Biomedical subjects

B Neumüller

Publications and source records attributed to B Neumüller.

3 recordsLinked to original sources

PubMed2001

Dialkylaluminum hydrazides derived from free hydrazine N2H4. Molecular Structures of [(MeC)2AlN2H3]2 and [(MeC)2Al]4(N2H2)2.

The reaction of di(tert-butyl)aluminum hydride with hydrazine N2H4 afforded the hydrazide (Me3C)2AlN2H3, 1, by the release of elemental hydrogen. Compound 1 is a dimer in solution and in the solid state and possesses a six-membered Al2N4 heterocycle in a twist conformation with two intact N-N bonds. Further reaction of 1 with an excess of HAl(CMe3)2 yielded the tricyclic aluminum and nitrogen rich Al4N4 compound [(Me3C)2AlN2H2]2[Al(CMe3)2]2, 2, in which each N-N bond of a central six-membered Al2N4 ring similar to that of 1 is side-on-coordinated to an Al(CMe3)2 group. The structure of 2 may be interpreted as a dimer of the dialuminum hydrazide (Me3C)2Al-NH-NH-Al(CMe3)2.

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PubMed2001

Synthesis of aluminum hydrazides by hydroalumination of 2,3-diazabutadienes--formation of an Al4(N2)3 cage compound and an Al3(N2)3 macrocyclic ligand.

Treatment of 1,1,4,4-tetramethyl-2,3-diazabutadiene with the alane adduct [AlH3(NMe2Et)] yielded the hydrazine derivative (AlH2)2-(AlH)2(N2iPr2)3 (1) by the hydroalumination of both C N double bonds. Compound 1 has a complicated cage structure formed by three hydrazido groups and four aluminium atoms. As a particularly interesting structural motif it contains a N-N group side-on-coordinated to one aluminium atom through its lone pairs of electrons. Sublimation of 1 gave a heterocubane-type compound (HAlNiPr)4 (2) by the complete cleavage of all N-N bonds, one face of which is bridged by weakly coordinated diisopropyldiazene with a N-N double bond. Repeated sublimation gave the pure, unsupported heterocubane molecule 3. Heating of the rough product of the reaction of alane and diazabutadiene to 90 degrees C in a closed vessel yielded another product Al(AlH2)3(N2iPr2)3 (4), which contains a cyclic chelating ligand formed by three hydrazido groups and three aluminium atoms. This heterocycle coordinates a fourth aluminum atom in the molecular center by close contacts to all six nitrogen atoms. A strongly flattened, distorted octahedral coordination sphere results for the inner metal atom.

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PubMed2001

Lithium amidohydridoaluminates.

The amidohydridometalates [Li(THF)4][HAl(NPh2)3] (1), [Li(DME)3][HAl(N(CH2Ph)2)3] (2), and [((THF)3Li)-(H2Al(NcHex2)2)].0.5toluene (3.0.5toluene; cHex = C6H11) have been prepared by reaction of the corresponding amines with LiAlH4 in THF. For 2 recrystallization from DME is required to obtain crystals, suitable for X-ray diffraction. The new compounds have been characterized by elemental analyses, IR, NMR, and MS techniques, and X-ray structure analyses. According to this the anions of 1, 2, and 3x0.5toluene possess distorted tetrahedral coordination spheres. In 3x0.5toluene a Li...H contact of 184(4) pm was detected to complete the tetrahedral coordination of the Li+ center.

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