Bernhard Neumüller

Einfache Synthese von Alkylaluminium‐ und Alkylgalliumhydriden – Kristallstrukturen von [(Me3C)2GaH]3 und den neuartigen Sesquihydriden [(Me3C)2EH]2[EH2CMe3]2 (E = Al, Ga)

Die Synthese von praparativ wichtigen, sterisch hoch abgeschirmten Dialkylaluminiumhydriden R2AlH [R = CMe3, CH(SiMe3)2] gelingt durch Umsetzung der entsprechenden Trialkylaluminiumverbindungen mit dem Alanaddukt AlH3 · NMe2Et im Molverhaltnis 2 : 1. Monoalkylaluminiumdihydride sind auf diesem Wege nicht zuganglich. Als Hydrid-reichste Verbindung isolierten wir bei der Reaktion mit uberschussigem AlH3 das neuartige Sesquihydrid [(Me3C)2AlH]2[AlH2CMe3]2 (3), das im festen Zustand einen bisher nicht beobachteten Heterozyklus aus vier Aluminium- und vier Wasserstoffatomen aufweist. Auf gleichem Weg bildet sich durch Umsetzung von Tri(tert-butyl)gallan mit GaH3 · NMe2Et das Dialkylgalliumhydrid (Me3C)2GaH (4), das nach der Kristallstrukturbestimmung trimer mit Ga3H3-Heterozyklus vorliegt. Ein zu 3 analoges Galliumsesquihydrid [(Me3C)2GaH]2[GaH2CMe3]2 (5) entsteht bei Verwendung von uberschussigem GaH3. Facile Syntheses of Alkylaluminium and Alkylgallium Hydrides – Crystal Structures of [(Me3C)2GaH]3 and the Novel Sesquihydrides [(Me3C)2EH]2[EH2CMe3]2 (E = Al, Ga) The facile syntheses of some important, sterically highly shielded dialkylaluminium hydrides R2AlH [R = CMe3, CH(SiMe3)2] succeeded by the reaction of the corresponding trialkylaluminium compounds with the alane adduct AlH3 × NMe2Et in a 2 to 1 molar ratio. This route is not suitable for the synthesis of monoalkylaluminium dihydrides. An excess of AlH3 yielded the novel sesquihydride [(Me3C)2AlH]2[AlH2CMe3]2 (3) as the hydride richest compound which possesses an unprecedented heterocycle comprising four aluminium and four hydrogen atoms in the solid state. The dialkylgallium hydride (Me3C)2GaH (4) was formed on a similar route by the treatment of tri(tert-butyl)gallane with the adduct GaH3 · NMe2Et. As shown by a crystal structure determination, compound 4 is a trimer in the solid state possessing a Ga3H3 heterocycle. A gallium sesquihydride analogous to compound 3, [(Me3C)2GaH]2[GaH2CMe3]2 (5), was formed on employing an excess of GaH3.

SYNTHESIS, SPECTROSCOPIC INVESTIGATIONS AND CRYSTAL STRUCTURES OF ORGANOTIN(IV) DERIVATIVES OF 2-AMINO-1-CYCLOPENTENE-1-CARBODITHIOIC ACID

The organotin(IV) chlorides R n SnCl 4− n ( n =2, R= n Bu or Ph; and n =3, R=Ph) react with 2-amino-1-cyclopentene-1-carbodithioic acid (ACDA) to give [Ph 2 SnCl(ACDA)] ( 1 ), [Ph 2 Sn(ACDA) 2 ] ( 2 ), [Ph 3 Sn(ACDA)] ( 3 ) and [Bu 2 Sn(ACDA) 2 ] ( 4 ). The new complexes have been characterized by elemental analysis, UV–Vis, IR, 1 H NMR, 119 Sn NMR spectroscopy and mass spectrometry. On the basis of 119 Sn NMR data the effective coordination number in solution is five. The structures of 1 , 3 and 4 have been confirmed by X-ray crystallography. Crystals of 1 are monoclinic with space group P 2 1 / n . The tin environment is distorted trigonal bipyramid with Cl and sulfur atoms in apical positions. Crystals of 3 are orthorombic, P 2 1 2 1 2 1 , and the structure is distorted trigonal bipyramid with one sulfur and phenyl in the axial position. Complex 4 crystallizes in the triclinic space group, P 1, and the Sn atom shows extremely irregular octahedral coordination with four S atoms laying in the equatorial plane. In all complexes ACDA coordinates as an anisobidentate ligand and its orientation lends to form a NH⋯S intramolecular hydrogen bond. The packing is also stabilized by intermolecular hydrogen bonding.

Triphenylphosphane complexes of copper(I): Structural and 31P NMR investigations

Abstract The phosphane complexes [(Ph 3 P) 2 CuCl 2 Li(THF) 2 ] · 1.5THF, [(Ph 3 P) 2 Cu-Cl]·0.5THF, [(Ph 3 P) 3 CuCl]·MeCN, [(Ph 3 P) 3 CuCl]·THF and [(Ph 3 P) 2 CuCl 2 Cu(PPh 3 )] (THF = tetrahydrofuran) have been prepared and characterized on the basis of analytical, IR, mass and NMR spectral techniques. The crystal structures of the complexes underline the ability of the copper(l) centre to exist in a distorted trigonal planar as well as in a distorted tetrahedral environment.

Two new neutral copper(II) complexes with dipicolinic acid and 3-amino-1H-1,2,4-triazole formed under different reaction conditions: Synthesis, characterization, molecular structures and DNA-binding studies

Two Cu(II) complexes, [Cu₂(μ-atr)(pydc)₂(H₂O)₄]·5H₂O (1) and [Cu(atr)(pydc) (H₂O)]·H₂O (2), with pyridine-2,6-dicarboxylic acid (H₂pydc) and 3-amino-1H-1,2,4-triazole (atr), have been synthesized and characterized. The interaction ability of the both complexes with native calf thymus DNA (CT-DNA) has been monitored as a function of the metal complex-DNA molar ratio. UV-vis spectrophotometry, circular dichroism (CD), thermal denaturation studies, cyclic voltammetry (CV) and viscosity measurements. The intrinsic binding constants K(b) of complexes 1 and 2, with CT-DNA obtained from UV-vis absorption studies were 4.7 (±0. 1) × 10(4) and 9.5 (±0. 1) × 10(4) M(-1), respectively. Further investigation of interaction mode was performed using viscosity, cyclic voltammetry and T(m) of CT-DNA studies as well as CD study, indicating complexes bind to DNA via an intercalation mode.

Enantioselective Norrish–Yang Cyclization Reactions of N‐(ω‐Oxo‐ ω‐phenylalkyl)‐Substituted Imidazolidinones in Solution and in the Solid State

The four N-(ω-oxo-ω-phenylalkyl)-substituted imidazolidinones 5–8 were prepared from N-acetylimidazolidinone (4). Upon irradiation, these substrates underwent Norrish–Yang cyclization to the racemic products rac-9–rac-12 (51–75 %). The reactions of the N-2-oxoethylimidazolidinones 5 and 6 were conducted in tBuOH, and yielded 1:1 mixtures of exo/endo diastereoisomers rac-9 a/rac-9 b and rac-10 a/rac-10 b, accompanied by Norrish type II cleavage products. The reactions of the N-3-oxopropylimidazolidinones 7 and 8 were performed in toluene. The exo diastereoisomers rac-11 a and rac-12 a were the major diastereoisomers (d.r. ≅4:1). In the presence of the chiral compounds 1–3, the photocyclization of substrate 8 proceeded with significant enantiomeric excess (5–60 % ee). The more sophisticated complexing agents 3 and ent-3 provided better enantiofacial differentiation (up to 60 % ee) than the lactams 1 and 2 (up to 26 % ee). Low temperatures and an excess of the complexing agent helped to increase the enantioselectivity. The absolute configuration of the major exo product 12 a obtained from compound 8 in the presence of complexing agent 3 was unambiguously established by single-crystal X-ray crystallography of its chiral N-methoxyphenylacetyl derivative 15 a. In a similar fashion, the absolute configurations of the endo products 12 b and ent-12 b were established. The N-2-oxoethylimidazolidinone 5, which crystallized in a chiral space group, was irradiated in the solid state. At low levels of conversion, the product 9 a/ent-9 a was formed with high enantiomeric excess (78 % ee). The enantioselectivity deteriorated at higher levels of conversion. Die vier N-(ω-oxo-ω-phenylalkyl)substituierten Imidazolidinone 5–8 wurden ausgehend von N-Acetylimidazolidinon (4) hergestellt und reagierten bei Bestrahlung unter Norrish–Yang-Cyclisierung zu den racemischen Produkten rac-9–rac-12 (51–75 %). Die Reaktion der N-2-Oxoethylimidazolidinone 5 und 6 wurde in tBuOH durchgefuhrt und ergab ein 1:1-Gemisch der exo/endo-Diastereoisomere rac-9 a/rac-9 b und rac-10 a/rac-10 b sowie Produkte der Norrish Typ II-Spaltung. Die Reaktion der N-3-Oxopropylimidazolidinone 7 und 8 konnte in Toluol als Losungsmittel durchgefuhrt werden. Die exo Diastereoisomere rac-11 a und rac-12 a waren die Hauptdiastereoisomere (d.r.≅4:1). In Gegenwart der chiralen Verbindungen 1–3 verlief die Photocyclisierung des Substrats 8 mit deutlichem Enantiomerenuberschus (5–60 % ee). Die neu entwickelten Komplexierungsreagentien 3 und ent-3 lieferten eine bessere Differenzierung der enantiotopen Seiten (bis zu 60 % ee) als die Lactame 1 und 2 (bis zu 26 % ee). Eine niedrige Reaktionstemperatur sowie ein Uberschus der Wirtverbindung begunstigen eine hohe Enantioselektiviat. Die Absolutkonfiguration des Hauptprodukts 12 a, das durch Umsetzung von Verbindung 8 in Gegenwart des Wirtes 3 erhalten wurde, wurde durch Kristallstrukturanalyse seines chiralen N-Methoxyphenylacetylderivats 15 a einwandfrei belegt. In ahnlicher Weise wurde die Absolutkonfiguration der endo Produkte 12 b und ent-12 b bestatigt. Das N-2-Oxoethylimidazolidinon 5, das in einer chiralen Raumgruppe kristallisiert, wurde als Feststoff bestrahlt. Bei niedrigem Umsatz wurde das Produkt 9 a/ent-9 a mit hohem Enantiomerenuberschus (78% ee) gebildet. Die Enantioselektivitat verschlechterte sich bei steigendem Umsatz.

Syntheses and Characterization of New Copper Complexes with the Heterocyclic Thione, AMTTO. X-Ray Structures of [Cu(AMTTO)Cl2], [Cu(AMTTO)2]Cl, and [Cu(AMTTO)(PPh3)2Cl] (AMTTO = 4-Amino-6-methyl-1, 2, 4-triazine-3-thione-5-one)

The complexes [Cu(AMTTO)Cl2] (2), [Cu(AMTTO)2]Cl (3), and [Cu(AMTTO)(PPh3)2Cl] (4) have been prepared and characterized by IR spectroscopy and elemental analyses. Also single-crystal X-ray diffraction studies on compound 2, 3 and 4 revealed that AMTTO acts in 2 as a bidentate ligand via nitrogen and sulfur atoms, in 3 and 4 as a monodentate via sulfur atoms. Complex 3 was already mentioned in literature, but the structure was not described in detail. The molecules in 2 form infinite chains through additional weak Cu—S interactions along [010] indicating the Jahn-Teller distortion of the d9 ion Cu2+. The infinite chains are connected by hydrogen bonding along [100]. Crystal data for 2 at —80°C: monoclinic, space group P21/m, a = 666.7(1), b = 609.4(1), c = 1132.6(2) pm, b = 95.46(2)°, Z = 2, R1 = 0.0365; for 3 at —80°C: orthorhombic, space group Pbcn, a = 1291.2(2), b = 1146.5(1), c = 1000.5(1) pm, Z = 4, R1 = 0.0315; for 4 at —80°C: monoclinic, space group, P21/n, a = 879.4(1), b = 1849.3(2), c = 2293.8(3) pm, β = 92.38(1)°, Z = 4, R1 = 0.0688.

Die Kristallstrukturen der silylierten Phosphanimine Me3SiNP(c‐C6H11)3 und (Me3SiNPPh2)2CH2

Die Kristallstrukturen von Me3SiNP(c-C6H11)3 (1) und (Me3SiNPPh2)2CH2 (2) werden durch Rontgenbeugung an Einkristallen ermittelt. In beiden Verbindungen entsprechen die PN-Abstande Doppelbindungen, die SiN-Abstande Einfachbindungen. Der SiNP-Bindungswinkel in 1 ist mit 149,8° auffallig gros, wahrend er in 2, das C2-Symmetrie aufweist, nur 138,5° betragt. 1: Raumgruppe P21/n, Z = 4, Gitterkonstanten bei –70 °C: a = 1143,0(1); b = 1743,0(2); c = 1152,5(1) pm; β = 90,42(1)°; R = 0,0677. 2: Raumgruppe I41/a, Z = 8, Gitterkonstanten bei –60 °C: a = b = 1959,7(1); c = 1695,8(1) pm; R = 0,0433. Crystal Structures of the Silylated Phosphaneimines Me3SiNP(c-C6H11)3 and (Me3SiNPPh2)2CH2 The crystal structures of Me3SiNP(c-C6H11)3 (1) and (Me3SiNPPh2)2CH2 (2) are determined by X-ray diffraction at single crystals. In both compounds the PN distances correspond to double bonds, the SiN distances to single bonds. With 149.8° the SiNP bond angle in 1 is noticeably large, while it is only 138.5° in 2, which shows C2 symmetry. 1: Space group P21/n, Z = 4, lattice dimensions at –70 °C: a = 1143.0(1), b = 1743.0(2), c = 1152.5(1) pm, β = 90.42(1)°; R = 0.0677. 2: Space group I41/a, Z = 8, lattice dimensions at –60 °C: a = b = 1959.7(1), c = 1695.8(1) pm, R = 0.0433.

Organometallic sesquialkoxides of aluminium, gallium and indium

Organometallic sesquihalides of aluminium are important intermediates in technical processes. However, those compounds and their homologues with gallium or indium centers have not been structurally characterized so far. On the other hand organometallic sesquialkoxides have been isolated. The major synthetic routes and the structures of the corresponding products will be discussed. Furthermore, cage-contructiveness reactions having sesquialkoxides as educts will be shown. Discussion will focus primarily on the syntheses, the spectroscopic findings and a structural comparison. Especially the structural motifs deserve attention because of the structural connection to the well-known earth metal alkoxides.

Pyridin-Komplexe von Seltenerd-Trichloriden. Synthese und Kristallstrukturen von [YCl3(Py)4] und [LnCl3(Py)4] · 0,5 Py mit Ln = La und Er

Die Pyridin-Komplexe [YCl3(Py)4] (1), [LaCl3(Py)4] · 0,5 Py (2 · 0,5 Py) und [ErCl3(Py)4] · 0,5 Py (3 · 0,5 Py) entstehen durch Verdrangungsreaktion der Diacetonalkohol-Komplexe [LnCl3(DAA)2] oder direkt aus den Trichloriden LnCl3 mit uberschussigem Pyridin als farblose, wenig feuchtigkeitsempfindliche Kristalle. Sie werden durch ihre IR-Spektren und durch Kristallstrukturanalysen charakterisiert. 1: Raumgruppe Pbca, Z = 16, Gitterkonstanten bei –80 °C: a = 1647,4(1); b = 1743,1(1); c = 3190,5(1) pm; R1 = 0,031. 2 · 0,5 Py: Raumgruppe P21/n, Z = 4, Gitterkonstanten bei –80 °C: a = 978,9(1); b = 1704,5(1); c = 1589,5(1) pm; β = 103,61(1)°; R1 = 0,0281. 3 · 0,5 Py: Raumgruppe P21/n, Z = 4, Gitterkonstanten bei –80 °C: a = 970,1(1); b = 1706,4(1); c = 1566,1(1) pm; β = 103,46(1)°; R1 = 0,0232. Alle Komplexe haben monomere Molekulstrukturen mit dem Metallatom in verzerrt pentagonal-bipyramidaler Koordination. Eines der Chloratome und die vier Pyridin-Molekule sind aquatorial angeordnet. Pyridine Complexes of Rare Earth Element Trichlorides. Syntheses and Crystal Structures of [YCl3(py)4] and [LnCl3(py)4] · 0.5 py with Ln = La and Er The pyridine complexes [YCl3(py)4] (1), [LaCl3(py)4] · 0.5 py (2 · 0.5 py), and [ErCl3(py)4] · 0.5 py (3 · 0.5 py) have been prepared from the diacetone-alcohol complexes [LnCl3(DAA)2] or directly from the metal trichlorides with excess pyridine to give colourless, only sparingly moisture sensitive crystals. They were characterized by IR spectroscopy and by crystal structure determinations. 1: Space group Pbca, Z = 16, lattice dimensions at –80 °C: a = 1647.4(1), b = 1743.1(1), c = 3190.5(1) pm, R1 = 0.031. 2 · 0,5 Py: Space group P21/n, Z = 4, lattice dimensions at –80 °C: a = 978.9(1), b = 1704.5(1), c = 1589.5(1) pm, β = 103.61(1)°, R1 = 0.0281. 3 · 0,5 Py: Space group P21/n, Z = 4, lattice dimensions at –80 °C: a = 970.1(1), b = 1706.4(1), c = 1566.1(1) pm, β = 103.46(1)°, R1 = 0.0232. All complexes realize monomeric molecular structures with the metal atom in a distorted pentagonal-bipyramidal coordination. One of the chlorine atoms and the four pyridine molecules are in the equatorial plane.

Organometal fluorides of aluminium, gallium, indium and thallium

Abstract Diorganometal fluorides can be synthesized by reaction of the corresponding metallanes with synthons like BF3 (OEt)2 and Me3SnF. A second general synthesis strategy is the fluoridation of diorganometal halides with alkali metal fluorides or silver fluoride. Organometal difluorides of Al, Ga and In are either unknown or can be obtained in special cases only. Arylthallium difluorides are the result of the reaction of arylthallium bis(trifluoroacetates) and alkali or ammonium fluorides. Various types of salts with anions like