M. V. Moskalev

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.

Complexes of Group 13 metals with redox-active ligands as catalysts for the hydroamination of carbodiimides

Complexes of Group 13 elements with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) catalyze the addition of aromatic amines (4-chloroaniline and 1-aminonaphthalene) and diphenylmethylidenehydrazine to carbodiimides.

Hydroamination of alkynes with aromatic amines catalyzed by digallane (dpp-bian)Ga—Ga(dpp-bian)

Digallane (dpp-bian)Ga—Ga(dpp-bian) (1) (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) catalyzes the addition of 4-chloroaniline to some terminal alkynes RC≡CH (R = Bun, Ph, 4-MeC6H4). The reaction orders in each of the substrates were found for the reaction of phenylacetylene with 4-chloroaniline catalyzed by compound 1. The reaction of compound 1 with phenylacetylene in a molar ratio of 1: 10 led to 1-[N-(2,6-diisopropylphenyl)imino]-2-(1-phenylethylidene)acenaphthene (5) and the compound [C12H6(NC6H3Pr2i)(PhC=CH2)(PhC=CH)]Ga(C≡CPh)2 (6). The reaction of digallane 1 with phenylacetylene and aniline in a stoichiometric ratio of 1: 2: 2 gave bis-anilide (dpp-bian)-Ga[N(H)Ph]2 (7) in 40% yield. The compound (PhC≡C)3Ga·THF (9) was obtained by the reaction of three equivalents of sodium phenylacetylide (prepared in situ from phenylacetylene and sodium) with one equivalent of GaCl3 in tetrahydrofuran. Compounds 5—7 and 9 were characterized by IR spectroscopy, 1H NMR spectroscopy was used to characterize products 5, 6, and 9, whereas EPR spectroscopy was used for amide 7. The structures of compounds 5—7 and 9 were determined by single crystal X-ray diffraction analysis.

Formation of carbon-carbon bonds between activated alkynes and diimine ligands in the aluminum complexes

The gallium and aluminum complexes containing the redox-active ligand (dpp-bian)Ga-Ga(dpp-bian) (1), (dpp-bian)Al-Al(dpp-bian) (2), or (dpp-bian)AlI(Et2O) (3) (dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) react with alkyl butynoates Me-C≡C-CO2R (R = Me, Et) to form C-C bonds between the dpp-bian ligand and alkyne. The reaction of complex 1 with methyl 2-butynoate and 4-chloroaniline in a molar ratio of 1: 2: 2 affords 7-(2,6-diisopropylphenyl)-10-methylacenaphtho[1,2-b]pyridin-8(7H)-one (4) containing no gallium. In the reaction of complex 2 with methyl 2-butynoate, alkyne is inserted into the skeleton of the dpp-bian ligand to form 4-(dpp-AIE)-9-(2,6-diisopropylphenyl)-8-(1,3-dpp-2MBIDP)-3,7-dimethoxy-1,5-dialuma-9-aza-2,6-dioxabicyclo[3.3.1]nonadiene-3,7 (5) (dpp-AIE is 1-[2-(2,6-diisopropylphenylimino)acenaphthen-1(2H)-ylidene]ethyl; 1,3-dpp-2MBIDP is 1,3-bis(2,6-diisopropylphenylimino)-2-methyl-2,3-dihydro-1H-phenalen-2-yl). The reactions of complex 3 with methyl and ethyl 2-butynoates afford dimeric derivatives [-OC(OR)=C(2,3-dpp-1MBIDP)Al(I)-]2 (2,3-dpp-1MBIDP is 2,3-bis(2,6-diisopropylphenylimino)-1-methyl-2,3-dihydro-1H-phenalen-2-yl; R = Me (6), Et (7)). The reaction of complex 3 with methyl 2-butynoate gives the product isomeric to compound 6: [-OC(OCH3)=C(1,3-dpp-2MBIDP)Al(I)-]2 (8), which cleaves THF resulting in complex [-OC(OCH3)=C(1,3-dpp-2MBIDP)Al(OC4H8I)-]2 (9). Complex (dpp-bian)Al(acac) (10), obtained by the reduction of dpp-bian with aluminum in the presence of Al(acac)3 in diethyl ether at ambient temperature, is inert towards acetylene, phenylacetylene, and alkyl butynoates. Compounds 4–7 and 10 were characterized using IR spectroscopy, and compounds 4, 7, and 10 were additionally characterized by 1H NMR spectroscopy. The structures of compounds 4–7, 9, and 10 were determined by X-ray diffraction analysis.

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.

Gallium Hydrides with a Radical-Anionic Ligand

The reaction of Cl2GaH with a sodium salt of the dpp-Bian radical-anion (dpp-Bian•-)Na (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) affords paramagnetic gallane (dpp-Bian•-)Ga(Cl)H (1). Oxidation of (dpp-Bian2-)Ga-Ga(dpp-Bian2-) (2) with N2O results in the dimeric oxide (dpp-Bian•-)Ga(μ2-O)2Ga(dpp-Bian•-) (3). A treatment of the oxide 3 with phenylsilane affords paramagnetic gallium hydrides (dpp-Bian•-)GaH2 (4) and (dpp-Bian•-)Ga{OSi(Ph)H2}H (5) depending on the reagents stoichiometry. The reaction of digallane 2 with benzaldehyde produces pinacolate (dpp-Bian•-)Ga(O2C2H2Ph2) (6). In the presence of PhSiH3, the reaction between digallane 2 and benzaldehyde (2: PhSiH3: PhC(H)O = 1:4:4) affords compound 4. The newly prepared complexes 1, 3-6 consist of a spin-labeled diimine ligand-dpp-Bian radical-anion. The presence of the ligand-localized unpaired electron allows the use of the ESR spectroscopy for characterization of the gallium hydrides reported. The molecular structures of compounds 1, 3-6 have been determined by the single-crystal X-ray analysis.

Gallium Complexes with Acenaphthene-1-Imino-2-one: Synthesis and Reactivity

The reduction of acenaphthene-1-(2,6-diisopropylphenyl)imino-2-one (Dpp-Mian) by gallium in the presence of iodine primarily results in a bis(ligand) paramagnetic derivative [(Dpp-Mian)2GaI] and then to a dimeric diamagnetic complex [(Dpp-Mian)GaI]2, the reaction of which with PhC≡CH gives a cycloaddition product [{Dpp-Mian(HC=CPh)}GaI]2. The new compounds are characterized by IR spectroscopy and 1H NMR spectroscopy. The structures of complexes (Dpp-Mian)2GaI and [{Dpp- Mian(HC=CPh)}GaI]2 are determined by X-ray structure analysis (CIF files CCDC nos. 1571860 and 1571861, respectively). The catalytic activity tests for compounds [(Dpp-Mian)GaI]2 and [{Dpp-Mian(HC=CPh)}GaI]2 are conducted in the reactions of 4-chloroaniline with phenylacetylene and carbodiimide and in the reaction of phenylacetylene with 1-naphthol.

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%.

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-Bu2t-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)AlBut(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.