Structural trans-effect

Thiocarbamate (tc, RHNCSO-) is a monodentate ambidentate ligand, and both oxygen- and sulfur-bonded forms are known for the simple pentaamminecobalt(III) complexes. These undergo redox reactions with chromium(II) ion in water via attack at the remote O or S atom of the S- and O-bound isomers respectively, with a structural trans effect suggested to direct the facile electron transfer in the former.1045 A cobalt-promoted synthesis utilizing the residual nucleophilicity of the coordinated hydroxide in [Co(NH3)5(OH)]2+ in reaction with MeNCS in (MeO)3PO solvent leads to the O-bonded monothiocarbamate, which isomerizes by an intramolecular mechanism to the S-bound isomer in water.1046... 

Taking into consideration the fact that the ratio of kTc/kRt was less than 0.1 and the kinetic parameter dS for [ReO(DBDS)]- was positive, it is clear that the exchange proceed in the associative mode. This was confirmed by the shorter bond length for Tc=0 (1.657A) than for Re=0 (1.681 A), exhibiting a larger structural trans effect. 

After several years of effort it has been possible to reproduce Schmidbaur fs addition of methyliodide W The problem appears to be that the methyliodide product is extremely photosensitive in solution. It decomposes with the production of methyl radicals and the ultimate formation of a mixture of the Au(I), and Au(II) diiodide products. The X-ray crystal structure of the methyliodide product is presented in Figure 5. Two features are to be noted. Firstly, the metal-metal distance lengthens only a small amount, 0.04A, but the Au iodide distance lengthens by approximately 0.20. The structural trans effect caused by the methyl group is not attenuated by the Au-Au bond. 

A. Ground-state properties a) Bond lengths b) Force constants c) Spin coupling constants d) Optical spectra e) Magnetic moments f) etc. Ground state tram effect Structural trans effect trans influence Static trans effect... 

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

Elder, R. C., Heeg, M. J., Payne, M. D., Trkula, M., and Deutsch, E. (1978). trans Effect in octahedral complexes. 3. Comparison of kinetic and structural trans effects induced by coordinated sulfur in sulfito- and sulfinatopentaamminecobalt(III) complexes. Inorg. Chem. 17,431-440. 

Titanyl acetylacetonate is dinuclear, containing a planar di-jt-oxo-dititanium ring. The longer bond between the metal and the acetylacetonate oxygen atom is trans to the bridging oxide, thus representing a structural trans effect.105... 

Another class of mthenium aUcene complexes contains those derived from the hexaaqua ion [Ru(H20)6] +. The thermodynamically stable complex [(cod)Ru(H20)4] + (74) forms directly from [Ru(H20)6] + and cod in alcohol at ambient temperature (equation 14). In (74), the redox potential of Ru has shifted more positive for the oxidation to Ru and more negative for the reduction to Ru or Ru°, so as to impose a high stability towards disproportionation see Disproportionation) (in contrast to the readily disproportionating aqua ion [Ru(H20)6] +). The X-ray crystal structure see X-ray Crystallography) of the Tosylate (Ots) salt disclosed quite different R-OH2 distances of 2.095(2) and 2.156(2) A for water gauche or trans to the alkene double bond, showing the structural trans effect see Trans Effect) of the latter on a a- (and tv-) donor ligand trans... 

Also called a structural trans effect. For a thorough discussion of the measurement and significance of the trans influence of ligands, see T. G. Appleton, H. C. Clark, and L. E. Manzer, Coord. Chem. Rev., 1973, 10, 335. 

The /raw-influence is not the same as the trans-cEect. The first is a ground state phenomenon, while the second is a kinetic effect (see Section 25.3). The two effects are sometimes distinguished by the names structural trans-effect and kinetic trans-effect. 

The inner-sphere reductions of [Co(NH3)5(SCONHR)] and [Co(NH3)5 (OCSNHR)] by Gr involve attack at the remote oxygen and sulfur atoms, respectively, with a subsequent isomerization of the 0-bonded ehromium(III) product in the former reaction. The unusually rapid reactions of the S-bonded cobalt(III) complexes are attributed to a structural tran -effect on the Co—N bond length, reducing the reorganization energy needed to form the transition state. A kinetic study of the Cr reduction of [Co(NH3)5(pyruvate)] reveals that the rate of reduction is dependent on the nature of pyruvate ligand, with the keto form about 400 times as reactive as the hydrated form. An inner-sphere mechanism has be postulated for the Cr reduction of [Co(NH3)5(pyridine N-oxide)] on the basis of the rate and activation parameters. The outer-sphere Cr reduction of [Co(sepulchrate)] is catalyzed by halide ions, with the ion-pair formation constants for [Co(sep), estimated to be 5.5, 2.3, and 1.7 M" for Cl", Br", and I", respectively. ... 

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