X rays, crystal structure using

Because the crystalline material (called, at that time, vincaleucoblastine) had what were reported to be interesting properties, further examination was undertaken, physical data were collected, and suggestions for the structure based on spectroscopic analysis were set forth. Finally, the X-ray crystal structure, using the Bijvoet method of anomalous dispersion vide supra), succeeded in establishing the structure and stereochemistry beyond reasonable doubt. 

Reductive coupling reaction of fluonnated vinyl iodides or bromides has been used as a route to fluorinated dienes [246, 247, 248, 249, 250. Generally, the vinyl iodide is heated with copper metal in DMSO or DMF no 1 ntermediate perfluorovmy I-copper reagent is detected. Typical examples are shown m equations 163-165 [246, 247, 249. The X-ray crystal structure of perfluorotetracyclobutacyclooctatetraene, prepared via coupling of tetrafluoro-l,2-diiodocyclobutene with copper, is planar... 

The X-ray crystal structures of many of these complexes have now been determined representative examples are. shown in Fig. 4.11 from which it is clear that, at least for the larger cations, coordinative saturation and bond rhrectionality are far less significant factors than in many transition element complexes. Further interest in these ligands stems from their use in biochemical modelling since they sometimes mimic the behaviour of naturally occurring, neutral, macrocydic antibiotics such as valinomycin, monactin, nonactin, nigericin... 

The alkaloid Nigellicine proved to be the pyridazino[l,2-u]indazolium-l 1-carboxylate (234) and forms yellow crystals (Scheme 77). It was isolated from the widely distributed herbaceous plant Nigella saliva L., which is used as a spice and for the treatment of various diseases (85TL2759). The structure was determined by an X-ray crystal structure analysis. The carboxylate bond distances are essentially equal (123.3 and 125.6 pm). An intramolecular hydrogen bond was found between the carboxylate oxygen atom and the hydroxy group. In mass spectrometry, the molecular peak was found at mjz —246 (20) and the base peak at mjz —202 which corresponds... 

The research work described here was carried out by an able group of students of Yamaguchi University and Ube Techinical College, and in collaboration with our laboratory staffs and industrial colleagues. In particular, Dr. S. Fujisaki and Dr. T. Okamoto made significant contributions. We thank them all, and also Dr. H. Tsuzuki of Central Analytical Center of Kyushu University undertook X-ray crystal structure analysis of BTMA Br3. Furthermore, we wish to thank Professor M. Tashiro of Kyushu University for useful discussions. Finally, we are grateful to Professor Y. Sasson of The Hebrew University of Jerusalem, Chairman of the Scientific Committee of Orgabrom 93, for the invitation to present this work in Jerusalem. 

Fig. 2.25 Conformational preferences and eight-membered turn motif of jS -peptides with 1 -aminomethylcyclopropanecarboxylic acid residues. X-ray crystal structures of dimer no, trimer m and tetramer 112 together with a model constructed using...

Dihalocarbene complexes are useful precursors to new carbenes by nucleophilic displacement of the chlorine substituents. This has been nicely illustrated for Fe(TPP)(=CCl2) by its reaction with two equivalents of Re(CO)5J to give the unusual /t-carbido complex Fe(TPP)=C=Re(CO)4Re(CO)5 which also contains a rhenium-rhenium bond. " The carbido carbon resonance was observed at 211.7 ppm in the C NMR spectrum. An X-ray crystal structure showed a very short Fe=C bond (1.605(13) A, shorter than comparable carbyne complexes) and a relatively long Re=C bond (1.957( 12) A) (Fig. 4, Table III). " ... 

Kimura, E., Kurogi, Y, Koike, T., Shionoya, M. and litaka, Y. (1993) Gold (Ill)-cyclam complexes. X-ray crystal structure and a useful macrocydic effect on the reduction of gold(III). Journal of Coordination Chemistry, 28, 33. 

Now that automated diffractometers and sophisticated computer data-reduction systems have become routinely used, the task involved in conducting an X-ray crystal-structure examination has been enormously simplified. As a result, the number of structures determined each year by crystallography has escalated dramatically. The logistics of maintaining this series in the original form would now entail such stupendous demands on our space that a volume of Advances could be completely occupied by this one article alone. As the original purpose of this series... 

---