Rudolf J. Wehmschulte

Deoxygenative Reduction of Carbon Dioxide to Methane, Toluene, and Diphenylmethane with [Et2Al]+ as Catalyst

The strong Lewis acid [Et(2)Al](+) catalyzes the reduction of carbon dioxide with hydrosilanes under mild conditions to methane. In benzene solution, the side products toluene and diphenylmethane are also obtained through Lewis acid catalyzed benzene alkylation by reaction intermediates.

Cationic Ethylzinc Compound: A Benzene Complex with Catalytic Activity in Hydroamination and Hydrosilylation Reactions

The tight ion pair [EtZn(η(3)-C(6)H(6))][CHB(11)Cl(11)]·C(6)H(6) (1·C(6)H(6)) was obtained through β-hydrogen abstraction and concomitant ethene elimination from Et(2)Zn with the trityl salt [Ph(3)C][CHB(11)Cl(11)]. This ionlike species shows catalytic activity in hydrosilylation and intramolecular hydroamination reactions. The amine adduct {CH(2)CHCH(2)C(Ph(2))CH(2)NH(2)}(3)ZnCB(11)Cl(11) (3), which features a rare transition metal-carborane σ bond, was isolated from a hydroamination experiment.

Primary alanes and alanates: useful synthetic reagents in aluminum chemistry

Abstract Primary alanes [RAlH2]2 can be stabilized kinetically by employment of very bulky alkyl or aryl substituents. They are easily prepared by reacting the appropriate lithium trihydroalanate precursor with organic halides, anhydrous hydrogen halides or halogens. Reactions of these aluminum hydrides with a wide variety of substrates ranging from protic reagents such as water, alcohols, amines, phosphines or thiols over ketones, nitriles or isonitriles to silylated species such as siloxanes or silyl halides are presented. Primary alanes were shown to be unique starting materials for a number of interesting compounds that were otherwise not accessible, or only available in low yields. In addition, postulated intermediates of aluminum hydride reductions of organic substrates such as ketones or nitriles can be isolated when using bulky primary alanes.

Chlorination of 1-Carba-closo-dodecaborate and 1-Ammonio-closo-dodecaborate Anions

Fully chlorinated carborate and dodecaborate cages such as [CHB11Cl11]- and [Me3NB12Cl11]- are prominent examples of valuable and chemically rather inert weakly coordinating anions. While both anions can be obtained by chlorination of the precursors [CH12B11]- and [H3NB12H11]- with SO2Cl2 followed by methylation for the synthesis of [Me3NB12Cl11]-, best results were found using photochemical chlorination with SO2Cl2 for [CH12B11]- and thermal chlorination with SO2Cl2 for [H3NB12H11]-. The hexachlorinated anion [n-Pr3NB12H5Cl6]- was formed readily within 30 min by chlorination of [n-Pr3NB12H11]-, but attempts to synthesize isopropyl-substituted ammonio-dodecaborates with a higher chlorination number resulted in the formation of mixtures and partial decomposition. The silver and trityl salts of the anions [CHB11Cl11]-, [Me3NB12Cl11]-, and [n-Pr3NB12H5Cl6]- as well as the contact ion-pair [Et2Al][Me3NB12Cl11] were also prepared, and the compounds [Ag(NCMe)][Me3NB12Cl11], [Et2Al][Me3NB12Cl11], and [Et4N][i-Pr3NB12H5Cl6] were also characterized by X-ray crystallography.

Multiple Ga−Ga Bonding Character in Na2[Ga(GaTrip2)3], and a Comparison with Neutral Ga(GaTrip2)3 (Trip=2,4,6‐iPr3C6H2)

Delocalized over the Ga4 framework, the two electrons are lost in the oxidation of Na2 [Ga(GaTrip2 )3 ] to Ga(GaTrip2 )3 . This leads to a lengthening of the Ga-Ga bond by about 0.08 Å. Ar=Trip=2,4,6-iPr3 C6 H2 .

Reaction of cyclopentadienyl zirconium derivatives with sterically encumbered arylaluminum hydrides: X-ray crystal structure of (η5-C5H5)2(H)Zr(μ2-H)2Al(H)C6H2-2,4,6-But3

Abstract The novel reactions between Cp2ZrMe2 (Cp=η5-C5H5) and (Mes*AlH)2 (Mes*=C6H2-2,4,6-But3) to afford Cp2(H)Zr(μ2-H)2Al(Me)Mes* (1) and between Cp2Zr(Cl)H and [Mes*AlH3Li(THF)2]2 to give Cp2(H)Zr(μ2-H)2Al(H)Mes* (2) are described. The X-ray crystal structure and NMR spectroscopy of 1 indicate that, in the crystalline product, a methyl group has been transferred from zirconium to aluminum, and the metals have been connected by two hydrogen bridges. The compounds Cp2ZrH2 and Mes*AlMe2 were also obtained as reaction products in the synthesis of 1. The aluminum center is four-coordinate in contrast to the five- or six-coordination observed in previously published complexes. Compound 2, which is believed to have a very similar structure to that of 1, was obtained in moderate yield as a colorless crystalline material.

Synthesis of novel nanostructured γ-Al2O3 by pyrolysis of aluminiumoxyhydride–HAlO

Thermolysis of amorphous nanosized aluminiumoxyhydride, HAlO, at 450 °C led to its decomposition into amorphous Al2O3, finely divided aluminium metal, and H2 gas. Thermolysis at 800–1100 °C afforded γ-Al2O3 nanorods consisting of aggregated nanocrystallites. The size of the nanorods varied between diameters of 30–300 nm and lengths of up to several µm leading to aspect ratios of 3–30. The onset of crystallization was at approximately 800 °C. Yields of up to 40% were obtained by thermolysis at 1100 °C for 6 h. Lower temperatures resulted in lower nanorod yield. The presence of aluminium metal appears to be crucial since no nanorod formation took place in the absence of it. The products were characterized by FTIR spectroscopy, X-ray diffraction and transmission electron microscopy (TEM).

Synthesis and Reactivity of Amidoaluminum Hydride Compounds as Potential Precursors to AlN

A new series of amidoaluminum hydride complexes HnAl[N(SiHMe2)2]3−n⋅NMe3 (1, n=2; 2, n=1), Al[N(SiHMe2)2]3 (3), and [H2AlN(SiHMe2)2]2 (4) were prepared by the metallation of tetramethyldisilazane (Me2HSi)2NH with either H3Al⋅NMe3 or H3Al⋅2OEt2. The molecular structures of 1 and 2 were shown by X-ray crystal structure determination to be monomeric Lewis acid-base adducts with four coordinate aluminum centers and terminal amido groups. The molecular structure of 4 was found to be a dimer with bridging disilylamides in the solid state. Attempts to obtain crystals of [H2AlN(SiMe3)2]2, a bulkier analogue of 4, led to the isolation of the unusual alumoxane μ2-(Me3Si)2 N-(AlH2)2-μ3-O-Al(H)N(SiMe3)2⋅OEt2 (6) in moderate yields. Thermolysis of 1 and 2 resulted only in the formation of ligand exchange and decomposition products, whereas thermolysis of 4 at 80°C afforded 1 equivalent of Me2SiH2 and a new species formulated as the imide complex [HAlNSiMe2H]n (7). Thermolysis of 4 in the presence of AlH3⋅NMe3 gave Me2SiH2 and 7 at a higher reaction rate even at a lower temperature.

Interaction of the bulky alane (H2AlC6H3-2,6-Mes2)2 (Mes=–C6H3-2,4,6-Me3) with H2EPh (E=N, P or As)

The reactions of the bulky primary alane (H2AlC6H3-2,6-Mes2)2 (Mes=–C6H2-2,4,6-Me3) with H2EPh (E=N, P or As) are described. With aniline, H2NPh, the dimeric products 2,6-Mes2H3C6{Ph(H)N}Al{µ-N(H)Ph}2Al(H)C6H3-2,6-Mes2 (1) and [2,6-Mes2H3C6(H)Al{µ-N(H)Ph}]2 (2) are obtained. The structures of both 1 and 2 feature two –C6H3-2,6-Mes2 substituted aluminums bridged by two –N(H)Ph groups. In 2 each aluminum is also bound to a terminal hydrogen whereas in 1 one of these hydrogens is replaced by a terminal –N(H)Ph substituent. The structure of the –P(H)Ph derivative [2,6-Mes2H3C6(H)Al{µ-P(H)Ph}]2 (3) is very similar to that of 2 (and presumably the arsenido derivative 4) and features bridging phosphido groups and four-coordinate aluminums. The arsenido dimer 4 is cleaved by ether to give the ether adduct 2,6-Mes2H3C6(H)Al{As(H)Ph}(OEt2) for which a partial X-ray structure was determined. Thermolysis of 2, 3 and 4 led to decomposition. However, heating (H2AlC6H3-2,6-Mes2)2 with excess H2AsPh led to the unique cluster (2,6-Mes2H3C6Al)2{µ-As(H)Ph}2(µ-PhAsAsPh) which has a basket-type Al2As4 core.

Ga-Ga-Mehrfachbindungscharakter in Na2[Ga(GaTrip2)3] und ein Vergleich mit dem neutralen Ga(GaTrip2)3 (Trip=2,4,6-iPr3C6H2)

Uber das Ga4-Gerust delokalisiert sind die beiden Elektronen in Na2[Ga(GaTrip2)3], die bei der Oxidation zu Ga(GaTrip2)3 abgegeben werden. Die Ga-Ga-Bindungslange verlangert sich dabei um 0.08 A. Ar=2,4,6-iPr3C6H2 (Trip).