5 research outputs found
Synthesis, Structure, and Catalytic Activity of New Ruthenium(II) Indenylidene Complexes Bearing Unsymmetrical N<i>-</i>Heterocyclic Carbenes
No full textNew robust and air-stable ruthenium(II)
indenylidene type second-generation
precatalysts with unsymmetrical N-heterocyclic carbene (NHC) ligands
were synthesized. The reaction profiles of these complexes were studied
in commercial-grade solvents in air with model substrates leading
to the di-, tri-, and tetrasubstituted olefins. In addition, application
of selected precatalysts for olefin metathesis reactions on a broad
spectrum of substrates with different functional groups was examined.
Studies of solvent effects for the selected precatalysts as well as
thermal activation of the corresponding complexes showed significant
differences in their activities. Observed relationships in connection
with single-crystal X-ray analysis revealed the influence of the unsymmetrical
NHC ligands on the initiation rate of precatalysts. Dissociation of
the phosphine ligand, the rate-determining step for our most active
precatalysts, is accelerated by the steric repulsion of the dangling
benzyl arm and the tricyclohexylphosphine ligand. A precatalyst with
a hemilabile benzyl arm evinced decreased activity, probably due to
coordination of the heteroatom to the ruthenium core taking place
after dissociation of the phosphine ligand
Dialkylgallium Complexes with Alkoxide and Aryloxide Ligands Possessing N‑Heterocyclic Carbene Functionalities: Synthesis and Structure
No full textMethods for the synthesis
of dialkylgalium compounds with alkoxide
or aryloxide ligands possessing N-heterocyclic carbene functionalities
have been established. As a result, the synthesis of a series of dialkylgallium
complexes Me<sub>2</sub>Ga(O,C) (<b>1</b>, <b>3</b>–<b>5</b>), and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga (<b>2</b>, <b>6</b>) is described, where (O,C) represents an
alkoxide or aryloxide monoanionic chelate ligand with an N-heterocyclic
carbene functionality. All complexes have been fully characterized
using spectroscopic and X-ray techniques. The presence of a strongly
basic NHC functionality in alkoxide or aryloxide ligands resulted
in the formation of monomeric Me<sub>2</sub>Ga(O,C) species. The reaction
of those complexes with the Lewis acid Me<sub>3</sub>Ga leads to Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga adducts (<b>2</b> and <b>6</b>) with a strong Me<sub>3</sub>Ga–O dative bond. The
effect of (O,C) ligands with various steric and electronic properties
on the structure of obtained Me<sub>2</sub>Ga(O,C) and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga has been discussed on the basis of
spectroscopic data. Finally, the bond valence vector model has been
used to estimate the effect of a chelating (O,C) ligand on strains
in complexes <b>1</b>–<b>6</b> on the basis of
X-ray data
Dialkylgallium Complexes with Alkoxide and Aryloxide Ligands Possessing N‑Heterocyclic Carbene Functionalities: Synthesis and Structure
No full textMethods for the synthesis
of dialkylgalium compounds with alkoxide
or aryloxide ligands possessing N-heterocyclic carbene functionalities
have been established. As a result, the synthesis of a series of dialkylgallium
complexes Me<sub>2</sub>Ga(O,C) (<b>1</b>, <b>3</b>–<b>5</b>), and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga (<b>2</b>, <b>6</b>) is described, where (O,C) represents an
alkoxide or aryloxide monoanionic chelate ligand with an N-heterocyclic
carbene functionality. All complexes have been fully characterized
using spectroscopic and X-ray techniques. The presence of a strongly
basic NHC functionality in alkoxide or aryloxide ligands resulted
in the formation of monomeric Me<sub>2</sub>Ga(O,C) species. The reaction
of those complexes with the Lewis acid Me<sub>3</sub>Ga leads to Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga adducts (<b>2</b> and <b>6</b>) with a strong Me<sub>3</sub>Ga–O dative bond. The
effect of (O,C) ligands with various steric and electronic properties
on the structure of obtained Me<sub>2</sub>Ga(O,C) and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga has been discussed on the basis of
spectroscopic data. Finally, the bond valence vector model has been
used to estimate the effect of a chelating (O,C) ligand on strains
in complexes <b>1</b>–<b>6</b> on the basis of
X-ray data
Paper Slips
No full textNew robust and air-stable ruthenium(II) indenylidene
second-generation precatalysts with unsymmetrical N-heterocyclic carbene
(NHC) ligands were synthesized. These complexes were studied using
ring-closing metathesis (RCM) of diethyl diallylmalonate (<b>5</b>; DEDAM) as a model substrate. Two new complexes containing OMe and
NMe<sub>2</sub> groups in the NHC ligand, namely [1-(2,4,6-trimethylphenyl)-3-(2-methoxybenzyl)-2-imidazolidinylidene]dichloro(3-phenyl-1<i>H</i>-inden-1-ylidene)(tricyclohexylphosphine)ruthenium(II)
(<b>4a</b>) and [1-(2,4,6-trimethylphenyl)-3-(2-<i>N,N</i>-dimethylaminobenzyl)-2-imidazolidinylidene]dichloro(3-phenyl-1<i>H</i>-inden-1-ylidene)(tricyclohexylphosphine)ruthenium(II)
(<b>4b</b>), show increased activity in comparison to the parent
[1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-phenyl-1<i>H</i>-inden-1-ylidene)(tricyclohexylphosphine)ruthenium(II)
(Umicore <b>M2</b>). Interestingly, the complex [1-(2,4,6-trimethylphenyl)-3-(2-thiomethylbenzyl)-2-imidazolidinylidene]dichloro(3-phenyl-1<i>H</i>-inden-1-ylidene)(tricyclohexylphosphine)ruthenium(II)
(<b>4c</b>), bearing a SMe substituent, showed very low activity
in the model RCM reaction with diethyl diallylmalonate (<b>5</b>). Application of the active complexes for metathesis reactions with
a broad spectrum of olefins in commercial-grade solvents in air was
examined
Dialkylgallium Complexes with Alkoxide and Aryloxide Ligands Possessing N‑Heterocyclic Carbene Functionalities: Synthesis and Structure
No full textMethods for the synthesis
of dialkylgalium compounds with alkoxide
or aryloxide ligands possessing N-heterocyclic carbene functionalities
have been established. As a result, the synthesis of a series of dialkylgallium
complexes Me<sub>2</sub>Ga(O,C) (<b>1</b>, <b>3</b>–<b>5</b>), and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga (<b>2</b>, <b>6</b>) is described, where (O,C) represents an
alkoxide or aryloxide monoanionic chelate ligand with an N-heterocyclic
carbene functionality. All complexes have been fully characterized
using spectroscopic and X-ray techniques. The presence of a strongly
basic NHC functionality in alkoxide or aryloxide ligands resulted
in the formation of monomeric Me<sub>2</sub>Ga(O,C) species. The reaction
of those complexes with the Lewis acid Me<sub>3</sub>Ga leads to Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga adducts (<b>2</b> and <b>6</b>) with a strong Me<sub>3</sub>Ga–O dative bond. The
effect of (O,C) ligands with various steric and electronic properties
on the structure of obtained Me<sub>2</sub>Ga(O,C) and Me<sub>2</sub>Ga(O,C)·Me<sub>3</sub>Ga has been discussed on the basis of
spectroscopic data. Finally, the bond valence vector model has been
used to estimate the effect of a chelating (O,C) ligand on strains
in complexes <b>1</b>–<b>6</b> on the basis of
X-ray data
