Arene complexes crystal structure

Zhang Z, Luo Y, Xia B, Han C, Yu Y, Chen X, Huang F (2011) Four constitutional isomers of BMpillar[5]arene synthesis, crystal structures and complexation with n-octyltrimethyl ammonium hexafluorophosphatew. Chem Commun 47 2417-2419... 

As was suggested in the preceding discussion, most of the arene complexes isolated by metal-atom techniques are benzene derivatives. However, heterocyclic ligands are also known to act as 5- or 6-electron donors in transition-metal 7r-complexes (79), and it has proved possible to isolate heterocyclic complexes via the metal-atom route. Bis(2,6-di-methylpyridine)Cr(O) was prepared by cocondensation of Cr atoms with the ligand at 77 K (79). The red-brown product was isolated in only 2% yield the stoichiometry was confirmed by mass spectrometry, and the structure determined by X-ray crystal-structure analysis, which supported a sandwich formulation. 

We reported the first crystal structure of a half-sandwich arene ruthenium(II)-enzyme complex (Fig. 21) (90). The crystal structure showed a Ru(r 6-p-cym)X2 half-sandwich fragment... 

Fig. 24. Comparison between the osmium- and ruthenium-arenes, exemplified by the respective [M(ri6-bip)Cl(en)]+ complexes. Although the crystal structures show the complexes to be isostructural with similar M-Cl bond lengths (a), the properties of the complexes are quite different, illustrated by the differences in hydrolysis rate h1/2), pAa, and 5 -GMP binding (the black box denotes the amount of OP03-bound 5 -GMP) (b).

Crystal structures of stable arene complexes are also known, for example the benzene complex of (lR,2R)-trans-l,2-bis((diphenylphosphino)-methyl)cyclobu-tane-Rh1 [46], [Rh((R,R)-Et-DuPHOS)(benzene)]BF4 (Fig. 44.7), and [Rh((S,S)-Me-DuPHOS)(toluene)]BF4 [47]. 

The crystal structure of (ij4-cyclooctatetraene)(hexamethylbenzene)ruthenium (16) indicates bonding as a tetrahapto ligand60. For this complex and similar iron-, ruthenium- and osmium-(ij4-cyclooctatetraene)(arene) complexes, their XH and 13C NMR spectra exhibit only a single signal for the cyclooctatetraene ligand at temperatures as low as —145 °C. Using this temperature, the barrier-to-metal migration is estimated to be <6.6 kcal mol 1. 

The intermediate cyclooctene complex appears to be more reactive with respect to CS coordination and more sensitive to oxidation when the arene ring bears electron-withdrawing groups (e.g., C02CH3). Dicarbonyl(methyl rj6-benzoate)-thiocarbonyl)chromium is air stable in the solid state and reasonably stable in solution.9 The infrared spectrum exhibits metal carbonyl absorptions at 1980 and 1935 cm"1 and a metal thiocarbonyl stretch at 1215 cm"1 (Nujol) (these occur at 1978, 1932, and 1912 cm"1 in CH2C12 solution).10 Irradiation of the compound in the presence of phosphite or phosphine leads to slow substitution of CO by these ligands, whereas the CS ligand remains inert to substitution. The crystal structure has been published."... 

Protonated polymethylbenzenes281 and the chlorohexamethylbenzenium cation,282 intermediates in aromatic electrophilic substitutions known as Wheland intermediates, have been isolated as crystalline salts, allowing investigators to obtain their X-ray crystal structure. Nitrosoarenium a complexes of various arenes were directly observed by transient absorption spectroscopy.283 Kochi presented a method combining appropriate instrumental techniques (X-ray crystallography, NMR, time-resolved UV-vis spectroscopy) for the observation, identification, and structural characterization of reactive intermediates fa and n complexes) in electrophilic aromatic substitution.284... 

Thuery, P., Nierlich, M., Bryan, J.C. et al. 1997. Crown ether conformations in 1,3-calix[4]arene bis(crown ether) Crystal structures of a cesium complex and solvent adducts and molecular dynamics simulations. J. Chem. Soc. Dalton Trans. 1997 (22) 4191 4202. 

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