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Novel P, N-ligand stabilized transition metal complexes as efficient catalysts for organic syntheses [Elektronische Ressource] / vorgelegt von Benoît Blank

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162 pages
Novel P,N-Ligand Stabilized Transition Metal Complexes as Efficient Catalysts for Organic Syntheses DISSERTATION Zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) im Fach Chemie der Fakultät für Biologie, Chemie und Geowissenschaften der Universität Bayreuth vorgelegt von Dipl. Chemiker Benoît Blank geboren in Frankfurt/Main Bayreuth, 2009 This thesis fulfills the requirements for the doctoral degree of the Faculty of Biology, Chemistry and Earth Sciences at the University of Bayreuth. Thesis submitted: 03.06.2009 Date of Scientific Colloquium: 31.08.2009 Examination Committee: First referee: Prof. Dr. Rhett Kempe Second referee: Prof. Dr. Rainer Schobert Third referee: Prof. Dr. Jürgen Senker Chairman: Prof. Dr. Thomas Hellweg This work was carried out from October 2006 to May 2009 at the Chair of Inorganic Chemistry II at the University of Bayreuth, Germany under the supervision of Professor Dr. Rhett Kempe.
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Novel P,N-Ligand Stabilized
Transition Metal Complexes as Efficient Catalysts
for Organic Syntheses



DISSERTATION



Zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
im Fach Chemie der Fakultät für Biologie, Chemie und Geowissenschaften
der Universität Bayreuth






vorgelegt von
Dipl. Chemiker Benoît Blank
geboren in Frankfurt/Main




Bayreuth, 2009
This thesis fulfills the requirements for the doctoral degree of the Faculty of Biology, Chemistry
and Earth Sciences at the University of Bayreuth.










Thesis submitted: 03.06.2009
Date of Scientific Colloquium: 31.08.2009










Examination Committee:

First referee: Prof. Dr. Rhett Kempe
Second referee: Prof. Dr. Rainer Schobert
Third referee: Prof. Dr. Jürgen Senker
Chairman: Prof. Dr. Thomas Hellweg

This work was carried out from October 2006 to May 2009 at the Chair of Inorganic Chemistry II at
the University of Bayreuth, Germany under the supervision of Professor Dr. Rhett Kempe.






























To my parents, for their constant support

and

to Uli, for her endless patience, encouragement and love…

Abbreviations
Ar aryl
Å Ångström
Bn benzyl
Bu butyl
br broad
°C degree celsius
cod cis-1,5-cyclooctadiene
d doublet
diglyme diethylene glycol dimethyl ether
δ chemical shift (ppm)
equiv equivalent
g gram
GC gas chromatography
h hours
Hz Hertz
Het N-heteroaromatics
J coupling constant (Hz)
K Kelvin
m multiplet
Me methyl
min minute
mL milliliter
mmol millimol
NMR nuclear magnetic resonance
Ph phenyl
Py 2-pyridyl
q quartet
rt room temperature
s singlet
t triplet
μL microliter


Table of Contents
1. Summary ..................................................................................................................................... 1
2. Introduction ................................................................................................................................ 7
3. Overview of Thesis Results...................................................................................................... 11
3.1. Single and Double C−Cl-Activation of Methylene Chloride by P,N-ligand
Coordinated Rhodium Complexes................................................................................. 11
3.2. An Efficient Method for the Selective Iridium-Catalyzed Monoalkylation of
(Hetero)Aromatic Amines with Primary Alcohols........................................................ 12
3.3. Selective Iridium-Catalyzed Alkylation of (Hetero)Aromatic Amines and Diamines
with Alcohols under Mild Reaction Conditions ............................................................ 13
3.4. Synthesis of Selectively Mono-N-Arylated Aliphatic Diamines via Iridium-
Catalyzed Amine Alkylation ......................................................................................... 13
3.5. Catalytic Alkylation of Methyl-N-Heteroaromatics with Alcohols............................... 14
3.6. Individual Contribution to Joint Publications................................................................ 15
4. Single and Double C−Cl-Activation of Methylene Chloride by P,N-ligand
Coordinated Rhodium Complexes.......................................................................................... 17
4.1. Introduction.................................................................................................................... 18
4.2. Results and Discussion .................................................................................................. 19
4.3. Conclusions.................................................................................................................... 28
4.4. Experimental Section..................................................................................................... 28
4.5. References...................................................................................................................... 33
5. An Efficient Method for the Selective Iridium-Catalyzed Monoalkylation of
(Hetero)Aromatic Amines with Primary Alcohols................................................................ 36
5.1. Introduction.................................................................................................................... 37
5.2. Results and Discussion .................................................................................................. 37
5.3. Conclusions.................................................................................................................... 50
5.4. Experimental Section..................................................................................................... 50
5.5. References...................................................................................................................... 54
5.6. Supporting Information ................................................................................................. 56
6. Selective Iridium-Catalyzed Alkylation of (Hetero)Aromatic Amines and Diamines
with Alcohols under Mild Reaction Conditions..................................................................... 71
6.1. Introduction.................................................................................................................... 71
6.2. Results and Discussion .................................................................................................. 72
6.3. Conclusions.................................................................................................................... 87
6.4. Experimental Section..................................................................................................... 87
6.5. References...................................................................................................................... 94
I
7. Synthesis of Selectively Mono-N-Arylated Aliphatic Diamines via Iridium-Catalyzed
Amine Alkylation...................................................................................................................... 97
7.1. Introduction.................................................................................................................... 97
7.2. Results and Discussion .................................................................................................. 98
7.3. Conclusions.................................................................................................................. 105
7.4. Experimental Section................................................................................................... 106
7.5. References.................................................................................................................... 113
8. Catalytic Alkylation of Methyl-N-Heteroaromatics with Alcohols.................................... 117
8.1. Main Text..................................................................................................................... 117
8.2. Experimental Section................................................................................................... 126
8.3. References.................................................................................................................... 127
8.4. Supporting Information ............................................................................................... 128
9. List of Publications................................................................................................................. 148
10. Acknowledgments................................................................................................................... 149
11. Declaration/Erklärung........................................................................................................... 153
II 1. Summary / Zusammenfassung
1. Summary

In the context of this work a library of novel P,N-ligands was synthesized and reacted with several
transition metals with the aim to prepare active complexes for the efficient application in the field of
homogeneous catalysis. Besides the synthesis and full characterization of these P,N-ligand
stabilized transition metal complexes, further important aspects, such as the elucidation of
mechanistic pathways and the development of novel catalytic methodologies for organic syntheses
were covered.
The preparation of the P,N-ligands is carried out in a one-pot reaction, in which first the amine is
selectively deprotonated with n-BuLi and subsequently treated with the corresponding
chlorophosphine. The desired ligand is thus obtained in excellent yields and the reaction can readily
be performed on a multi-gram scale.
1) n-BuLi, -30°C --> rt
2) R PCl, -30°C --> rt2
R'R' N NN N hexane / Et O (toluene)2
H PR2
Scheme 1. Synthesis of the P-functionalized aminopyridine ligands (P,N-ligands).
P,N-ligand stabilized transition metal complexes can usually be prepared and isolated by adding
stoichiometric amounts of the corresponding ligand to a metal precursor complex. However, a
highly dynamic behavior was observed for the formation of P,N-rhodium complexes, which was
dependent on the employed ligand and the used solvent. In the case of methylene chloride, these
complexes even reacted with the solvent and for the first time the single and double activation of
the rather stable C−Cl bonds of methylene chloride were observed simultaneously, affording both a
III IIIdimeric Rh complex with terminal chloromethyl groups and a dinuclear Rh complex with a
bridging µ-CH group. The obtained activation products were characterized with single crystal X-2
ray analysis, and further synthetic as well as NMR kinetic experiments were carried out to identify
Ithe active species for this reaction. A most-likely fivefold-coordinated Rh complex was determined
to be responsible for the activation of the solvent and a possible reaction mechanism that includes
the formation of both activation products was postulated.
1 1. Summary / Zusammenfassung
R2 Cl
P Cl RR' 2Cl NR' Cl ClCH Cl N ClN2 2N N PR' N+ ClRhCl Rh RhRhN N R'R P ClRh N R'2 R P2P NClH H ClR2

Scheme 2. Single and double C−Cl bond activation with P,N-rhodium complexes.
The isolation of a single crystal of this fivefold-coordinated rhodium species, suitable for X-ray
analysis, could not be achieved due to its high reactivity and instability, whereas analogous
complexes with iridium were readily prepared in quantitative yields and fully characterized. These
P,N-ligand stabilized iridium complexes were hence evaluated as potential catalysts for the N-
alkylation of amines with alcohols.
H 2
N RNH [P,N-IrCl(cod)]2
21 1R OH+R R
YtY KO Bu, diglyme, 110°C XX
2X= C, Y= C, N R = Ar, Alkyl
X= N, Y= C
Scheme 3. Iridium-catalyzed N-alkylation of amines with alcohols.
For this purpose, the reaction conditions were first optimized by systematic variation of important
parameters such as solvents, bases or catalyst loadings. Later on the possible substrate scope of this
method was demonstrated. The obtained results showed that our P,N-iridium catalyst has an
excellent activity in this reaction and also a very narrow selectivity profile, because in all reactions
only the selective monoalkylation of the corresponding amine was observed without any side-
product formation. In addition, only aromatic amines can be alkylated with this catalyst, whereas no
conversion is observed with aliphatic amines.
Further optimization of the reaction conditions for the N-alkylation of amines with alcohols led to a
significant improvement, so that such a reaction could for the first time be performed at a
temperature of only 70°C, along with a catalyst loading as low as 0.1 mol% Ir. Moreover, the
excellent selectivity of the catalyst for monoalkylation was successfully exploited for the symmetric
and non-symmetric N,N’-dialkylation of diamines under mild reaction conditions.
2