Transcript Catalytic, Enantioselective Nucleophilic Addition to N

New Progress of Gold in Organic Chemistry
Recent Contribution of F. Dean Toste
William S. Bechara
Charette Group Literature Meeting
Department of Chemistry
University of Montreal
March 17th , 2009
Outline
•
General Properties of Gold
•
Particularities and advantages of Gold in Homogeneous Catalysis
•
Relativistic effects of Gold (Quantum Chemistry studies)
•
Examples of the Relativistic Effect
•
Initial Tryouts with Gold in Organic Chemistry
•
Contribution of F. Dean Toste in Homogeneous Gold(I) Catalysis
•
Mechanistic Studies
•
Applications in Total Synthesis
2
General Properties of Gold
Au : [Xe] 6s1 4f14 5d10
AuIII
Au I
Linear
Square Planar
•
Oxidation States : Au-I to AuIII and AuV but AuI and AuIII dominate.
•
Electronegativity : Au  2.54 (~highest electronegativity of all metals)
•
Industrial use : medicine, dentistry, electronics, jewelry, food, etc  good resistance to
oxidative corrosion, good conductor of heat and electricity, ductile, malleable….
•
Organic Chemistry : heterogeneous and homogeneous catalysis
(Au0)
(AuI and AuIII)
J. Phys. Chem. A, 2006, 110 , 11332
3
Advantages of Gold in Organic Chemistry
•
Most reactions catalyzed by Au can be done without precautions to exclude air
and humidity (sometimes done in water or MeOH).
•
Gold catalysts can be used for heterogeneous and homogeneous catalysis.
•
Relatively fast reactions.
•
Good potential to stabilize cationic reaction intermediates.
•
Versatile Lewis Acid  Gold species can activate various substrates, specially
unsaturated molecules. e. g. alkynes, alkenes, allenes, diynes, allenynes,
enynes...
•
A wide array of nucleophiles can be added to the activated substrates in an
intramolecular or intermolecular fashion. e.g. O, N, C, F, S.
F. Dean Toste Nature, 2007, 446, 395
F. Dean Toste J. Am. Chem. Soc., 2008, 130, 4517
Hashmi Angew. Chem. Int. Ed. 2005, 44, 6990
4
Particularities of Gold in Homogeneous Catalysts
•
Gold catalysts are considered as soft and mostly carbophilic Lewis acid.
•
Au(I) complexes are known to activate C-C p-bonds towards nucleophilic
addition.
•
Au(III) can also complex carbonyls and other heteroatoms (e.g. N, O, S)
•
Au(I) species are not nucleophilic (relative to the copper complexes).
•
Gold catalysts have a low propensity for β-H elimination and reductive
elimination.
•
Au(I) and Au(III) complexes do not readily cycle between oxidation states in the
catalysis. Difficult for cross-coupling.
•
Au(I) can pass through a cationic intermediate and a carbenoid species in the
reaction mechanism.
•
Strong relativist effect. Relativistic effects are crucial to understanding the
electronic structure of heavy elements.
F. Dean Toste Nature, 2007, 446, 395
P. Pyykko Angew. Chem. Int. Ed. 2004, 43, 4412
F. Dean Toste Chem. Rev., 2008, 108 , 3351
5
Relativistic Effect of Gold
•
6s
4f
5d
Au:
Relativistic Quantum chemistry describes the electron dynamics, chemical bonding and
particularly the behaviour of the heavier elements of the periodic table (specially the elements
in which the 4f and 5d orbitals are filled), aurophilicity (strong Au-Au interaction), etc.
•
It describes that Gold has a relativistic contraction of the 6s and 6p orbitals and an expansion
of the 5d orbitals. This correspond to a lowering of the lowest unoccupied molecular orbital
(LUMO) and therefore a strong Lewis acid.
•
It also results in greatly strengthened Au–L bonds (which can induce high chirality).
•
Different oxidation state influences the activity of the catalyst.
•
76Os
73Ta
77Ir
78Pt
Contraction of 6s and
expansion of 5d
orbitals
82Pb
81Ti
80Hg
79Au
F. Dean Toste Nature, 2007, 446, 395 , P. Pyykko Angew. Chem. Int. Ed. 2004, 43, 4412
6
Influence of Oxidation States
•
Gold(I) and (III) can furnish different regioisomers :
Br
H
AuCl3 (2 mol%)
O
95 : 5
n-Oct
H
Br
PhCH 3
Et3PAuCl (2 mol%)
O
Br
PhCH 3
n-Oct
n-Oct
O
< 1: 99
hydride shift
[Au]
Br
[(III)Au] O
•
Br
Br
n-Oct
[(III)Au] O
n-Oct
Gold(III) catalyses the reaction
by activating the ketone.
V. Gevorgyan J. Am. Chem. Soc., 2005, 127, 10500
F. Dean Toste Nature, 2007, 446, 395
[Au]
Br
[Au]
O
n-Oct
O
n-Oct
•
Gold(I) catalyses the reaction
Br
H
O
n-Oct
by activating the allene.
7
Initial tryouts with Gold in Organic Chemistry
•
First attempts using gold catalysis was mainly for oxidations :
•
Au(III) species
NH 2
R1
R2
HAuCl4 (0.3-0.5 eq)
H 2 O, NaOH (pH~6)
O
R1
R 1, R 2 = alkyl
R2
9 - 72%
1
R
S
Bu4 N(AuCl4 ) (5 mol%)
R2
MeNO2, HNO 3 10%
R
O
1 S
R2
R 1 = alkyl
R 2 = aryl or alkyl
76 - 97%
J. Org. Chem., 1976, 41, 2742
Tetrahedron 1983, 39, 3181
8
Contribution in Homogeneous Gold Catalysis
Prof. F. Dean Toste
•
•
•
Dean was born in 1971 in Azores, Portugal and
soon moved to Canada. He majored in Chemistry
and obtained a M.Sc. in Organic Chemistry at the
University of Toronto with Prof. Ian W. J. Still. He
then pursued his Ph.D. with Barry Trost at Stanford
and a post-doctoral appointment with Robert
Grubbs at Caltech. Dean is currently an Associate
Professor of Chemistry at UC Berkeley.
His main research interest is the Gold(I)-Catalyzed
C-C Bond Formation.
Published around 30 publications (~25 JACS) just
on Gold chemistry in the past 5 years.
 Around 10 reviews on gold chemistry in the past few years (2 by Toste).
9
Conia-Ene Reaction of b-Ketoesters with Alkynes
O
O
R1
OR 2
R5
3
R
R1
CH2 Cl2, rt, 15min - 24h
R
O
R1
Me
O
R1
R1
R1
R1
94%
93%
81%
79%
Et
95% (17:1)
CO 2Me
O
O
MeO
Me
O
= Me, R2 = Me
= Ph, R2 = Et
= Me, R2 = t-Bu
= Me, R2 = CH2 CCH
O
O
MeO
CO2Me
R5
O 3
R
4
R 2O
O
R 2O
Ph3PAuCl (1-5 mol%)
AgOTf (1-5 mol%)
R4
O
MeO
MeO
Me
O
Ph
86% (4.2:1)
O
CO2 R 2
O
Me
O
n-Pr
O
Ph
96% (4:1)
97% (2.9:1)
O CO2 Me
O
CO2 Me
O
n
H
n = 1 90%
n = 2 90%
F. Dean Toste J. Am. Chem. Soc., 2004, 126 , 4526
H
R3
H
88%
R 2 = Et, R 3 = H
90%
R 2 = Me, R 3 = Me 83%
86%
H
99%
10
Proposed Mechanism
Me
MeO 2C
Ac
OH
Au
A
O
CO 2Me
+
H+
Au
O
MeO 2C
Me
Ac
OMe
Me
X
MeO 2C
O
B
CO 2Me
H+
Ac Au
Au+
Syn
O
O
Me
O
Ph3 PAuOTf
OMe
H
D
MeO
Me
H
O
O
D
via
Anti
O
Me
O
O
Ph3 PAuOTf
OMe
D
H
F. Dean Toste J. Am. Chem. Soc., 2004, 126 , 4526
MeO
Me
O
H
MeO
Me
D
Au
in both cases
O
D
11
Allenyne Cycleisomerisation – Activated Ene Reaction
R1
Me
n
Me
Me
[(Ph3 PAu)3 O]BF 4 (1-5 mol%)
R2
R3
R1
R2
CHCl3, 60 oC, 6-48h
R4
n
4R
3
R
Me
Me
Me
H
H
H
Bn
H
84%
H
88%
Ph
7:1
Z:E
Me
Me
Ph
H
H
89%
CO2 Me
CO2 Me
H
99%
CO 2Et
CO2 Et
40%
Me
H
H
Me
+
Ph
H
H
2.4
1
64%
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
H
H
cis
78%
H
trans
70%
H
H
H
70%
12
Mechanistic Studies – Ene Type Reaction
CD3
Catalyst
Me
Me
+
D
D 3C
D
CH2 D
Catalyst
DH 2C
D
D
DH 2 C
CH2 D
+
D
D
D
D
 Intramolecular proton transfer
Me
Bn
PMP
+
Me
Me
Catalyst
CD3
D 3C
+
D 3C
H
Me
Me
Me
D
D
PMP
Bn
D
Me
H
H
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
13
Mechanistic Studies
Me
Me
Me
H
Me
H
Ene Reaction
Mono
Gold
Phosphine
Metallacycles
Me Me
Me
Me
PPh 3Au
Ph3PAu
H
AuPPh3
B
Me Me
Ph3 PAu
PPh 3Au
F
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
Me
Me
Me
H
A
Dual
Gold
Phosphine
Me
Me
Ph3 PAu
p-Coordinations
Vinylidenes
Me
C
AuPPh 3
D
Me
Me
PPh 3Au
Ph3PAu
Me
Me
AuPPh3
G
E
Me
PPh 3Au
H
Me
PPh 3Au
AuPPh 3
I
14
Mechanistic Studies
Me
Me
PPh 3Au
A
Bn
Me
Me
H
o
LDA, THF, -78 C
then Ph3PAuCl
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
Bn
Me
CHCl3, 60o C
No reaction
Me
PPh3 Au
15
Mechanistic Studies
Me Me
Me Me
Metallacycles :
Ph3 PAu
Ph3 PAu
PPh 3Au
H
B
•
Experimentally :
Me
Oxidative
Addition
Me Me
X
Me
Ph3 PAu
AuPPh 3
•
F
Me
b-Hydride
Elimination
X
H
Me
Reductive
Elimination
H
Au
Ph 3P
X
AuPPh 3
H
Computationally :
Me Me
Computational
Ph3 PAu
Energy Minimization
H
Me
Me
AuPPh 3
 Similar computational results for dual phosphine gold intermediate
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
16
Mechanistic Studies
Vinylidenes :
Me
Me
Me
Me
PPh 3Au
H
AuPPh3
AuPPh3
G
C
Me
Me
 Very unstable by computational energy
minimization, hight DG+
H
AuPPh3
Me
Me
PPh 3Au
Me
Computational
Energy Minimization
AuPPh3
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
Me
PPh 3Au
AuPPh 3
17
Mechanistic Studies
p-Coordinations :
Ph3PAu
Ph3PAu
Me
Me
Me
PPh 3Au
Me
D
H
Ph3PAu
Me
H2 C
H
 Formation of unstabilized vinyl cation
Ph3PAu
Me
H2 C
H
PPh 3Au
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
 Need of concerted C-C bond formation and
asynchronous hydrogen transfer to avoid
unstable intermediate.
 Very hight activation energy (computational
calculus)
18
Mechanistic Studies
Me
Me
Me
PPh 3Au
Me
AuPPh 3
AuPPh 3
E
I
Catalyst
Me
No reaction
Me
R
R = Ph
R = Me
Me
Bn
Me
Catalyst
Me
PPh3Au
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
 Intermediate I also approved
Bn
by computational analysis
19
Catalytic Cycle
Ph3 PAu
Me
Me
+
Me
-BF4
Me
Me
Ph3 PAu
+
Me
Catalyst transf er
Me
H
O
AuPPh3
AuPPh 3
O
AuPPh3
AuPPh 3
-BF4
C-C Bond formation
+
Ph3 PAu
AuPPh 3
O
AuPPh3
Me
Me
-
BF4
H
H
H
Ph3PAu
H
Ph3 PAu
AuPPh 3
AuPPh3
Aurophilicity
1,5-Hydrogen shift
F. Dean Toste J. Am. Chem. Soc., 2008, 130 , 4517
20
Synthesis of Benzopyrans
1
R OPiv
R
(R)-MeO-DTBM-BIPHEP(AuCl) 2 (5 mol%)
AgSbF6 (10 mol%)
O
R
Ar
R2
OPiv
MeCN, rt
R2
O
R1
Ph
Ph
Ph
Et
OPiv
X
O
Ar = Ph
m-MeO-C 6H 4
p-Cl-C 6H 4
o-Me-C 6H 4
O
X = Cl
69% 97% ee
= Br
60% 94% ee
= t-Bu 65% 99% ee
= Ph 64% 97% ee
= OPh 60% 97% ee
74% 97%ee
78% 99%ee
72% 98%ee
58% 98%ee
OPiv
OPiv
35%
98% ee
OPiv
OPiv
t-Bu
O
O
64%
98% ee
53%
99% ee
Ph
Ph
O
OPiv
O
44%
99% ee
F. Dean Toste J. Am. Chem. Soc., 2009, 131 , 3463
OPiv
O
55%
97% ee
OPiv
OPiv
O
51%
97% ee
O
49%
91% ee
> 95:5, E:Z
21
Proposed Mechanism
Me OPiv
Ph
Me
OPiv
O
AuL
O
?
Ph
Rearrangement of allylic
oxonium intermediate
Me
Me OPiv
OPiv
O
AuL
O
Ph
Ph
Nucleophilic
attack
1,2-Migration of
propargyl ester
Me
Me
OPiv
O
F. Dean Toste J. Am. Chem. Soc., 2009, 131 , 3463
AuL
OPiv
AuL
Ph
O
Backbonding
AuL
Ph
22
Mechanistic Studies
Me
OPiv
2,3-rearrangement
Me
OPiv
3,3-rearrangement
X
O
Ph
Ph
Me
OPiv
1,4-sigmatropic rearrangement
O
X
AuL
Ph
Me
O
OPiv
O
AuL
Ph
Me OPiv
(R)-MeO-DTBM-BIPHEP(AuCl) 2 (5 mol%)
AgSbF6 (10 mol%)
O
Me
Inversion of
allyl moiety
OPiv
MeCN, rt
O
Me OPiv
OMe
(R)-MeO-DTBM-BIPHEP(AuCl) 2 (5 mol%)
AgSbF6 (10 mol%)
O
Me
OPiv
MeCN, rt
OMe
O
F. Dean Toste J. Am. Chem. Soc., 2009, 131 , 3463
Impossible
inversion
23
1,3-Dipolar Cycloaddition of Munchnones
N
Ar
R
+
O
O
O
O
N
Ph
1.5 equiv.
(S)-Cy-SEGPHOS(AuOBz)2 (2 mol%)
PhF (0.5 M)
then TMSCHN2
or CH 2N 2
X
N
O
N
Ph
O
N
N
Ph
CO2 Me
H
O
N
Ph
X = p-OMe 77% 95%ee
p-Br
75% 93%ee
p-Cl
72% 92%ee
p-NO2 98% 91%ee
O
84%
98% ee
O
N
N
Ph
CO 2Me
Me
O
76%
95% ee
F. Dean Toste J. Am. Chem. Soc., 2007, 129 , 12638
Ph
O
N
N
Ph
CO 2Me
O
86%
87% ee
N
N
Ph
CO2 Me
R
O
MeO
O
O
Ph
O
CO 2Me
Me
N
CO 2Me
Me
73%
86% ee
Ph
Ar
N
O
N
Ph
CO2 Me
Me
O
77%
95% ee
Ph
O
N
N
Ph
CO2 Me
Ph
O
35%
78% ee
Ph
O
N
N
Ph
CO 2Me
Bn
O
71%
68% ee
24
Proposed Mechanism
CO2 Me
Me
N
Ph
O
LAuOBz
O
N
Ph
N
Ph
Me
O
LAu
O
OBz
HOBz
AuL
O
Ph
N
N
Ph
Ph
O
O
O
O
N Me
AuL
H
N
Me
O
O
OBz
Ph
O
1,3-Dipolar
Cycloaddition
F. Dean Toste J. Am. Chem. Soc., 2007, 129 , 12638
Ph
AuL
N
Me
HOBz
Generation of 1,3- dipole
O
O
25
Intramolecular Cyclopropanation
R 1 OR 2
R1
L*(AuCl)2 (2.5 mol%)
AgSbF6 (5 mol%)
MeNO 2 (0,1 M), -25o C
n
n
R3
R3
Me
H
OAc
91%
49% ee
OR2
H
OAc
49%
15% ee
Me
OPiv
44%
85% ee
OAc
Et
94%
92% ee
OAc
91%
92% ee
O
O
OAc
OAc
OAc
Me
OAc
Me
98%
90% ee
F. Dean Toste J. Am. Chem. Soc., 2009, 131 , 2056
80%
90% ee
96%
90% ee
88%
75% ee
26
Proposed Mechanism
OPiv
OPiv
AuPPh 3
1,2-Shift
AuPPh 3
Backbonding
Syn
Anti
AuPhPh3
OPiv
OPiv
AuPhPh3
 Carbenoid
Intermediates
Ph
Ph
OR 2
Ph
OPiv Ph
F. Dean Toste J. Am. Chem. Soc., 2009, 131 , 2056
27
Stereoselective Olefin Cyclopropanation
OR
R
R1
+
R1 R2
Ph3 PAuCl (5 mol%)
AgSbF6 (5 mol%)
3
R4
R3
R4
MeNO2 , rt
R2
RO

Cis cyclopropanes – major product
H
TMS
Ph
PivO
74% (6:1)
(cis:trans)
O
C 5H 11
AcO
62% (1.3:1)
PivO
48% (1.3:1)
Ph
Ph
Ph
PivO
BzO
73%
73%
F. Dean Toste J. Am. Chem. Soc., 2005, 127 , 18002
n H
H
PivO
84% (5:1)
H
PivO
61% (>20:1)
Me
H
AcO
69% (1.2:1)
H
PivO
n = 1 68% (>20:1)
n = 2 69% (1.2:1)
Me Me
Me
Me
AcO
67%
28
Reaction Mechanism
Ph
Z
H
Ph


A
OAc
LAu
Ph
Ph
OAc
OAc
AuL
LAu
H
Ph
OAc
AuL H
H
Ph
Ph
Ph3 PAuCl (2 mol%)
AgSbF6 (2 mol%)
MeNO2 , rt
91% ee
F. Dean Toste J. Am. Chem. Soc., 2005, 127 , 18002
OAc
Syn
Ph
Z
AuL
OAc
Ph
PivO
AuL H
Ph
Z
H

OAc
Ph
Ph
B
H
Ph
Z
Ph
OAc
Anti
 Complete loss of ee, consistent with
the formation of a vinyl gold(I) species
65% (95:5 cis:trans)
0% ee
29
Pyrrole Synthesis – Acetylenic Schmidt Reaction
R1
(dppm)Au2 Cl2 (2,5 mol%)
AgSbF6 (5 mol%)
N3
R2
DCM, 35o C
R3
H
N
n-Bu
n-Bu
H
82%
H
H
N
61%
H
N
n-Hex
H
H
N
68%
F. Dean Toste J. Am. Chem. Soc., 2005, 127 , 11260
H
N
n-Bu
76%
O
R
H
MeO
88%
H
N
R3
R2
n-Bu
78%
H
N
1
H
N
H
N
Ph
41%
H
Ph
73%
H
N
H
H
N
I
CF 3
93%
87%
30
Reaction Mechanism
N3
NH
N
LAu
R3
H
R
R
1,2-proton shif t
N
H
LAu
N2
N
R
LAu
R
N2
N N2
Backbonding
stabilises cation
intermediate
F. Dean Toste J. Am. Chem. Soc., 2005, 127 , 11260
LAu
R
31
Intramolecular Hydroamination of Allenes
R1
NHTs
n
R2
R1
(R)-xylyl-Binap(AuOPNB) 2 (10 mol%)
R1
TsN
R1
DCE
2
n
R
R2 R2
Me
Me
TsN
Me
Me
Me
TsN
Me
Et
Et
TsN
Me
TsN
TsN
Me Me
98%
99% ee
Me
TsN
Ph Ph
94%
93% ee
90%
99% ee
75%
83% ee
99%
70% ee
99%
87% ee
O
TsN
TsN
Me
Me
TsN
88%
98% ee
88%
98% ee
Me
TsN
Me
76%
96% ee
Et
TsN
Me
88%
81% ee
41%
74% ee
F. Dean Toste J. Am. Chem. Soc., 2007, 129 , 2452
79%
98% ee
Me
Et
TsN
O
TsN
Me
70%
98% ee
Me
TsN
80%
98% ee
Me
Me
TsN
Ph
Me
TsN
Me
Ph
70%
88% ee
66%
97% ee
32
Cyclization of Silyl Enol Ethers
PGO
Ph3 PAuCl (10 mol%)
AgBF4 or AgOTf (10 mol%)
R1
O
n
R1
n
R2
MeO 2C
CO2 Me
CH2 Cl2 or toluene/H2 O or MeOH
40 oC or 0o C
R2
MeO2 C
CO 2Me
PG = TBS or TIPS
O
O
Me
H
MeO2 C
CO 2Me
O
H
R
I
O
Me
Me
H
MeO 2C CO 2Me
R 1 = H, R2 = H 83%
R 1 = Ph, R 2 = H 83%
R 1 = Me, R 2 = Me 90%
78%
O
R2
MeO2 C
CO 2Me
O
R1
94%
O
O
Me
H
MeO 2C
O
77%
91%
CO2 Me
80%
O
O
S
Me
O
TsN
O
Me
TsN
Me
H
77%
Me
H
85%
F. Dean Toste Angew. Chem. Int. Ed. 2006, 45, 5991
H
73%
H
75%
H
91%
75%
33
Ring Expanding Cycloisomerisation
EtO 2C CO2 Et
EtO2C CO 2Et
Ph3 PAuCl (5 mol%)
AgSbF6 (5 mol%)
DCM, rt
X
EtO 2C CO2 Et
X
EtO2 C CO 2Et
Me
EtO2C CO 2Et
EtO2 C CO2Et
EtO2 C CO2Et
Me
I
Me
75%
75%
EtO2 C CO2Et
91%
Me
35%
Cl
44%
EtO 2C CO2 Et
Cl
86%
EtO2C CO 2Et
Ph3 PAuCl (5 mol%)
AgSbF6 (5 mol%)
I
DCM, rt
I
F. Dean Toste Org. Lett.. 2008, 10, 4315
91%
82%ee
34
Proposed Mechanism
Nazarov-type electrocyclisation
EtO 2C CO2 Et
EtO2 C
EtO2 C
EtO2 C
EtO2 C
EtO2C CO 2Et
AuL
LAu
LAu
Backbonding
F. Dean Toste Org. Lett.. 2008, 10, 4315
35
Applications in Total Synthesis
•
Ventricosene : Ring Expanding Cycloisomerization
Ph3 PAuCl (3 mol%)
AgSbF6 (3 mol %)
HO
CO2 Me
O
H
CH2 Cl2, 23o C, 2h
87%
H
H
H
Ventricosene
•
(+)-Lycopladine A : Cyclisation os Silyl Enol Ether
BnO
O
OTBS
OBn
I
H
F. Dean Toste Org. Lett.. 2008, 10, 4315
F. Dean Toste Angew. Chem. Int. Ed. 2006, 45, 5991
Ph3 PAuCl (10 mol%)
AgBF4 (10 mol %)
CH 2Cl2 /MeOH,
95%
O
HO
I
O
N
40 oC
H
H
(+)-Lycopladine A
36
Conclusion
•
Properties and Avantages of Gold in Homogeneous Catalysis
•
Relativistic Effects of Gold and Examples
•
Applicationd of Gold in Organic Chemistry
•
Very Versatile and Useful Catalyst (Hight Yields and ee)
•
Large Contribution of F. Dean Toste
•
Mechanistic Studies
•
Applications in Total Synthesis
•
 Future Work : Further the understanding of Enantioselective and Seteroselective
Mechanisms. (Transition States with Chiral Ligands)
37
Are Gold Chemicals Expensive???
$/g
Rh
Pt
Au
Pd
Ag
Cu
RhCl(PPh3)
98$
PtCl2
135$
AuCl
140$
PdCl2
42$
AgCl
3$
CuCl
5$
TiCl2Cp2
2$
RhCl3
438$
PtCl4
114$
AuCl3
94$
Pd(OAc)2
59$
AgF6Sb
12$
CuBr2
0.5$
TiCl4
0.13$
Rh2(OAc)4
371$
PtCl2(PEt3) 2
149$
PPh3AuCl
108$
Pd(PPh3)4
66$
AgOTf
6$
Cu(OTf)4
7$
Ti
TiCl3
0.5$
$$$
38
Myths – Does the Chemistry Comes from Gold????
•
A very long time ago, the main goal of the alchemists was to produce
gold from other substances, such as lead — presumably by the
interaction with a mythical powerful substance called the philosopher’s
stone. Although they never succeeded in this attempt, the alchemists
promoted an interest in what can be done by reacting different
substances and this apparently laid a foundation for today‘s chemistry.
39