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@PHDTHESIS{Henkel:993863,
author = {Henkel, Johanna},
othercontributors = {Klankermayer, Jürgen and Herres-Pawlis, Sonja},
title = {{T}argeted adaptation of the coordination sphere in
ruthenium triphos complexes and their catalytic application
in homogeneously catalyzed hydrogenation reactions},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2024-09020},
pages = {1 Online-Ressource : Illustrationen},
year = {2024},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2024},
abstract = {With the aim of improving the catalytic activity and
stability of the versatile [Ru(tiphos)(tmm)] complex and
broadening its range of applications, the present thesis
introduces novel concepts such as the introduction of
magnesium into the ruthenium triphos coordination sphere,
catalyst recycling, and the directed adaptation of the
ligand environment. Chapter 1 provides an overview on the
organometallic catalyzed activation of molecular hydrogen
focussing on ruthenium triphos systems. In addition to their
range of applications, possibilities to tailor the triphos
ligand are presented for selected reactions.In the second
chapter, the preparation of the heterobimetallic formyl
complex [Ru(triphos)(µ-CHO)(µ-H)2Mg(dippnacnac)] is
described. Besides the structural characterization of the
novel complex, its reactivity was investigated, focusing on
the transformation with different electrophiles. The concept
of reducing a CO ligand to a more reactive formyl species is
addressed to reactivate the catalytically inactive ruthenium
dicarbonyl species [Ru(triphos)(CO)2H]+. In the first
reactivation step, one carbonyl ligand was reduced to obtain
a heterobimetallic formyl complex. In the subsequent
reactivation step, the complex [Ru(triphos)CO(H)2] was
formed by the addition of hydrogen. Although the formyl
complex already showed activity for the hydrogenation of CO2
to methanol, the activity was almost quintupled with the
isolation of the formed [Ru(triphos)CO(H)2]. The introduced
reactivation strategy allowed catalyst recycling without
loss of activity for the hydrogenation of CO2 to methanol
using [Ru(triphos)CO(H)2] as catalyst.The third part of this
work focusses on the synthesis of triphos systems with two
or even three distinct phosphine donors aiming to tailor the
molecular complexes specifically to the substrate. In
detail, synthesis methods for a series of ruthenium triphos
derivative complexes bearing one dialkylphosphine (alkyl =
iPr, Cy) moiety and two diarylphosphine moieties were
established. Their catalytic performance was studied in the
hydrogenation of CO2 and carboxylic amides. For the CO2
hydrogenation to methanol, the introduction of electron
donating alkyl groups resulted in a significant increase of
the initial activity compared to the triphos derivative
systems with three equal phosphine donor groups. However,
the novel complexes demonstrated accelerated formation of
the catalytically inactive ruthenium dicarbonyl species.
Despite this observation, the overall highest TON was
reached using the complex [Ru(triphos-Cy(mOMe)2)(tmm)]
combined with 2 eq. HNTf2 in THF. For the hydrogenation of
different secondary amides using B(C6F5)3 as Lewis acidic
additive, the highest conversions were obtained using
[Ru(triphos mOMe)(tmm)]. Albeit with lower conversions,
[Ru(triphos-Cy(mOMe)2)(tmm)] outperformed in terms of
selectivity to the desired secondary amines for the
hydrogenation of N-hexylhexanamide and N-hexylbenzamide.},
cin = {154310 / 150000},
ddc = {540},
cid = {$I:(DE-82)154310_20190725$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2024-09020},
url = {https://publications.rwth-aachen.de/record/993863},
}
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