Cluster compounds spectra

Cluster Compounds.—The green nitrosyl cluster Os3(CO)jo(NO)2 has been reported in 13% yield from the reaction of NO with Os3(CO) 2 benzene. Its i.r. spectrum suggests bridging nitrosyl groups, which was confirmed from an X-ray analysis of the Ru analogue. I.r. studies show that the structure (23)... 

Augite, Mossbauer spectrum of, 6 474 Au(PRj) fragment, addition to homonuclear gold cluster compounds, 39 329-332 Auranofin, 36 21 cytotoxicity, 36 22, 34 Auro-bis(thiosulfate), 36 18-19 Aurosomes, gold in, 36 21-22 Aurothioglucose, 36 18-19 Aurothiomalate, 36 18-21... 

The stability of the Au, cluster compound is of course supplied at least in part by the ligand shell, and this complicates a direct comparison of the above theoretical predictions for imaginary bare Au,. But experimentally, the presence of an MES spectrum consisting of a superposition of distinct lines of the natural linewidth for gold from four different structural sites also constitutes proof that gold core of the Au, cluster is, at least on the time scale of the MES measurements (i.e. 0.1 ps < t < 10 ps) [112,113], a solid up to temperatures of at least 30 K. Surface melting on this time scale can also be refuted for Au, for the same reason. The same has also been observed by MES on the water soluble compound Au, [46],... 

Fast atom bombardment mass spectroscopy has proved to be most useful when applied to the characterization of heteronuclear gold cluster compounds containing hydride ligands (137,149,155). Characterization is aided by the observation that peaks are invariably present in the spectrum corresponding to ions that contain all of the hydride... 

The 31P H NMR spectra of a number of heteronuclear gold cluster compounds are found to be deceptively simple and NMR studies have been used as a probe of the behavior of these species in solution. This is especially true of the higher nuclearity clusters, which often exhibit spectra that are much simpler than would be predicted on the basis of their solid-state structures. For example, [Pt(H)(PPh3)(AuPPh3)7]2+, which adopts the solid-state structure illustrated in Fig. 9 (137) in which the phosphine ligands occupy several different chemical environments within the molecule, shows only two resonances in the 31P 1H NMR spectrum. These are in a ratio of 7 1 and exhibit satellites due to coupling to the central platinum nucleus as Fig. 10 illustrates. 

H NMR spectroscopy has been used extensively in the characterization of gold heteronuclear cluster compounds that possess hydride ligands. For example, Fig. 12 illustrates the hydride region of the H NMR spectrum of [Au4Rh(H)2 P(0-i-C3H7)3 2(PPh3)4]+ (155). 

Trifluoromethyl)phenylcopper was found to be an octamer by consideration of the kinetics of its decomposition, and by cryoscopy and vapor pressure osmometry in benzene solution 36). Its F NMR spectrum in ether at room temperature is a sharp singlet. Consequently, the suggested structure is a central copper cube with equivalent bridging benzotri-fluoride groups. The initial decomposition product, Cu8( n-CF3CgH4)e, is considered to be a Cu(0)—Cu(I) octanuclear cluster compound 36). For the octameric m-(trifluoromethyl)phenylcopper, the tetrameric ortho isomer, and pentafluorophenylcopper tetramer, the F NMR spectra were found to vary with temperature. The changes are not considered to involve important structural alterations, but only variations in solvent complexes and rotamer populations 32, 37). The spectra also... 

The 252(]f.pp) niajj spectrum of metal halides and oxides consists of a family cluster ions of these compounds extending to over mIz 10000, produced by the ejection of small domains of the crystal lattice in the region around the fission track. In addition, cluster ions are also observed that do not correlate with the composition of the crystal lattice, indicating that some of the cluster ions are involved in gas phase reactions in the desorption plume. One of the unique applications of 252(]f.pj) jg elucidation of the composition of large transition metal cluster compounds with values approaching 10. ... 

Not only the molecular ion peak but all the peaks m the mass spectrum of benzene are accompanied by a smaller peak one mass unit higher Indeed because all organic com pounds contain carbon and most contain hydrogen similar isotopic clusters will appear m the mass spectra of all organic compounds... 

Molecular Identification. In the identification of a compound, the most important information is the molecular weight. The mass spectrometer is able to provide this information, often to four decimal places. One assumes that no ions heavier than the molecular ion form when using electron-impact ionization. The chemical ionization spectrum will often show a cluster around the nominal molecular weight. 

Although this spectrum had never been observed for any Fe-S protein, it was reminiscent of, and indeed nearly identical to the EPR spectrum of the synthetic model compound [FeeSeiLIe] where L = Cl, Br, I, RS, or RO (S). The spectrum of this synthetic cluster. 

A preliminaiy characterization of a new iron—sulfur protein isolated from Desulfovibrio vulgaris Hildenborough was reported in 1989 124). The protein contained approximately 6 iron and 6 inorganic sulfur atoms per molecule. The FPR spectrum of the dithionite reduced protein exhibited an S = signal similar to what was found for synthetic compounds with a [6Fe-6S] core (prismane core). No other FPR signals were reported at this time, and based on the observed similarity it was suggested that this peculiar iron-sulfur protein contained a [6Fe-6S] cluster. Because it had no known function, the pro-... 

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