. G. Pearson, The trans effect in Metal Complexes , Prog. Inorg. Chem. (1962) 4, 381. 

Pt(II) metal complexes, are known to exhibit a structural trans effect. In octahedral complexes, trans effects can also occur, even if these effects are less pronounced... 

Gs, trans, or metal effects occur when, e.g., an octahedral coordination compound ML6 [7] is transformed into a new complex, either MLSX [2], where a ligand has been altered, or M L6 [5], where the metal M has been replaced by an isovalent metal M. The comparison of either [2] with [7], or [2] with [7], discloses either cis and trans effects or metal effects inasmuch as the properties of the ligands L are altered by this variation in the first case, the substituent effect of X is subdivided into the cis and trans effects. 

For a recent review on trans-effects in octahedral transition metal complexes, see ... 

Poe and co-workers have extensively studied the thermodynamics, kinetics and the trans effect in the reactivity of such complexes.623-634 635 638,64Cl-650-653 The thermodynamics of the successive anations of [Rh(en)2X(H20)]"+ by halogens suggests that the Rh center is a marginally soft acid, and that its softness is increased by the coordination of a soft base (such as I- ) in a position trans to the reaction site a halide ligand weakens the metal-ligand bond trans to itself, and an I- causes a more dramatic weakening than a Br-, which has more effect than a coordinated q-.634,638-640 The spectrophotometrically obtained thermodynamic parameters are summarized in Table 38. 

Comparison of cobalt(III) and platinum(II) complexes, therefore, provides further evidence for the duality of mechanism (a and v) for the trans effect in the latter and shows that there is no single order of ligands which can be transferred from one metal cation to another. A comparison of the ligand orders observed for different metal cations should lead to a much better understanding of the importance of different types of bonds between the metal and ligand, and hence of the chemical properties of complexes. It is hoped that this review will stimulate interest in obtaining more experimental data on cis and trans effects in complexes of other metal cations. 

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