Single crystal X-ray diffraction studies

These hydrated salts contain bidentate carbonate ligands and no water molecules are bound directly to the central metal atom. The only single-crystal x-ray diffraction studies available are those for salts of (4) (52—54) and the mineral tuliokite [128706 2-3], Na2BaTh(C03)2 -6H20], which contains the unusual Th(C02) 2 anion (5) (55). 

A single-crystal x-ray diffraction study has shown that the borate anion in anhydrous borax is polymeric in nature and is formed via oxygen bridging of triborate and pentaborate groups (83). The chemistry of anhydrous borax has been reviewed (73,84). 

A single-crystal x-ray diffraction study gives a stmctural formula of Na2 [B5 0g (0H)4]-3H2 0 and contains the pentaborate ion analogous to that found in the corresponding potassium compound (86). 

Kennard, O., Hunter, W.N. Oligonucleotide structure a decade of results from single crystal x-ray diffraction studies. Q. Rev. Biophys. 22 327-379, 1989. 

Up to now, fifteen group 13-stibine R3AI—SbR and four group 13-bismuthine adducts R3AI—BiR3 have been structurally characterized by single crystal X-ray diffraction studies. Their central structural parameters are summarized in Table 5. Structures 1-4 show the solid state structures of four representative adducts. 

Other single-crystal x-ray diffraction studies of transition element dopants in jS-rh boron are based on the results of a refinement of the /3-rh boron structure that establishes the occurrence of four new low-occupancy (3.7, 6.6, 6.8 and 8.5%) B positions in addition to the earlier known ones. The dopant elements studied, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Hf and Ta, do not enter B positions in the framework, but they enter the Al, A2, D and E positions. In some cases the doping elements have been studied at several concentrations for each element and for different cooling rates. The percentage occupancies of certain positions are eorrelated with the atomie sizes of the dopants. The bond distances between the polyhedra are shorter than those within the polyhedra. The mechanism of doping for some cases is denoted displacive, rather than interstitial or substitutional, because of competing interactions between the six different partially occupied B positions and dopant atoms. 

The Ca-Cu system has been reexamined using thermal analysis and x-ray diffraction methods an independent study of the CaCuj-Cu section has also been completed. The resultant phase diagram, although similar to that in ref. 3 at the Cu-rich end, differs markedly for Ca-rich alloys. Supporting evidence for the modifications has been obtained from the Ca-Mg-Cu ternaiy system. Three intermediate compounds are formed in the system CaCuj (950 C) melts congruently, whereas CajCu (488 C) and CaCu (567°C) are formed in peritectic reactions. Single-crystal x-ray diffraction studies verify the stoichiometry of CajCu and examine the polymorphism of CaCu. ... 

The identities of 12 and 13 were confirmed by single crystal X-ray diffraction studies. Structural models of 12 and 13 along with selected metrical parameters are presented in Figs, 10 and 11 and Table III, respectively. 

Apart from characterization of the individual types of six-membered heterocycles by routine spectroscopic methods, several cationic cyclic diketiminato-phosphenium ions and 1,8-diamidonaphthalene-derived P-chlorophosphines and phosphenium ions, respectively, were characterized by single-crystal X-ray diffraction studies. The P-halogen- and P-hydroxy-substituted cyclic diketiminato-phosphenium ions 28... 

Furthermore, a series of single crystal X-ray diffraction studies were reported for several thiadiazole 1-monoxides and 1,1-dioxides, allowing a direct comparison in bond lengths and angles for an identical 3,4-substitution pattern (Table 4). The related fused phenanthro[9,10-r-]-l,2,5-thiadiazole 1,1-dioxide 51 and acenaphtho[l,2-f]-l,2,5-thiadiazole 1,1-dioxide 53 have similar bond lengths to 3,4-diphenyl-1,2,5-thiadiazole 1,1-dioxide 10 <2001JST157>. 

BC13, BBr3 and BI3. B-N distances obtained from single crystal X-ray diffraction studies as well as gas phase measurements yielded only small variations (X-ray 158.5-161.Opm gas phase 165.2-167.4pm),38 again demonstrating that the thermodynamic stability of group 13/15 adducts not necessarily correlates with their M-E bond length. 

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