Reactivity of Transition Metal Gallylene Complexes Toward Substrates with Multiple Carbon-Element Bonds.

Reactivity of transition metal complexes containing the redox-active gallylene (dpp-bian)Ga ligand (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) toward isocyanide, isocyanate, isothiocyanate, and ketene substrates is described. The reaction of [(dpp-bian)GaCr(CO)] () with tBuNC results in a dative complex [(dpp-bian)Ga(CNtBu)Cr(CO)] (), while compound [(dpp-bian)GaCr(CO)][Na(THF)] () reacts with tBuNC to give the coordination polymer [(dpp-bian)GaCr(CO)][Na(CNtBu)(THF)] (). Treatment of [(dpp-bian)GaCr(CO)][Na(THF)] with an excess of PhNCO results in trimerization of the latter and formation of complex [(dpp-bian)GaCr(CO)][Na(PhNCO)(EtO) (DME)] ().

Reactions of Iso(thio)cyanates with Dialanes: Cycloaddition, Reductive Coupling, or Cleavage of the C═S or C═O Bond.

The dialanes [(dpp-Bian)Al-Al(dpp-Bian)] () and [(dpp-dad)Al(THF)-(THF)Al(dpp-dad)] () (dpp-Bian = 1,2-[(2,6-PrCH)NC]CH, dpp-dad = [(2,6-PrCH)NC(CH)]) react with some isothiocyanates, isocyanates, and diphenylketene via [2 + 4] cycloaddition of the C═O or C═S bond across the C═C-N-Al fragment to afford complexes [L(X═C-Y)Al-Al(X═C-Y)L] with an intact Al-Al single bond (, L = dpp-Bian, X = PhN, Y = O; , L = dpp-Bian, X = PhC, Y = O; , L = dpp-dad, X = BnN, Y = S; , L = dpp-dad, X = BuN, Y = O; , L = dpp-dad, X = PrN, Y = S; and , L = dpp-dad, X = CyN, Y = S). A mixed C═N and C═O mode cycloadduct, [(dpp-Bian)(TosN═C-O)Al-Al(TosN-C═O)(dpp-Bian)] , was obtained in the reaction of with tosylisocyanate. Heating the solution of resulted in a thermal transformation and a change of the cycloaddition mode from C═O to C═N to give the product [(dpp-Bian)(PhN-C═O)Al(O)Al(PhN-C═O)(dpp-Bian)] .

Reversible Addition of Carbon Dioxide to Main Group Metal Complexes at Temperatures about 0 °C.

The reaction of dialane [LAl-AlL] (1; L=dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, dpp-bian) with carbon dioxide results in two different products depending on solvent. In toluene at temperatures of about 0 °C, the reaction gives cycloadduct [L(CO )Al-Al(O C)L] (2), whereas in diethyl ether, the reaction affords oxo-bridged carbamato derivative [L(CO )(Et O)Al(μ-O)AlL] (3). The DFT and QTAIM calculations provide reasonable explanations for the reversible formation of complex 2 in the course of two subsequent (2+4) cycloaddition reactions.

Low-coordinate Sm(II) and Yb(II) complexes derived from sterically-hindered 1,2-bis(imino)acenaphthene (Ar-bian).

Reduction of ArBIG-bian (1, 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with an excess of samarium in tetrahydrofuran (thf) and crystallization of the crude product from a thf/toluene mixture affords [(ArBIG-bian)Sm]·C7H8 (2a), which is free of the coordinating solvent. The use of 1,2-dimethoxyethane (dme) as the reaction medium resulted in the same product, [(ArBIG-bian)Sm]·C4H10O2 (2b), which differs from 2a only in the crystal lattice solvent. Reduction of 1 with an excess of ytterbium in dme gives compound [(ArBIG-bian)Yb(dme)]·2.

Redox-Active Ligand-Assisted Two-Electron Oxidative Addition to Gallium(II).

The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η -All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7).

Gallium Hydrides with a Radical-Anionic Ligand.

The reaction of ClGaH 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-Bian)Ga-Ga(dpp-Bian) (2) with NO results in the dimeric oxide (dpp-Bian)Ga(μ-O)Ga(dpp-Bian) (3). A treatment of the oxide 3 with phenylsilane affords paramagnetic gallium hydrides (dpp-Bian)GaH (4) and (dpp-Bian)Ga{OSi(Ph)H}H (5) depending on the reagent's stoichiometry.

Adaptive behavior of a redox-active gallium carbenoid in complexes with molybdenum.

A gallium(I) carbenoid derived from redox-active diimine 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) in complexes with molybdenum may serve either as a neutral [(dpp-bian)Ga:] or an anionic [(dpp-bian)Ga:](-) two-electron donor depending on the electronic state of the transition metal.

Acenaphthene-1,2-diimine chromium complexes.

The reaction of (dpp-BIAN)Mg(THF)3 (1) with anhydrous CrCl3 in THF at 80 degrees C affords the mixed chromium-magnesium complex (dpp-BIAN)Cr(mu-Cl)3Mg(THF)3 (2). The treatment of 2 with 1,4-dioxane causes the elimination of MgCl2 and the formation of dimeric [(dpp-BIAN)Cr(mu-Cl)(THF)]2 (3). The reaction of (dpp-BIAN)Na2 with CrCl3 gives the chlorine-free compound [Na(THF)6][(dpp-BIAN)2Cr] (4).