Sheldrick studies

Hz. Ebsworth and Sheldrick studied the dependence of the chemical shift and H—P coupling constant of phosphine on concentration, temperature and solvent. Two phases are formed in fairly concentrated solutions of phosphine in liquid ammonia below -30 °C, one of these is phosphine-rich and the other ammonia-rich. In the phosphine-rich phase, the coupling constant, /h-p, increases from 185.2 to 186.6 Hz on cooling from -32 to -79 °C, while in the ammonia-rich phase between the same temperatures it increases from 191.1 to 195.1 Hz. 

The aldohexoses have not been extensively studied by X-ray crystal-lographers. Crystals of a- and jS-D-galactose were examined by Sheldrick,21 who gave directions for crystallizing both anomers. In one preparation, the crystals of a-D-galactose were small plates large prismatic crystals of jS-D-galactose were also obtained. 

Single crystal X-ray diffraction studies of both 9 and 10 (J.W. Gilje D. Schorriburg W.S. Sheldrick) have confirmed that the P-P bond in these compounds has remained intact. Both can-pounds represent a novel structural feature, A 5pA4P, in phosphorus chemistry. Compound IQ, in addition, is noteworthy as it carbines both a nonmetallic and a metallic five-coordinate center in the same molecule. 

If such a solution is cooled down to room temperature colorless squares precipitate. An X-ray structure determination triclinic,P a = 997.1(2),b = 1090.5(2),c = 2037.2(4)pm a = 75.98(1)°, p = 84.56(2)°, y = 71.66(1)° 9 = -100 °C Z = 2 formula units R = 0.078 shows monomeric l-bis(tetrahydrofuran)-lithium 2,2,4,4,6,6-hexaphenyl-cyc/o-trisilazane 1 to be present in the solid state. Contrary to this result the analogous 2,2,4,4,6,6-hexamethyl derivative studied by Sheldrick and Haase [2] is dimeric with only one THF-substituent bound to the three coordinated lithium. In compound 1 all Si-Cphenyi bonds adjacent to the N-Li(THF)2 fragment are slightly elongated, whereas the corresponding distances in the opposite... 

Kessler, H. Zimmermann, G. Foerster, H. Engel, J. Oepen, G. Sheldrick, W.S. Is the conformation of a molecule the same in the crystal form as in the solution form NMR spectroscopic studies of solids and solutions as compared to their X-ray structural analysis. Angew. Chem. 1981, 93 (12), 1085-1086. 

This review is not the first to discuss the structural chemistry of organosilicon compounds. There have been a few earlier reviews discussing various aspects of the structural chemistry of organosihcon compounds. The stereochemistry of elements of Group 15 and 16 bonded to silicon was reviewed in 1973 °. In 1985 the geometry of silatranes was reviewed and simulation of the reaction pathway for Sis/2 substitution reactions at tetrahedral silicon using structural data was published. Later on, in 1986, the structural chemistry of tricoordinate silicon was reviewed and the X-ray and NMR studies on penta- and hexacoordinate silicon compounds were summarized. The most comprehensive review on the structural chemistry of organosilicon compounds was published in 1989 by W. S. Sheldrick ... 

Bitterer, R, Herd, O., Hasseler, A., Kuhnel, M., Rettig, K., Stelzer, O., Sheldrick, W.S., Nagel, S. and Rosch, N., Water-soluble phosphines. 6. Tailor-made syntheses of chiral secondary and tertiary phosphines with sulfonated aromatic substituents structural and quantum chemical studies, Inorg. Chetrt, 19%, 35,4103. 

Koleva, B.B., T. Kolev, H. Mayer-Figge, R.W. Seidel, and W.S. Sheldrick. 2008. Are there preferable conformations of the tryptammonium cation in the solid state Crystal structure and sohd-state linear polarized IR-spectroscopic study of tryptammonium hydrogentartarate. Stracf. Chem. 19 147-154. 

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