Ammines spectroscopy

Platinum ammine complexes have been a fertile area for studying transinfluence. Table 3.21 lists data for a range of ammines showing how /(195Pt-15N) depends upon the trans-atom [153]. (A further selection of data can be found in R.V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in Inorganic Chemistry, Ellis-Horwood, Chichester, 1991, pp. 76, 87.) Possibly the most detailed study (of complexes of tribenzylphosphine) examined over a hundred neutral and cationic complexes [154] (Table 3.22). 

A number of structures in solution, of ammine and related complexes, have been determined by X-ray diffraction techniques, supported by the use of Raman spectroscopy. A study on... 

N-NMR spectroscopy can be useful for ammine and amine complexes, but 14N is a quadrupolar nucleus, and quadrupolar relaxation is dominant when the environment of 14N has a low symmetry. This can lead to very broad lines and a consequent reduction in sensitivity. On the other hand, short relaxation times also have the advantage of allowing rapid pulsing so that a large number of transients can be acquired. Thus it is possible to follow reactions of cisplatin in blood plasma and cell-culture media at milli-molar drug concentrations and to detect ammine release [6],... 

Cisplatin is able to bind to a number of extra- and intracellular proteins. Most of the platinum (65-98%) in blood plasma is protein-bound one day after rapid intravenous infusion of cisplatin [46]. H NJ-NMR spectroscopy can be used to study binding sites of Ptn ammines and amines on these proteins, such as albumin and serum transferrin. 

In the metal refining of ores, the metal is solubilized in an aqueous solution. The optical control of metal refining requires quick, accurate analysis of the major chemical species present in solution. Raman spectroscopy and resonance Raman are used to identify the amine complexes of Co, Ni, and Cu species, as well as ammonia sulfate and sulfamate, present in these industrial solutions. The Raman spectra of an industrial plant solution from mine tailings are shown in Fig. 7-15. Each solution contains one or more metal species, sulfate, sulfamate, ammonia, ammonium sulfate, and water. From a comparison with model ammine complexes, the vibrations in the spectra are identifiable. Bands were observed at 615, 980 and 1,110 cm-1 and were assigned to the sulfate ion. No bands were observed for free ammonia. A band at 376 cm-1 was assigned to the Ni(NH3)j + specie. A band at 490 cm-1 was assigned to the Co(NH3)g+ specie. 

This conclusion is further confirmed by data obtained with Co(NH3)6. In this case, amminated Co ions remain in supercages at calcination temperatures below 300°C (77). Therefore, a pronounced reduction enhancement of Co ions by Pd is found after calcination at low temperatures, e.g., 250°C. Evidence for direct interaction of Pd ions with amminated Co ions is obtained by UV-Vis diffuse reflectance spectroscopy and temperature-programmed oxidation. The oxidation of the ammine ligands of the Co ion is catalyzed by Pd, so that ammine oxidation is complete below 350°C for [Pd(NH3)4 + Co(NH3)6 ]/NaY, whereas 450°C is required in the absence of Pd. Ammine destruction of the [Co(NH3)6] ion is a stepwise process, the last step being the conversion of the tetrahedral complex [CoCOzlsNHs], where stands for framework oxygen at the SII site, to a naked Co ion inside a hexagonal prism. The locations and coordinations of Co and Pd ions in NaY are summarized in Table III. 

The chemistry of non-peroxo polynuclear cobalt(III) ammines is reviewed with particular emphasis on Werner s major contributions. Modern work in this area has shown that Werner s conclusions regarding the structures of these compounds are substantially correct in spite of the relatively primitive techniques he had available. There is much current interest in polynuclear cobalt(III) complexes because of their relationship to oxygen carriers and intermediates in electron transfer reactions. Modern techniques such as spectroscopy and x-ray diffraction have been used to determine the electronic and molecular structures of these compounds. 

EXPERIMENT 2.7 CONFIRMING YOUR ANALYSIS—VISIBLE SPECTROSCOPY OF COBALT AMMINE COMPLEXES... 

Results Summary for Visible Spectroscopy of Cobalt Ammine Complexes... 

This work lead to an interest in the luminescence of lower symmetry chromium ammine complexes. In these complexes, the 2Eg state is split into two components by the lower symmetry ligand field. The tetragonal ligand field parameters for many of these compounds were well known or easily available from optical spectroscopy, but the splitting of the 2Eg as measured by the absorption and emission spectroscopy... 

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