Coordination compounds group transfer

Diorgano ditellurium compounds react with transition metal salts and carbonyl complexes to form coordination compounds (Table 5, p. 283). Complexes with the following transition metals have been reported Ti, Cr, Mo, W, Mn, Re, Fe, Ir, Ni, Pd, Pt, Cu, Ag, Cd, Hg, Yb, and U. In many of these complexes, the organyltelluro group bridges the metal atoms in binuclear complexes. The Te —Te bond seems to remain intact upon complexation to mercury halides, rhenium carbonyls, and uranium pentachloride. For details on tellurolatO bridged complexes see p. 212. Complexes with SnCl are also known. Diphenyl ditellurium and bis[4-ethoxyphenyl] ditellurium formed charge-transfer complexes when equimolar amounts of the ditellurium compound and tetracyano-p-quinodime-thane were refluxed in acetonitrile. ... 

Ammonium salts have been grouped in a separate chapter to emphasize the similarities of behaviour in reactions involving the NH4 ion, or yielding the volatile NH3 molecule, following a proton transfer step. Detailed kinetic studies have been published for the sohd-state decompositions of many ammonium salts. Comparisons with the metal salts containing the same anion are often useful. The reactions of sohd coordination compounds in which ammonia is present as a ligand are discussed in Chapter 17. 

It is anticipated that this concept of intramolecular assistance by heteroatom-tin coordination will be shown to be extremely useful in reactions comprising metal-mediated group transfer from tin to an oiganic substrate by C—C bond formation (111,112). In this context similar reactivity of tetraorganosilicon compounds with intramolecular heteroatom coordination can be expected. 

The modular construction of fluorescent supramolecular proton sensors allows the use of a great variety of fluorophore and receptor units. The majority of the supramolecular fluorescent proton sensors possess an amine component as the receptor. The simplest and most common cases are those having an aromatic hydrocarbon as the fluorophore, but systems based on coordination compounds have also been proposed. For example Grigg and Norbert have synthesized supramolecular species where amine units are covalently linked to Ru(bpy)3 (see, e.g., 9). In neutral solution the amine units are unprotonated and the luminescence of the Ru(bpy)3 moiety is completely quenched when AG for electron transfer is negative. Protonation of the amine groups (pKa=2.4 for 9) leads to the retrieval of the luminescence. The luminescence maxima and quantum yields of the protonated forms, however, are different from those of free Ru(bpy)3 " , presumably because of the presence of the positive charges in the vicinity of the luminophore. 

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