Molecular and Gold Nanoparticles Supported N-Heterocyclic Carbene Silver(I) Complexes

1
Molecular and Gold Nanoparticles Supported
N-Heterocyclic Carbene Silver(I) Complexes
Synthesis, Characterization and Catalytic
Applications
? ? ??? ???? ??? ?? 2009 / 07 / 20 Department
of Chemistry Biochemistry Chung Cheng
University
2
N-Heterocyclic Carbenes (NHC)
L-type two electrons

• NHCs are strongers-donors than the most electron
  rich phosphine
• - less likely to dissociate from the metal
  during the reaction
• NHCs have come to replace phosphines in many
  organometallic and organic reactions
• NHCs can be useful spectator ligands, tunable
  electronically and sterically
• NHCs are most frequently prepared via
  deprotonation of the corresponding azolium salts

3
N-Heterocyclic Carbenes as Ligands
- In the early 90's NHC were found to have
bonding properties similar to
trialklyphosphanes( -PR3 ) and alkylphosphinates(
-OP(OR)R2 ). - compatible with both high and low
oxidation state metals - examples - reaction
employing NHC's as ligands
Herrmann, W. A. Öfele, K Elison, M. Kühn, F.
E. Roesky, P. W. J. Organomet. Chem. 1994, 480,
C7-C9.
Herrmann, W. Angew. Chem. Int. Ed. 2002, 41,
1290-1309.
4
The Applications of Ag(I) NHC

• Silver(I)-carbene complexes as carbene transfer
  agents
• Addition of arenes to imines
• Aza-Diels-Alder reaction
• Asymmetric aldol reaction
• Barbier-Grignard-type reaction

5
The First Silver(I)-Carbene Complexes and
Carbene-Copper(I) Complexes
Linear di-coordination
Arduengo A.J. et al. Organometallics 1993, 21,
3405-3409
6
Silver(I)-Carbene Complexes as Carbene Transfer
Agents
Wang, H. M. J. Lin, I. J. B. Organometallics
1998, 17, 972-975
7
Quantum Chemical Calculations for the
N-Heterocyclic Carbene Complexes of MCl (M
Cu, Ag, Au)
The trend of the bond energies for the metal
fragments is AuCl gt CuCl gt AgCl
Boehme, C. and Frenking, G. Organometallics 1998,
17, 5801-5809
8
Motivation

• Using NHCs ligand to replace phosphine ligand in
  
• organomatallic catalysis.
• In comparison with other transition metals (Cu,
  Au), silver has been virtually untouched as a
  catalyst for coupling reactions.
• To promote silver-catalyzed three-component
  coupling of aldehyde, alkyne, and amine.
• Easy recovered effectivetly recycled
• Immobilization of NHC-Ag(I) complexs onto Au
  Nanoparticles.

9
Experimental Preparation of Ag(hmim)2PF6 Complex
10
Experimental Preparation of Au NPs-Ag(I)(NHC)2(PF6
)
Space linker synthesis
11
Experimental Preparation of Au NPs-Ag(I)(NHC)2(PF6
)
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1H NMR Spectra of HmimHPF6 and Ag(hmim)2PF6
2H
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13C NMR Spectra of HmimHPF6 and Ag(hmim)2PF6
c
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ESI-MS Spectrum of Ag(hmim)2PF6
Experimental MS Data
Calculated MS Data
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IR Spectra of HmimHPF6 and Ag(hmim)2PF6
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UV Spectra of HmimHPF6 and Ag(hmim)2 PF6
b
Ag(hmim)2PF6 a
a
(hmim)2PF6 b
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Single-Crystal X-ray Structure of Ag(hmim)2PF6
p p interaction
Dihedral Angle 1.802o(221)
bond lengths Å bond lengths Å bond angles deg bond angles deg
Ag(1)-C(1) 2.083(3) C(2)-Ag(1)-C(11) 177.16
Ag(1)-C(11) 2.083(3) N(1)- C(1)-N(2) 104.06
N(3)- C(11)-N(4) 104.67
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1H, 31P, and 19F Spextra of Au-NPs-NHC Ligand
-CH2SH
DMSO
-SH

19F NMR
31P NMR
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Synthesis of Au NPs-Ag(I)-(NHC) Complex
Cross-link network structure
20
1H, 31P, and 19F of Au NPs-Ag(I)-NHC Complex
DMSO
2 H
1 H

19F NMR
31P NMR
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1H NMR Spectra of Ligand, Molcular and Au
Nanoparticles
DMSO



22
Synthesis of Octanethiol Protected Au-SR NPs
Particle size 2.1 1.12 nm
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TEM Image and UV Spectrum of Au NPs-Immobilized
(NHC) Ligand
Particle size 3.1 1.3 nm
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TEM Image and EDS of Au NPs-Ag(I) Complex
245 nm
Particle size 2.1 0.7 nm
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IR Spectra of Ligand Au Nanoparticles series
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Aldehyde, Amine, and Alkyne-coupling Reactions
(A3-Coupling) Have attracted much attention from
organic chemists for the coupling products,
propargylamines, which are major skeletons or
synthetically versatile building blocks for the
preparation of many nitrogen-containing
biologically active compounds
J. Org. Chem. 1995, 60, 1590-1594
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The First Silver-Catalyzed Three-Component
Coupling of Aldehyde, Alkyne, and Amine
Entry Catalyst (3 mol) Time (h) Conversion ()
1 AgOTf 14 40
2 AgBF4 14 35
3 Ag2O 14 40
4 Ag2SO4 14 42
5 AgNO3 14 40
6 AgF 14 40
7 AgBr 14 55
8 AgCl 14 60
9 AgI 14 75
Chao J. L. et. al. Org. Lett., Vol. 5, No. 23,
2003,4473-4475
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Proposed Mechanism for the Three Component
Coupling
C-H activation
Chao J. L. et. al. Org. Lett., Vol. 5, No. 23,
2003,4473-4475
29
Ag(I)-Catalyzed A3-Coupling Reactions
Entry Solvent, Temperature Time Conversion ()a
1 Propionitrile (97oC) 1hr 91
2 Acetonitril (83oC) 1hr 73
3 (hmim)Br 1hr 29
4 (hmim)PF6 1hr 78
5 1,4-dioxane (105 oC) 1hr 20
6 DMF (154oC) 1hr 38
Reaction conditions catalyst loading 3 mol
Benzaldehyde 1.00 mmol Pyperidine 1.20 mmol
Phenylacetylene 1.50 mmol solvent 1.0 mL
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Ag(I)-Catalyzed A3-Coupling Reactions
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A3-Coupling Reactions of Aliphaticaldehyde,
Amine, and Alkyne
Entry Time (h) Yielda ()
1 0.5 93
2 0.5 92
3 0.5 95
4 0.5 95
5 0.5 93
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
32
A3-Coupling Reactions of Aromaticaldehyde, Amine,
and Alkyne
Entry R Time (h) Yielda ()
1 H 0.5 1 2 91 95 98
2 p-OMe 0.5 1 2 2.5 35 51 65 85
3 p-Me 2 65
4 p-Cl 2 2.5 73 88
5 o-Cl 2 2.5 3 68 75 83
Reaction conditions catalyst loading 3 mol
Benzaldehyde 1.00 mmol Pyperidine 1.20 mmol
Phenylacetylene 1.50 mmol solvent 1.0 mL
33
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
Entry Time (min) Yielda ()
1 30 93
2 30 95
3 30 80
4 30 93
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
34
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
Entry Time (min) Yielda ()
5 30 60 75 90
6 30 60 90 63 75 89
7 30 60 80 88
8 30 60 90 71 89 94
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
35
A3-coupling Reactions of Benzaldehyde, Amine, and
Alkyne
Entry R Time (h) Yielda ()
1 0.5 92
2 0.5 4 12 24 0 2 6 10
3 0.5 4 12 10 15 18
pKa
19.9
26.5
24
Reaction conditions catalyst loading 3 mol
Benzaldehyde 1.00 mmol Pyperidine 1.20 mmol
Phenylacetylene 1.50 mmol solvent 1.0 mL
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Thermal v.s. Microwave Heating
microwave
thermal
Convection transition
Kappe, C. O. Angew. Chem. Int. Ed. 2004, 43,
6250-6284.
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A3-Coupling Reactions of Aliphaticaldehyde,
Amine, and Alkyne
Entry Time (sec) Yielda ()
1 40 89
2 40 95
3 30 85
4 40 92
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
38
A3-coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
Entry Time (sec) Yielda ()
1 20 89
2 20 92
3 40 90
4 20 93
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
39
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
Entry Time (sec) Yielda ()
5 30 90
6 40 85
7 20 80
8 30 83
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
40
A3-Coupling Reactions of Benzaldehyde, Amine, and
Alkyne
Entry Time (sec) Yielda ()
1 60 89
2 60 83
3 60 78
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
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Proposed Mechanism for the A3-Coupling Reaction
42
A3-Coupling Reactions Catalyzed by a Reusable
PS-supported Ag(I)-NHC complex
1.Structure indefinite 2.Quantitative NHC-Silver
(I) by ICP-Mass
24 h
Wang, Li. P. Zhang, Y. L. Wang M. Tetrahedron
Letters 49 2008 66506654
43
4 H
2 H
d6-DMSO
0.25 0.13 X 0.03725 X 0. 07164 mmol
lignad 0.071640.5 0.0358 mmol- metal
center 0.0358/9 0.004 mol/g
Au-hmim2AgPF6 9 mg
1,2,4,5-tetramethylbenzene 5 mg
44
Reusable Au NPs-Ag(I)(NHC)2PF6 Catalyst for
A3-Coupling Reaction
Recycle No. Time (h) Yield ()
1 2 93
2 2 97
3 2 96
4 2 95
5 2 93
6 2 94
7 2 92
8 2 93
9 2 91
10 2 90
11 2 90
12 2 91
Reaction conditions Catalyst loading 20 mol
para-formaldehyde 1.00 mmol pyperidine 1.10
mmol phenylacetylene 1.50 mmol propionitrile
1.0 mL
45
Reactivity Comparision Between Au
NPs-Ag(I)(NHC)(PF6) and Ag(hmim)2PF6
Entry Time (min) Cat. 3 Yield () Cat. 10 Yield ()
1 10 20 30 65 83 95 83 92 gt 99
2 10 20 30 52 78 93 44 67 88
3 10 20 30 68 81 93 61 77 91
4 10 20 30 69 82 92 58 74 93
Reaction conditions catalyst loading 1.5 mol
Benzaldehyde 1.00 mmol Piperidine 1.20 mmol
Phenylacetylene 1.50 mmol Propionitrile 1.0
mL
46
Conclusions

• 1.The air- and water-stable catalyst
  Ag(hmim)2PF6 was synthesized and characterized
  by 1H- and 13C-NMR, ESI-MS, IR, UV, X-ray.
• 2.We have developed a methodology to successfully
  immobilize
• Ag(hmim)2PF6 onto surfaces of Au NPs. The
  structure of the supported Ag(I)-NHC complex
  catalyst was characterized
• by 1H-NMR, IR, TEM, UV, EDS, AA, ICP-Mass.
• 3.Since the Au NPs- Ag(I) hybrid catalysts are
  highly soluble in
• organic solvents, their structures and
  reactions were studied by simple solution NMR
  technique.
• 4. We have successfully demonstrated the
  catalytic activity of
• the Ag(I) complex for the three-component
  coupling reactions of aldehyde, alkyne, and
  amine.
• 5. The Au NPs- Ag(I) catalyst can be
  quantitatively recovered and effectively reused
  for many times without any loss of reactivity.