Mossbauer coordination

It is an intensely reactive and hygoscopic yellow-brown substance (m.p. 75-78°C) its volatility suggests a low molecular mass Mossbauer spectra indicate 6-coordinate gold while the Raman spectrum is interpreted in terms of cw-bridged octahedral units. In the gas phase at 170°C, it comprises dimers and trimers [29] (electron diffraction). 

Magnetically perturbed Mossbauer spectra of iron and tin coordination compounds. W. M, Reiff, Coord. Chem. Rev., 1973,10, 37-77 (138). 

Mossbauer spectroscopy has also been widely used to investigate the structures of dialkylstannylene derivatives of carbohydrates in the solid state. The usual magnitude of A = 2.78-3.07 mms indicated a coordination number larger than four, with Sn centers in a penta- or hexacoordinated environment. 

The coordination of [Me2Sn(IV)f to captopril (cap) [(2S)-l-[(2S)-2-methyl-3-sulfanyl propanoyl]pyrrolidine-2-carboxylic acid] in aqueous solution was studied by means of pH-metric titration, electrospray mass spectrometry, H NMR, and Mossbauer spectroscopies in the 2-11 pH range. The results obtained proved that only monomeric complexes are formed in solution. In the acidic pH... 

R3Sn(IV)]4H2TPPS, (R = Me, Bu, Ph), respectively, in the solid state, are maintained in solution. Pentacoordination, in a Tbp configuration, eq-Rs, has been proposed for RsSnflV) derivatives of L-homocysteic acid on the basis of IR and Mossbauer spectroscopy The SO3 and NH3 groups of L-homocysteic acid are not involved in the coordination. 

Nitrogen coordination of the Rieske cluster had been suggested by Blumberg and Peisach (4) as early as 1974. However, it was only after the pioneering Mossbauer studies of Fee et al. (5) that the coordina-... 

First isolated from D. desulfuricans (28), desulfoferrodoxin (Dfe) was also isolated from D. vulgaris (29). D is a 28-kDa homodimer that contains two monomeric iron centers per protein. These iron centers were extensively characterized by UV/visible, EPR, resonance Raman, and Mossbauer spectroscopies (30). The data obtained were consistent with the presence of one Dx-like center (center I) and another monomeric iron center with higher coordination number (penta or hexacoordinate), with 0/N ligands and one or two cysteine residues (center II). Comparison of known Dfx sequences led to the conclusion that only five cysteines were conserved, and that only one of them could be a ligand of center II (31). 

The magnetic and electronic properties of the D. gigas Fdll [3Fe-4S] center were revealed by different and complementary spectroscopic techniques EPR 89), Mossbauer 90, 91), resonance Raman (RR) 92), magnetic circular dichroism MCD) 93), EXAFS 94), saturation magnetization (95), electrochemistry 96), and NMR (97, 98). The [4Fe-4S] center is also well characterized and surprising information has been obtained in relation to cluster interconversions and noncysteinyl coordination, as illustrated for D. gigas Fdl and D. africanus Fdlll, as well as the possibility of generating unusual reduced states. 

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