Heinrich Puff

Synthesis of diastereo- and enantiomerically pure α-amino-γ-oxo acid esters by reaction of acyliminoacetates with enamines derived from 6-membered ketones

Abstract A new efficient diastereo- and enantioselective synthesis of α-amino-γ-oxo acid esters by reaction of acyliminoacetates with enamines is described. By employing the concept of double stereodifferentiation, complete asymmetric induction (de ≧99.9%) for the C-C bond formation is obtained. Desulphurization of a sulphur containing product leads to the corresponding acyclic amino acid derivatives. The virtually complete anti -diastereo- and enantioselectivities are interpreted by a Diels-Alder like transition state.

Zur hydrolyse von monoorganylzinn-trihalogeniden III. Isolierung und röntgenstrukturanalyse von verbindungen mit dem neuartigen käfig-ion [(i-PrSn)12O14(OH)6]2+☆

Abstract Single crystals of the compounds [(i-PrSn) 12 O 14 (OH) 6 ]Cl 2 · L with L = 3H 2 O (I), 2DMF (II) and 4H 2 O · 4DMPU (III) have been isolated and investigated by an X-ray diffraction study. Common to all is the cage cation [(i-PrSn) 12 O 14 (OH) 6 ] 2+ with a “football” like tin-oxygen framework from which the organic moieties produced. Square-pyramidally coordinated tin atoms and six-membered tin-oxygen rings with half-chair conformation are the most remarkable primary and secondary building units of this ion. The cations, anions and solvent molecules are connected by hydrogen bonds to chains in I, to a three-dimensional network in II and to isolated structure units in III.

Niedermolekulare diorganozinn-sauerstoff-verbindungen: di-t-butyl- und di-t-amylzinnoxid

Abstract Di-t-butyltin oxide (t-Bu2SnO)3 and di-t-amyltin oxide (t-Am2SnO)3 were synthesized by hydrolysis of the diorganotin dichlorides. Their molecular and crystal structures were investigated by X-ray diffraction techniques and vibrational spectroscopy. Both compounds form isolated molecules with planar six-membered tin-oxygen rings.

Hydroxid-halogenid-verbindungen des di-t-butyl-substituierten zinns

Abstract The di-t-butyltin hydroxide halides t-Bu 2 Sn(OH)X (X = F, Cl or Br) have been prepared starting from the dihalides t-Bu 2 SnX 2 or the oxide (t-Bu 2 SnO) 3 . X-Ray analysis of the three compounds shows dimeric molecules: two 5-coordinated tin atoms and the oxygen atoms of the hydroxyl groups are linked to a four-membered ring. As confirmed by the IR spectra, the molecules in the crystal are held together by OH⋯X hydrogen bonds. These are strong in the hydroxide fluoride but are weak in the analogous chloride and bromide.

Trimesitylzinn-hydroxid und -fluorid als modellsubstanzen zur bestimmung der “normal”-kovalenzabstände Zinn—Sauerstoff und Zinn—Fluor

Abstract Trimesityltin hydroxide and fluoride have been prepared and have been studied by single crystal X-ray diffraction and IR spectroscopy. In both compounds the tin atoms are tetrahedrally coordinated, and the oxygen and fluorine atoms twofold and singly coordinated, respectively. The observed bond lengths are 199.9 pm for SnO and 195.7/196.5 pm (av. 196.1 pm) for SnF.

Kristallstrukturen von isopropyl- und trimethylsilylmethylen-substituierten Chloro-hydroxo-tetraorganyl-distannoxanen

Abstract According to the results of the X-ray analysis, 1-chloro-3-hydroxo-tetra-isopropyl-distannoxane and 1-chloro-3-hydroxo-tetra-(trimethylsilylmethylene)-distannoxane are dimeric and show a “ladder-type” structure analogous to the 1,3-dichloro-and 1,3-dihydroxo derivatives. In contrast to the terminal chlorine atoms, the hydroxyl groups form strong asymmetric bridges between two tin atoms; the two compounds differ slightly in the asymmetry of these bridges.

Darstellung und struktur von di-t-butylgermaniumdi-hydroxid und di-t-butylgermaniumoxid

Abstract Hydrolysis of di-t-butylgermanium dichloride yields di-t-butylgermanium dihy-droxide which could be isolated as a crystalline solid. X-ray structure determination shows t-Bu 2 Ge(OH) 2 tetrahedra held together by hydrogen bonds and thus forming continuous double chains. Di-t-butylgermanium oxide has been prepared by dehydration of the dihydroxide. The structure consists of trimeric molecules (t-Bu 2 GeO) 3 with planar germanium-oxygen rings.

Bindungsabstände zwischen organylsubstituierten Zinnatomen: III. Offenkettige Verbindungen☆

Abstract A series of organyl di-, tri- and tetrastannanes have been synthesized and investigated by an X-ray diffraction study. Like the cyclic compounds, the open-chain stannanes show a dependence of the tintin bond length on the bulkiness of the organyl groups.

Metalmetal spin coupling through chalcogenides. Correlation of 2J(119Sn, 119Sn) with molecular structure. Crystal structure of [(2-MeC6H4CH2)3Sn]2O and [(2-MeC6H4)3Sn]2O

The dependence of 2J(119Sn 119Sn) on the molecular structure of compounds containing the SnXSn moiety (where X = 0, S, Se, Te) has been investigated using new and earlier 119Sn solution and solid-state NMR and X-ray structural data for 46 linear and cyclic organotins. While 2J(119Sn, 119Sn) is found generally to vary with the size of the SnXSn angle for the chalcogenides, there is considerable scatter of the data. A plot of 2J(119Sn, 119Sn) (in Hz) vs. the angle SnXSn (in deg.) for compounds with X = O gives a straight line defined by the equation: angle SnOSn = 0.087 2J(110Sn, 119Sn) man(.6 with r = 0.990 and n = 8 (assuming no sign change in 2J(119Sn, 119Sn)). The quantity of data presently available does not permit regression analysis to be carried out for X = S, Se and Te. The range of SnX distances for a given X is small, and no meaningful relationships with 2J(119Sn, 119Sn) or the SnXSn angle were found. The X-ray crystal structures of [(2-methylbenzyl)3Sn]2O and (o-tolyl3Sn)2O are reported.

Die Molekül- und Kristallstruktur des triphenylsilanols

Abstract Single crystals of triphenylsilanol have been grown from toluene solution and the molecular and crystal structure determined by low temperature X-ray diffraction. Ph 3 SiOH crystallizes in the triclinic space group P − 1 (No. 2) with a = 1513.1(4), b = 1972.4(5), c = 2310.7(5) pm, α = 108.34(2), β = 103.30(2), γ = 101.26(2)°, V = 6.097 nm 3 and Z = 16. The structure was solved by direct methods and refined by block-matrix least-squares methods to a final R w -value of 0.080 ( R = 0.079) for 9079 reflections and 1431 parameters. The crystal structure consists of eight nearly tetrahedral Ph 3 SiOH molecules which are connected by -OH … O-hydrogen bridges to two tetrameric building units. Inside these units the four silicon atoms are arranged in form of a flat tetrahedron. The crystal data of the isotypic triphenylgermanol are mentioned.