D. Mootz

Polyhedral clathrate hydrates of a strong base: Phase relations and crystal structures in the system tetramethylammonium hydroxide-water

The tetramethylammonium hydroxide-water system has been studied by low-temperature differential thermal analysis and X-ray powder diffraction. The melting diagram was constructed for concentrations between 66.7 and 100 mol% H2O. It shows the existence and stability ranges of as many as eight crystalline hydrate phases:α- andβ-Me4NOH·2H2O (phase transition at −85°C, decomposition atca. 105°C), Me4NOH·4 H2O (melting point 44°C, incongruent),α andβ-Me4NOH·5 H2O (phase transition at 42°C, melting point 68°C, congruent),α- andβ-Me4NOH·7.5 H2O (phase transition at 6°C, melting point 16°C, incongruent), and Me4NOH·10 H2O (melting point −20°C, incongruent). The structures of all these phases, except the already known one ofα-Me4NOH·5 H2O, were determined from single-crystal MoKα diffractometer data. The decahydrate and the high-temperatureβ forms of the 7.5-hydrate and the pentahydrate are genuinepolyhedral clathrate hydrates, the first ones reported of a strong base. Their mostly novel three-dimensional anionic host structures, formed by the hydrogen-bonded OH− ions and H2O molecules, arefour-connected throughout, in spite of their proton deficiency which is apparently leveled by disorder. Disorder also affects the enclosed cationic Me4N+ guest species. Like the low-temperatureα form of the pentahydrate, that of the 7.5-hydrate has a clathrate-related, but not fully polyhedral structure, some of the oxygen atoms being three-connected only. The tetrahydrate presents the rare case of both a hydrogen bond of the type OH−...OH2 and a (deprotonated) water-channel structure. This is fully ordered and apart from that can be derived from the polyhedral one of theβ-pentahydrate just by removing the appropriate number of water molecules from certain positions. The structures ofα- andβ-Me4NOH·2 H2O contain identical one-dimensionalspiro chains [HO−(HOH)/42] with the hydroxide protonnot participating in the hydrogen bonding. The Me4N+ ion is ordered in theα and disordered in theβ phase.

AMINE-POLY(HYDROGEN FLUORIDE) SOLID COMPLEXES : NEW STUDIES OF FORMATION, CRYSTAL STRUCTURES, AND HN-1FN- ION DIVERSITY

Triethylamine tris(hydrogen fluoride), a versatile fluorinating agent, solidifies at −27 °C forming pairs of hydrogen-bonded Et3NH+ and H2F3− ions. Six further low-melting ionic amine–HF adducts have also been identified and their structures determined. The Hn−1Fn− ions with n here taking values between 3 and 7 are classified along with those observed in other crystals.

[(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.

The 7.25-hydrate oftert-butylamine. A semi-clathrate and complex variant of the cubic 12 Å structure type

Of the various hydrates oftert-butylamine, the title compound has been identified as the second-highest, melting incongruently at −19°C. Its crystal structure (orthorhombic, space groupPca21,Z=32 formula units per unit cell,a=24.80,b=16.440,c=25.29 Å) and the exact composition have been determined from X-ray diffraction at −150°C. The hydrate is a rather complex semi-clathrate, with the amine molecules not merely encaged, but also hydrogen-bonded, in a three-dimensional water host structure, which in turn is not fully four-connected. Nevertheless, it bears a clear relationship to the basic and genuine clathrate-hydrate cubic 12 Å type.

Kristallstrukturen von Chlordifluor- und Dichlorfluoressigsäure. Assoziation zu einem cyclischen Dimeren und einer stark gefalteten Kette

Abstract The crystal structures of CClF 2 COOH (monoclinic, space group P2 1 c , Z = 4 molecules per unit cell; lattice parameters a = 8.242, b = 5.658, c = 9.435 A and β = 102.58°) and CCl 2 FCOOH (orthorhombic, Pbcn , Z = 16; a = 16.158, b = 5.976 and c = 20.93 A) have been determined at −150 °C. The molecules form hydrogen-bonded cyclic dimers in CClF 2 COOH (just as in solid CF 3 COOH and CCl 3 COOH), but strongly folded chains of a new type in CCl 2 FCOOH.

SYNTHESIS, NMR AND X-RAY STRUCTURE OF PHOSPHORYLATED TETRAM ERIC METACYCLOPHANES

Abstract The synthesis of mesitylene-derived 1,3 alternate [1.1.1.1] metacyclophanes functionalized with pendant methylene-phosphonic acid diethyl ester groups is described. The compounds were fully characterized by 1H, 13C and 31P-NMR spectra and by FAB-MS spectroscopy. The preferred conformation in solution was established by NMR methods, whereas the solid state conformation of one of them, solved by X-ray diffraction techniques, is also reported. The macrocycle forms a lattice clathrate with cyclohexane in the ratio 1:2 (macrocycle over guest) and alternates with an additional molecule of water in a hydrogen-bonded 1D array.

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.

Crystal and molecular structure of 1-amino-benzylphosphonous acid monohydrate

Abstract The crystal and molecular structure of 1-amino-benzylphosphonous acid monohydrate (C7H10PO2N · H2O) has been determined from single crystal MoKα diffractometer data. The crystals are monoclinic: P21/n, a = 540.0(4), b = 666.3(3), c = 2485.1(19)pm, β = 90.70(6)°, Z = 4. The structure was solved by direct methods and refined to a final R = 0.0519. The molecule exists as a zwitterion, C6H5-CH(NH+ 3)-PO2H−. The crystal structure is stabilized by several hydrogen intermolecular bonds.

Zum System Essigsäure-Trifluoressigsäure: Bildung und Kristallstruktur eines über zwei sehr ungleiche Wasserstoffbrücken cyclisch-heterodimeren 1:1-Addukts

Abstract Acetic acid forms an equimolar adduct with trifluoroacetic acid which melts congruently at −38 °C. Its crystal structure is monoclinic with the space group P1/n and Z=4 formula units CH3COOH·CF3COOH per unit cell. The lattice parameters are a = 5.241 (4), b = 6.684(4)and c= 19.45(2) A, and β = 93.33(6)° at −150 °C. The adduct is molecular with the acid molecules being linked by two hydrogen bonds with very unequal O···O distances of 2.761(5) and 2.571(4) A to form cyclic heterodimers.

Crystal structure of N,N-dimethylpyrrolidinium hydroxide dihydrate, [C6H14N]OH 2H2O

Source of material: The title compound has been identified, together with four higher hydrates of the same hydroxide, by phase analysis (see ref. 1 ). Crystals of the compound were grown by cooling a solution with some water in excess. The organic cation and hydroxide anion lie on the mirror plane, the water molecule is in a general position. The latter two species are hydrogen-bonded to each other in four-membered rings spiro-linked at the hydroxide anions to form onenlimensional chains along the a-axis direction. Weaker bonds of the type C-HO from the cations to the chains (uncorrected H0 distances as dashed lines in the drawings at 2.48 Â to 2.72 Â) create an ultimately three-dimensional network. The compound is isostructural to the low-temperature form of the dihydrate of tetramethylammonium hydroxide (see ref. 2).