Nitrite labilizing effect

Reaction of the newly prepared and characterized cation trans-[Co(en)2(S203)(OH2)], containing S-bonded thiosulfate, with nitrite or thiocyanate follows a second-order rate law. It is much more likely that this is to be explained by a dissociative interchange than by an associative mechanism. Rate constants and activation parameters (A// and A5 ) are reported. The S-thiosulfate ligand has a considerably smaller fran -labilizing effect than S-sulfite. The hydroxo complex tr(3n5 -[Co(en)2(S203)(OH)] is less reactive than the aquo complex. 

Even cis-trans and mer-fac isomers are usually well-separated in the spectrum 10 ppm for the isomers of PtClaBra " 208 ppm for Pt(NH3)2(Ha0)a, and 310 ppm for Pt(N0a) Cla " (12). Substitut-ion shifts are smallest for substitutions trans to ligands with high trans influences. Thus, in Pt(IV) nitrite complexes, a Br" for Cl substitution is ca. 50 ppm larger when trans to Cl compared to trans to NOa (12). The term trans influence is used to denote the dependence of NMR (ground-state) parameters on the nature of the trans ligand. This is distinct from the trans effect" which is related to bond labilization as measured by ligand substitution rates. 

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