Volume 60, Issue 7

Colourless single crystals of TbPS 4 (a = 10.696(2), c = 19.053(4) Å ) were obtained by reaction of the elements (750 °C; 30 h). The compound crystallizes with the PrPS 4 type structure (I4 1 /acd; Z = 16). The structure consists of isolated PS 4 tetrahedra each surrounded by four Tb 3+ cations. Both crystallographically different Tb 3+ cations are coordinated by eight sulfur atoms which are part of four PS 4 tetrahedra. Orange single crystals of LiEuPS 4 (a = 11.498(2), c = 19.882(4) Å ) were prepared by reaction of Eu and P with Li2S4 (700 Å; 20 h). The crystal structure corresponds to the PrPS 4 type, in which tubes running along [001] are occupied by Li atoms, which are surrounded by four S atoms in strongly distorted tetrahedra. LiS 4 and PS 4 tetrahedra are connected via common edges into alternating chains.

Syntheses and structures of two novel “doubledecker” silicon complexes [R-Si(o-O-p-OMe-C 6 H 3 - C(Ph)=N-(CH 2 ) 2 -N=C(Ph)-C 6 H 3 -p-OMe-o-O)-CH 2 -] 2 (R = Ph, p-tBu-C 6 H 4 -O) with the silicon atoms hexacoordinated by two salen-type tetradentate 〈ONNO〉-chelating ligands are described. Hydrogen bonding between the halves of the bridged complexes as well as with chloroform solvate molecules determines the conformation. Compared with analogous mononuclear silicon complexes these ”doubledeckers” show bathochromically shifted Vis-absorption.

The barbiturate salts 2-amino-1,3-dimethylimidazolium N,N’-dimethylbarbiturate (8) and 1,3- diisopropyl-4,5-dimethylimidazolium N,N’-dimethylbarbiturate (10) are obtained from N,N’- dimethylbarbituric acid (6) and 2-imino-1,3-dimethylimidazoline (7) or 2,3-dihydro-1,3-diisopropyl- 4,5-dimethylimidazol-2-ylidene (9) in good yields. Their crystal structures reveal the presence of strong interionic N-H-O (8) and C-H-O (10) hydrogen bonds to give dimeric (8) and monomeric (10) ion pairs. These pairs are linked by weak C-H-O hydrogen contacts to give three-dimensional networks.

For the shortly discovered formula type M 2 Te 5 O 13 (triclinic, P1̄), the establishment of an isostructural series in the last third of the lanthanide family (M = Dy - Lu) was possible. The excessive formula unit TeO 2 additional to the well-known composition M 2 Te 4 O 11 (monoclinic, C2/c) leads to the slicing of the [M 2 O 10 ] 14− layers which are typical for the tellurium-oxide poorer compounds. By coupling together the bicapped trigonal prismatic (M1, CN = 8) and the pentagonal bipyramidal (M2, CN = 7) lanthanide-oxygen polyhedra via edges, [M 4 O 20 ] 28− bands are formed stretching along the a axis and piling up to a primitive rod-packing. The linkage of these bands occurs parallel to the (010) plane via Te3 as well as via Te4 parallel to (100). Besides the usual 3+1 coordination, two of the five crystallographically independent tellurium sites are coordinated regularly fourfold (d(Te−O) ≈ 186−213 pm) and even 3+2-fold by oxygen atoms. The tellurium-oxygen polyhedra form corrugated layers running parallel to (101) which follow so close to each other that the tellurium-oxygen partial structure appears to be almost three-dimensional at a passing glance. As in M 2 Te 4 O 11 -type representatives, the non-bonding electron pair (lone pair) of each Te 4+ cation shows stereochemical activity which always appears to flock together in large tellurium neighboured positions.

Synthesis, crystallographic characterization and magnetic properties of the new dinuclear iron(III) complex Fe 2 L(OCH 3 )Cl 2 (L=1,3-bis[N-(3,5-dichloro-2-hydroxybenzylidene)-2-aminoethyl]-2-(3,5- dichlo ro-2-hydroxyphenyl)imidazolidine) are reported. The structure consists of dinuclear units. The two iron(III) atoms are asymmetrically bridged by a phenoxo and a methoxo group. The iron(III) centers are separated by 3.133(2) Å . The Magnetic susceptibility of the complex was measured over the range 5 - 298 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator H = −JS⃗ 1 .S⃗ 2 . Magnetic susceptibility measurements indicate very weak antiferromagnetic coupling between the iron ions with J = −10.8 cm −1 and g = 2.0.

The title compounds were synthesized at temperatures between 775 and 1175 K from (mostly stoichiometric) mixtures of Fe 2 O 3 , elemental rubidium or potassium (A) and their hyperoxides AO 2 . The structures have been determined by single crystal X-ray diffraction. The alkaline rich ferrate(III) Rb 8 [Fe 2 O 7 ] (Cs 8 [Fe 2 O 7 ] structure type, space group P2 1 /c, a = 696.7, b = 1722.1, c = 692.0 pm, β = 119.40°, Z = 2, R1 = 0.0496) exhibits diferrate anions [Fe 2 O 7 ] 8- composed of two vertexsharing [Fe III O 4 ] tetrahedra with a linear Fe-O-Fe bridge and nearly ideal 3m symmetry. This is in marked contrast to the Na homologue, where the diferrate anions are decidedly angular. In the series A 3 [FeO 3 ], the anions in the compounds of the light alkaline cations are chains 1 ∞ [FeO 2 O 2/2 ] 3− , but similar to the isotypic K 6 [Fe 2 O 6 ] and to Cs 6 [Fe 2 O 6 ] the new ferrate Rb 6 [Fe 2 O 6 ] (K 6 Fe 2 O 6 structure type, space group C2/m, a=741.8(2), b=1148.7(2), c=680.08(12) pm, β =103.65(2)°, Z = 4, R1 = 0.0370) contains isolated binuclear anions [O 2 FeO 2 FeO 2 ] 6− composed of two edge sharing [FeO 4 ] tetrahedra. The new potassium ferrate of the series A 4 [Fe 2 O 5 ], K 4 [Fe 2 O 5 ] (space group P2 1 /c, a = 645.91(14), b = 593.69(13), c = 1003.0(2) pm, β = 103.124(4)°, Z = 4, R1 = 0.0355), constitutes a new structure type, but its structure is still closely related to the Na compound, which crystallizes in the isomorphous subgroup P2 1 /n with a doubled a axis. Both compounds are phylloferrates with layers 2 ∞ [Fe 2 O 5 ] 4− consisting of six-membered rings of [FeO 4 ] tetrahedra. In contrast, Rb 4 [Fe 2 O 5 ] contains chains of vertex and edge sharing tetrahedra, so that in both series, A 3 [FeO 3 ] and A 4 [Fe 2 O 5 ], the linkedness of the ferrate tetrahedra increases with the ionic radii of the A counterions.

Determination of the structure of the [Tl 2 (phthalate)] by X-ray crystallography shows that there are six (TlO 6 ) and five (TlO 5 ) coordinate Tl atoms. The complex is a two-dimensional coordination polymer.

Starting from 4,4’-dimethyl-2,2’-bipyridine, five new 2,2’-bipyridines symmetrically disubstituted in the 4,4’-positions with either terminal alkenyl, (trimethylsilyl)aryl- or (trimethylsilyl)alkynyl groups, have been synthesized and structurally characterized.

Pr(Man) 3 (ManH) and Er(Man) 3 (H 2 O) 2 (ManH = mandelic acid) have been synthesized by slow evaporation of aqueous solutions of rare-earth salts (Pr(OH) 3 , ErCl 3 · 6H 2 O) with mandelic acid (α-hydroxy-phenyl acetic acid, C 8 H 8 O 3 ) and their crystal structures were determined on the basis of X-ray data. In the crystal structure of Pr(Man) 3 (ManH) (1) (monoclinic, P2 1 , a = 574.8(1), b = 3042.5(4), c = 908.4(1) pm, β = 92.09(2)°, Z = 2) the Pr(III) ions are surrounded by eight oxygen atoms in a distorted square antiprismatic fashion with distances Pr-O in the range 241 to 254 pm. These polyhedra are connected by coordinative bonds to chains paralleling the crystallographic [100] direction. In Er(Man) 3 (H 2 O) 2 (2) (orthorhombic, P212121, a = 577.7(3), b = 1816.3(13), c = 2329.4(13) pm, Z = 4) the crystal structure contains isolated complexes with octa-coordinated erbium atoms chelated by three mandelate anions through one of their carboxylate oxygen atoms and the alcoholic hydroxyl group. Two water molecules complete the distorted square antiprismatic coordination sphere.

Aryl substituted dipyrromethanes [di(pyrrol-2-yl)-phenyl-methanes] with hydrogen acceptor substituents R in para position of the aryl ring [R = CO 2 Me, CO 2 H, CONH(iPr) and NH 2 ] located 7 Å apart from the hydrogen donor pyrrole nitrogen atom are shown to self-assemble in the solid state via hydrogen bonds to form rings or chains.

Various tetrahydropyranyl and trimethylsilyl ethers are efficiently transformed into the corresponding sulfonate esters with sulfonyl chlorides in the presence of FeCl 3 -Montmorillonite K-10 clay.

The lithiation of bis(triisopropylsilyl)phosphane with n-butyllithium in THF gave quantitatively dimeric (thf)LiP(SiiPr 3 ) 2 (1) with three-coordinate lithium atoms. The molecular structure of 1 shows Li-P bond lengths of 253.3(6) pm. In order to obtain the pentacarbonyltungsten complex of the sterically demanding phosphanide, (thf)W(CO)5 was reacted with (thf)LiP(SiiPr 3 ) 2 in THF. The resulting solvent-separated complex [(thf) 4 Li] + [(OC) 5 WP(SiiPr 3 ) 2 ] − (2) was structurally characterized and shows a very large W-P distance of 266.65(7) pm.

The modification of 2-azaanthraquinones with selected C 1 building blocks gives a series of new imidazo-fused derivatives. Employing 2,3-dichloro-5,6-dicyanopyrazine as cyclization partner a rearrangement to yield derivatives of benzo[f ]isoindole-4,9-dione takes place. The Sonogashira crosscoupling reaction of the aminalester derivative of the azaanthraquinone resulted in well soluble silyl substituted acetylenes as well as ethinyl aniline which allows further derivatization reactions.

Quantum chemical (DFT) calculations on the course of the electroreductive carboxylation of chloroarenes were performed. An explanation for the extraordinary behaviour of 2- chlorodibenzofuran (2) as compared with the corresponding 1-chloro, 3-chloro and 4-chloro derivatives was sought for and was found in the particular reaction coordinate of 2 and in the SOMO spin density distributions of the four isomers. In the same way, the regioselectivity in the formation of dicarboxylic acids from hexachloro- and 1,2,4,5-tetrachlorobenzene was investigated by DFT-MO calculations and was shown to be due to orbital effects besides steric hindrance.

The stems of Pilocarpus grandiflorus have afforded the new imidazole alkaloid 4,6-dehydro- 1,2,4,5-tetrahydro-2,5-dioxopilocarpine in addition to the 17 known compounds germanicol, β - amiryn, ocotillone, stigmast-4-en-3-one, 3β -hydroxy-stigmast-5-en-7-one, 6β -hydroxy-stigmast-4- en-3-one, β -sitosterol, scopoletin, 3-(1’,1’-dimethylallyl)-scopoletin, elisin, dictamine, 4-methoxy-2- quinolone, platydesmine, syringaresinol, syringaldehyde, syringic acid and vanillic acid. Their structures were elucidated on the basis of chemical and spectroscopic evidence. The phenolic compounds vanillic acid and syringaldehyde and the furoquinoline alkaloid platydesmine exhibited antifungal activity against Leucoagaricus gongylophorus, the symbiotic fungus of leaf-cutting ants (Atta sexdens rubropilosa).

An efficient procedure to deoxygenate hydroxy substituted flavonoids, isoflavonoids and related compounds via their trifluoromethanesulfonates is presented. Their reduction with formic acid in the presence of a catalytic amount of palladium acetate, triethylamine and 1,3-bis(diphenylphosphanyl) propane (dppp) in DMF results in their des-hydroxy derivatives without affecting other functional groups.

In the presence of tin(II)chloride, bromonitromethane reacts with imines derived from aromatic aldehydes and ammonia to yield 2-amino-2-aromatic substituted nitroethane derivatives via an addition reaction in good yields.

Mango (Mangifera indica L.) is one of the most important tropical fruits and its pulp is known to be a rich source of carotenoids. Investigations on the phenolic composition of the peels of a red-colored cultivar (cv. ‘Tommy Atkins’) revealed the presence of a new anthocyanin, 7-O-methylcyanidin 3-O- β -D-galactopyranoside. Its structure was elucidated by extensive 1D and 2D NMR studies, MS, and chemical transformation.

The new ent-kaurane diterpenoid weisiensin C (1) (1α,7α,14β ,18,20-pentahydroxy-ent-kaur-16- en-15-one), together with four known ent-kaurene diterpenoids, glaucocalyxin A (2), kamebanin (3), macrocalyxin D (4), and excisanin K (5), was isolated from the leaves of Isodon weisiensis C.Y. Wu. The structure of the new constituent (1) was elucidated by spectroscopic methods and confirmed by single-crystal X-ray diffraction.

Starting from 4,5-(ethylenedithio)-1,3-dithiol-2-one and 1,3-dithiol-2-one the disodium 5,6-dihydro-1,4-dithiin-2,3- dithiolate (Na 2 dddt) and disodium 1,2-dithiolate (Na 2 edt) salts were prepared, which react with NiCl 2 in air to give the complex Ni(dddt)(edt) (3ab). This compound was characterized analytically and spectroscopically. The method is applicable for the preparation of similar unsymmetrical complexes.