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(C₅H₄CH₂CH₂NMe₂) (KCp^Do) or K­(OCH₂CH₂NMe₂) (KOR^Do) to produce the monomeric species (dpp-Bian)­GaCp^Do (<b>3</b>) and (dpp-Bian)­GaOR^Do (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative (dpp-Bian)­Ga­(CCPh)₂ (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)­Ga­(S₂CNMe₂) (<b>6</b>) reacts with PhCCH and HCCH to give the cycloaddition products [dpp-Bian­(PhCCH)]­Ga­(S₂CNMe₂) (<b>7</b>) and [dpp-Bian­(HCCH)]­Ga­(S₂CNMe₂) (<b>8</b>). The related compounds [dpp-Bian­(MeCCC­(O)­OMe)]­Ga­(S₂CNMe₂) (<b>9</b>) and [dpp-Bian­(CH₂CHC­(Me)­O)]­Ga­(S₂CNMe₂) (<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 ¹H 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

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(C₅H₄CH₂CH₂NMe₂) (KCp^Do) or K­(OCH₂CH₂NMe₂) (KOR^Do) to produce the monomeric species (dpp-Bian)­GaCp^Do (<b>3</b>) and (dpp-Bian)­GaOR^Do (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative (dpp-Bian)­Ga­(CCPh)₂ (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)­Ga­(S₂CNMe₂) (<b>6</b>) reacts with PhCCH and HCCH to give the cycloaddition products [dpp-Bian­(PhCCH)]­Ga­(S₂CNMe₂) (<b>7</b>) and [dpp-Bian­(HCCH)]­Ga­(S₂CNMe₂) (<b>8</b>). The related compounds [dpp-Bian­(MeCCC­(O)­OMe)]­Ga­(S₂CNMe₂) (<b>9</b>) and [dpp-Bian­(CH₂CHC­(Me)­O)]­Ga­(S₂CNMe₂) (<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 ¹H 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

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(C₅H₄CH₂CH₂NMe₂) (KCp^Do) or K­(OCH₂CH₂NMe₂) (KOR^Do) to produce the monomeric species (dpp-Bian)­GaCp^Do (<b>3</b>) and (dpp-Bian)­GaOR^Do (<b>4</b>), respectively. Complex <b>3</b> reacts with PhCCH to give the paramagnetic derivative (dpp-Bian)­Ga­(CCPh)₂ (<b>5</b>), while compound <b>4</b> is inert toward this alkyne. In contrast, monomeric (dpp-Bian)­Ga­(S₂CNMe₂) (<b>6</b>) reacts with PhCCH and HCCH to give the cycloaddition products [dpp-Bian­(PhCCH)]­Ga­(S₂CNMe₂) (<b>7</b>) and [dpp-Bian­(HCCH)]­Ga­(S₂CNMe₂) (<b>8</b>). The related compounds [dpp-Bian­(MeCCC­(O)­OMe)]­Ga­(S₂CNMe₂) (<b>9</b>) and [dpp-Bian­(CH₂CHC­(Me)­O)]­Ga­(S₂CNMe₂) (<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 ¹H 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(μ₂-AcQ)­Ga­(dpp-Bian) (<b>2</b>), in which diolate [AcQ]^2– 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(μ₂-AcQ)₂Ga­(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(μ₂-AcQ)­(μ₂-O)­Ga­(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO₂ produces, depending on the ratio (1:2 or 1:4), dithionites (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)­Ga­(dpp-Bian) (<b>5</b>) and (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)₂Ga­(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(μ₂-NPh)₂Ga­(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

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(μ₂-AcQ)­Ga­(dpp-Bian) (<b>2</b>), in which diolate [AcQ]^2– 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(μ₂-AcQ)₂Ga­(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(μ₂-AcQ)­(μ₂-O)­Ga­(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO₂ produces, depending on the ratio (1:2 or 1:4), dithionites (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)­Ga­(dpp-Bian) (<b>5</b>) and (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)₂Ga­(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(μ₂-NPh)₂Ga­(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

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 I₂ 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(C₆F₅)₃ 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]^2–). Treatment of <b>4</b> with AgBF₄ gives a mixture of [(dpp-Bian)₂Ag]­[BF₄] (<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 C₃₆H₄₀N₂ (<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 CN 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(μ₂-AcQ)­Ga­(dpp-Bian) (<b>2</b>), in which diolate [AcQ]^2– 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(μ₂-AcQ)₂Ga­(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(μ₂-AcQ)­(μ₂-O)­Ga­(dpp-Bian) (<b>4</b>). The reaction of digallane <b>1</b> with SO₂ produces, depending on the ratio (1:2 or 1:4), dithionites (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)­Ga­(dpp-Bian) (<b>5</b>) and (dpp-Bian)­Ga­(μ₂-O₂S–SO₂)₂Ga­(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(μ₂-NPh)₂Ga­(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^II(dme)₂ (<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^II(bipy)₂ (<b>9</b>). In contrast the reaction of related ytterbium complex (dpp-Bian)­Yb^II(dme)₂ (<b>4</b>) with bipy in dme proceeds with the electron transfer from the metal to bipy and results in (dpp-Bian)­Yb^III(bipy)­(bipy^–̇) (<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^II­(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^II(dme)₂ (<b>3</b>) caused oxidation of the dpp-Bian ligand to radical-anion to afford (dpp-Bian)­(ArO)­Eu^II(dme) (ArO = OC₆H₂-3,6-<i>t</i>Bu₂-2-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