Ruthenium Mediated Catalytic Hydrogenation of CX XC or O Bonds

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Ruthenium Mediated Catalytic Hydrogenation of CX
(XC or O) Bonds

• Magaly A. Ramírez
• John P. Lee
• T. Brent Gunnoe
• Chemistry Department,
• North Carolina State University

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Catalytic Hydrogenation
(g)
Addition of hydrogen across an unsaturated bond
Hydrogenation
Catalyst
?
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Industrial Applications
Hydrogenated vegetable oils
Fatty alcohols
Hydrogenation
Nylon
Liquid fuels
Methanol
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Objectives

• To study the reactivity of neutral and cationic
  ruthenium (IV) dihydride complexes for catalytic
  hydrogenation.
• To determine catalyst chemoselectivity in
  catalytic hydrogenation reactions. For example,
  internal vs. terminal olefins and CC vs. CO
  double bond.

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Ruthenium Catalysts
(IMes)2RuCl(H)2(CO)BAr4'
(IMes)2RuCl2(H)2(CO)
Ru(H)2
Ru(H)2
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Synthesis of Ru(H)2 and Ru(H)2
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Hydrogenation of Terminal and Internal CC bonds
Styrene
Cyclohexene
Cyclohexadiene
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1H NMR Spectrum of Styrene Hydrogenation
Initial
styrene
Final
ethyl benzene
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Hydrogenation of Linear Alkenes
1-hexene
2-hexene
3-hexene
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Hydrogenation of Aldehydes and Ketones
acetone
benzaldehyde
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Intramolecular Hydrogenation Competition
3-vinylbenzaldehyde

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Catalyst Comparison

• Ru(H)2 is more active than Ru(H)2

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Proposed Hydrogenation Mechanism
Oxidative addition
substrate coordination
Insertion
Reductive elimination
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Conclusions

• The ruthenium (IV) dihydride complexes catalyze
  the hydrogenation of olefins.
• The cationic Ru(H)2 is more active than Ru(H)2.
• Linear alkenes are isomerized to the more stable
  branched alkenes before hydrogenation.
• The catalyst hydrogenates selectively CC bonds
  faster than CO.

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Future Work

• Kinetic studies to understand the mechanism which
  could lead to more active catalysis.
• Hydrogenation of aromatic substrates
• Hydrogenation reactions involving CO2

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Acknowledgements

• Dr. T. Brent Gunnoe, Research advisor
• Alison Al- baati
• NCSU facilities
• NSF Alliances For Graduate Education and The
  Professoriate (AGEP) SRE
• Department of Energy DE-FG02-03ER15490

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Ruthenium Mediated Catalytic Hydrogenation of CX
(XC or O) Bonds

• Magaly A. Ramírez
• John P. Lee
• T. Brent Gunnoe
• Chemistry Department,
• North Carolina State University