Nitrite trans effect

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. 

Hydrolysis of [Rh(NH3)5(N02)] and of cis-[Rh(NH3)4(N02)2] results in replacement of ammonia, but hydrolysis of trans-[Rh(NH3)4(N02)2] results in replacement of a nitro ligand. This pattern parallels that established earlier for the analogous cobalt(III) complexes, and derives from the dominance of the trans effect of NO2. Activation parameters for the cobalt(III) and rhodium(III) complexes are compared. It is concluded that ammonia loss occurs by an Id mechanism at both metals, but that loss of nitrite has more associative character in the case of rhodium(III). " Evidence from aquation, base hydrolysis, and ligand replacement studies gives an indication of chemically nonequivalent coordination sites in [Rh(tren)Cl2]. ... 

Reactivity of Triatomic Molecules.— The outermost, unpaired electron of the ground state of the NOj molecule lies in the i sa-Su orbital. From the arguments above, this electron is more localized on the N atom than on the 0 atoms. Reaction of NOj with a free radical is therefore likely to form a nitro-compound rather than a nitrite. Inhibition of certain free-radical reactions by NOj may plausibly be attributed to such reaction the inhibition occurs under conditions where addition of a nitro-compound has no effect, but addition of a nitrite catalyses the reaction. Similarly, initiation of chains by H-abstraction by NOj (see, e.g., McDoweU and Thomas, Trans. Faraday Soc., 1950, 46,... 

The dependence of rate constant on ionic strength is still widely used, often in conjunction with the dependence of rate constant on dielectric constant, as an indicator of substitution mechanism. Recent instances of this classical approach include the reaction of /ra j-[Co(dmgH)2(SCN)(tu)] with thiourea (tu), aquation of trans-[Rh(dmgH)2Cl(tu)], aquation of the [Co(02CCHaCl)(NH3)6]"+ cation, and substitution at the [Fe(CN)6(OH2)] anion by nitrite, thiocyanate, sulphite, or nitrosobenzene. Salt effects on observed rate constants for the reaction of nickel(n) with pyrophosphate operate via the outer-sphere association constant rather than via the interchange rate constant. ... 

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. 

Antonisse MMG, Snellink-Ruel BHM, Engbersen JFJ, Reinhoudt DN (1998) Chemically modified field effect transistors with nitrite or fluoride selectivity. J Chem Soc Perkin Trans 2 773-777... 

Paik and Jung (2012) have examined the effect of ligands and solvents in Cu catalyzed Ullmann-type reaction using 10 mol% of Cul, 20 mol% of ligand, and 1 eq. of nitrite salt with 4-iodoanisole as a model substrate under microwave irradiation for 10 min. The desired compound was obtained in 84% and 83% yields in presence of N,N -dimethylethylenediamine and trans-N,N -dimethyl-1,2-cyclohex-anediamine, respectively. However, desired product could not be obtained in good amount in presence of other ligands. 

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