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The iridium complex of pentamethylcyclopentadiene and (S,S)-1,2-diphenyl-N ′ -tosylethane-1,2-diamine is an effective catalyst for the asymmetric transfer hydrogenation of imine substrates under acidic conditions. Using the Ir catalyst and a 5:2 ratio of formic acid: triethylamine as the hydride source for the asymmetric transfer hydrogenation of 1-methyl-3,4-dihydroisoquinoline and its 6,7-dimethoxy substituted derivative, in either acetonitrile or dichloromethane, shows unusual enantiomeric excess (ee) profiles for the product amines. The reactions initially give predominantly the (R) enantiomer of the chiral amine products with >90% ee but which then decreases significantly during the reaction. The decrease in ee is not due to racemisation of the product amine, but because the rate of formation of the (R)-enantiomer follows first-order kinetics whereas that for the (S)-enantiomer is zero-order. This difference in reaction order explains the change in selectivity as the reaction proceeds -the rate formation of the (R)-enantiomer decreases exponentially with time while that for the (S)-enantiomer remains constant. A reaction scheme is proposed which requires rate-limiting hydride transfer from the iridium hydride to the iminium ion for the first-order rate of formation of the (R)-enantiomer amine and rate-limiting dissociation of the product for the zero-order rate of formation of the (S)-enantiomer.

The dimeric iodo-iridium complex [IrCp*I 2 ] 2 (Cp*=pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the corresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature 1 H NMR data is consistent with the formation of a 1:1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp* results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect k H /k D = 3.24 indicating that hydride transfer is involved in the rate-limiting step.

Gender issues, and specifically the lack of women in the physical sciences, has been a subject of intense debate for decades. The problem is so acute, that national initiatives have been developed to analyse and address the issues, with some success in STEM, particularly in higher education and also in industry. However, despite this progress, there is little understanding as to why women are less likely to study the chemical sciences in particular. In this research, a survey and interviews were used to find out why female A-level chemistry students choose, or do not choose, to study chemistry at higher education level. Two distinct phases were identified. Firstly, intelligence gathering to understand the location, content, entry requirements, and career options for potential course and institution combinations. Secondly, self-reflection to establish whether, knowing themselves, students feel as though they would be successful on a particular course at a particular institution. These findings align with research into gender imbalance in STEM and Higher Education more broadly, but go beyond this to broaden current debates with a focus on chemistry in particular.

and dried in a vacuum oven at 110°C. Fifty to seventy-five percent yields were obtained.The solubilities of the sodium salts of the tetrazoles were found to be equal to or greater than those of the corresponding sodium salts of the iodinated benzoic acids. TABLE I Iodinated Benzamidotetrazoles