X-ray structure determination, for

The zinc teflate Zn(OTeF5)2 has been synthesized and characterized by IR and 19F NMR spectroscopy. The interaction with a number of weakly coordinating solvents was studied and the single-crystal X-ray structures determined for nitrobenzene derivatives [Zn(OTeF5)2 (PhN02)2]2 and Zn(0TeF5)2(PhN02)3.428... 

Zinc boryloxides with a tetrameric Zn404 core (45) have only recently been characterized. The single-crystal X-ray structure and multinuclear NMR spectroscopy studies were used as a basis for discussion of deformation of the central core.435 Alkali metal zinc orthoborates MZn4(B03)3 (M = K, Rb, Cs) have been synthesized and single-crystal X-ray structures determined for M = K and Rb.436... 

Complexes with type II structures are compiled in Table II along with their S—S distances and S—S vibrational frequencies. There are several examples of complexes of structure type Ila (planar trans end-on bridging coordination). Vibrational spectroscopy 174) indicates that this structure occurs in [(CN)5Co(S2)Co(CN)5] (7). Trans arrangement of the metal atoms has been proved by X-ray structure determination for [(NH3)5Ru(S2)Ru(NH3)5]Cl4 2H20 15, 44). 

Sheppard, 1963) and tripeptide oxazoline [18] spontaneously yields cyclol [19] when dissolved in ethyl acetate (Jones et al., 1963). The cyclol structure was confirmed by an X-ray structure determination for compound [21a] which was obtained by treatment of the peptide-nitrophenyl ester [20a] with 1 1 carbonate bicarbonate buffer in aqueous dioxan [21ft] was obtained similarly from [20ft] (Lucente and Romeo, 1971 Cerrini et al., 1971). 

Structures of five derivatives of 13 were obtained in the solid state by X-ray diffraction analysis the experimentally determined bond lengths differed from those calculated by the Hartree-Fock method <2001AXB63>. X-ray structures determined for the dispirans 14 and 15 revealed an interesting facet. In the solid state the heterorings of... 

X-Ray structure determinations for 1,2-dithiolylium salts (4) (80MI43100) showed S—S bond distances of 2.02 A. For 1,2-dithiolylium iodides (4 X = I), charge transfer between the cation and iodide was found. 3,5-Diamino-l,2-dithiolylium ions (8) and derivatives showed long S—S bonds ( 2.07 A), indicating substantial iminium character, i.e. from structures of type (8a). The mesoionic l,2-dithiolylium-4-olates (7) have typical dithiolylium bond distances (78AJC297) and are best represented as shown. 

There are now three different proteins of the XDH/XO family whose structures have been determined by X-ray protein crystallography. The structure of aldehyde oxidoreductase from the bacterium Desulfovibrio gigas was the first X-ray structure determined for an oxo-molybdenum enzyme (17) and has been followed by stmctures of XO/XDH (10) and carbon monoxide dehydrogenase (CODH) (19, 21). Although the three enzymes are placed in the same family, there are structural differences among them at the active site and at the phosphate remote from the Mo center. 

The Appendix gives calculated patterns based on the results of X-ray structure determinations for the clinker phases. For each pattern, a Reference Intensity Ratio (H23) is included. This is the integrated intensity of the strongest individual reflection (which may be a component of an overlap) relative to that of the strongest peak of corundum in a 1 1 mixture by... 

On the basis of the known structure for c-type lysozyme and the nature of the groups involved in its catalytic activity, and early models of a-lactalbumin structure, there were good structural reasons that militated against a-lactalbumin having lytic activity. This point of view was well developed in the useful reviews by Hill and Brew (1975) and by Brew and Hill (1975). Recent X-ray structural determinations for a-... 

Several monomeric and polymeric hexacoordinate siloxane complexes with phthalo-cyanine as a planar tetradentate ligand have been the subjects of X-ray structure determination, for example the bis-trimethylsiloxy compound 55118. 

In additional papers, Doyle s group reported that the same catalyst also gives very high optical yields in alkyne cyclopropenations and in other CH insertions (Doyle et al., 1991b Doyle et al., 1992b, 1993c, 1994 Protopopova et al., 1992). Mechanistically most important are the X-ray structures determined for [Rh2((5iS)-... 

Figure 3. The centro-symmetric molecule [Me2Si(NtBu)2Sn] [Fe(CO)4]2 (9) from an X-ray structure determination. For further details see caption to Fig. 1.

Che and coworkers [152] were able to isolate and characterize a pure bis-carbene (TPFPP)Os(CPh2)2 (Fig. 3). The bis-carbene species represents the first structurally characterized fra s-bis-carbene metal complex whose carbene groups are not stabilized by heteroatoms. The related pentacoor-dinated mono-carbene complex was also prepared and characterized by an X-ray structure. A comparison of the reactivity of these complexes with olefins suggests that the bis-carbene species acts as an intermediate in cy-clopropanation. Thus, the inertness of the mono-carbene complex towards stoichiometric styrene cyclopropanation and the observation of an efficient cyclopropanation of styrene in the presence of the bis-carbene complex as a catalyst support this suggestion [152]. A recent X-ray structure determination for (TPFPP)Os(CPh2)(MeIm) revealed an Os = C distance of 1.902(3) A (Table 3) [141]. Recently, Che and coworkers [153] and Miyamoto and coworkers [154] reported oxo-bridged carbene complexes of osmium porphyrins (see Table 3). These compounds are rare examples of oxo-binuclear carbene complexes. 

It has been supposed [40] that the symmetrical stereochemistry of the six-coordinate metal binding site in mono- and bimetallic species can be achieved if the ethylenediamine chelate ring is expanded by one aliphatic carbon atom. Indeed, the X-ray structure determination for [Zn(H2L1676)](PF6)2 and [Zn(L1676)Zn(CH3C00)]PF6-CH30H revealed essentially C2 symmetric structures with tra/i -coordinated pyridyl ligands (8.12) [40]. 

An X-ray structure determination for the stable benzocyclobutadiene (49) indicates, as expected, that the canonical form shown best describes the structure. Sophisticated calculations have been carried out for a wide range of benzo-fused cyclobutadiene derivatives. The agreement between calculated and experimental transition energies and moments for the few known compounds is impressive enough to suggest that predictions for the (as yet) unknown compounds are reliable. Because of the discrepancy between the calculated spectra and the data reported for the tentatively claimed 1,2-diphenylphenan-thro[l]cyclobutene (50), the alternative structure (51) has been proposed. ... 

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