X-ray structural data

Transition-metal complexes of the thionylimide anion exhibit characteristic vibrations in the regions 1260-1120, 1090-1010 and 630-515 cm , which are assigned to Oas(NSO), Os(NSO) and <5(NSO), respectively. X-ray structural data for several M-NSO complexes reveal N-S and S-O bond lengths of ca. 1.46 0.04 A indicative of double bond character in both of these bonds. 

X-Ray structural data and recent high level theoretical calculations confirm that this neutral, diamagnetic dithiadiazole is an aromatic six k-electron ring system. The gas-phase infra-red and photoelectron spectra of S2N2CO have also been reported. ... 

MCl3(NS)(PPh3)2]. In the few complexes for which X-ray structural data are available the M-N-S group is essentially linear (170-177°) (see p. 453 and refs. 233, 235) but spectroscopic data on others suggest that bent and even ij -bridging modes may be possible. 

Numerous solid complexes have been crystallized from brown solutions of iodine and extensive X-ray structural data are available. Complexes of the type L—>-I-X and L—>-I-X-t—L... 

Tire and NMR spectral data demonstrated the existence of 121 in the amino form (in CDCI3) (91H727) and 122 as the thione (in DMSO) (95H497). Tire structure of 122 (R = NHCOPh) was also confirmed by X-ray structural data (95H497). 

On the basis of these results it seems to the present author that inner and outer complexes can reasonably be assumed for the electron transfer to the diazonium ion, but that an outer-sphere mechanism is more likely for metal complexes with a completely saturated coordination sphere of relatively high stability, such as Fe(CN) (Bagal et al., 1974) or ferrocene (Doyle et al., 1987 a). Romming and Waerstad (1965) isolated the complex obtained from a Sandmeyer reaction of benzenediazonium ions and [Cu B ]- ions. The X-ray structural data for this complex also indicate an outer-sphere complex. 

Table 2 X-ray structural data for iron porphyrin carbene complexes...

Figure 7.28. Molecular representations of the crystallized salts (a) 78s-(S)-PEA and (b) 79s-(S)-PEA, from the X-ray structure data. (Taken from reference 179.)...

Figure 7.29. (Top) Molecular representations based on X-ray structural data of the diazo compound 88N2 and the alkene product 89Z (the migrating hydrogen is shown in black in both reactant and product). (Bottom) Schematic reaction path showing the minimal structural changes in the transition from the diazo compound to the product, via the probable transition structure 88TS.

The DNA binding of [cp Ir(dppz)(Aa)]"+, dppz = dipyrido[3,2-a 2, 3 -c]phenazine, Aa = S-coor-dinated amino acid or peptide, has been investigated by UV-vis spectroscopy, 2D-NOESY, and gel electrophoresis. The complexes intercalate into DNA adjacent to T2 from the major groove. The X-ray structural data for [cp IrCl(dppz)](CF3S03)4 and [ cp Ir(9-EtG)(Phen)](CF3S03)2, where GH = guanine, are reported.423... 

This review cannot claim to be a comprehensive account of all the coordination chemistry of zinc since the early 1980s. The approach has been to attempt selection of references by key workers or important results in areas where much work has been carried out. It is hoped that it will be possible by following the key references and articles to gain an overview of achievements and advances in the important areas. In many cases, examples where X-ray structural data is included have been selected preferentially for inclusion. 

The CSD reveals that the mean zinc phosphorus bond length is 2.404(5) A based on all singlecrystal X-ray structural data in the database and uncorrected for temperature. 

It should be noted that equatorial or diequatorial conformers of substituted cyclohexanes could be accommodated in the thiourea canals by the stacking of guests at an oblique angle or parallel to the canal axis. X-ray structural data is so far unavailable... 

Table 10 Selected X-ray structural data for 1 -borabarrelene derivatives...

On the basis of the X-ray structural data as well as the mode of polymerization, Yasuda et al. [3a] proposed a coordination anionic mechanism involving an eight membered transition state for the organolanthanide-initiated polymerization of MM A (Fig. 6). The steric control of the polymerization reaction may be ascribed to the intermolecular repulsion between C(7) and C(9) (or the polymer chain), since completely atactic polymerization occurred when the monomer was methyl or ethyl acrylate. 

In the hydrogenation of 1, catalysts 31 a—j gave 87-97% ee, whereas catalyst 31 k, with the very bulky trityl substituent on the alkyl backbone, only gave 38% ee. The silyl substituent was found to have a significant effect on selectivity catalyst 311 gave 88% ee, while catalyst 31 n gave only 4% ee with substrate 1 [35]. This remarkable effect was rationalized based on X-ray structural data. 

It was clear for some time that a number of zinc enzymes required two or more metal ions for full activity, but in the absence of X-ray structural data the location of these metal centres with regard to one another was often uncertain. When the first 3-D structures began to appear, it became clear that the metals were in close proximity. A particular feature of many of these enzymes was the presence of a bridging ligand between two of the metal sites, usually an Asp residue of the protein, which is occasionally replaced by a water molecule. While some of the sites contain only Zn ions, several contain Zn in combination with Cu (in cytosolic superoxide dismutases) Fe (in purple acid phosphatases) or Mg (in alkaline phosphatase and the aminopeptidase of lens). 

Figure 8 X-ray structural data of the active site of the oxygenated form of haemocyanin from Limulus polyphemus...

Using X-ray structure data, amino acids which were believed to affect the desired characteristics were identified. Using either site-directed mutagenesis or "cassette" mutagenesis (8) different amino acid substitutions were made in the subtilisin structural gene (2,9). 

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