Wolfgang Poll

Trimethylsilyl-substituierte Derivate des Dimethylzinks — Synthese, spektroskopische Charakterisierung und Struktur

Abstract The trimethylsilyl-substituted derivatives of dimethylzinc [(Me 3 Si) n CH 3− n ] 2 Zn with n = 1, 2 and 3 give NMR data which are strongly dependent on the substitution grade, which indicates an increasing flattening of the α-carbon atom. Whereas the pyrophoric compounds with n = 0, 1 and 2 are distillable liquids, the air and water resistent bis[tris(trimethylsilyl)methyl]zinc ( n = 3) has a melting point of about 300°C. The derivative crystallizes from n-pentane in the monoclinic space group C 2/ c with a 1628.5(3), b 908.2(1), c 2265.4(4) pm, β 108.82(1)°, Z = 4. The ZnC bond length has a value of 198 pm, and the CZnC moiety is linear owing to the crystallograhically enforced symmetry. The flattening of the CSi 3 fragment is obvious but noticeably smaller than expected from the NMR parameters.

A Convenient Synthesis of Phosphonic Anhydrides − Trimers [RPO2]3 (R = tert-Butyl, 2-Methylphenyl, 2,4,6-Trimethylphenyl): Their Structures and Reaction Products

By reaction of RP(O)Cl2 with RP(O)(OSiMe3)2, phosphonic anhydrides (RPO2)3 (R = tBu, 2-methylphenyl, 2,4,6-trimethylphenyl) 1a−c are conveniently obtained. In contrast to 1b and 1c, compound 1a is remarkably stable against protolysis. Intermediates of hydrolysis of 1a, namely tris(tert-butyl)triphosphonic acid (2) and bis(tert-butyl)diphosphonic acid (3), can also be isolated in good yield. The structures of 1−3 were determined mainly by NMR spectroscopy (1 H, 13C, 31P). Assuming an energetic preference for the chair conformations in solution, and considering the steric requirements of the bulky substituents R, configurations Ia (point group Cs, two R in equatorial positions) for 1a and b, and IIa (point group C3v, all R equatorial) for 1c are suggested. − Reaction of 1a with N-benzyloxycarbonylglycine (4) in methanol affords strong evidence that in the first step of peptide synthesis with (RPO2)3, a mixed anhydride of triphosphonic acid and the N-protected amino acid is formed. − The crystal structure of 1a (monoclinic, space group P21/n) widely corresponds to the suggested configuration Ia, but reveals an envelope conformation for the six-membered ring with a P3O2 plane in the crystal. In the crystal structure of the octahydrate of the disodium salt of 2 (monoclinic, space group P21/c), it can be seen that the polar end groups of the anions [tBu3P3O7]2− together with the water molecules and the Na+ cations, form hydrogen-bonded double-layers, strictly separated from each other by the non-polar tert-butyl groups of the anions.

[(C5H5)Co{P(O)(OH)2}3H]: A novel organometallic tris-phosphonic acid that dissolves glass to form a six-coordinate silicon complex

The sodium salt of the tripodal oxygen ligand Na[(C5H5)Co(P(O)(OMe)2)3] (1) reacts with gaseous hydrogen chloride in dichloromethane to give sodium chloride and [(C5H5)Co(P(O)(OMe)2)3H2]Cl (2). Addition of an equimolar amount of 1 leads to precipitation of sodium chloride again to yield the acid form of the ligand [(C5H5)Co(P(O)(OMe)2)3H] (3). Its solid-state structure contains a very short intramolecular OH.O hydrogen bond. The compound hydrolyses in boiling water to give methanol and the title complex [(C5H5)Co(P(O)(OH)2)3H] (4). This complex is a rather strong tris-phosphonic acid (pK(a1) 2.0, pK(a2) 4.0, pK(a3) 6.3, and pK(a4) 9.6). Attempts to grow single crystals of this highly water-soluble yellow crystalline compound lead to the silicon complex [((C5H5)Co[P(O)(OH)2]2[P(O)2(OH)])(2)Si].8 H2O (5). The crystal structure determination shows that it is a molecular complex of two tris-phosphonic acids that each act as a tris-chelating ligand. Additional water molecules form a complex net of hydrogen bonds between the complexes of 5. The SiO6 octahedron is only insignificantly distorted with Si-O bond lengths of 1.78 A. Complex 4 reacts with stoichiometric amounts of potassium carbonate to yield the potassium salt K[(C5H5)Co(P(O)(OH)2)3] (6). The crystal structure of 6 has also been determined. In the solid state it is a two-dimensional coordination polymer with each potassium ion being coordinated by twelve oxygen atoms of six tris-phosphonic acids.

Die Kristallstrukturen von PHF4, PH2F3 und PHF2. Moden molekularer Packung bei tiefer Temperatur [1] / The Crystal Structures of PHF4, PH2F3 and PHF2. Molecular Packing Modes at Low Temperature

The title com pounds have been prepared in partly new ways and their crystal structures determined. The molecular geometries are found similar to those of the respective gas phases and those obtained by ab initio calculations. On the intermolecular level, there are indications of weak hydrogen bonds P-H···F in all three structures and of likewise weak fluorine bridges P-F···P in PH2F3 and PHF2 with the latter further featuring a close P···P contact.

New Synthetic Route to Phosphonic Acid Anhydrides

Abstract Phosphonic acid anhydrides are useful condensation reagents in the peptide and polyamide synthesis [1,2]. A new method for the preparation of well defined anhydrides is now described and intermediates of the peptide synthesis are elucidated. Cryoscopic and mass spectrometric data confirm the suggested cyclic trimeric molecular structure and the 31P{1H}- as well as 1H-NMR spectra can be explained with the structures: Reaction of t-BuP(O)(SiMe3)2 and PhBCl2 yields the mixed anhydride of t-butylphos-phonic and phenylboronic acid C40H57B4O12P4. The compound forms colourless crystals and the obtained data are in agreement with a 16 membered P-0-B- ring.

Darstellung von Difluormethanimin F2C = NH und F2C = ND durch Hydrolyse von CF3NCO / Preparation of Difluoromethanimine F2C = NH and F2C = ND by Hydrolyses of CF3NCO

Abstract The title compounds have been prepared by controlled hydrolysis of CF3NCO in NEt3. Their 13C, 19F and 1H NMR spectra are reported and their I R gas and I R matrix spectra are discussed in terms of a normal coordinate analysis. The photoelectron spectrum of F2C = NH is compared with those of F2C = NF and H2C = NH revealing a strong fluoro effect. In the solid state F2C = NH is aggregated to infinite zig-zag chains by N • • • H hydrogen bonding.

Zum System Wasser—Fluorwasserstoff: Phasenverhalten und Kristallstruktur von 2 D2O• 3 DF, einer deuterierten Verbindung ohne protoniertes Analogon / Concerning the System Water—Hydrogen Fluoride: Phase Behaviour and Crystal Structure of 2 D2O· 3 DF, a Deuterated Compound Lacking the Protonated Analogue

The melting diagram of the quasibinary system D2O— DF was determined by low-temperature DTA and X-ray powder diffraction. It was found to be largely similar to that of the corresponding non-deuterated system H2O—HF with the striking exception of an additional phase with a composition of its own, 2D2O· 3 DF, and stable between ca. —78 and —71°C. Its structure, determined from single-crystal MoKā diffractometer data at —150°C, is rhombohedral (space group R3c, Z = 6, a = 769.9, c = 1242.1 pm) and strongly related to that of NH, · 4 HF or NH4[F(HF)3] with also seven H (as to be compared to D) and five non-H (non-D) atoms per formula unit. But with the O atom involved in four hydrogen bonds, one O · · · O and three O · · · F. at distances of 273.9 and 259.5 pm, respectively, the compound appears to be a molecular adduct rather than an oxonium salt. The D atoms in the hydrogen bonds are distributed over two positions each. — The remaining intermediary phases of the deuterated system, i. e. D2O · DF, D2O· 2 DF and D2O · 4 DF, are isotypic to their protonated counterparts of known crystal structure. For D2O · DF and D2O-2 DF these results from powder patterns were confirmed by two more single-crystal studies. The ionic structures — D3OF and D3O[F(DF)], respectively — show no distinctive effect of the H/D substitution even on details of the interatomic geometries.

(R)-5-[(1R,2R)-1-Ethyl-2- (4-oxocyclohexyl)butyl]oxepan-2-one, an Enantiopure ‘Pseudosteroid′

The title compound C18H30O3 represents an optically pure member of a class of ‘pseudosteroids’, i. e. perhydrostilbene derivatives which mimic steroidal androgens (in the way like hexestrols or stilbestrols serve to substitute natural estrogens). The molecule 2 is characterized by three consecutive chiral centers leading to eight possible stereoisomers including four diastereomers. All enantiomers have been separated and their biological profile has been determined. As the result of the crystal structure presented here the two symmetry independent molecules display the configuration R,R,R at the centers of chirality.

P-Analog of Carbamic Acid: Crystal Structure of (CO)5CRH2P-COOH and Ab Initio Calculations

Abstract Phosphinoformic acid is unstable like the N-analogue carbamic acid. We found however that the acid can be stabilized by coordination via P to a (CO)5Cr-moiety [1]. In accordance with the conclusions of Leiserowitz [2] about solid carboxylic acids the crystal formic acid consists of hydrogen of the Cr atom is a distorted bonds between 1.881 and 1.928 A bond of 2.335 A. The angular distortion is small as shown by a maximum deviation of about 2.3° fiom the ideal geometry. At the P atom all bonding angles involving the Cr atom are widened to a maximum of 124° and the other ones are reduced to a minimum of 95°. In the crystal structure two symmetry-related molecules are connected to each other by means of two equivalent hydrogen bonds 06… 07′ and 07… 06′ of 2.660 c length between the carboxylic groups. Because of a twofold disorder along the bond P-C6, proven by bond lengths of 1.269(2) A for C6–06 and 1.264(2) A for C6–07 as well as by the localization and refinement of two H atoms with an occupancy ...

Untersuchung zur 6-Hydroxyindol-Bildung bei der Nenitzescu-Reaktion, IV [1]. Cyclisierung von N-(Chinonylalkyl)enaminon-Derivaten, II [2] / Investigation on the Formation of 6-Hydroxyindole in the Nenitzescu Reaction, IV [1]. Cyclization of N-(Quinonylalkyl)enaminone Derivatives, II [2]

Quinonylmethylenaminones 5 and 6 are synthesized and cyclized to spiro compounds 7 and 8. Quinonylpropylenaminone 15 is made in the same way. Cyclization in acetic acid yields quinolines 11 and 12, in trifluoroacetic acid/trifluoroacetic anhydrid diacylenamine 16 is obtained. The product of 15 in perchloric acid is benzazocine 20. The structure of 20 is proven by X-ray analysis. The course of the reaction is discussed.