Single-crystal X-ray diffraction analysis

FIGURE 1.19 X-ray crystal structures of selector-selectand complexes (ion-pairs) (a) O-9-(P-chloro-fert-butylcarbamoyl)quinine with iV-(3,5-dinitrobenzoyl)-(5)-leucine, (b) tbe pseudoenantiomeric complex of 0-9-( 3-cbloro-tert-butylcarbamoyl)quinidine with N-(3,5-dinitrobenzoyl)-(i )-leucine, (c) 0-9-( 3-cbloro-terf-butylcarbamoyl)quinine with N-(3,5-dinitrobenzoyl)-(5)-alanyl-(5)-alanine, and (d) comparison of tbe complexes of (a) and (c). Most hydrogens have been omitted for the purpose of clarity. (Reprinted from C. Czerwenka et al., Anal. Chem., 74 5658 (2002). With permission.) 

FIGURE 1.20 X-ray crystal structure of the more stable complex between 0-9-(tert-butylcarbamoyl)quinine and (5)-2-methoxy-2-(l-naphthyl)propionic acid (two distinct perspectives). (Reprinted from K. Akasaka et al., Chirality, 17 544 (2005). With permission.) 

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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). 

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... 

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- ). 

This chapter deals with single crystal x-ray diffraction as a tool to study marine natural product structures. A brief introduction to the technique is given, and the structure determination of PbTX-1 (brevetoxin A), the most potent of the neurotoxic shellfish poisons produced by Ptychodiscus brevis in the Gulf of Mexico, is presented as an example. The absolute configuration of the brevetoxins is established via the single crystal x-ray diffraction analysis of a chiral 1,2-dioxolane derivative of PbTX-2 (brevetoxin B). 

The structures of compounds 55a,c and 56a,c were established by means of NMR spectroscopy and mass spectrometry. Due to the different polarity of the C=N and C=P triple bonds, the silicon ring atom in 55a,c is bound to the nitrogen atom, and in 56a,c to the carbon atom of the C=P moiety. The molecular structure of 55a was further determined by single-crystal X-ray diffraction analysis (Fig. 16).14 The four-membered SiNAsC framework is slightly puckered (folding angle N—Si—C/Si—C—As 7°), and... 

Ring-closing metathesis of diene 318 with a Grubbs second-generation catalyst gave 2,5-dihydropyrrole 319 (Equation 56). The absolute stereochemistry was assigned based on single crystal X-ray diffraction analysis... 

Reduction of the metal dimer [CpMo(NO)l2]2 with Na/Hg in the presence of a variety of acyclic dienes generates the (diene)MoCp(NO) complexes in moderate to low isolated yield (equation 8)12,31,89. For the majority of diene ligands, complexes 60 are formed exclusively as the s-trans isomers as evidenced by NMR spectroscopy and single-crystal X-ray diffraction analysis. In comparison, complexation of the 2,3-dimethyl-l,3-butadiene initially gives a separable mixture of the s-trans (60) and s-d.v-complex (61). The s-cis isomer isomerizes to the more thermodynamically stable s-trans isomer in solution (THF, 1/2 = 5 min C6H6, ti/2 = 24 h). 

Alkyne complexation by iridium(I) results in substantial deviation from linearity, as revealed by single crystal X-ray diffraction analysis [190-194]. 

The bidentate K2-mode of binding has been observed by single crystal X-ray diffraction analysis for a related palladium W-arylsulfonamidate complex. 

The BINAP derivative of the ort/io-cyclometallated iridium catalyst has been characterized by single crystal X-ray diffraction analysis [280]. Remarkably, although the reaction sequence depends upon oxidation of either the reactant alcohol or isopropanol, the enantiomeric purity of the homoallylic alcohol product... 

The structure of ketene imine 188 was elucidated by means of a single-crystal X-ray diffraction analysis. Surprisingly, bond lengths of 133 and 120 pm for the cumulated system (C=C=N) hardly deviate from those found in a linear analogue (i.e., diphenylketene p-toluylimine) (193). Apparently, the cumulated bond system of 188 is not linear but rather is bent to an angle of 163.8°. 

A library of trifluoromethyl-substituted thieno[2,3- ]pyridines has been established <2000JC024>. Structures have been confirmed by a combination of H NMR and IR spectral analysis as well as single crystal X-ray diffraction analysis. 

Highly diastereoselective alkylation at C-2 of benzo-l,4-diazepin-3-ones 41 was accomplished in 40-85% chemical yield using an (R)-phenylglycinol moiety at N-4, as the chirality-inducing element (Scheme 10) <2005EJ01590>. The optimum conditions involve deprotonation of 41 with 2 equiv of -BuLi at — 40 °C and alkylation at — 78 °C to give products 42 with 86-96% de. A single crystal X-ray diffraction analysis of the methylated derivative determined that the major product formed was the 2-(R)-isomer, as depicted in the product 42. 

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