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Research areas: Hydrides | CATALYSTS | Ligands | Mechanisms | Materials | Bioinorganic models



CATALYSTS: Hydrogenation | Michael and HX Addition Reactions | Modular catalyst design

Hydrogenation

Current research The conventional homogeneous catalysts for the enantioselective hydrogenation or transfer hydrogenation of ketones are based on platinum metals and particularly ruthenium. This method provides valuable enantiopure alcohols as additives for perfumes or intermediates in the synthesis of pharmaceuticals. Industry is looking for replacements for expensive and toxic ruthenium- and rhodium-based catalysts. Iron is much cheaper and is not toxic. We have developed very active ruthenium catalysts for the hydrogenation of C=O and C=N multiple bonds to valuable enantio-enriched alcohols and amines and have had exciting recent success at extending this work to iron (see references 160, 168 below).

References
171. "Iron(II) Complexes for the Efficient Catalytic Asymmetric Transfer Hydrogenation of Ketones." Chem. Eur. J. 2009,17 5605-5610. At the journal website.
168. A. A. Mikhailine, A. J. Lough, R. H. Morris "Efficient Asymmetric Transfer Hydrogenation of Ketones Catalyzed by an Iron Complex Containing a P-N-N-P Tetradentate Ligand Formed by Template Synthesis" J. Am. Chem. Soc. 2009,131, 1394-1395(At the journal website).
163. F. N. Haque, A. J. Lough, R. H. Morris. "Ruthenium Hydrogenation Catalysts With P-N-N-P Ligands Derived from 1,3-Diaminopropane and the Formation of a b-Diiminate Complex by a Base-induced Isomerization." Inorg. Chim. Acta 2007,361 3149-3158 (invited for special issue dedicated to R. Angelici) (At the Science Direct website).
160. Sui-Seng, C.; Freutel, F.; Lough, A. J.; Morris, R. H.Highly Efficient Catalyst Systems Using Iron Complexes with a Tetradentate PNNP Ligand for the Asymmetric Hydrogenation of Polar Bonds. Angew. Chem. Int. Ed. Engl. 2008,47, 940-943(At the journal website).
159. Li, T.; Bergner, I.; Haque, F. N.; Iuliis, M. Z.-D.; Song, D.; Morris, R. H. The hydrogenation of benzonitrile to benzylamine catalyzed by ruthenium hydride complexes with P-NH-NH-P ligands. Organometallics 2007,26, 5940 - 5949 (At the Organometallics website).
157. Sui-Seng, C.; Hadzovic, A.; Lough, A. J.; Morris, R. H. Novel Hydrido-Ruthenium(II) Complexes of Histidine Derivatives and Their Application in the Hydrogenation of Ketones Dalton Transactions 2007, 2536 - 2541 (featured on cover).
150. R. H. Morris “Ruthenium and Osmium.” In The Handbook of Homogeneous Hydrogenation; Elsevier, C. J., de Vries, J. G., Eds.; WILEY-VCH: New York, pp 45-70, 2006.
142. Abdur-Rashid, K.; Guo, R.; Lough, A. J.; Morris, R. H.; Song, D. Synthesis of ruthenium hydride complexes containing beta-aminophosphine ligands derived from amino acids and their use in the H2-hydrogenation of ketones and imines Adv. Syn. Catal. 2005, 347, 571-579.
139. Li, T.; Churlaud, R.; Lough, A. J.; Abdur-Rashid, K.; Morris, R. H. Dihydridoamine and Hydridoamido Complexes of Ruthenium(II) With a Tetradentate P-N-N-P Donor Ligand Organometallics 2004, 23, 6239 - 6247.
138. Guo, R.; Lough, A. J.; Morris, R. H.; Song, D. Asymmetric Hydrogenation of Ketones Catalyzed by Ruthenium Hydride Complexes of a Beta-aminophosphine Ligand Derived from Norephedrine Organometallics 2004, 23, 5524-5529.
131. V. Rautenstrauch, R. Challand, R. Churlaud, R.H. Morris, K. Abdur-Rashid. "Process for hydrogenation of carbonyl and iminocarbonyl compounds using ruthenium catalysts comprising tetradentate diimino-diphosphine ligands." Patents: EP 1337334 (Europe)/ CA 2,428,824 (Canada)/ US 2004/0015017 (USA) issued as US6,878,852 (Apr 2005)/ IL 155869 (Israel), JP 2002-542516 / JP2004513929T (Japan).
126. Abdur-Rashid, K.; Lough, A. J.; Morris, R. H. RuHCl(diphosphine)(diamine): Catalyst Precursors for the Stereoselective Hydrogenation of Ketones and Imines Organometallics 2001, 20, 1047-1049.

120. K. Abdur-Rashid, A.J. Lough and R.H. Morris "Ruthenium dihydride RuH2(PPh3)2(R,R-Cyclohexyldiamine) and Ruthenium Monohydride RuHCl (PPh3)2(R,R-Cyclohexyldiamine): Active Catalyst and Catalyst Precursor for the Hydrogenation of Ketones and Imines" Organometallics 2000, 19, 2655-2657.


Michael and HX Addition Reactions

Our research on the mechanisms of the hydrogenation catalysts show that they proceed via metal-amido intermediates. We have shown that such intermediates can add weak acids HX such as dimethylmalonate across the Ru-N bond. Such reactions explain the high reactivity of our complexes for the Michael addition reaction of malonates to alpha,beta-unsaturated ketones. This has lead to the development of the first tandem Michael addition- Hydrogenation catalyst systems. Further extensions of this chemistry are being explored.

References

154. Clapham, S. E.; Guo, R.; Iuliis, M. Z.-D.; Rasool, N.; Lough, A.; Morris, R. H. Probing the Effect of the Ligand X on the Properties and Catalytic Activity of the Complexes RuHX(diamine)(PPh3)2 (X = OPh, 4-SC6H4OCH3, OPPh2, OP(OEt)2, CCPh, NCCHCN, CH(COOMe)2; diamine = 2,3-diamino-2,3-dimethylbutane or (R,R)-1,2-diaminocyclohexane) Organometallics 2006, 25, 5477 - 5486.
146. Guo, R.; Elpelt, C.; Chen, X.; Song, D.; Morris, R. H. Applications of Ruthenium Hydride Borohydride Complexes Containing Phosphinite and Diamine Ligands to Asymmetric Catalytic Reactions Org. Lett. 2005, 7, 1757 - 1759.
143. Guo, R.; Morris, R. H.; Song, D. Enantioselective Tandem Michael Addition/H2-Hydrogenation Catalyzed by Ruthenium Hydride Borohydride Complexes Containing Beta-aminophosphine Ligands J. Am. Chem. Soc. 2005, 127, 516 - 517.

 

Modular catalyst design

Reactions involving each combination of substrates will probably require a unique catalyst structure to achieve high enantioselectivity. Therefore we are developing catalysts that are easily prepared from ligand and metal precursor modules.

Reference

165. A. A. Mikhailine, E. Kim, C. Dingels, A. J. Lough, R. H. Morris "Template Syntheses of Iron(II) Complexes Containing Chiral P-N-N-P and P-N-N Ligands for Use as Asymmetric Catalysts."Inorg. Chem. 2008, 47, 6587-6589 (At the journal website).
148. Guo, R.; Elpelt, C.; Chen, X.; Song, D.; Morris, R. H. A Modular Design of Ruthenium Catalysts with Diamine and Binol-derived Phosphinite Ligands that are Enantiomerically-Matched for the Effective Asymmetric Transfer Hydrogenation of Simple Ketones Chem. Commun. 2005, 3050–3052.

 


Research areas: Hydrides | CATALYSTS | Ligands | Mechanisms | Materials | Bioinorganic models

Copyright Robert H. Morris, 2007. Email Robert Morris: rmorris@utoronto.ca