APPLICATION OF PALLADIUM ON GRAPHENE/GRAPHENE OXIDE CATALYST SYSTEMS TO CROSS-COUPLING AND

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APPLICATION OF PALLADIUM ON GRAPHENE/GRAPHENE
OXIDE CATALYST SYSTEMS TO CROSS-COUPLING AND C-H
ACTIVATION REACTIONS
Christopher T. Williams USC Keith C. Ellis VCU
B. Frank Gupton VCU M. Samy El-Shall VCU
Center for Rational Catalyst Synthesis Planning
Grant Workshop University of South Carolina,
Columbia, SC June 16, 2014
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Overview Understanding the unique performance of
heterogenous Pd on graphene/graphene oxide
catalysts for cross-coupling and C-H activation
reactions

• Excellent activity extremely high TOF (108,000
  h-1)
• Less than 200 ppb Pd in the reaction product.
• Easily recovered and recycled under batch
  reaction conditions

? How does this work? ? Can we expand to other
Pd- catalyzed reactions?
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Industrial Relevance

• Pd-catalyzed cross-coupling reactions are widely
  used due to their high atom economy and synthetic
  versatility
• Pharmaceutical drug discovery/development, fine
  chemicals
• Pd-catalyzed C-H activation reactions are an
  emerging complimentary technology with the same
  advantages
• Palladium-catalyzed reactions are typically run
  homogeneously
• Significant downsides and liabilities
• Use ligands to stabilize catalyst and broaden
  reactivity window.
• Commercial viability is limited due to product
  contamination
• Proposed Solution Development of heterogeneous
  catalysts can provide greater performance,
  stability, and recyclability with less
  contamination!

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Goals of the Proposal

• Characteriztion of Cross-Coupling Catalysts
• Use in-situ and ex-situ analytical methods to
  determine the surface properties of novel
  Pd/graphene catalysts that impart the remarkable
  catalytic activities before, during, and after
  use in cross-coupling reactions.
• Expand Scope to C-H Activation Chemistry
• Explore the ability of Pd(II)/graphene oxide to
  catalyze each of six CH activation reactions

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Proposed Hypotheses

• Increased activity and stability of Pd in this
  system is related to the unique surface
  properties of graphene, which if understood, can
  be further tailored and optimized
• Pd electronic properties influenced by graphene
• Water is key actor for high activity due to
  surface interactions
• Analytical methods can be applied to graphene
  surfaces in situ to examine Pd-graphene and
  Pd-substrate interactions
• ATR-IR, HRTEM, AFM, Resonance Raman spectroscopy
  and flow reactor kinetic measurements
• Technique can be employed under reaction
  conditions
• Pd(II)/graphene oxide will catalyze C-H
  activation reactions, which utilize a novel
  Pd(II)/Pd(IV) catalytic cycle
• We expect this system will exhibit similar
  catalytic properties that will overcome the
  current limitations of homogeneous reactions

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Research Methods/ Techniques

• ATR-IR
• HRTEM
• AFM
• Resonance Raman
• kinetic measurements
• Techniques can be employed under reaction
  conditions

In-Situ ATR-IR of Thin Catalyst Films
Optimize reaction parameters, including

• Time
• Temperature
• Heating Method
• Solvent

• Additives
• Alternative Oxidants
• Chemo-/Regioselectivity
• Substrate Scope

Continuous Flow Reactor Obtain kinetics and
stability data under identical conditions to
spectroscopic measurements
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Outcomes/ Deliverables Year 1

• Successful characterization of surface properties
  of Pd/graphene under cross-coupling reaction
  conditions and identification of the critical
  catalyst properties that drive catalytic activity
• Quantify the surface interactions between the
  metal and graphene support
• CO adsorption in EtOH, H2O, and EtOH/H2O mixtures
  on Pd/graphene
• Identification of adsorbed species (coupling
  reactants/products) on graphene and Pd/graphene
  in various solvents at room temperature
• Obtain detailed kinetics of heterogeneous
  cross-coupling reactions
• Measurement of adsorption behavior (including
  competitive adsorption) at different
  concentrations and temperatures in order to
  develop mechanistic models for these processes
• Real-time monitoring of surface during
  cross-coupling reaction under optimized condition
• Successful demonstration that Pd(II)/graphene
  oxide catalyzes C-H activation reactions
• Feasibility studies in each of the six
  transformations
• Optimization of reaction parameters for two of
  the transformation
• Begin to characterize the surface properties of
  the catalyst in the Pd(II)/Pd(IV) catalytic cycle

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Impact

• Optimization of heterogeneous Pd(0)/graphene
  catalyst synthesis based on increased mechanistic
  understanding
• Enhanced reaction performance under continuous
  flow conditions
• Broaden the scope of heterogeneous catalysis by
  Pd(II)/graphene oxide
• Add six additional heteroatom functionalizations
  to the toolkit of available reactions

Duration of Project and Proposed Budget

• One Year
• 60,000