Hydrogen transition metals

The development of chiral phosphorus ligands has made undoubtedly significant impact on the asymmetric hydrogenation. Transition metal catalysts with efficient chiral phosphorus ligands have enabled the synthesis of a variety of chiral products from prochiral olefins, ketones, and imines in a very efficient manner, and many practical hydrogenation processes have been exploited in industry for the synthesis of chiral drugs and fine chemicals. 

The oxidative addition at a transition metal is utilized in the synthesis of these complexes. The opposite reaction, i.e. reductive elimination, is a general route to the cleavage of the metal-metal bond, especially in complexes also containing a hydrogen-transition metal bond. 

As a result of the recognized role of transition metal hydrides as l reactive intermediates or catalysts in a broad spectrum of chemical reactions such as hydroformylation, olefin isomerization, and hydrogenation, transition metal hydride chemistry has developed rapidly in the past decade (J). Despite the increased interest in this area, detailed structural information about the nature of hydrogen bonding to transition metals has been rather limited. This paucity of information primarily arises since, until recently, x-ray diffraction has been used mainly to determine hydrogen positions either indirectly from stereochemical considerations of the ligand disposition about the metals or directly from weak peaks of electron density in difference Fourier maps. The inherent limi-... 

Brookhart, M. and Green, M.L.H. (1983) Carbon—hydrogen—transition metal bonds./. Organomet. Chem., 250, 395. 

M. Brookhart, and M. L. H. Green, Carbon-Hydrogen-Transition Metal Bonds,... 

The replacement of a nitrogen-bonded hydrogen by a metal ion should form a strong bond. However, due to the weak acidity of the peptide hydrogen it is improbable that alkali or alkaline-earth metal ions would be able to remove this hydrogen. Transition metal ions, however, should be more effective in substitution for the nitrogen-bound hydrogen. The problem with transition metal ions is... 

Key words Bioconjugation, Directed evolution, Enantioselectivity, Hybrid catalysts, Hydrogenation, Transition metal catalysis... 

Goryachev Yu. M., Dekhteruk V. I. et al. Electron mechanism of baric depedences of hydrogen - transition metal interaction. Proceedings of the Conference on hydrides and frillerenes, Kyiv - Yalta, IPMS NASU, 1999, 11 - 12. 

Transfer Hydrogenations. Transition metal-catalyzed transfer hydrogenation is thought to occur via two different intermediates, monohydrides or dihydrides, depending on the transition metal species employed. For Wilkinson s catalyst the mono-hydridic pathway was shown to be operative with the aid of deuterium labeling experiments (eq 59). ... 

These M-C-H interactions were named agostic interactions by Brookhart and Green [13] in 1983. They reported in detail on agostic interactions in their 1988 review entitled Carbon-Hydrogen-Transition Metal Bonds [14]. ... 

Brookhart M, Green MLH (1988) Carbon-hydrogen-transition metal bonds. Prog Inorg Chem 36 1-124... 

Brookhart, M. Green, M.L.H. Wong, L.L. In Carbon-Hydrogen-Transition Metal Bonds Lippard, S.J., Ed. Progress in Inorganic Chemistry John Wiley Sons New York, NY, 1991 Vol. 36 pp 1-124. 

Brookhart, M. Green, M. L. H. Carbon-hydrogen-transition metal bonds. J. Organomet. Chem. 1983, 250, 395 08. 

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