9 research outputs found
Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal Structures, and Reactivity toward Alkynes and Enones
Treatment
of (dpp-Bian)Ga–Ga(dpp-Bian) (<b>1</b>)
(dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with
iodine gives (dpp-Bian)Ga(I)–Ga(I)(dpp-Bian) (<b>2</b>), which reacts in situ with K(C<sub>5</sub>H<sub>4</sub>CH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KCp<sup>Do</sup>) or K(OCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KOR<sup>Do</sup>) to produce the
monomeric species (dpp-Bian)GaCp<sup>Do</sup> (<b>3</b>) and
(dpp-Bian)GaOR<sup>Do</sup> (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative
(dpp-Bian)Ga(CCPh)<sub>2</sub> (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>6</b>) reacts with PhCCH
and HCCH to give the cycloaddition products [dpp-Bian(PhCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>7</b>) and [dpp-Bian(HCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>8</b>). The related compounds
[dpp-Bian(MeCCC(O)OMe)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>9</b>) and [dpp-Bian(CH<sub>2</sub>CHC(Me)O)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>10</b>) have been obtained in
the reactions of complex <b>6</b> with methyl 2-butynoate and
methyl vinyl ketone, respectively. New complexes have been characterized
by <sup>1</sup>H NMR (<b>3</b>, <b>4</b>, and <b>7</b>–<b>10</b>) and ESR (<b>5</b>) spectroscopy; their
molecular structures have been established by single-crystal X-ray
analysis. The catalytic activity of complex <b>6</b> in the
hydroamination and hydroarylation of alkynes has been examined
Ligand “Brackets” for Ga–Ga Bond
The reactivity of digallane (dpp-Bian)Ga–Ga(dpp-Bian)
(<b>1</b>) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)
toward acenaphthenequinone (AcQ), sulfur dioxide, and azobenzene was
investigated. The reaction of <b>1</b> with AcQ in 1:1 molar
ratio proceeds via two-electron reduction of AcQ to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)Ga(dpp-Bian) (<b>2</b>), in which diolate [AcQ]<sup>2–</sup> acts as “bracket” for the Ga–Ga
bond. The interaction of <b>1</b> with AcQ in 1:2 molar ratio
proceeds with an oxidation of the both dpp-Bian ligands as well as
of the Ga–Ga bond to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)<sub>2</sub>Ga(dpp-Bian) (<b>3</b>). At 330 K in
toluene complex <b>2</b> decomposes to give compounds <b>3</b> and <b>1</b>. The reaction of complex <b>2</b> with atmospheric oxygen results in oxidation of a Ga–Ga bond
and affords (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)(μ<sub>2</sub>-O)Ga(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO<sub>2</sub> produces, depending on the ratio (1:2
or 1:4), dithionites (dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)Ga(dpp-Bian) (<b>5</b>) and
(dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)<sub>2</sub>Ga(dpp-Bian) (<b>6</b>). In compound <b>5</b> the Ga–Ga bond is preserved and supported by dithionite
dianionic bracket. In compound <b>6</b> the gallium centers
are bridged by two dithionite ligands. Both <b>5</b> and <b>6</b> consist of dpp-Bian radical anionic ligands. Four-electron
reduction of azobenzene with 1 mol equiv of digallane <b>1</b> leads to complex (dpp-Bian)Ga(μ<sub>2</sub>-NPh)<sub>2</sub>Ga(dpp-Bian) (<b>7</b>). Paramagnetic compounds <b>2</b>–<b>7</b> were characterized by electron spin
resonance spectroscopy, and their molecular structures were established
by single-crystal X-ray analysis. Magnetic behavior of compounds <b>2</b>, <b>5</b>, and <b>6</b> was investigated by
superconducting quantum interference device technique in the range
of 2–295 K
Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal Structures, and Reactivity toward Alkynes and Enones
Treatment
of (dpp-Bian)Ga–Ga(dpp-Bian) (<b>1</b>)
(dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with
iodine gives (dpp-Bian)Ga(I)–Ga(I)(dpp-Bian) (<b>2</b>), which reacts in situ with K(C<sub>5</sub>H<sub>4</sub>CH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KCp<sup>Do</sup>) or K(OCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KOR<sup>Do</sup>) to produce the
monomeric species (dpp-Bian)GaCp<sup>Do</sup> (<b>3</b>) and
(dpp-Bian)GaOR<sup>Do</sup> (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative
(dpp-Bian)Ga(CCPh)<sub>2</sub> (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>6</b>) reacts with PhCCH
and HCCH to give the cycloaddition products [dpp-Bian(PhCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>7</b>) and [dpp-Bian(HCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>8</b>). The related compounds
[dpp-Bian(MeCCC(O)OMe)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>9</b>) and [dpp-Bian(CH<sub>2</sub>CHC(Me)O)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>10</b>) have been obtained in
the reactions of complex <b>6</b> with methyl 2-butynoate and
methyl vinyl ketone, respectively. New complexes have been characterized
by <sup>1</sup>H NMR (<b>3</b>, <b>4</b>, and <b>7</b>–<b>10</b>) and ESR (<b>5</b>) spectroscopy; their
molecular structures have been established by single-crystal X-ray
analysis. The catalytic activity of complex <b>6</b> in the
hydroamination and hydroarylation of alkynes has been examined
Digallane with Redox-Active Diimine Ligand: Dualism of Electron-Transfer Reactions
The reactivity of digallane (dpp-Bian)Ga–Ga(dpp-Bian)
(<b>1</b>), which consists of redox-active ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene
(dpp-Bian), has been studied. The reaction of <b>1</b> with
I<sub>2</sub> proceeds via one-electron oxidation of each of two dpp-Bian
ligands to a radical-anionic state and affords complex (dpp-Bian)IGa–GaI(dpp-Bian)
(<b>2</b>). Dissolution of complex <b>2</b> in pyridine
(Py) gives monomeric compound (dpp-Bian)GaI(Py) (<b>3</b>) as
a result of a solvent-induced intramolecular electron transfer from
the metal–metal bond to the dpp-Bian ligands. Treatment of
compound <b>3</b> with B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> leads to removal of pyridine and restores compound <b>2</b>. The reaction of compound <b>1</b> with 3,6-di-<i>tert</i>-butyl-<i>ortho</i>-benzoquinone (3,6-Q) proceeds with
oxidation of all the redox-active centers in <b>1</b> (the Ga–Ga
bond and two dpp-Bian dianions) and results in mononuclear catecholate
(dpp-Bian)Ga(Cat) (<b>4</b>) (Cat = [3,6-Q]<sup>2–</sup>). Treatment of <b>4</b> with AgBF<sub>4</sub> gives a mixture
of [(dpp-Bian)<sub>2</sub>Ag][BF<sub>4</sub>] (<b>5</b>) and
(dpp-Bian)GaF(Cat) (<b>6</b>), which both consist of neutral
dpp-Bian ligands. The reduction of benzylideneacetone (BA) with <b>1</b> generates the BA radical-anions, which dimerize, affording
(dpp-Bian)Ga–(BA–BA)–Ga(dpp-Bian) (<b>7</b>). In this case the Ga–Ga bond remains unchanged. Within 10
min at 95 °C in solution compound <b>7</b> undergoes transformation
to paramagnetic complex (dpp-Bian)Ga(BA–BA) (<b>8</b>) and metal-free compound C<sub>36</sub>H<sub>40</sub>N<sub>2</sub> (<b>9</b>). The latter is a product of intramolecular addition
of the C–H bond of one of the <i>i</i>Pr groups to
the CN bond in dpp-Bian. Diamagnetic compounds <b>3</b>, <b>5</b>, <b>6</b>, and <b>9</b> have been characterized
by NMR spectroscopy, and paramagnetic complexes <b>2</b>, <b>4</b>, <b>7</b>, and <b>8</b> by ESR spectroscopy.
Molecular structures of <b>2</b>–<b>7</b> and <b>9</b> have been established by single-crystal X-ray analysis
Ligand “Brackets” for Ga–Ga Bond
The reactivity of digallane (dpp-Bian)Ga–Ga(dpp-Bian)
(<b>1</b>) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)
toward acenaphthenequinone (AcQ), sulfur dioxide, and azobenzene was
investigated. The reaction of <b>1</b> with AcQ in 1:1 molar
ratio proceeds via two-electron reduction of AcQ to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)Ga(dpp-Bian) (<b>2</b>), in which diolate [AcQ]<sup>2–</sup> acts as “bracket” for the Ga–Ga
bond. The interaction of <b>1</b> with AcQ in 1:2 molar ratio
proceeds with an oxidation of the both dpp-Bian ligands as well as
of the Ga–Ga bond to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)<sub>2</sub>Ga(dpp-Bian) (<b>3</b>). At 330 K in
toluene complex <b>2</b> decomposes to give compounds <b>3</b> and <b>1</b>. The reaction of complex <b>2</b> with atmospheric oxygen results in oxidation of a Ga–Ga bond
and affords (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)(μ<sub>2</sub>-O)Ga(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO<sub>2</sub> produces, depending on the ratio (1:2
or 1:4), dithionites (dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)Ga(dpp-Bian) (<b>5</b>) and
(dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)<sub>2</sub>Ga(dpp-Bian) (<b>6</b>). In compound <b>5</b> the Ga–Ga bond is preserved and supported by dithionite
dianionic bracket. In compound <b>6</b> the gallium centers
are bridged by two dithionite ligands. Both <b>5</b> and <b>6</b> consist of dpp-Bian radical anionic ligands. Four-electron
reduction of azobenzene with 1 mol equiv of digallane <b>1</b> leads to complex (dpp-Bian)Ga(μ<sub>2</sub>-NPh)<sub>2</sub>Ga(dpp-Bian) (<b>7</b>). Paramagnetic compounds <b>2</b>–<b>7</b> were characterized by electron spin
resonance spectroscopy, and their molecular structures were established
by single-crystal X-ray analysis. Magnetic behavior of compounds <b>2</b>, <b>5</b>, and <b>6</b> was investigated by
superconducting quantum interference device technique in the range
of 2–295 K
Mononuclear dpp-Bian Gallium Complexes: Synthesis, Crystal Structures, and Reactivity toward Alkynes and Enones
Treatment
of (dpp-Bian)Ga–Ga(dpp-Bian) (<b>1</b>)
(dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with
iodine gives (dpp-Bian)Ga(I)–Ga(I)(dpp-Bian) (<b>2</b>), which reacts in situ with K(C<sub>5</sub>H<sub>4</sub>CH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KCp<sup>Do</sup>) or K(OCH<sub>2</sub>CH<sub>2</sub>NMe<sub>2</sub>) (KOR<sup>Do</sup>) to produce the
monomeric species (dpp-Bian)GaCp<sup>Do</sup> (<b>3</b>) and
(dpp-Bian)GaOR<sup>Do</sup> (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative
(dpp-Bian)Ga(CCPh)<sub>2</sub> (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>6</b>) reacts with PhCCH
and HCCH to give the cycloaddition products [dpp-Bian(PhCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>7</b>) and [dpp-Bian(HCCH)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>8</b>). The related compounds
[dpp-Bian(MeCCC(O)OMe)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>9</b>) and [dpp-Bian(CH<sub>2</sub>CHC(Me)O)]Ga(S<sub>2</sub>CNMe<sub>2</sub>) (<b>10</b>) have been obtained in
the reactions of complex <b>6</b> with methyl 2-butynoate and
methyl vinyl ketone, respectively. New complexes have been characterized
by <sup>1</sup>H NMR (<b>3</b>, <b>4</b>, and <b>7</b>–<b>10</b>) and ESR (<b>5</b>) spectroscopy; their
molecular structures have been established by single-crystal X-ray
analysis. The catalytic activity of complex <b>6</b> in the
hydroamination and hydroarylation of alkynes has been examined
Ligand “Brackets” for Ga–Ga Bond
The reactivity of digallane (dpp-Bian)Ga–Ga(dpp-Bian)
(<b>1</b>) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)
toward acenaphthenequinone (AcQ), sulfur dioxide, and azobenzene was
investigated. The reaction of <b>1</b> with AcQ in 1:1 molar
ratio proceeds via two-electron reduction of AcQ to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)Ga(dpp-Bian) (<b>2</b>), in which diolate [AcQ]<sup>2–</sup> acts as “bracket” for the Ga–Ga
bond. The interaction of <b>1</b> with AcQ in 1:2 molar ratio
proceeds with an oxidation of the both dpp-Bian ligands as well as
of the Ga–Ga bond to give (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)<sub>2</sub>Ga(dpp-Bian) (<b>3</b>). At 330 K in
toluene complex <b>2</b> decomposes to give compounds <b>3</b> and <b>1</b>. The reaction of complex <b>2</b> with atmospheric oxygen results in oxidation of a Ga–Ga bond
and affords (dpp-Bian)Ga(μ<sub>2</sub>-AcQ)(μ<sub>2</sub>-O)Ga(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO<sub>2</sub> produces, depending on the ratio (1:2
or 1:4), dithionites (dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)Ga(dpp-Bian) (<b>5</b>) and
(dpp-Bian)Ga(μ<sub>2</sub>-O<sub>2</sub>S–SO<sub>2</sub>)<sub>2</sub>Ga(dpp-Bian) (<b>6</b>). In compound <b>5</b> the Ga–Ga bond is preserved and supported by dithionite
dianionic bracket. In compound <b>6</b> the gallium centers
are bridged by two dithionite ligands. Both <b>5</b> and <b>6</b> consist of dpp-Bian radical anionic ligands. Four-electron
reduction of azobenzene with 1 mol equiv of digallane <b>1</b> leads to complex (dpp-Bian)Ga(μ<sub>2</sub>-NPh)<sub>2</sub>Ga(dpp-Bian) (<b>7</b>). Paramagnetic compounds <b>2</b>–<b>7</b> were characterized by electron spin
resonance spectroscopy, and their molecular structures were established
by single-crystal X-ray analysis. Magnetic behavior of compounds <b>2</b>, <b>5</b>, and <b>6</b> was investigated by
superconducting quantum interference device technique in the range
of 2–295 K
Ytterbium and Europium Complexes of Redox-Active Ligands: Searching for Redox Isomerism
The reaction of (dpp-Bian)Eu<sup>II</sup>(dme)<sub>2</sub> (<b>3</b>) (dpp-Bian is dianion of
1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; dme is 1,2-dimethoxyethane)
with 2,2′-bipyridine (bipy) in toluene proceeds with replacement
of the coordinated solvent molecules with neutral bipy ligands and
affords europium(II) complex (dpp-Bian)Eu<sup>II</sup>(bipy)<sub>2</sub> (<b>9</b>). In contrast the reaction of related ytterbium
complex (dpp-Bian)Yb<sup>II</sup>(dme)<sub>2</sub> (<b>4</b>) with bipy in dme proceeds with the electron transfer from the metal
to bipy and results in (dpp-Bian)Yb<sup>III</sup>(bipy)(bipy<sup>–</sup>̇) (<b>10</b>) – ytterbium(III) derivative containing
both neutral and radical-anionic bipy ligands. Noteworthy, in both
cases dianionic dpp-Bian ligands retain its reduction state. The ligand-centered
redox-process occurs when complex <b>3</b> reacts with <i>N</i>,<i>N</i>′-bis[2,4,6-trimethylphenyl]-1,4-diaza-1,3-butadiene
(mes-dad). The reaction product (dpp-Bian)Eu<sup>II</sup>(mes-dad)(dme)
(<b>11</b>) consists of two different redox-active ligands both
in the radical-anionic state. The reduction of 3,6-di-<i>tert</i>-butyl-4-(3,6-di-<i>tert</i>-butyl-2-ethoxyphenoxy)-2-ethoxycyclohexa-2,5-dienone
(the dimer of 2-ethoxy-3,6-di-<i>tert</i>-butylphenoxy radical)
with (dpp-Bian)Eu<sup>II</sup>(dme)<sub>2</sub> (<b>3</b>) caused oxidation of the dpp-Bian ligand to radical-anion to afford
(dpp-Bian)(ArO)Eu<sup>II</sup>(dme) (ArO = OC<sub>6</sub>H<sub>2</sub>-3,6-<i>t</i>Bu<sub>2</sub>-2-OEt) (<b>12</b>). The molecular structures of complexes <b>9</b>–<b>12</b> have been established by the single crystal X-ray analysis.
The magnetic behavior of newly prepared compounds has been investigated
by the SQUID technique in the range 2–310 K. The isotropic
exchange model has been adopted to describe quantitatively the magnetic
properties of the exchange-coupled europium(II) complexes (<b>11</b> and <b>12</b>). The best-fit isotropic exchange parameters
are in good agreement with their density functional theory-computed
counterparts