STUDIES ON CATALYTIC OXIDATION OF
ALKENES BY (SALEN)RUTHENIUM(III)
COMPLEXES AND BF3-ACTIVATED OXIDATION
OF HYDROCARBONS BY PERMANGANATE
LEE MEI NGOR JOYCE
MASTER OF PHILOSOPHY
CITY UNIVERSITY OF HONG KONG
AUGUST 2005
CITY UNIVERSITY OF HONG KONG
香港城市大學
Studies on Catalytic Oxidation of Alkenes by
(Salen)Ruthenium(III) complexes and
BF3-activated Oxidation of Hydrocarbons by
Permanganate
釕和席夫鹼配合物對烯烴類催化氧化和三氟化磞激活
高猛酸鹽氧化碳氫化合物的性能研究
Submitted to
Department of Biology and Chemistry
生物及化學系
in Partial Fulfillment of the Requirements
for the Degree of Master of Philosophy
哲學碩士學位
by
Lee Mei Ngor Joyce
李美娥
August 2005
二零零五年八月
Abstract
i
Abstract
This thesis is divided into two parts. Part I is concerned with catalytic
oxidation of alkenes by (salen)ruthenium(III) complexes, Part II describes
BF3-activated oxidation of hydrocarbons by permanganate.
In Part I , a series of (salen)ruthenium(III) solvento species, [RuIII(L)(S)2]+
(L = N,N’-bis(salicylidiene)-o-cyclohexyldiamine dianion) and its derivatives (S =
solvent, e.g. H2O,CH3OH, CH3CH2OH) have been prepared either by N…N coupling
of [RuVI(N)(L)(MeOH)]+ in refluxing acetone/water or by direct reaction of
[NnBu4][RuVI(N)Cl4] with the salen ligand in methanol followed by the addition of
thallium(I) hexafluorophosphate.
H2O
N
X
O
N
Ru
MeOH
N
O
PF6-
X
Acetone/H2O
N
X
O
Ru
H2O
N
X
O
PF6
-
X = H, CH3, CH3O, Cl, Br
These complexes have been characterized by IR, electrospray ionization
mass spectrometry (ESI-MS) and CHN elemental analysis. The structure of
[RuIV(3,3’,5,5’-tBu4salchda)Cl2] has been determined by X-ray crystallography.
These (salen)ruthenium(III) solvento complexes are effective catalysts for
the oxidation of alkenes in the presence of various oxygen donors such as
iodosylbenzene and 2,6-dichloropyridine-N-oxide. It was found that catalysts with
Abstract
ii
electron withdrawing groups give better yields. A reaction scheme involving the
formation of a ruthenium(V) oxo species as the active intermediate is proposed.
A
series
of
chiral
(salen)ruthenium(III)
solvento
species
(R,R’)-[RuIII(L)(S)2]+ and its derivatives have also been synthesized by similar
methods. These complexes have also been characterized by IR, electrospray mass
spectrometry
(ESI-MS)
and
CHN
elemental
analysis.
These
chiral
(salen)ruthenium(III) complexes catalyze the asymmetric epoxidation of alkenes
with moderate to good enantioselectivity. The asymmetric epoxidation of styrene and
trans-β-methylstyrene catalyzed by (R,R’)-[RuIII(3,3’,5,5’-Br4salchda)(EtOH)2]+
proceeds with 73 % and 62 % ee respectively.
In Part II, the effects of BF3 on the oxidation of hydrocarbons have been
investigated. It was found that the oxidizing power of MnO4- could be greatly
enhanced by just adding a few equivalents of BF3. The BF3/MnO4- system is able to
oxidize various alkanes and alkyl aromatics. A mechanism involving the formation of
an adduct between the permanganate and BF3 is proposed. This adduct is proposed to
be the active species, as the electron withdrawing effect by BF3 would enhance the
oxidizing power of permanganate.
Declaration iii
Declaration
I hereby declare that the thesis summarizes my own works carried out
since my registration for the Degree of Master of Philosophy in July 2003 and that it
has not been previously included in a thesis, dissertation or report submitted to this or
any other institution for a degree, diploma or other qualification.
Lee Mei Ngor Joyce
August 2005
Table of Contents vi
Table of Contents
Page
Abstract
i
Declaration
iii
Acknowledgements
iv
Table of Contents
vi
List of Tables
xii
List of Figures
xiv
List of Appendixes
xvi
Abbreviations
xviii
Chapter 1 Synthesis, Characterization and Catalytic Oxidation of
Alkenes by (Salen)Ruthenium(III) complexes
1.1 Introduction
1
1.1.1 Oxidation by oxoiron species
2
1.1.2 Epoxidation by metalloporphyrins
5
1.1.3 Epoxidation by metal complexes containing non-porphyrin type
10
multi-anionic chelating ligands
1.1.4 Epoxidation by metal salen complexes
12
1.1.5 Reactivities of ruthenium complexes
15
1.1.6 Asymmetric alkene epoxidation
17
Table of Contents vii
1.1.7 Asymmetric alkene epoxidation by metalloporphyrins
19
1.1.8 Asymmetric epoxidation of alkenes by metallosalen complexes
22
1.2 Objectives
30
1.3 Experimental
31
1.3.1 Materials and Solvent
31
1.3.2 Schiff base ligands
31
1.3.3 [NnBu4][RuVI(N)Cl4]
34
1.3.4 Preparation and characterization of (salchda)ruthenium(VI) nitrido
35
complexes
1.3.4.1 [RuVI(N)(salchda)(CH3OH)]PF6 (1.1a)
35
1.3.4.2 [RuVI(N)(5,5’-(MeO)2salchda)(CH3OH)]PF6 (1.1b)
35
1.3.4.3 [RuVI(N)(5,5’-Cl2salchda)(CH3OH)]PF6 (1.1c)
35
1.3.4.4 [RuVI(N)(5,5’-Br2salchda)(CH3OH)]PF6 (1.1d)
36
1.3.5 Preparation and characterization of (salchda)ruthenium(III) solvento
36
complexes
1.3.5.1 [RuIII(salchda)(H2O)2]PF6 (2.1a)
36
1.3.5.2 [RuIII(5,5’-(MeO)2salchda)(H2O)2]PF6 (2.1b)
36
1.3.5.3 [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (2.1c)
37
1.3.5.4 [RuIII(5,5’-Br2salchda)(H2O)2]PF6 (2.1d)
37
1.3.5.5 [RuIII(3,3’,5,5’-Cl4salchda)(CH3CH2OH)2]PF6 (2.1e)
37
1.3.5.6 [RuIII(3,3’,5,5’-Br4salchda)(CH3CH2OH)2]PF6 (2.1f)
38
1.3.5.7 [RuIII(3,3’,5,5’-tBu4salchda)(CH3OH)2]PF6 (2.1g)
38
1.3.5.8 [RuIV(3,3’,5,5’-tBu4salchda)Cl2] (2.2)
38
1.3.6 Preparation and characterization of chiral (salchda)ruthenium(IV) nitrido
complexes
39
Table of Contents viii
1.3.6.1 (R,R’)-[RuVI(N)(5,5’-Cl2salchda)(CH3OH)]PF6 (3.1)
39
1.3.7 Preparation and characterization of chiral (salchda)ruthenium(III)
39
solvento complexes
1.3.7.1 (R,R’)-[RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (3.2a)
39
1.3.7.2 (R,R’)-[RuIII(3,3’,5,5’-Cl4salchda)(CH3CH2OH)2]PF6 (3.2b)
39
1.3.7.3 (R,R’)-[RuIII(3,3’-Br2-5,5’-Cl2salchda)(CH3CH2OH)2]PF6 (3.2c)
40
1.3.7.4 (R,R’)-[RuIII(3,3’,5,5’-Br4salchda)(CH3CH2OH)2]PF6 (3.2d)
40
1.3.7.5 (R,R’)-[RuIII(3,3’,5,5’-tBu4salchda)(CH3OH)2]PF6 (3.2e)
40
1.3.8 Instrumentation
41
1.3.9 Catalytic oxidation of alkenes
43
1.3.9.1 General procedure for the oxidation of styrene by (salen)Ru(III)
43
complexes using PhIO as terminal oxidant
1.3.9.2 Oxidation of styrene by [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 using
43
various oxidants
1.3.9.3 Oxidation of trans-β-methylstyrene by (tetra-substituted
43
salen)Ru(III) complexes
1.3.9.4 General procedure for the oxidation of styrene by
44
[RuIII(5,5’-Cl2salchda)(H2O)2]PF6 using
2,6-dichloropyridine-N-oxide as terminal oxidant at 55oC (Table
2.8)
1.3.9.5 Oxidation of various alkenes by 2.1c, 2.1e and 2.1f
44
1.3.9.6 Stability of styrene oxide to the reaction conditions of
44
epoxidation
1.3.9.7 General procedure for asymmetric epoxidation of alkenes by
chiral (salen)Ru(III) solvento complexes
45
Table of Contents ix
1.4 Results and Discussions
46
1.4.1 Synthesis of Schiff base ligand
46
1.4.2 Synthesis and characterizations of (salen)Ru(III) solvento complexes
47
1.4.3 Structural study of [RuIV(3,3’,5,5’-tBu4salchda)Cl2] (2.2)
54
1.4.4 Oxidation of alkenes catalyzed by (salen)Ru(III) complexes
56
1.4.4.1 Activities of (di-substituted salen)Ru(III) complexes
56
1.4.4.2 Effects of various oxidants on the catalytic oxidation of styrene
57
with [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (2.1c)
1.4.4.3 Solvent effects on the catalytic oxidation of styrene with
60
[RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (2.1c)
1.4.4.4 Catalytic activities of (tetra-substituted salen)Ru(III) complexes
63
1.4.4.5 Effects of donor ligands on (salen)ruthenium (III) complexes
63
catalyzed oxidation of trans-β-methylstyrene with PhIO
1.4.4.6 Catalytic oxidation of various alkenes by (salen)Ru(III)
68
complexes
1.4.4.7 Proposed mechanism of the oxidation of alkenes by
72
(salen)Ru(III) complexes
1.4.5 Synthesis and characterizations of (R,R’)-(salen)Ru(III) solvento
73
complexes
1.4.6 Asymmetric epoxidation of alkenes catalyzed by chiral (salen)Ru(III)
79
complexes
1.5 Conclusions
1.5.1 Future work
87
88
Table of Contents
x
Chapter 2 BF3 activated Oxidation of Hydrocarbons by
Permanganate
89
2.1 Introduction
2.1.1 Complexes of manganese
91
2.1.2 Activation of metal-oxo species by Lewis acid
94
2.1.3 Activation of permanganate oxidation by Lewis acid
96
2.1.4 General chemistry of BF3
97
2.2 Objectives
98
2.3 Experimental
99
2.3.1 Materials
99
2.3.2 Instrumentation
99
2.3.3 Stoichiometric oxidation of alkanes
100
2.3.3.1 General procedure for the stoichiometric oxidation of alkanes in
100
the presence of BF3·CH3CN
2.3.3.2 Procedure for measurement of kinetic isotopic effect (KIE) on
100
oxidation of cyclohexane and ethylbenzene
2.3.3.3 General procedure for the oxidation of alkanes in the presence of
101
BF3·CH3COOH
2.3.3.4 Stability of cyclohexanone to the reaction conditions of oxidation
2.4 Results and Discussions
101
102
2.4.1 Effects of BF3 on the oxidation of cyclohexane by permanganate
102
2.4.2 Stoichiometric oxidation of various alkanes by BF3/MnO4-
107
2.4.3 Stoichiometric oxidation of alkyl aromatics by BF3/MnO4-
109
Table of Contents xi
2.4.4 Proposed mechanism
111
2.5 Conclusions
112
References
113
Appendixes
125
List of Tables xii
List of Tables
Table 1.1
Typical P-450 reactions
Table 1.2
Summary of Crystal Data, Details of Data Collection Solution and
Refinement Parameters for Compound (2.2)
Table 1.3
Summary of the absorption peaks of some (salen)ruthenium(VI) nitrido
complexes and (salen)ruthenium(III) solvento complexes (KBr mode)
Table 1.4
Summary of the mass spectrum data of (salen)Ru(III) solvento complexes
Table 1.5
Selected
bond
lengths
(Å)
and
bond
angles
(o)
of
[RuIV(3,3’,5,5’-tBu4salchda)Cl2] (2.2)
Table 1.6
Oxidation of styrene by (salen)Ru(III) complexes using PhIO as terminal
oxidant
Table 1.7
Oxidation of styrene by [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 with different
oxidants
Table 1.8
Effect
of
solvent
on
the
oxidation
of
styrene
by
[RuIII(5,5’-Cl2salchda)(H2O)2]PF6
Table 1.9
Effect of 2,6-dichloropyridine-N-oxide on the oxidation of styrene by
[RuIII(5,5’-Cl2salchda)(H2O)2]PF6
Table 1.10
Oxidation
of
(E)-β-methylstyrene
by
(tetrasubstituted-salen)Ru(III)
complexes with PhIO as oxidant
Table 1.11
Effect of donor ligand on the catalytic oxidation of trans-β-methylstyrene by
[RuIII(5,5’-Cl2salchda)(H2O)2]PF6 with PhIO
Table 1.12
Effect of donor ligand on the catalytic oxidation of trans-β-methylstyrene by
[RuIII(3,3’,5,5’-Cl4salchda)(CH3CH2OH)2]PF6 with PhIO
List of Tables xiii
List of Tables (continued)
Table 1.13
Oxidation
of
various
alkenes
by
(salen)Ru(III)
complexes
using
2,6-dichloropyridine-N-oxide at 55 oC
Table 1.14
Summary of the absorption peaks of some (R,R’)-(salen)ruthenium(VI)
nitrido complexes and (R,R’)-(salen)ruthenium(III) solvento complexes (KBr
mode)
Table 1.15
Summary of the mass spectrum data of (R,R’)-(salen)Ru(III) solvento
complexes
Table 1.16
Asymmetric epoxidation of styrene by (R,R’)-(salen)Ru(III) complexes
Table 1.17
Asymmetric epoxidation of trans-β-methylstyrene by (R,R’)-(salen)Ru(III)
complexes
Table 1.18
Asymmetric
epoxidation
of
various
alkenes
by
(R,R’)-[RuIII(3,3’,5,5’-Br4salchda)(EtOH)2]PF6
Table 2.1
Effect of BF3·CH3CN on the stochiometric oxidation of cyclohexane by
MnO4-
Table 2.2
Effect of BF3·CH3COOH on the stochiometric oxidation of alkanes by MnO4-
Table 2.3
Stoichiometric oxidation of various alkanes by BF3·CH3CN/MnO4-
Table 2.4
Stoichiometric oxidation of alkyl aromatics by BF3·CH3CN /MnO4-
List of Figures xiv
List of Figures
Figure 1.1
Basic structures of metallo-porphyrin and –salen complexes
Figure 1.2
A variety of nickel (II) complexes
Figure 1.3
Chiral (salen)vanadium complex
Figure 1.4
Chiral (salen)manganese complexes prepared by Jacobsen
Figure 1.5a
Various Mn(salen) complexes
Figure 1.5b
Jacobsen’s catalyst
Figure 1.6
Ruthenium complex containing a chiral tri-N-donor ligand
Figure 1.7
Schiff base ligands prepared
Figure 1.8
chiral Schiff Base ligands prepared
Figure 1.9
Electrospray mass spectrum of [RuIII(salchda)(H2O)2]PF6 (2.1a) and
experimental and simulated isotopic distribution pattern insets
Figure 1.10
Electrospray mass spectrum of [RuIII(5,5’-(MeO)2salchda)(H2O)2]PF6 (2.1b)
and experimental and simulated isotopic distribution pattern insets
Figure 1.11
Electrospray mass spectrum of [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (2.1c) and
experimental and simulated isotopic distribution pattern insets
Figure 1.12
Electrospray mass spectrum of [RuIII(5,5’-Br2salchda)(H2O)2]PF6 (2.1d)
and experimental and simulated isotopic distribution pattern insets
Figure 1.13
Electrospray mass spectrum of [RuIII(3,3’,5,5’-Cl4salchda)(CH3CH2OH)2]PF6
(2.1e) and experimental and simulated isotopic distribution pattern insets
Figure 1.14
Electrospray mass spectrum of [RuIII(3,3’,5,5’-Br4salchda)(CH3CH2OH)2]PF6
(2.1f) and experimental and simulated isotopic distribution pattern insets
Figure 1.15
Electrospray mass spectrum of [RuIII(3,3’,5,5’-tBu4salchda)(CH3OH)2]PF6
(2.1g) and experimental and simulated isotopic distribution pattern insets
List of Figures xv
List of Figures (continued)
Figure 1.16
ORTEP diagram of [RuIV(3,3’,5,5’-tBu4salchda)Cl2]
Figure 1.17
Electrospray mass spectrum of (R,R’)-[RuIII(5,5’-Cl2salchda)(H2O)2]PF6
(3.2a) and experimental and simulated isotopic distribution pattern insets
Figure 1.18
Electrospray
mass
spectrum
of
(R,R’)-[RuIII(3,3’,5,5’-Cl4salchda)(CH3CH2OH)2]PF6 (3.2b) and experimental
and simulated isotopic distribution pattern insets
Figure 1.19
Electrospray
mass
spectrum
(R,R’)-[RuIII(3,3’-Br2-5,5’-Cl2salchda)(CH3CH2OH)2]PF6
of
(3.2c)
and
experimental and simulated isotopic distribution pattern insets
Figure 1.20
Electrospray
mass
spectrum
of
(R,R’)-[RuIII(3,3’,5,5’-Br4salchda)(CH3CH2OH)2]PF6 (3.2d) and experimental
and simulated isotopic distribution pattern insets
Figure 1.21
Electrospray
mass
spectrum
of
(R,R’)-[RuIII(3,3’,5,5’-tBu4salchda)(CH3OH)2]PF6 (3.2e) and experimental
and simulated isotopic distribution pattern insets
Figure 2.1
A plot of % yield of cyclohexanone against no. of equivalents of BF3·CH3CN
List of Appendixes xvi
List of Appendixes
Appendix I (a)
IR spectrum of [RuVI(N)(salchda)(MeOH)]PF6 (1.1a)
Appendix I (b)
IR spectrum of [RuIII(salchda)(H2O)2]PF6 (2.1a)
Appendix II (a)
IR spectrum of [RuVI(N)(5,5’-(MeO)2salchda)(MeOH)]PF6 (1.1b)
Appendix II (b)
IR spectrum of [RuIII(5,5’-(MeO)2salchda)(H2O)2]PF6 (2.1b)
Appendix III (a)
IR spectrum of [RuVI(N)(5,5’-Cl2salchda)(MeOH)]PF6 (1.1c)
Appendix III (b)
IR spectrum of [RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (2.1c)
Appendix IV (a)
IR spectrum of [RuVI(N)(5,5’-Br2salchda)(MeOH)]PF6 (1.1d)
Appendix IV (b)
IR spectrum of [RuIII(5,5’-Br2salchda)(H2O)2]PF6 (2.1d)
Appendix V (a)
IR spectrum of [RuIII(3,3’,5,5’-Cl4salchda)(EtOH)2]PF6 (2.1e)
Appendix V (b)
IR spectrum of [RuIII(3,3’,5,5’-Br4salchda)(EtOH)2]PF6 (2.1f)
Appendix VI
IR spectrum of [RuIII(3,3’,5,5’-tBu4salchda)(MeOH)2]PF6 (2.1g)
Appendix VII (a)
IR spectrum of (R,R’)-[RuVI(N)(5,5’-Cl2salchda)(MeOH)]PF6 (3.1)
Appendix VII (b)
IR spectrum of (R,R’)-[RuIII(5,5’-Cl2salchda)(H2O)2]PF6 (3.2a)
Appendix VIII (a) IR spectrum of (R,R’)-[RuIII(3,3’,5,5’-Cl4salchda)(EtOH)2]PF6 (3.2b)
Appendix VIII (b) IR spectrum of (R,R’)-[RuIII(3,3’-Br2-5,5’-Cl2salchda)(EtOH)2]PF6 (3.2c)
Appendix IX (a)
IR spectrum of (R,R’)-[RuIII(3,3’,5,5’-Br4salchda)(EtOH)2]PF6 (3.2d)
Appendix IX (b)
IR spectrum of (R,R’)-[RuIII(3,3’,5,5’-tBu4salchda)(MeOH)2]PF6 (3.2e)
Appendix X (a)
Electrospray mass spectrum of [RuVI(N)(salchda)MeOH)]PF6 (1.1a) and
experimental and simulated isotopic distribution pattern insets
Appendix X (b)
Electrospray
mass
spectrum
of
[RuVI(N)(5,5’-(MeO)2salchda)(MeOH)]PF6 (1.1b) and experimental and
simulated isotopic distribution pattern insets
List of Appendixes xvii
List of Appendixes (continued)
Appendix XI (a)
Electrospray mass spectrum of [RuVI(N)(5,5’-Cl2salchda)(MeOH)]PF6
(1.1c) and experimental and simulated isotopic distribution pattern insets
Appendix XI (b)
Electrospray mass spectrum of [RuVI(5,5’-Br2salchda)(MeOH)2]PF6
(1.1d)
and experimental and simulated isotopic distribution pattern
insets
Appendix XII (a)
Electrospray
mass
spectrum
of
(R,R’)-[RuVI(N)(5,5’-Cl2salchda)(MeOH)]PF6 (3.1) and experimental and
simulated isotopic distribution pattern insets
List of Appendixesxviii
Abbreviations
N
N,N’-bis(3,3’,5,5’-tetrasubstituted-salicylidene)
N
OH HO
X2
X1
X'2
-1,2-cyclohexyldiamine
X'1
X1, X2 = H, H2salchda
X1 = H, X2 = OMe, H2(5,5’-(MeO)2salchda)
X1 = H, X2 = Cl, H2(5,5’-Cl2salchda)
X1 = H, X2 = Br, H2(5,5’-Br2salchda)
X1, X2 = Cl, H2(3,3’,5,5’-Cl4salchda)
X1, X2 = Br, H2(3,3’,5,5’-Br4salchda)
X1, X2 = tBu, H2(3,3’,5,5’-tBu4salchda)
X1 = Br, X2 = Cl, H2(3,3’-Br2-5,5’-Cl2salchda)
N
N
N,N’-bis(salicylidene)o-ethylenediamine
OH HO
H2salen
2,6-Cl2PyNO
2,6-dichloropyridine-N-oxide
PhIO
iodosylbenzene
[NnBu4][RuVI(N)Cl4]
tetrabutylammonium nitridotetrachlorideruthenate
TBHP / tBuOOH
tert-butyl hydroperoxide
TPP
meso-tetraphenylporphyrin dianion
List of Appendixes xix
Abbreviations (continued)
TMP
tetramesitylporphyrin dianion
TTP
meso-tetra-p-tolyporphyrin dianion
bbpc
1,2-bis(tert-butylpyridine-2-carboxamido)-4,5-dichlorobenzene dianion
bpb
1,2-bis(2-pyridylcarboxamido) benzene dianion
PPh3
triphenylphosphine
MeOH
methanol
EtOH
ethanol
CH3CN
acetonitrile
CH2Cl2
dichloromethane
NaOCl
sodium perchlorite
Py
pyridine
TlCl
thallium chloride
TlPF6
thallium hexafluorophosphate
NH4PF6
ammonium hexafluorophosphate
H2O2
hydrogen peroxide
chba-Et
1,2-bis((2-hydroxy-3,5-dichlorophenyl)-1carboxamido)
ethane dianion