9 research outputs found
Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity
The
reaction of [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub>] with PhCî—¼CPh furnished a three-coordinate ironÂ(II)
dialkenyl complex, [(IPr<sub>2</sub>Me<sub>2</sub>)ÂFeÂ(σ-CPhî—»CPh<sub>2</sub>)<sub>2</sub>] (<b>1</b>, IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents
a rare example of isolable low-coordinate iron alkenyl complexes with
a high-spin ground state. Complex <b>1</b> was characterized
by <sup>1</sup>H NMR spectroscopy, solution magnetic susceptibility
measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction
study, and elemental analyses. A reactivity study revealed the reactions
of <b>1</b> with PhCH<sub>2</sub>Cl to produce cross-coupling
product Ph<sub>2</sub>Cî—»CPhCH<sub>2</sub>Ph (<b>2</b>), with [Cp<sub>2</sub>Fe]Â[BAr<sup>F</sup><sub>4</sub>] to yield
Ph<sub>2</sub>CCPh–CPhCPh<sub>2</sub> (<b>3</b>), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl
azide to produce novel iron(0) and ironÂ(II) complexes <b>4</b>–<b>6</b> bearing triphenylvinyl-derived ligands. These
transformations demonstrated the high reactivity of the low-coordinate
iron alkenyl complex
Three-Coordinate Cobalt(IV) and Cobalt(V) Imido Complexes with N‑Heterocyclic Carbene Ligation: Synthesis, Structure, and Their Distinct Reactivity in C–H Bond Amination
The reaction of the
cobalt(0) alkene complex [(IMes)ÂCoÂ(η<sup>2</sup>:η<sup>2</sup>-dvtms)] (<b>1</b>) (IMes = 1,3-bisÂ(1′,3′,5′-trimethylphenyl)Âimidazol-2-ylidene,
dvtms = divinyltetramethyldisiloxane) with 2 equiv of DippN<sub>3</sub> (Dipp = 2,6-diisopropylphenyl) afforded the cobaltÂ(IV) imido complex
[(IMes)ÂCoÂ(NDipp)<sub>2</sub>] (<b>2</b>), which could be oxidized
by [Cp<sub>2</sub>Fe]Â[BAr<sup>F</sup><sub>4</sub>] (Ar<sup>F</sup> = 3,5-diÂ(trifluoromethyl)Âphenyl) to give the cobaltÂ(V) imido species
[(IMes)ÂCoÂ(NDipp)<sub>2</sub>]Â[BAr<sup>F</sup><sub>4</sub>] (<b>3</b>). The molecular structures of all these complexes were established
by single-crystal X-ray diffraction studies. Characterization data
and theoretical calculations suggest ground spin states of <i>S</i> = <sup>1</sup>/<sub>2</sub> and <i>S</i> = 0
for the cobaltÂ(IV) and cobaltÂ(V) species, respectively. When heated,
the cobaltÂ(IV) imido species was converted to a cobaltÂ(II) diamido
complex via an intramolecular C–H bond amination reaction,
but the cobaltÂ(V) species was stable under similar conditions. The
different outcomes suggest that a high oxidation state does not guarantee
C–H bond activation reactivity of late-transition-metal imido
species
Selective Double Carbomagnesiation of Internal Alkynes Catalyzed by Iron-N-Heterocyclic Carbene Complexes: A Convenient Method to Highly Substituted 1,3-Dienyl Magnesium Reagents
Controlled
multicarbometalation of alkynes has been envisaged as
an efficient synthetic method for dienyl and polyenyl metal reagents,
but an effective catalyst enabling the transformation has remained
elusive. Herein, we report that an ironÂ(II)-N-heterocyclic carbene
(NHC) complex (IEt<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeCl<sub>2</sub> (IEt<sub>2</sub>Me<sub>2</sub> = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)
can serve as a precatalyst for the double carbometalation of internal
unsymmetrical alkynes with alkyl Grignard reagents, producing highly
substituted 1,3-dienyl magnesium reagents with high regio- and stereoselectivity.
Mechanistic studies suggest the involvement of low-coordinate organoironÂ(II)-NHC
species as the in-cycle intermediates. The strong σ-donating
nature of IEt<sub>2</sub>Me<sub>2</sub> and its appropriate steric
property are thought the key factors endowing the iron-NHC catalyst
fine performance
Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity
The
reaction of [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub>] with PhCî—¼CPh furnished a three-coordinate ironÂ(II)
dialkenyl complex, [(IPr<sub>2</sub>Me<sub>2</sub>)ÂFeÂ(σ-CPhî—»CPh<sub>2</sub>)<sub>2</sub>] (<b>1</b>, IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents
a rare example of isolable low-coordinate iron alkenyl complexes with
a high-spin ground state. Complex <b>1</b> was characterized
by <sup>1</sup>H NMR spectroscopy, solution magnetic susceptibility
measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction
study, and elemental analyses. A reactivity study revealed the reactions
of <b>1</b> with PhCH<sub>2</sub>Cl to produce cross-coupling
product Ph<sub>2</sub>Cî—»CPhCH<sub>2</sub>Ph (<b>2</b>), with [Cp<sub>2</sub>Fe]Â[BAr<sup>F</sup><sub>4</sub>] to yield
Ph<sub>2</sub>CCPh–CPhCPh<sub>2</sub> (<b>3</b>), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl
azide to produce novel iron(0) and ironÂ(II) complexes <b>4</b>–<b>6</b> bearing triphenylvinyl-derived ligands. These
transformations demonstrated the high reactivity of the low-coordinate
iron alkenyl complex
Carbon–Carbon Bond Formation Reactivity of a Four-Coordinate NHC-Supported Iron(II) Phenyl Compound
The
preparation and characterization of a NHC-coordinated (NHC
= N-heterocyclic carbene) ferrous phenyl complex [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub>] (<b>1</b>; IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
as well as its C–C bond formation reactivity have been studied.
The four-coordinate ironÂ(II) phenyl complex was prepared from the
reaction of ferrous chloride with PhMgBr and IPr<sub>2</sub>Me<sub>2</sub>. It reacts with nonactivated primary and secondary alkyl
bromides and chlorides to furnish cross-coupling products and the
ironÂ(II) monophenyl species (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePhX (X = Br (<b>2</b>), Cl). When it is treated with cyclooctatetraene
(cot) or [Cp<sub>2</sub>Fe]Â[BAr<sup>F</sup><sub>4</sub>] in the presence
of PMe<sub>3</sub>, it undergoes coordination or one-electron oxidation
induced reductive elimination of biphenyl to form the corresponding
iron(0) or ironÂ(I) species [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeÂ(η<sup>4</sup>-cot)] (<b>3</b>) or [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeÂ(PMe<sub>3</sub>)<sub>2</sub>]Â[BAr<sup>F</sup><sub>4</sub>] (<b>4</b>). All of these iron-containing
products have been fully characterized by various spectroscopic methods.
Complex <b>1</b> and (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeCl<sub>2</sub> catalyze the reaction of <i>n</i>-C<sub>8</sub>H<sub>17</sub>Br with (<i>p</i>-tolyl)ÂMgBr to afford
the cross-coupling product in moderate yields (49% and 47%), whereas
the reactions employing <b>4</b> and <b>1</b>/PMe<sub>3</sub> as catalysts give the cross-coupling product in very low
yields. The results reflect the complexity of the reaction mechanism
of iron-catalyzed coupling reactions
Carbon–Carbon Bond Formation Reactivity of a Four-Coordinate NHC-Supported Iron(II) Phenyl Compound
The
preparation and characterization of a NHC-coordinated (NHC
= N-heterocyclic carbene) ferrous phenyl complex [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub>] (<b>1</b>; IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
as well as its C–C bond formation reactivity have been studied.
The four-coordinate ironÂ(II) phenyl complex was prepared from the
reaction of ferrous chloride with PhMgBr and IPr<sub>2</sub>Me<sub>2</sub>. It reacts with nonactivated primary and secondary alkyl
bromides and chlorides to furnish cross-coupling products and the
ironÂ(II) monophenyl species (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePhX (X = Br (<b>2</b>), Cl). When it is treated with cyclooctatetraene
(cot) or [Cp<sub>2</sub>Fe]Â[BAr<sup>F</sup><sub>4</sub>] in the presence
of PMe<sub>3</sub>, it undergoes coordination or one-electron oxidation
induced reductive elimination of biphenyl to form the corresponding
iron(0) or ironÂ(I) species [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeÂ(η<sup>4</sup>-cot)] (<b>3</b>) or [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeÂ(PMe<sub>3</sub>)<sub>2</sub>]Â[BAr<sup>F</sup><sub>4</sub>] (<b>4</b>). All of these iron-containing
products have been fully characterized by various spectroscopic methods.
Complex <b>1</b> and (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeCl<sub>2</sub> catalyze the reaction of <i>n</i>-C<sub>8</sub>H<sub>17</sub>Br with (<i>p</i>-tolyl)ÂMgBr to afford
the cross-coupling product in moderate yields (49% and 47%), whereas
the reactions employing <b>4</b> and <b>1</b>/PMe<sub>3</sub> as catalysts give the cross-coupling product in very low
yields. The results reflect the complexity of the reaction mechanism
of iron-catalyzed coupling reactions
Additional file 1: of IL-10/STAT3 is reduced in childhood obesity with hypertriglyceridemia and is related to triglyceride level in diet-induced obese rats
Table S1. mRNA expression in adipose tissue and serum levels of IL-10. (DOCX 17 kb
Four-Coordinate Iron(II) Diaryl Compounds with Monodentate <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution
The
salt elimination reactions of (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeCl<sub>2</sub> (IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
with the corresponding aryl Grignard reagents afford [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeAr<sub>2</sub>] (Ar = Ph, <b>3</b>; C<sub>6</sub>H<sub>4</sub>-<i>p</i>-Me, <b>4</b>; C<sub>6</sub>H<sub>4</sub>-<i>p</i>-<sup><i>t</i></sup>Bu, <b>5</b>; C<sub>6</sub>H<sub>3</sub>-3,5-(CF<sub>3</sub>)<sub>2</sub>, <b>6</b>) in good yields. X-ray crystallographic
studies revealed the presence of both tetrahedral and trans square
planar isomers for <b>3</b> and <b>6</b> and the tetrahedral
structures for <b>4</b> and <b>5</b>. Magnetic susceptibility
and <sup>57</sup>Fe Mössbauer spectrum measurements on the
solid samples indicated the high-spin (<i>S</i> = 2) and
intermediate-spin (<i>S</i> = 1) nature of the tetrahedral
and square planar structures, respectively. Solution property studies,
including solution magnetic susceptibility measurement, variable-temperature <sup>1</sup>H and <sup>19</sup>F NMR, and absorption spectroscopy, on <b>3</b>–<b>6</b>, as well as an <sup>57</sup>Fe Mössbauer
spectrum study on a frozen tetrahydrofuran solution of tetrahedral
[(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub><sup>57</sup>FePh<sub>2</sub>] suggest the coexistence of tetrahedral and trans square
planar structures in solution phase. Density functional theory calculations
on (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub> disclosed
that the tetrahedral and trans square planar isomers are close in
energy and that the geometry isomerization can occur by spin-change-coupled
geometric transformation on four-coordinate ironÂ(II) center
Four-Coordinate Iron(II) Diaryl Compounds with Monodentate <i>N</i>‑Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution
The
salt elimination reactions of (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeCl<sub>2</sub> (IPr<sub>2</sub>Me<sub>2</sub> = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene)
with the corresponding aryl Grignard reagents afford [(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FeAr<sub>2</sub>] (Ar = Ph, <b>3</b>; C<sub>6</sub>H<sub>4</sub>-<i>p</i>-Me, <b>4</b>; C<sub>6</sub>H<sub>4</sub>-<i>p</i>-<sup><i>t</i></sup>Bu, <b>5</b>; C<sub>6</sub>H<sub>3</sub>-3,5-(CF<sub>3</sub>)<sub>2</sub>, <b>6</b>) in good yields. X-ray crystallographic
studies revealed the presence of both tetrahedral and trans square
planar isomers for <b>3</b> and <b>6</b> and the tetrahedral
structures for <b>4</b> and <b>5</b>. Magnetic susceptibility
and <sup>57</sup>Fe Mössbauer spectrum measurements on the
solid samples indicated the high-spin (<i>S</i> = 2) and
intermediate-spin (<i>S</i> = 1) nature of the tetrahedral
and square planar structures, respectively. Solution property studies,
including solution magnetic susceptibility measurement, variable-temperature <sup>1</sup>H and <sup>19</sup>F NMR, and absorption spectroscopy, on <b>3</b>–<b>6</b>, as well as an <sup>57</sup>Fe Mössbauer
spectrum study on a frozen tetrahydrofuran solution of tetrahedral
[(IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub><sup>57</sup>FePh<sub>2</sub>] suggest the coexistence of tetrahedral and trans square
planar structures in solution phase. Density functional theory calculations
on (IPr<sub>2</sub>Me<sub>2</sub>)<sub>2</sub>FePh<sub>2</sub> disclosed
that the tetrahedral and trans square planar isomers are close in
energy and that the geometry isomerization can occur by spin-change-coupled
geometric transformation on four-coordinate ironÂ(II) center