Structure determinations complexes

Trans oxidative addition of CH3I to [Ir(acac)(cod)] affords the structurally determined complex [Ir(acac)(cod)(CH3)1].241 The reaction of [(Npet)2Ir]Cl, Npet = o-(diphenylphosphino)benzylide-nejethylamino, with tetrachloro-o-quinone yields the structurally characterized product (135).242 The synthesis and characterization of the water-soluble complex (136) have been described.243... 

Treatment of [IrH5(PPh3)]2 with 2-hydroxy-pyridine in benzene yields the structurally determined complex (153), which reacts with HY (Y = Cl, Br, I) to give (154).287... 

Complexes of stable diatomic ions and molecules (e.g. 02, N2, CO, CN ) are well known and have been extensively studied. In recent years a number of metal complexes containing one or more coordinated S2 units have been prepared and characterized by X-ray structure determination. Complexes with S2 units can be formed for many metals under a variety of conditions and coordinated S2 ligands exhibit a rich chemistry. 

The formation of a complex prior to reaction is well supported in the case of bromination. Molecular bromine forms charge transfer complexes with benzene even in the absence of Lewis acid catalysts. The complexes can be detected spectroscopically and can even be crystallized for structure determination. Complexes of Br with the aromatic compound may also be formed. For a summary of experimental data in this area, see the discussion in reference 178. 

Cram s group has determined the free energy of complexation for a variety of lipophilic hosts. His data have yielded a wealth of information on the conformational structural determining complexation, and will undoubtedly enable future preparation of the desirable microcyclic hosts for the specific binding of Li, Na, K, Cs or Mg, as well as various organic ammonium derivatives. 

B. Jensen, Phase and Structure determination of a New Complex Alkali Aluminum Fluoride, Institute of Inorganic Chemistry, Norwegian Technical University, Trandheim, 1969. 

Figure 9.19 shows the sequence of the DNA that was used for the structure determination of the p53-DNA complex the bases involved in sequence-specific binding to the protein are shaded. One molecule of the DNA-bind-ing domain of p53 binds to the minor and the major grooves of the DNA making sequence-specific interactions with both strands (Figure 9.20). 

Figure 10.2 (a) Amino acid sequence of a fragment of the Zif 268 protein that contains three zinc fingers. Residues forming the p strands and a helices are red and green, respectively, and those involved in the turn between the last p strand and the a helix are blue, (b) The nucleotide sequence of the DNA fragment that was used in the x-ray structure determination of the Zif 268 fragment complexed with DNA. 

The prolactin receptor, PER, which regulates milk production in mammals, belongs to the same receptor class as the growth hormone receptor. In addition to binding the hormone prolactin, PER also binds and is activated by growth hormone. The extracellular domain of PER forms a very stable 1 1 complex with growth hormone in solution this complex has been crystallized and its structure determined (Figure 13.21). We shall compare this structure with the 1 2 complex of the same hormone with GHR. 

To date, there has not been a reported structure determination of a class 11 MHC-peptide-TCR complex. However, T-cell receptors that recognize class... 

LEED is the most powerfiil, most widely used, and most developed technique for the investigation of periodic surface structures. It is a standard tool in the surface analysis of single-crystal surfaces. It is used very commonly as a method to check surface order. The evolution of the technique is toward greater use to investigate surface disorder. Progress in atomic-structure determination is focused on improving calculations for complex molecular surface structures. 

Crystal structure determination has also been done with -butyllithium. A 4 1 n-BuLi TMEDA complex is a tetramer accommodating two TMEDA molecules, which, rather than chelating a lithium, link the tetrameric units. The 2 2 -BuLi TMEDA complex has a structure similar to that of [PhLi]2 [TMEDA]2. Both 1 1 -BuLi THF and 1 1 -BuLi DME complexes are tetrameric with ether molecules coordinated at each lithium (Fig. 7.2). These and many other organolithium structures have been compared in a review of this topic. ... 

The formation of acyl halide-Lewis acid complexes have been observed by several methods. For example, both 1 1 and 1 2 complexes of acetyl chloride, with AICI3 can be observed by NMR spectroscopy. The existence of acylium ions has been demonstrated by X-ray diffraction studies on crystalline salts. For example, crystal structure determinations have been reported for /i-methylphenylacylium and acetylium ions as SbFg salts. There is also a good deal of evidence from NMR measurements which demonstrates that acylium ions can exist in nonnucleophilic solvents. " The positive charge on acylium ions is delocalized onto the oxygen atom. This delocalization is demonstrated in particular by the short O—C bond lengths in acylium ions, which imply a major contribution from the structure having a triple bond ... 

The structure of complexes containing the tf-Sc2 ligand have recently been determined and, where appropriate, compared with analogous rp--Sx. tJ -Pi and t) As2 complexes (p. 587). Examples are in F ig. 16.3 and the original papers should be consulted for further details. " Complexes... 

The natural world is one of eomplex mixtures petroleum may eontain 10 -10 eomponents, while it has been estimated that there are at least 150 000 different proteins in the human body. The separation methods necessary to cope with complexity of this kind are based on chromatography and electrophoresis, and it could be said that separation has been the science of the 20th century (1, 2). Indeed, separation science spans the century almost exactly. In the early 1900s, organic and natural product chemistry was dominated by synthesis and by structure determination by degradation, chemical reactions and elemental analysis distillation, liquid extraction, and especially crystallization were the separation methods available to organic chemists. 

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