Ioannis Tiritiris

Untersuchungen zur Kristallstruktur von Lithium-dodecahydro-closo- dodecaborat aus wäßriger Lösung: Li2(H2O)7(B12H12)

Durch Neutralisation einer wasrigen Losung der Saure (H3O)2[B12H12] mit Lithiumhydroxid (LiOH) und anschliessendem isothermen Eindampfen der Losung kann mit Li2[B12H12] · 7 H2O (≡ Li2(H2O)7[B12H12]) das Heptahydrat von Lithium-dodecahydro-closo-dodecaborat erhalten werden. Es fallen farblose, lattenformige, zerfliesliche Einkristalle an, die mittels Rontgenbeugung bei Raumtemperatur strukturell gut charakterisierbar sind. Die Verbindung kristallisiert orthorhombisch in der Raumgruppe Cmcm mit den Gitterkonstanten a = 1215, 18(7), b = 934, 31(5), c = 1444, 03(9) pm und vier Formeleinheiten pro Elementarzelle. Die Kristallstruktur von Li2(H2O)7[B12H12] ist nicht auf einen einfachen AB2-Strukturtyp zuruckzufuhren, sondern bildet in Analogie zu Ba(H2O)6[B12H12] eine Schichtstruktur aus. Ihr charakteristisches Merkmal stellen isolierte Kationenpaare [Li2(H2O)7]2+ dar, die aus zwei eckenverknupften [Li(H2O)4]+-Tetraedern in ekliptischer Konformation bestehen. Das gemeinsame Bruckensauerstoffatom (∢(Li-O-Li) = 112°) dieser dimeren Einheit ubernimmt dabei gemas (H2O)Li2(H2O)6[B12H12] die Funktion von Ba2+ in Ba(H2O)6[B12H12]. Ein direkter koordinativer Einflus der quasi-ikosaedrischen [B12H12]2—-Clusteranionen auf die Li+-Kationen ist allerdings nicht zu bemerken. Die Lagen aller Wasserstoffatome der in der Kristallstruktur vorhandenen Wassermolekule lassen sich ebenso wie jene der [B12H12]2—-Gruppen eindeutig ermitteln. B-Hδ—···δ+H-O-Wasserstoffbrucken zwischen den Wasserstoffatomen der Wassermolekule und jenen der anionischen [B12H12]2—-Einheiten werden konstatiert sowie deren Reichweite und Starke diskutiert. Differenzthermoanalytische und thermogravimetrische Untersuchungen zum thermischen Verhalten des Heptahydrats belegen einen zweistufigen Abbau bei 56 und 151 °C, welcher schlieslich zum wasserfreien Lithium-dodecahydro-closo-dodecaborat Li2[B12H12] fuhrt. Investigations on the Crystal Structure of Lithium Dodecahydro-closo-dodecaborate from Aqueous Solution: Li2(H2O)7[B12H12] By neutralization of an aqueous solution of the acid (H3O)2[B12H12] with lithium hydroxide (LiOH) and subsequent isothermic evaporation of the resulting solution to dryness, it was possible to obtain the heptahydrate of lithium dodecahydro-closo-dodecaborate Li2[B12H12] · 7 H2O (≡ Li2(H2O)7[B12H12]). Its structure has been determined from X-ray single crystal data at room temperature. The compound crystallizes as colourless, lath-shaped, deliquescent crystals in the orthorhombic space group Cmcm with the lattice constants a = 1215.18(7), b = 934.31(5), c = 1444.03(9) pm and four formula units in the unit cell. The crystal structure of Li2(H2O)7[B12H12] can not be described as a simple AB2-structure type. Instead it forms a layer-like structure analogous to the well-known barium compound Ba(H2O)6[B12H12]. Characteristic feature is the formation of isolated cation pairs [Li2(H2O)7]2+ in which the water molecules form two [Li(H2O)4]+ tetrahedra with eclipsed conformation, linked to a dimer via a common corner. The bridging oxygen atom (∢(Li-O-Li) = 112°) thereby formally substitutes Ba2+ in Ba(H2O)6[B12H12] according to (H2O)Li2(H2O)6[B12H12]. A direct coordinative influence of the [B12H12]2— cluster anions to the Li+ cations is not noticeable, however. The positions of the hydrogen atoms of both the water molecules and the [B12H12]2— units have all been localized. In addition, the formation of B-Hδ—···δ+H-O-hydrogen bonds between the water molecules and the hydrogen atoms from the anionic [B12H12]2— clusters is considered and their range and strength is discussed. The dehydratation of the heptahydrate has been investigated by DTA-TG measurements and shown to take place in two steps at 56 and 151 °C, respectively. Thermal treatment leads to the anhydrous lithium dodecahydro-closo-dodecaborate Li2[B12H12], eventually.

Single Crystals of the Dodecaiodo-closo-dodecaborate Cs2[B12I12] · 2 CH3CN (≡ {Cs(NCCH3)}2[B12I12]) from Acetonitrile

Colourless, lath-shaped single crystals of Cs2[B12I12] · 2 CH3CN (monoclinic, C2/m; a = 1550.3(2), b = 1273.2(1), c = 1051.5(1) pm, β = 120.97(1)°; Z = 2) are obtained by the reaction of Cs2[B12H12] with an excess of I2 and ICl (molar ratio: 1 : 2) in methylene iodide (CH2I2) at 180 °C (8 h) and recrystallization of the crude product from acetonitrile (CH3CN). The crystal structure contains quasi-icosahedral [B12I12]2– anions (d(B–B) = 176–182 pm, d(B–I) = 211–218 pm) which arrange in a cubic closest-packed fashion. All octahedral interstices are filled with centrosymmetric dimer-cations {[Cs(N≡C–CH3)]2}2+ containing a diamond-shaped four-membered (Cs–N–Cs–N) ring of Cs+ cations and nitrogen atoms of the solvating acetonitrile molecules (d(Cs–N) = 321 pm, 2 ×). The cesium cations themselves actually reside in the distorted tetrahedral voids of the cubic [B12I12]2– packing (d(Cs–I) = 402–461 pm, 10 ×) if one ignores the solvent particles.

N,N,N',N'-Tetra-methyl-N''-[3-(trimethyl-aza-nium-yl)prop-yl]guanidinium bis-(tetra-phenyl-borate) acetone disolvate.

In the title solvated salt, C11H28N4 2+·2C24H20B−·2C3H6O, the C—N bond lengths in the central CN3 unit of the guanidinium ion are 1.3331 (16), 1.3407 (16) and 1.3454 (16) Å, indicating partial double-bond character in each. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry [N—C—N angles = 118.96 (11), 120.51 (12) and 120.53 (11)°] and the positive charge is delocalized in the CN3 plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety all have values close to a typical single bond [1.4601 (16)–1.4649 (16) Å]. In the crystal, the guanidinium ion is connected by N—H⋯O and C—H⋯O hydrogen bonds with the acetone molecules. C—H⋯π interactions are present between the guanidinium H atoms and the phenyl rings of both tetraphenylborate ions. The phenyl rings form aromatic pockets, in which the guanidinium ions are embedded.

Zur kubischen Modifikation von Cs2[B12Cl12] im Defekt-W3O-Typ

Das bei der Umsetzung von Cs2[B12H12] [1] mit elementarem Chlor anfallende perchlorierte Caesium-Dodekachloro-closo-dodekaborat Cs2[B12Cl12] ist mittlerweile strukturell wohlcharakterisiert. Die Verbindung kristallisiert bei Raumtemperatur trigonal in der Raumgruppe R3 (Z 6) [2]. Zusatzlich war es moglich, auch Einkristalle zu isolieren, die eine kubische Metrik aufwiesen. Die Rontgenstrukturanalyse (IPDS, Stoe) ergab, das es sich hierbei um eine zweite Modifikation von Cs2[B12Cl12] (a 1051,98(6) pm; Vm 351 cm3/mol; Z 2) handelt, die offenbar bei Raumtemperatur mit der trigonalen Form (a 959,67(5), c 4564,2(3) pm; Vm 365 cm3/mol; Z 6) koexistiert. Nach der numerischen Absorptionskorrektur (Rint 0,060; Rσ 0,010) erfolgte die Strukturlosung aus 274 symmetrieunabhangigen Reflexen mit dem Programmpaket SHELX-97. Die Strukturverfeinerung fuhrte zu Residualwerten von R1 0,041 und wR2 0,086. Der Aufbau lasst sich analog zur „β-Wolfram-Struktur“ von W3O [3] in der Raumgruppe Pm3n als Defektvariante (Besetzungswahrscheinlichkeit fur Cs : 0,0834(4), also rund 4 von 6) beschreiben.

N,N,N',N',N''-Penta-methyl-N''-[3-(tri-methyl-aza-nium-yl)prop-yl]guanidinium bis-(tetra-phenyl-borate).

In the crystal structure of the title salt, C12H30N4 2+·2C24H20B−, the C—N bond lengths in the central CN3 unit of the guanidinium ion are 1.3388 (17), 1.3390 (16) and 1.3540 (17) Å, indicating partial double-bond character in each. The central C atom is bonded to the three N atoms in a nearly ideal trigonal-planar geometry and the positive charge is delocalized in the CN3 plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety, all have values close to a typical single bond [1.4630 (16)–1.4697 (17) Å]. C—H⋯π interactions are present between the guanidinium H atoms and the phenyl C atoms of one tetraphenylborate ion. The phenyl rings form a kind of aromatic pocket, in which the guanidinium ion is embedded.

2-Dimethylamino-1-(2-ethoxy-2-oxo-ethyl)-3-methyl-3,4,5,6-tetrahydro-pyrimidin-1-ium tetraphenylborate.

Isolated guanidinium ions and tetraphenylborate ions are present in the crystal structure of the title compound, C11H22N3O2 +·C24H20B−. In the guanidinium ion, the dihedral angle between the N/C/N and C/C/C planes being 49.9 (1)°. The six-membered ring exhibits a half-chair conformation. The C—N bond lengths in the cation range between 1.3335 (16) and 1.3552 (16) Å, indicating charge delocalization on the CN3 plane. In the crystal, the cations are connected by C—H⋯O hydrogen bonds, generating a chain along the c axis.

Synthesis of 4-Aminocoumarin Derivatives with N-Substitutents Containing Hydroxy or Amino Groups

Reactions of 4-hydroxycoumarin (1a) and 4-chlorocoumarin-3-carbaldehyde (1b) with amino alcohols or alkylene diamines led to the formation of the corresponding N-substituted 4-aminocoumarins 3, 5 and 6. However, 4-hydroxycoumarin-3-carbaldehyde (8) reacted with 2-aminoethanol and ethylenediamine to give N-substituted 3-(aminomethylene)-chromane-2,4-diones 9a, b. The structure and the E-configuration of compound 6 were proven by X-ray crystal structure analysis. Products 9a, b displayed signals of both E- and Z-isomers in their NMR spectra. All novel products have been characterized by means of spectral (IR, NMR, MS) data and elemental analyses Graphical Abstract Synthesis of 4-Aminocoumarin Derivatives with N-Substitutents Containing Hydroxy or Amino Groups

N-[3-(Di­methyl­amino)­prop­yl]-N,N′,N′,N′′,N′′-penta­methyl­guanidinium tetra­phenyl­borate

In the title salt, C11H27N4 +·C24H20B−, the C—N bond lengths in the central CN3 unit of the guanidinium ion are 1.333 (4), 1.334 (4) and 1.351 (4) Å, indicating partial double-bond character. The C atom of this unit is bonded to the three N atoms in a nearly ideal trigonal-planar geometry [N—C—N angles = 118.8 (3), 120.0 (3) and 121.2 (3)°] and the positive charge is delocalized in the CN3 plane. The bonds between the N atoms and the terminal C-methyl groups of the guanidinium moiety have values in the range 1.459 (4)–1.478 (4) Å, close to a typical single bond. In the crystal, there are C—H⋯π interactions between the guanidinium H atoms and the phenyl rings of the tetraphenylborate ion. These interactions combine to form a ladder of linked chains of ions which runs parallel to the c axis.

The Molecular Behaviour of Six-Membered Ring Guests in Cyclophosphazene Inclusion Compounds

Abstract The molecular behaviour of six-membered ring compounds in cyclophosphazene inclusion compounds is studied by dynamic 2H NMR spectroscopy. The analysis of the variable temperature NMR experiments provides a detailed picture about the guest mobility as well as the ordering behaviour of the guest species in such systems. It is found that the guest dynamics is rather complex with various intramolecular and intermolecular motional contributions, both of which giving rise to dynamic guest disorder. The intermolecular motions are found to depend strongly on the particular guest compound and dominate the experimental NMR data in the low temperature range beyond 150 K.

Crystal structure of N,N,N',N',N'',N''-hexa-methyl-guanidinium cyanate 1.5-hydrate.

The title hydrated salt, C7H18N3 +·OCN−.1.5H2O, was synthesized starting from N,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidinium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H⋯N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H⋯O hydrogen bonds between the water molecules are present, resulting in a two-dimensional hydrogen bonded network running parallel to the (001) plane. The hexamethylguanidinium ions are packed in between the layers built up by water molecules and cyanate ions.