University of Groningen
A journey into the coordination chemistry, reactivity and catalysis of iron and palladium
formazanate complexes
Milocco, Francesca
DOI:
10.33612/diss.160960083
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Milocco, F. (2021). A journey into the coordination chemistry, reactivity and catalysis of iron and palladium
formazanate complexes. University of Groningen. https://doi.org/10.33612/diss.160960083
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A journey into the coordination
chemistry, reactivity and
catalysis of iron and palladium
formazanate complexes
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The work described in this thesis was carried out at the Stratingh Institute of Chemistry, University of Groningen, The Netherlands.
This work was financially supported by the Netherlands Organisation for Scientific Research (NWO).
Cover designed by Francesca Milocco
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A journey into the coordination
chemistry, reactivity and
catalysis of iron and palladium
formazanate complexes
PhD thesis
to obtain the degree of PhD at the University of Groningen
on the authority of the Rector Magnificus Prof. C. Wijmenga
and in accordance with the decision by the College of Deans. This thesis will be defended in public on
Friday 4 June 2021 at 16.15 hours
by
Francesca Milocco
born on 17 April 1991 in Udine, Italy
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Supervisors
Prof. E. Otten Prof. W.R. BrowneAssessment Committee
Prof. M. Tromp Prof. M. Albrecht554702-L-bw-Milocco 554702-L-bw-Milocco 554702-L-bw-Milocco 554702-L-bw-Milocco Processed on: 2-2-2021 Processed on: 2-2-2021 Processed on: 2-2-2021
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Table of contents
Chapter 1
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1IIntroduction
1.1 Catalytic transformations ... 2 1.1.1 CO2 conversion ... 21.2 Development of non-noble metal catalysts for 2-electron redox-transformations ... 3
1.2.1 Iron... 4
1.3 Metal-ligand bonding: the electrons and orbitals dance ... 5
1.4 Redox active ligands ... 6
1.4.1 Redox active ligands acting as electron reservoir for catalytic reactions ... 8
1.4.2 Redox active ligands: a useful tool for CO2 conversion ... 10
1.5 Formazanate ligands ... 11
1.5.1 Redox activity of formazanate ligands ... 13
1.5.2 Iron formazanate complexes ... 14
1.6 Thesis outline ... 16 1.7 References ... 16
Chapter 2
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19Electronic control of spin-crossover properties in four-coordinate
bis(formazanate) iron(II) complexes
2.1 Introduction ... 202.2 Synthesis of bis(formazanate) iron(II) complexes ... 21
2.3 X-ray crystallography ... 22
2.4 Mössbauer spectroscopy and SQUID magnetometry studies in the solid state ... 24
2.5 Variable-temperature NMR and UV-Vis spectroscopy in solution ... 26
2.6 Computational studies ... 32
2.7 Conclusion ... 35
2.8 Experimental Section ... 36
2.8.1 General Considerations ... 36
2.8.2 Synthesis of the ligands... 36
2.8.3 Synthesis of the complexes ... 37
2.8.4 X-ray crystallography ... 40
2.8.5 X-ray powder diffraction ... 42
2.8.6 Mössbauer spectroscopy ... 42
2.8.7 SQUID magnetometry ... 44
2.8.8 DSC ... 45
2.8.9 VT-NMR spectral data ... 45
2.8.10 Analysis of temperature dependence of γHS ... 49
2.8.11 Computational details ... 50
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Chapter 3
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55W
Widening the window of spin-crossover temperatures in bis(formazanate)
iron(II) complexes via steric and non-covalent interactions
3.1 Introduction ... 56
3.2 Bis(formazanate) iron(II) complexes ... 57
3.3 Solid state characterization ... 58
3.3.1 X-ray crystallography of 4-coordinate compounds ... 58
3.3.2 Mössbauer spectroscopy and SQUID magnetometry studies ... 60
3.3.3 X-ray crystallography of the 6-coordinate compound 12 ... 61
3.4 Solution characterization ... 62
3.4.1 Variable-temperature NMR spectroscopy ... 62
3.4.2 Computational studies ... 64
3.4.3 Variable-temperature UV-Vis spectroscopy ... 65
3.5 Conclusion ... 68
3.6 Experimental Section ... 69
3.6.1 General Considerations... 69
3.6.2 Synthesis of the ligands ... 69
3.6.3 Synthesis of the complexes ... 69
3.6.4 X-ray crystallography ... 71
3.6.5 Mössbauer spectroscopy ... 73
3.6.6 DSC ... 73
3.6.7 VT-NMR spectral data ... 74
3.6.8 UV-Vis analysis of temperature dependence of molar extinction coefficient ... 79
3.6.9 Analysis of temperature dependence of γHS ... 80
3.6.10 DFT calculations ... 80 3.7 References ... 81
Chapter 4
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83Isocyanide derivatives of bis(formazanate) iron complexes."To be or not to be
(bonded)?"
4.1 Introduction ... 844.1.1 Carbon monoxide... 84
4.1.2 Isocyanide ... 85
4.1.3 Fe(II) and Fe(I) complexes with carbon monoxide and isocyanide ligands ... 85
4.2 Isocyanide coordination to Fe(L1)2 ... 86
4.2.1 Studies of the reactivity of 1 and 1-Red toward CO and CNAr ... 86
4.2.2 Synthesis and solid state characterization of 1-CNAr: X-Ray and IR ... 89
4.2.3 Isocyanide dissociation ... 91
4.2.4 Cyclic voltammetry studies of 1-CNAr ... 94
4.3 Characterization of a derivative with asymmetric, fluorinated formazanate ligands ... 95
4.3.1 J coupling in 19F NMR spectroscopy ... 96
4.3.2 NMR characterization of 11-CNpAn ... 98
4.3.3 Proposed structural model for 11-CNpAn ... 105
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4.4 Conclusion ... 109
4.5 Experimental Section ... 110
4.5.1 General Considerations ... 110
4.5.2 Synthesis of the complexes ... 110
4.5.3 IR spectral data ... 112 4.5.4 X-ray crystallography ... 113 4.5.5 NMR spectral data ... 114 4.5.6 Cyclic voltammetry... 118 4.6 References ... 119
Chapter 5
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121R
Redox behavior of formazanate iron complexes
5.1 Introduction ... 1235.1.1 Redox chemistry of formazans ... 123
5.1.2 Redox behavior of formazanate ligands ... 123
5.2 Cyclic voltammetry studies of FeL2 ... 125
5.3 Attempts of oxidative addition to the iron(I) complex 1-Red ... 128
5.4 Fe(III) formazanate complexes ... 129
5.4.1 Synthesis and characterization of 12-Ox... 132
5.4.2 Investigation of the coordination ability of L12 toward Fe(II) and Fe(III) ... 136
5.5 Conclusion ... 139
5.6 Experimental Section ... 140
5.6.1 General Considerations ... 140
5.6.2 Synthesis of the complexes ... 140
5.6.3 In situ NMR reactivity studies ... 140
5.6.4 Test reactions ... 141 5.6.5 X-ray crystallography ... 142 5.6.6 Cyclic voltammetry... 144 5.7 References ... 146
Chapter 6
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147Ferrate(II) complexes with redox-active formazanate ligands
6.1 Introduction ... 1486.2 Mono(formazanate) ferrate complexes ... 149
6.2.1 NMR studies on the formation of [Bu4N][FeLX2] ... 149
6.2.2 Synthesis and characterization of [Bu4N][FeLX2] ... 150
6.3 Reactivity of [Bu4N][LFeBr2] with isocyanide... 155
6.3.1 Cyclic voltammetry studies of 1Br-CNpAn ... 157
6.4 Conclusion ... 159
6.5 Experimental Section ... 160
6.5.1 General Considerations ... 160
6.5.2 Synthesis of the complexes ... 160
6.5.3 In situ NMR reactivity studies ... 161
6.5.4 X-ray crystallography ... 163
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Chapter 7
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165H
Highly selective single-component formazanate ferrate(II) catalysts for the
conversion of CO
2into cyclic carbonates
7.1 Introduction ... 166
7.2 Synthesis and characterization of [Bu4N][FeLX2] ... 167
7.2.1 Cyclic voltammetry studies of [Bu4N][FeLX2] ... 169
7.3 NMR studies on the reactivity of 1Br ... 170
7.4 Catalytic studies with [Bu4N][FeLX2] ... 173
7.4.1 Halide effect ... 173
7.4.2 Electronic effects of substituted formazanate ligands ... 174
7.4.3 Substrate scope ... 175
7.5 Conclusion ... 178
7.6 Future perspective ... 179
7.7 Experimental Section ... 182
7.7.1 General Considerations... 182
7.7.2 Synthesis of the ligands ... 182
7.7.3 Synthesis of the complexes ... 183
7.7.4 Catalytic tests ... 185
7.7.5 UV-Vis absorption spectroscopy ... 186
7.7.6 X-ray crystallography ... 187
7.7.8 NMR spectral data of product mixtures after catalysis ... 188
7.7.9 FTIR spectra of product mixtures after catalysis ... 189
7.8 References ... 190
Chapter 8
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193Palladium alkyl complexes with a formazanate ligand: synthesis, structure and
reactivity
8.1 Introduction ... 1948.2 Synthesis and characterization of palladium formazanate complexes ... 194
8.2.1 Bis(formazanate) palladium complex ... 194
8.2.2 Mono(formazanate) palladium complex ... 196
8.2.3 Attempts of chloride abstraction ... 197
8.3 Ligand exchange and insertion reactions ... 198
8.4 Conclusion ... 200
8.5 Experimental Section ... 201
8.5.1 General Considerations... 201
8.5.2 Synthesis of the complexes ... 201
8.5.3 In situ NMR reactivity ... 202
8.5.4 Attempted chloride abstraction from Pd-1c ... 205
8.5.5 DFT calculations ... 210
8.5.6 UV-Vis absorption spectroscopy ... 210
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Appendix A
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213G
General considerations on techniques and measurements
A.1 Synthetic methods ... 214
A.1.1 Ligands ... 214
A.1.2 Complexes ... 214
A.2 Physical methods ... 214
A.2.1 Elemental Analysis ... 214
A.2.2 X-Ray Crystallography ... 214
A.2.3 X-ray powder diffraction ... 214
A.2.4 DSC ... 215
A.2.5 Mössbauer Spectroscopy ... 215
A.2.6 SQUID magnetometry ... 215
A.2.7 IR spectroscopy ... 215
A.2.8 NMR Spectroscopy ... 215
A.2.9 UV-Vis spectroscopy ... 215
A.2.10 EPR spectroscopy ... 216
A.2.11 Cyclic Voltammetry ... 216
A.3 Analysis of the thermodynamic parameters for the spin crossover equilibrium in Chapter 2 and 3 ... 216
A.3.1 Analysis of temperature dependence of NMR chemical shifts ... 216
A.3.2 Analysis of temperature dependence of the magnetic susceptibility and of the molar extinction coefficient ... 217
A.3.3 Magnetic measurements in solution ... 218
A.4 References ... 219
A.5 List of compounds ... 219
A.5.1 Abbreviations ... 219 A.5.2 Ligands ... 220 A.5.3 Complexes ... 220
Summary
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
Su
u
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um
u
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u
u
u
u
u
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u
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m
mm
m
m
m
m
m
m
m
m
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m
m
m
m
m
m
m
m
m
m
m
ma
m
m
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m
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a
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r
ry
r
r
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y
y
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y
y
y
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221Samenvatting
S
S
S
S
S
S
S
S
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S
S
S
S
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Sa
a
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n
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n
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v
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g
g
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g
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g
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g
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g
g
g
226Acknowledgments
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Ac
c
c
ck
c
c
c
c
c
c
c
c
c
c
c
c
c
c
c
k
kn
k
k
k
k
k
k
k
k
k
k
k
k
k
k
k
k
k
no
n
n
n
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n
n
n
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o
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o
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o
o
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o
o
w
wl
w
w
w
w
w
w
w
w
w
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w
w
w
w
w
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le
l
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dg
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
g
gm
g
g
g
g
g
g
g
g
g
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g
g
g
g
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m
me
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m
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t
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ts
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s
s
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s
229554702-L-bw-Milocco 554702-L-bw-Milocco 554702-L-bw-Milocco 554702-L-bw-Milocco Processed on: 2-2-2021 Processed on: 2-2-2021 Processed on: 2-2-2021
Processed on: 2-2-2021 PDF page: 10PDF page: 10PDF page: 10PDF page: 10
