Solution chemistry species identification

Some important examples of the application of N NMR spectroscopy in S-N chemistry include (a) investigations of the (NSCOj 3NSC1 equilibrium in solution and (b) identification of the S-N species present in solutions of sulfur in liquid ammonia. The half-width of N NMR resonances is dependent on the symmetry of the atomic environment as well as other factors, such as solvent viscosity. The values may vary from ca. 10 Hz for solutions of NS2" AsFe in liquid SO2 to >1000 Hz in metal-S-N complexes. However, the chemical shift range for S-N compounds is ca. 800 ppm, so that useful information may frequently be obtained despite the broad lines. Liquid SO2 is a particularly good solvent for N NMR studies of cationic S-N species, while liquid ammonia is well suited to investigations of S-N anions/ ... 

Some illustrative examples of the application of " N NMR spectroscopy in sulfur-nitrogen chemistry include (a) studies of the (NSC1)3<->3NSC1 equilibrium in solution and (b) identification of the S-N species present in solutions of sulfur in liquid ammonia. ... 

The arrangement of ions is a major driving force in both solid and liquid salts, and crystallography is one of the only tools which can extract this information tmambiguously. While emphasis is placed on molecular stmcture identification, packing phenomena relevant to metal speciation and distribution in ILs were observed in each of the structures examined here. This is especially important when considering that the majority of solution chemistry is still based on a foundation of molecular systems where neutral species dominate and ions, if present, are considered dissociated. The phenomena observed here such as the formation of ion pairs with hydrophobic exteriors, the effect of outer-sphere interactions on metal-extractant stoichiometry, and the formation of mixed metal ion pairs, which are all still relatively unexplored even IL-based separations, may not even be observed in neutral systems. 

UV/visible spectroscopy of organometallic transients has been extremely important for kinetic measurements on previously identified species, but the spectra are less valuable for structural identification since most spectra show broad and featureless bands. One way round this problem has been to utilise matrix IR spectroscopy for characterisation and to use the data obtained from the matrix UV/visible spectrum to monitor the room-temperature kinetics. A more satisfactory method is to record the IR spectra of transients directly and there has been much activity in both gas phase and solution organometallic chemistry this field has been recently reviewed ( 35). In our laboratory,... 

When six ligands are attached to a central metal ion, Werner predicted an octahedral structure. Thus, for Co(NH3)5Cl3, he postulated a structure in which the five ammonia molecules and only one of the three chloride ions are ligands tightly bound to cobalt. The other two chloride ions are free in aqueous solution and readily precipitate with Ag. He termed such chemical species coordination compounds and identified six as the coordination number for Co. Further proof came from Werner s identification of cfr-(Cl-Co-Cl angle 90°) and trans- (Cl-Co-Cl angle 180°) isomers for Co(NH3)4Cl3, and the acmal isolation of enantiomers (see the structures depicted) in 1911. For this work, Werner received the Nobel Prize in chemistry in 1913. 

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