Crystal structures of the methanol and hexanol adducts of tris(8-quinolinolato)manganese(III)

Both the methanol and hexanol adducts of tris(8-quinolinolato)manganese (III) have been shown to be isomorphic. They crystallize in the monoclinic space groupP2₁/n with four molecules in the unit-cell. The cell dimensions of the methanol adduct area= 10.847(3),b= 13.201(4),c= 17.285(5) Å β = 97.56(5) °; the asymmetric molecular unit being Mn(C₉H₆NO)₃.CH₃OH. For the hexanol adduct,a =11.201(4),b=13.342(4),c = 17.200(5) Å, β = 97.09(6) °, with an asymmetric molecular unit, Mn(C₉H₆NO)₃ · 1/2(C₆H₁₃OH). The methanol adduct structure was deduced from CuKα. intensities visually estimated from Weissenberg films, but refined on data rerneasured on a four-circle diffractometer. Data measured with Mokα radiation on a diffractometer was used for the analysis of the hexanol adduct. Both structures were solved by the heavy-atom method and refined by difference and least-squares procedures. AnR of 0.079 for the 1536 observed terms of the methanol structure and anR of 0.063 for the 2509 observed terms of the hexanol structure were attained. The complexes are in themeridional conformation, with the manganese atoms coordinated to the bidentate 8-quinolinol ligands in a distorted octahedral configuration. In the methanol structure, two methanol molecules related by the crystallographic center of symmetry lie in a “cage-like” cavity in the crystal structure, whereas in the hexanol structure only one hexanol molecule is so accommodated. The latter is disordered, the crystallographically imposed symmetry requiring that it adopts two orientations in the unit-cell.     

Kinetochromic spectrophotometry-III Determination of fluoride by catalysis of the zirconimn-Methylthymol blue reaction

The determination of 0.5-4.75 mug of fluoride ion by its catalytic action upon the slow reaction between Methylthymol Blue and zirconium(IV) in aqueous solution is described. Calibration curves obtained after 60 min under optimal conditions are smooth, and yield an effective molar absorptivity of 3.23 x 10(4) 1.mole(-1)mm(-1) at 586 nm. There is considerably less cationic interference than in the alizarin complexan-cerium(III) or lanthanum procedure, but more serious anionic interference is encountered when phosphate, arsenate and, to a lesser extent, sulphate ions are present in the sample solution.     

A catalyst for efficient and highly enantioselective hydrogenation of aromatic, heteroaromatic, and alpha,beta-unsaturated ketones

PhanePhos-ruthenium-diamine complexes catalyze the asymmetric hydrogenation of a wide range of aromatic, heteroaromatic, and alpha, beta-unsaturated ketones with high activity and excellent enantioselectivity.     

Carbohydrate-derived amino-alcohol ligands for asymmetric alkynylation of aldehydes

[reaction: see text] Conformationally restricted amino alcohols based on carbohydrate scaffolds provide flexible and fine-tuneable libraries that greatly expand the range of ligands available in the Zn(OTf)(2)-mediated addition of alkynes to aldehydes, in some cases with very high stereoselectivities.     

Asymmetric hydrogenation of ketones with polymer-supported chiral 1,2-diphenylethylenediamine

[reaction: see text] A poly(ethylene glycol)-supported chiral diamine (PEG-2), in which the polymer is attached to the phenyl rings, has been synthesized and shown to be highly effective in asymmetric hydrogenation of unfunctionalized aromatic ketones with the possibility of reuse. PEG-2 can also serve as a chiral scaffold on which various immobilized chiral catalysts could be easily built.     

Electrophilic substitution of dibromoparacyclophane: a route to novel paracyclophane phosphine ligands

[reaction: see text] The regioselective functionalization of 4,12-dibromoparacyclophane via electrophilic aromatic substitution is reported for the first time. The functionalization of the paracyclophane backbone allows the development of a new family of paracyclophane-based phosphines (named ParaPhos) that opens the possibility of improved catalyst development and tuning while retaining all the catalysis potential of the PhanePhos family of ligands.     

Accelerated asymmetric transfer hydrogenation of aromatic ketones in water

Asymmetric transfer hydrogenation of various simple aromatic ketones by the Ru-TsDPEN catalyst was shown to be feasible in aqueous HCOONa without calling for any catalyst modification, furnishing ee's of up to 95% and significantly faster rates than in the HCOOH-NEt(3) azeotrope.