Single crystals X-ray diffraction

This method requires a single crystal and is time consuming, but will reveal all information about the structure. [Pg.470]

Single crystal X-ray diffraction is the predominant means of crystal structure determination and is central to crystal engineering. Key to its importance is the relative ease of use and the accurate and typically unambiguous structural characterisation it provides. [Pg.243]

Analysis by single crystal X-ray Effraction leads to the full determination of the structure of a compound. [Pg.122]

Single crystals suitable for X-ray diffraction can be grown by a number of methods, all of which lower the solubility of the compound in solution [Pg.122]

In addition, it may be possible to grow crystals by subUma-tion or from a melt. Problems sometimes occur with the intergrowth of two crystals crystal twinning). Large crystals are not necessary for use with modem diffractometers, and ideal crystal dimensions are 0.1 to 0.3 mm. [Pg.122]

In order to obtain a complete data set (i.e. enough reflection data to solve the structure of the compound under investigation), many hundreds or thousands of frames are recorded. Each frame contains diffraction data from different reflections, and at the end of the experiment, the data are extracted and assembled to produce a numerical datafile. The methods of solving a crystal structure from the reflection data are beyond the scope of this book, and further details can be found in the texts listed at the end of the chapter. [Pg.123]

In Chapter 6, we discuss solid state structures of metals and ionic compounds, and detail the unit cells of a number of prototype stuctures. The unit cell is the smallest repeating unit in a crystal lattice, and its dimensions are characteristic of a particular polymorph of a compound. A unit cell is characterized by three cell edge lengths (a, b and c) and three angles (a, (3 and 7). Distances are often given in the non-SI unit of the angstrom (A), because lA=10 °m and [Pg.123]

Problems stUl remain, though, in this area of endeavour. Any destruction of the perfection in the crystal structure degrades the sharpness of the diffracted beams. This in itself can be used for crystallite size determination. Poorly crystalline material gives poor information, and truly amorphous samples give virtually no crystallographic information this way. [Pg.124]

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. [Pg.74]

X-Ray Diffraction. Because of the rapid advancement of computer technology (qv), this technique has become almost routine and the stmctures of moderately complex molecules can be estabUshed sometimes in as Htde as 24 hours. An example illustrating the method is offered by Reference 24. The reaction of the acrylate (20) with phenyldiazo derivatives results in the formation of pyrazoline (21). The stereochemistry of the substituents and the conformation of the ring can only be estabUshed by single crystal x-ray diffraction. [Pg.309]

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). [Pg.38]

The trimetaUic uranyl cluster (U02)3(C03) 3 has been the subject of a good deal of study, including nmr spectroscopy (179—182) solution x-ray diffraction (182), potentiometric titration (177,183,184), single crystal x-ray diffraction (180), and exafs spectroscopy in both the soHd and solution states (180). The data in this area have consistendy led to the proposal and verification of a trimeric (U02)3(C03) 3 cluster (181,182,185). [Pg.327]

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). [Pg.199]

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). [Pg.199]

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. [Pg.126]

Table 16-3. Single-crystal X-ray diffraction data for OPVs. [Pg.302]

No matter how thorough, a kinetic study does not really determine a mechanism in the same sense that single-crystal X-ray diffraction measurements determine a structure. The reaction mechanism is but a scientific postulate that is open to revision when new data, new insights, or new theories of reactivity emerge. [Pg.1]

R = CH3, CH3, CD3), which were characterized by single-crystal X-ray diffraction and NMR and IR spectroscopy These complexes are rare examples of first-row transition metal alkyl-hydrido species. ... [Pg.323]

A single-crystal. X-ray diffraction analysis of the structure has recently been performed that shows that the compound is, in fact, a tin-tin bonded dimer, having an Sn-Sn bond length of 276 pm, similar to that in hexaphenylditin this was interpreted in terms of overlap of a filled spaPy orbital with the vacant p orbitals on the other tin atom resulting in a "bent, weak, Sn-Sn double bond (332). [Pg.27]

A major goal was to investigate the solid state structures of such compounds by single crystal X-ray diffraction. It was found that Lewis acid-base adducts R3M—ER3 show general structural trends, which allow estimations on the relative stability of the adducts. The experimental results were confirmed by computational calculations, giving even deeper insights into the structural parameters and the thermodynamic stability of simple Lewis acid-base adducts. In addition, their thermodynamic stability in solution was investigated by temperature-dependent NMR spectroscopy. [Pg.121]

The acid-base interaction in group 13-stibine and -bismuthine adducts seems to be very weak as is indicated by mass spectroscopic studies, which never showed the molecular ion peak but only the respective Lewis acid and Lewis base fragments. The extreme lability in the gas phase may also account for the fact that there are only very few reports on thermodynamic data of group 13-stibine or bismuthine adducts in the literature. Therefore, multinuclear NMR spectroscopy and single crystal X-ray diffraction are the most important analytical tools for the characterization of such adducts. [Pg.125]

Reliable information on the thermodynamic stability of group 13/15 adducts is usually obtained by gas phase measurements. However, due to the lability of stibine and bismuthine adducts in the gas phase toward dissociation, temperature-dependent H-NMR studies are also useful for the determination of their dissociation enthalpies in solution [41b], We focussed on analogously substituted adducts t-BusAl—E(f-Pr)3 (E = P 9, As 10, Sb 11, Bi 12) since they have been fully characterized by single crystal X-ray diffraction, allowing comparisons of their thermodynamic stability in solution with structural trends as found in their solid state structures. [Pg.126]

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. [Pg.127]

Table 5. Selected bond lengths (pm) and angles (°) of adducts R3M—ER3 (M = B, Al, Ga, In E = Sb, Bi) as obtained from single crystal X-ray diffraction...

$Table 5. Selected bond lengths (pm) and angles (°) of adducts R3M—ER3 (M = B, Al, Ga, In E = Sb, Bi) as obtained from single crystal X-ray diffraction...$

Comparison of calculated and experimental data. Since the homologous series of adducts of the type Et3Al—E(Tms)3 (E = P 28, As 29, Sb 15, Bi 14) has been structurally characterized by single crystal X-ray diffraction, their structures and thermodynamic stabilities were calculated to allow a comparison between experimental and theoretical data (Table 7). [Pg.133]

Al—E monomers. Table 15 summarizes the central structural parameters as determined by single crystal X-ray diffraction. [Pg.153]

A comparable compound, (Me2N)2BPPh2-Cr(CO)5, was synthesized by Noth et al. but not structurally characterized by single crystal X-ray diffraction Noth H, Sze SN (1978) Z Naturforsch B Anorg Chem Org Chem 33 1313... [Pg.166]

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. [Pg.257]

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. ... [Pg.442]

In C 2 solution, SsO reacts with SbCls within one week at —50 °C followed by cooling to —78 °C to orange crystals of Si202-2SbCl5-3CS2 which have been characterized by a single-crystal X-ray diffraction analysis at -115 °C... [Pg.215]

The density of 87O has been determined as 2.15 g cm at 25 °C and calculated from the lattice constants as 2.179 g cm at —110 °C, measured by a single-crystal X-ray diffraction analysis [1, 64, 65]. The 87O molecules are of Cl symmetry and consist of chair-hke seven-membered homocycles with the exocyclic oxygen atom in an axial position see Fig. 2. Most remarkably are the two almost planar groups 0-8-8-8 (torsion angle r=2.9°) and 8-S-8-8 (r=6.3- ). [Pg.216]

See also in sourсe #XX -- [ Pg.185 , Pg.186 , Pg.187 , Pg.188 , Pg.189 , Pg.190 , Pg.191 , Pg.192 , Pg.193 , Pg.194 , Pg.195 ]

See also in sourсe #XX -- [ Pg.134 ]

See also in sourсe #XX -- [ Pg.2940 ]

See also in sourсe #XX -- [ Pg.243 ]

See also in sourсe #XX -- [ Pg.76 ]

See also in sourсe #XX -- [ Pg.150 ]

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