Crystallography recrystallization

During the course of an attempted recrystallization of this complex from benzene containing chlorinated impurities the solution was exposed to light. The crystalline compound that formed from this solution was identified by X-ray crystallography as Mo(TPP)(Ph)Cl (Fig. 3). The complex contains Irons phenyl and chloro ligands, and the Mo—C and Mo—N4 plane distances are 2.241(1) and 0.125 A, respectively. A systematic synthesis of the complex could not subsequently be developed and consequently other spectroscopic and magnetic data were not collected. 

Recrystallization of 24e from hexane yielded yellow crystals, which were analyzed by X-ray crystallography. The conformation of the thioamide chro-... 

Themal treatment of the dimeric species 279 brings about a rearrangement to tetramer 281 (equation 56). The structure of 281 can be characterized by H, C H, P H and Li NMR spectroscopies. Recrystallization of 281 from toluene yields solvated crystals of formula 281-3PhMe, which show a core 12-membered macrocycle of C, P and Li atoms according to XRD crystallography ... 

A mixture of sulfanes (H S, n = 3, 4,... n = 6) known as crude sulfane reacts with both SeCl4 and Se Cl in carbon disulfide at low temperatures to form cyclic selenium sulfides of types Se Sg and Se Sj2 - On extraction and recrystallization from carbon disulfide a mixture of twelve-membered ring molecules was obtained as yellow crystals with a selenium content of up to 29 weight-% corresponding to the formula SOj 3. As this sample was much less soluble in CSj than both S,2 and compounds of type Se S8 , it could easily be separated from the latter. The twelve-membered ring molecules have so far been characterized by X-ray crystallography only (see 3.2). 

Anatoxin-a (3) is a powerful neurotoxin (inhibitor of acetylcholine esterase) found in freshwater blue-green algae. The compound was required as an analytical standard and also for development of an immunoassay. It was synthesized by the 8-step sequence summarized in Scheme 29.1. The key intermediate 4 was resolved by separation of the dibenzoyl tartrates, and the remaining steps then gave both (+)- and (-)-anatoxin-a.2 The efficiency of the resolution was monitored by formation of the BocAla derivatives, which were distinguishable by NMR an ee of >98% was achieved even before recrystallization of the salts. It is also noteworthy that the published absolute configuration of the intermediate 53 was shown to be in error by X-ray crystallography. 

The synthesis described by Lambert and coworkers145 is outlined in Scheme 10. The final step afforded the first generation dendrimer in 85% yield after recrystallization. The structure of the dendrimer was confirmed by mass spectroscopy, NMR spectroscopy and X-ray crystallography, which indicated significant steric interaction between the three dendritic wedges. There exist twenty-seven pathways with seven silicon atoms within the dendrimer, but none of these pathways corresponds to an all-anti configuration which is optimal for electron delocalization. In spite of this, the maximum absorbance in the UV spectrum is red-shifted with respect to linear heptasilane and very similar to that of linear... 

Preparative Methods a solution of [Rh(nbd)acac] in THF is treated with fluoroboric acid, followed by addition of l,4-bis(diphenylphosphino)butane (dppb). The solution becomes deep red and ether is added to precipitate the catalyst, which is then isolated by filtration. The unpurified product is generally adequately pure for most applications. Recrystallization from methanol can be performed to obtain orange needles of [Rh(nbd)(dppb)]BF4. Although air-sensitive in solution, the crystalline complex is indefinitely stable when prepared pure and stored under N2 or Ar below 0 °C. A convenient preparation of the corresponding trifluoromethane-sulfonate has been described. The cyclooctadiene (cod) analog has been characterized by X-ray crystallography, ... 

Compound (CsF[-2,3-Me2-l,4-Ph2)2TiCl2 has been prepared by the reaction of the lithium salt of 2,3-dimethyl-1,4-diphenylcyclopentadiene with TiCl3(THF)3 after oxidation with CC14 and recrystallization from a toluene/hexane mixture. The crystal structure has been determined by X-ray crystallography. In the presence of MAO, this compound is inactive for the polymerization of ethylene.1046... 

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