Coordination polymers derived from magnesium and barium complexes of redox-active ligands

The reactions of monomeric complexes [(dpp-bian)M(THF)_n](M = Mg, n = 3; M = Ba, n = 5; dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) with 4,4'-bipyridine (4,4'-bipy) in THF proceed with electron transfer from dpp- bian2– to 4,4'-bipy0 to afford 1D coordination polymers [(dpp-bian)M(4,4'-bipy)(THF)_n]_m (M = Mg, n = 1; M = Ba, n = 2) that contain simultaneously radical anion ligands dpp-bian– and 4,4'-bipy . Addition of DME to coordination polymer [(dpp-bian)Mg(4,4'-bipy)(THF)_n]_m results in fragmentation of polymeric chains to give dinuclear magnesium species [{(dpp-bian)Mg(DME)}₂(4,4'-bipy)]. Barium analogue [{(dpp-bian)Ba(DME)₂}₂(4,4'-bipy)] has been prepared by reacting of complex [(dpp-bian)Ba(DME)2.5] with 4,4'-bipy in DME.     

Reactions of ytterbium and magnesium gallylene complexes with carbon dioxide and diphenylketene

Reactivity of ytterbium and magnesium complexes of gallylenes against carbon dioxide and diphenylketene has been assessed. Ytterbium complex of redox-active gallylene [{(dpp-bian)Ga}₂Yb(DME)₂] (dpp-bian = 1,2-bis[(2,6-diiso-propylphenyl)imino]acenaphthene) on treatment with CO₂ gives complex [(dpp-bian)Ga(DME)Me], while the treatment of magnesium-stabilized gallylene[{(dpp-bian)Ga}₂Mg(DME)₂] with Ph₂CCO affords cycloadduct [(dpp-bian)(Ph₂CCO)GaMe].     

(dpp-bian)Ga-Ga(dpp-bian)] and [(dpp-bian)Zn-Ga(dpp-bian)]: synthesis, molecular structures, and DFT studies of these novel bimetallic molecular compounds

1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene) (dpp-bian) stabilizes gallium-gallium and zinc-gallium bonds (compounds 1-3). The compound [(dpp-bian)Ga-Ga(dpp-bian)] (2) was prepared by the reaction of GaCl3 with K3[dpp-bian] and the heterometallic [(dpp-bian)Zn-Ga(dpp-bian)] (3) was prepared by a simple one-pot reaction of [{(dpp-bian)ZnI}(2)] with GaCl3 and K4[dpp-bian]. In contrast to [(dpp-bian)Zn-Zn(dpp-bian)] (1) and 3, compound 2 is ESR silent, thus proving the dianionic character of both dpp-bian ligands. The solution ESR spectrum of 3 reveals the coupling of an unpaired electron with the gallium nuclei (69)Ga and (71)Ga (A((69)Ga)=0.97, A((71)Ga)=1.23 mT), thus confirming the presence of Zn-Ga bonds in solution. According to the results of the X-ray crystal structure analyses the metal-metal bond lengths in 2 (2.3598(3) A) and 3 (2.3531(8) A) are close to that found in 1 (2.3321(2) A). The electronic structures of compounds 2 and 3 were studied by DFT (B3 LYP/6-31G* level). The metal-metal pi bond in 2 is mainly formed by overlap of the p orbitals of Ga in the HOMO and HOMO-1, the latter showing a stronger interaction. The s and p orbitals of Ga overlap in the deeper located HOMO-17 producing a Ga-Ga sigma bond. In contrast to the Zn-Zn bond in 1, which has 95 % s character, the NBO (natural bond order) analysis of 2 reveals 67.8 % s, 32.0 % p, and 0.2 % d character for the Ga-Ga bond. Compound 3 has a doublet electronic ground state. The unpaired electron occupies the alpha HOMO-1 localized at the Zn-containing fragment. The Ga-Zn bond is mainly formed by overlap of the metal orbitals in the alpha HOMO-6 and beta HOMO-5. According to the results of the NBO analysis, the Zn wave functions are responsible for 28.7 % of the Zn-Ga bond, with 96.7 % s, 1.0 % p, and 2.3 % d character.     

Synthesis and reactivity of the complexes [(dpp-bian)SiCl2] and [(dpp-bian)Si{FeCp(CO)}2(μ-CO)] (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)

Russian Chemical Bulletin - The complex [(dpp-bian)SiCl2] (1) was synthesized by the reaction of the free 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) ligand with Si2Cl6. Despite...     

Hydroamination of 2-vinylpyridine,styrene, and isoprene with pyrrolidine catalyzed by alkali and alkaline-earth metal complexes

The complexes (dpp-bian)Mg(thf)₃, (dpp-bian)Ca(thf)₄ and (dpp-bian)Mg(pyr)₃ (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion; pyr is the pyrrolidine) catalyze the addition of pyrrolidine to 2-vinylpyridine at room temperature. The compound (dppbian)Mg[N(SiMe₃)₂] containing a dpp-bian radical anion catalyzes the addition of pyrrolidine to styrene at 60 °C. The dpp-bian radical anion lithium-sodium salt [(dpp-bian)Li{N-(SiMe₃)₂}][Na(C₇H₈)] is an active catalyst of the addition of pyrrolidine to styrene and isoprene at 60 °C. In all the case, the content of the catalyst was from 1 to 2 mol.%. For styrene and 2-vinylpyridine, the reactions proceeded with the formation of anti-Markovnikov addition product, while 1,4-addition product was obtained in the case of isoprene.     

Reactivity of an aluminum hydride complex with a redox-active diimine ligand

Russian Chemical Bulletin - The reaction of the hydride [(dpp-bian)Al(H)Cl] (1) containing the 1,2-bis[(2,6-diisopropylphenyl) imino]acenaphthene (dpp-bian) radical anion with MeLi affords the...     

Coordination polymers derived from gallium and zinc metal–metal bonded species

The reaction of (dpp-bian)Ga–Zn(dpp-bian) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with 1,3-di(4-pyridyl)propane results in 1D coordination polymer [(dpp-bian)Ga–Zn(dpp-bian)(μ²-1,3-Py₂(CH₂)₃)]_n with the retained Ga–Zn bond. In contrast, the coordination of 1,3-di(4-pyridyl)propane to Zn atoms in the (dpp-bian)Zn–Zn(dpp-bian) complex induces the cleavage of the Zn–Zn bond which is accompanied by reduction of dpp-bian radical anions to dianions. The reaction product represents 1D coordination polymer [{(dpp-bian)Zn}(μ²-1,3-Py₂(CH₂)₃)]_n.     

Synthesis and structure of bischelate gallium complexes (dpp-bian)Ga(acac) and (dpp-bian)Ga(2,2´-bipy) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene)

A reaction of digallane [(dpp-bian)Ga—Ga(dpp-bian)] (1) (dpp-bian is the 1,2-bis[(2,6-disopropylphenyl)imino]acenaphthene) with one equivalent of I₂ leads to oxidation of (dpp-bian)^2– in compound 1 to (dpp-bian)–and gives [(dpp-bian)GaI—GaI(dpp-bian)] (2). In the reaction of compound 2 with two equivalents of (acac)Na, not only exchange of the iodide and acetylacetonate ions takes place, but also a transfer of electrons from the metal—metal bond to dpp-bian with the formation of the complex [(dpp-bian)Ga(acac)] (3), in which the dpp-bian ligand is a dianion. A reaction of digallane 1 with 2,2´-bipyridyl at 200 °C in toluene in a sealed tube leads to the reduction of 2,2´-bipyridyl and gives the complex [(dpp-bian)Ga(bipy)] (4), which contains two different chelate redox-active ligands. The new compounds were characterized by IR (3, 4), NMR (3), and ESR spectra (4), the structures of both derivatives were established by X-ray diffraction.     

Dialane with a Redox-Active Bis-amido Ligand: Unique Reactivity towards Alkynes

The treatment of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with one equivalent of AlCl(3) and three equivalents of sodium in toluene at 110?°C produced a stable dialane, (dpp-bian)Al?Al(dpp-bian) (1). The reaction of compound?1 with pyridine gave Lewis-acid-base adduct (dpp-bian)(Py)Al?Al(Py)(dpp-bian) (2). Acetylene and phenylacetylene reacted with compound 1 to give cycloaddition products [dpp-bian(R(1) R(2) )]Al?Al[(R(2) R(1) )dpp-bian] (3: R(1) =R(2) =CH; 4: R(1) =CH, R(2) =CPh). These addition reactions occur across Al-N-C moieties and result in the formation of new C?C and C?Al bonds. At elevated temperatures, compound 4 rearranges into complex 5, which consists of a radical-anionic dpp-bian ligand and two bridging alken-1,2-diyl moieties, (dpp-bian)Al(HCCPh)(2) Al(dpp-bian). This transformation is accompanied by cleavage of the dpp-bian-ligand-alkyne C?C bond, as well as of the Al?Al bond. In contrast to its analogous gallium complex, compound 1 is reactive towards internal alkynes. In the reaction of compound 1 with PhC?CMe, besides symmetrical addition product [dpp-bian(R(1) R(2) )]Al?Al[(R(2) R(1) )dpp-bian] (R(1) =CMe, R(2) =CPh; 6), monoadduct [dpp-bian(R(1) R(2) )]Al?Al(dpp-bian) (R(1) =CMe, R(2) =CPh; 7) was also isolated. Complexes 1-7 were characterized by IR, (1) H?NMR (1-4), and electronic absorption spectroscopy (3-5); the molecular structures of compounds 1-7 were determined by single-crystal X-ray diffraction.     

Chromium and tungsten complexes with a paramagnetic gallaimidazole ligand

Russian Chemical Bulletin - The reaction of digallane [(dpp-bian)Ga—Ga(dpp-bian)] (1) (dpp-bian is 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene dianion) with chromium or tungsten...     

Addition of nitriles to alkaline earth metal complexes of 1,2-bis[(phenyl)imino]acenaphthenes

Compounds [Sr(dpp-bian)(thf)4] (2), [Ba(dpp-bian)(dme)2.5] (3) and [Mg(dtb-bian)(thf)2] (4) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; dtb-bian = 1,2-bis[(2,5-di-tert-butylphenyl)imino]acenaphthene) were prepared by reduction of dpp-bian and dtb-bian with an excess of metallic Mg, Sr, or Ba in THF or DME. Reactions of [Mg(dpp-bian)(thf)3], 3, and 4 with diphenylacetonitrile gave keteniminates [Mg(dpp-bianH)(NCCPh2)(thf)2] (5), [Mg(dtb-bianH)(NCCPh2)(thf)2] (6), and [Ba(dpp-bianH)(NCCPh2)(dme)2] (7), respectively. The reaction of 2 with CH3C[triple chemical bond]N in THF gave [{Sr(dpp-bianH)[N(H)C(CH3)C(H)CN](thf)}2] (8). The compounds 2, 3, 5-8 were characterized by elemental analysis, and IR and NMR spectroscopy. Molecular structures of 2, 3, 7, and 8 were determined by single-crystal X-ray diffraction. In contrast to reactions of alkali-metal reagents, magnesium amides, or yttriumalkyls with alpha-H acidic nitriles, which are accompanied by an amine or an alkane elimination, the reactions of [Mg(dpp-bian)(thf)3] (1), 2, 3, and 4 with such nitriles proceeded with formation of Mg, Sr, and Ba keteniminates and simultaneous protonation of one nitrogen atom of the bian ligand. The NMR spectroscopic data obtained for complex 5 indicated that in solution the amino hydrogen atom underwent the fast (on the NMR timescale) shuttle transfer between both nitrogen atoms of the dpp-bianH ligand.     

Aluminum hydrides with radical-anionic and dianionic acenaphthene-1,2-diimine ligands

The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with LiAlH₄ affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether). These products were isolated as green and colorless crystals. Green crystals of the complex [(dpp-bian)Al(H)₂Li(THF)₃] (1) were obtained from tetrahydrofuran; colorless crystals of the complex [{dpp-bian(H₂)}Al(H)₂Li(Et₂O)₂] (2), from diethyl ether. The reactions of compound 1 with 2,6-di-tert-butyl-4-methylphenol and benzophenone gave monohydrides [(dpp-bian)Al(H)(OC₆H₂-2,6-Bu₂ ^t-4-Me)][Li(THF)₄] (3) and [(dpp-bian)Al(H)(OCHPh₂)- Li(THF)₂] (4), respectively. The diamagnetic aluminum hydride [(dpp-bian)AlH(THF)] (5) was synthesized by the reaction of dichloroalane HAlCl₂ (in situ) with the disodium salt of dpp-bian in THF; the paramagnetic hydride [(dpp-bian)AlH(Cl)] (6) containing the dpp-bian radical anion was synthesized by the reaction of the monosodium salt (dpp-bian)Na with monochloroalane H₂AlCl (in situ) in diethyl ether. The reaction of compound 6 with tert-butyllithium gives the complex [(dpp-bian)AlBu^t(Et₂O)] (7). Diamagnetic derivatives 1—5 and 7 were characterized by ¹Н NMR spectroscopy; paramagnetic compound 6, by ESR spectroscopy. The molecular structures of compounds 1—7 were determined by single-crystal X-ray diffraction.     

Carbon—carbon and carbon—nitrogen bond formation reactions catalyzed by the magnesium and calcium acenaphthene-1,2-diimine complexes

A mixture of allylbromide and diphenylacetonitrile is reduced to afford 2,2-diphenylpentene-4-nitrile as a major product in the presence of catalytic amounts of the magnesium complex (dpp-bian)Mg(thf)3 (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion). The overall conversion of nitrile is 71% within 3 h at 85 °С. 4,4-Diphenylbutene-1 and diphenylmethane are by-products in this process. Complexes (dpp-bian)Mg(thf)₃ and (dpp-bian)Ca(thf)₄ (in an amount of 0.5—5 mol.%) catalyze the intramolecular hydroamination of some aminopentenes and aminohexenes with the conversion from 67 to 99%.     

An N-heterocyclic carbene adduct of diatomic tin, :Sn[double bond, length as m-dash]Sn:

Reduction of an N-heterocyclic carbene (NHC) adduct of SnCl(2), viz. [(IPr)SnCl(2)] (IPr = :C{N(Dip)C(H)}(2); Dip = 2,6-diisopropylphenyl), with a magnesium(i) dimer, has afforded the first NHC complex of a row 5 element in its diatomic form, [(IPr)Sn[double bond, length as m-dash]Sn(IPr)]; a computational analysis of the complex indicates that it comprises a singlet state, doubly bonded tin(0) fragment, :Sn[double bond, length as m-dash]Sn:, datively bonded by two NHC ligands.     

Transition metal 1,3,2-diazagallol derivatives

Reduction of digallane (dpp-bian)Ga—Ga(dpp-bian) (1) (dpp-bian is the 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene dianion) with metallic sodium in THF leads to the formation of gallylsodium (dpp-bian)Ga—Na(thf)₄ (2). Reduction of digallane 1 with dicyclopentadienyltetracarbonyldiiron, vanadocene, and nickelocene furnishes the corresponding gallyl complexes (dpp-bian)Ga—FeCp(CO)₂ (3), (dpp-bian)Ga—VCp₂ (4) and [(dpp-bian)Ga]₂NiCp (5). The reaction of 1 with Cp₂Mn gives a gallium-free complex (dpp-bian)MnCp(dme) (6). Carbonylates [{(dpp-bian)Ga—M(CO)₅}{Na(thf)₂}]₂ (M = Cr (7), W (8)) and [{(dppbian)Ga}₂FeCp(CO)][Na(dme)₃] (9) were obtained by the reaction of carbonyls Cr(CO)₆, W(CO)₆, and [CpFe(CO)₂]₂ with compound 2. Diamagnetic derivatives 3, 7, 8, and 9 were characterized by ¹H NMR spectra. The structures of products 3—9 were established by single crystal X-ray diffraction.     

Addition of phenylacetylene and camphor to the complex [(dpp-bian)Eu(dme)<Subscript>2</Subscript>] (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion)

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with an excess of europium metal in 1,2-dimethoxyethane (dme) produces a divalent europium complex with the dpp-bian dianion, [(dpp-bian)Eu(dme)₂] (1). The reactions of 1 with phenyl-acetylene and camphor proceed via protonation of the diimine ligand to form the monomeric amido-amino complexes of divalent europium — [H(dpp-bian)Eu(C≡CPh)(dme)₂] (2) and [H(dpp-bian)Eu(camphor)(dme)₂] (3), respectively. Compounds 2 and 3 were characterized by IR spectroscopy and elemental analysis. Their molecular structures were determined by X-ray diffraction. Compounds 2 and 3 were shown to be monomeric seven-coordinate europium(ii) complexes with terminal phenylethynyl and enol ligands, respectively. According to the IR spectroscopic data, the terminal ligands in complexes 2 and 3 undergo tautomerization involving backward proton transfer from the amido-amino ligand to the substrate. The magnetic moment of compound 2 (8.03 μB) remains constant in the temperature range of 4—300 К and confirms the presence of divalent europium.     

1,3,2-Diazasilols based on 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene

Reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (1, dpp-bian) in the presence of SiCl₄ with two equivalents of potassium graphite (KC₈) in tetrahydrofuran leads to the formation of compound (dpp-bian)SiCl₂ (2), which was also synthesized by the exchange reaction of SiCl₄ with the magnesium complex (dpp-bian)Mg(THF)₃. An analog of compound 2, the bromo derivative (dpp-bian)SiBr₂ (3), was obtained by the reaction of SiBr4 with one equivalent of Na2(dpp-bian) (in situ from Na and dpp-bian) in toluene. The silylene (dpp-bian)Si (4) was synthesized by the reduction of a mixture of dpp-bian and SiCl₄ (1: 1) with four equivalents of potassium graphite in tetrahydrofuran. Treatment of compound 4 with diimine 1 gives the derivative (dpp-bian)₂Si (5). Compounds 2–5 were characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy, as well as by elemental analysis, their molecular structure was established by X-ray diffraction studies.     

Capture of phosphorus(I) and arsenic(I) moieties by a 1,2-bis(arylimino)acenaphthene (aryl-BIAN) ligand. A case of intramolecular charge transfer

The reaction of PCl3 with SnCl2 in THF solution, followed by treatment with dpp-BIAN (dpp = 2,6-i-Pr2C6H3), affords the phosphenium complex [(dpp-BIAN)P][SnCl5.THF]. The 31P chemical shift (delta 232.5) and the metrical parameters from a single-crystal X-ray diffraction study indicate that the oxidation state of phosphorus in this compound is +3. A similar conclusion was reached regarding the phosphorus oxidation state in [(dpp-BIAN)P][I3], which was prepared via the reaction of dpp-BIAN with PI3 in CH2Cl2 solution. The arsenium salt [(dpp-BIAN)As][SnCl5.THF] was prepared by treatment of AsCl3 with SnCl2 in THF solution, followed by the addition of dpp-BIAN. The X-ray crystal structure of this salt was determined, and the pattern of bond distances and angles indicates that arsenic is present in the +3 oxidation state.     

Synthesis and spectroscopic and X-ray structural characterization of R2Sn(IV)-oxydiacetate and -iminodiacetate complexes

Seven novel R2Sn(IV)-oxydiacetate (oda) and -iminodiacetate (ida) compounds of the form [R2Sn(oda)(H2O)]2 (R = Me, nBu, and Ph) (1-3), [(R2SnCl)2(oda)(H2O)2]n (R = Et, iBu, and tBu) (4-6), and [Me2Sn(ida)(MeOH)]2 (7) have been synthesized and characterized by IR, 1H, 13C, and 119Sn NMR (solution), solid-state 119Sn CPMAS NMR, and (119m)Sn M?ssbauer spectroscopy. The crystal structure of [Me2Sn(oda)(H2O)]2, 1, shows it to be dinuclear (centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each oda. By contrast, the crystal structure of [(Et2SnCl)2(oda)(H2O)2]n, 4, comprises a zigzag polymeric assembly containing a pair of different alternating subunits, {Et2SnCl(H2O)} and {Et2SnCl(H2O)(oda)}, which are connected by way of bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of [Me2Sn(ida)(MeOH)]2, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-coordinate tin. The 119Sn solid-state CPMAS NMR and (119m)Sn Mossbauer suggest the presence of seven-coordinate Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R2SnCl)2(oda)(H2O)2]n compounds.     

Trapping of Ag+ into a Perfect Six-Coordinated Environment: Structural Analysis,Quantum Chemical Calculations and Electrochemistry

Self-assembly of (Bu₄N)₄[β-Mo₈O₂₆], AgNO₃, and 2-bis[(2,6-diisopropylphenyl)-imino]acenaphthene (dpp-bian) in DMF solution resulted in the (Bu₄N)₂[β-{Ag(dpp-bian)}₂Mo₈O₂₆] (1) complex. The complex was characterized by single crystal X-ray diffraction (SCXRD), X-ray powder diffraction (XRPD), diffuse reflectance (DR), infrared spectroscopy (IR), and elemental analysis. Comprehensive SCXRD studies of the crystal structure show the presence of Ag⁺ in an uncommon coordination environment without a clear preference for Ag-N over Ag-O bonding. Quantum chemical calculations were performed to qualify the nature of the Ag-N/Ag-O interactions and to assign the electronic transitions observed in the UV–Vis absorption spectra. The electrochemical behavior of the complex combines POM and redox ligand signatures. Complex 1 demonstrates catalytic activity in the electrochemical reduction of CO₂.