Volume 43, Issue 7

[nBU 4 N] 2 [AS 2 I 8 ] (1), [pyH][AsI 4 ] (2) and [Et 3 NH] 4 [As 8 I 28 ] (3) have been prepared hy reaction of Asl 3 with the iodide of the respective nitrogen base (present in a 1:1 molecular ratio) in acetonitrile and their structures determined by X-ray structural analysis. 1 contains discrete [As 2 I 8 ] 2- anions with Q symmetry; the As atoms display a pseudo-octahedral AX 4 Y'E geometry with bridging A s - I distances of 2.931(1) and 3.289(1) Å. The iodoarsenate(III) anions in 2 form infinite [Asl 4 - ] ∞ chains, in which the individual units are edge-bridged distorted AsI 6 -octahedra with AX 4 Y' 2 E geometry. In contrast, 3 contains discrete centrosymmetric anions [As 8 I 28 ] 4- . in which the individual As atoms all display a distorted octahedral AX,Y,E geometry. The lone pairs are stereochemically inert in 2 and 3. The structures of 1-3 are compared with those of analogous chloro- and bromoarsenate(III) anions.

The reaction of tetrachlorocyclopropene with NbOCl 3 yields NbCl 5 ·OC 3 Cl 2 (1); 1 is also formed by partial hydrolysis of C 3 Cl 3 + NbCl 6 - (2), which is prepared from C 3 Cl 4 and NbCl 5 . [NbOCl 3 ·OC 3 Cl 2 ] 4 (3) was obtained by hydrolysis of 1 in form of pale-yellow, moisture sensitive, non-explosive crystals, and characterized by its IR spectrum and an X-ray crystal structure determination (1871 independent observed reflexions, R = 0.048). Crystal data: space group P1̄. Z = 2. a = 993.7(4), b = 1090.5(5). c = 1097.4(3) pm, α = 69.51(3), β = 70.47(3), γ = 66.51(4)° (at -17 °C). 3 consists of centrosymmetrical tetramers; the four Nb atoms form a square and are linked via almost linear oxo groups with alternating short and long NbO bonds with mean bond lengths of 175 and 208 pm. In trans position of each of the short NbO bonds a dichlorocyclopropenone molecule is attached via its oxygen atom with an NbO distance of 223 pm.

Lithium, sodium, potassium, caesium and magnesium salts of the dianion of 1,2-di-tert-butyl-3- [bis(trimethylsilyl)methylene]-1,2-diborirane have been synthesized and charactarized by 13 C and 11 B NMR spectroscopy. X-ray structure analysis of the di-potassium salt proves cyclic derealization of two. π-electrons in the CB 2 -ring by short C-B (150 pm) and B -B (158 pm) bonds. The exocyclic C-C bond (150 pm) is bridged by two potassium ions. One of them contacts the boron atoms of a neighbouring dianion leading to a helicoidal infinite chain with 4 1 -symmetry along the c direction.

Various salts M(AuX 4 ) 2 with X = OCOCH 3 or OCOC 2 H 5 have been prepared by two methods: (i) the reaction of metal hydroxides M(OH) 2 with HAuCl 4 , followed by treatment of the intermediate products with acetic or propionic acid, or (ii) the reaction of aurates M{Au(OH) 4 } 2 with the carboxylic acids. The crystal structure of Pb{Au(OCOCH 3 ) 4 } 2 ·2H 2 O shows that it is isostructural to the strontium salt, consisting of molecular units Pb{Au(OCOCH 3 ) 4 } 2 with crystallographic symmetry 2. The water of crystallization forms neither coordinate bonds to a metal nor hydrogen bonds. In the analogous zinc salt the water is coordinated to the zinc atom, and the structure is a layer polymer. The two compounds that crystallize in anhydrous form. Ba{Au(OCOCH 3 ) 4 } 2 and Pb{Au(OCOC 2 H 5 ) 4 } 2 , have not yet yielded crystals suitable for X-ray analysis.

Fe 4 S 4 I 2 (SPPh 3 ) 2 (1) was prepared by the reaction of Fe(THF) 6 Fe 4 S 4 I 4 (THF = C 4 H 8 O). SPPh,. and sulfur in toluene and CH 2 Cl 2 . 1 has a lower stability than Fe 4 S 4 I 4 2- and decomposes in solvents like THF and CH 3 CN. The crystal structure of 1 was determined from single crystal X-ray diffraction data. The compound crystallizes in the triclinic space group P1̄ with a = 1025.5(1). b = 1082.4(1), c = 2135.5(3) pm. α = 89.82(1), β - 77.37(1), γ = 73.56(1)°, V = 2214.1×10 6 pm 3 and Z = 2. The [Fe 4 S 4 ] 2+ core of 1 exhibits a slight tetragonal distortion. The mean Fe-S and Fe-Fe distances were found to be 227.6 (225.8-228.7) pm and 273.3 (272.9-274.4) pm, respectively. The Fe-SPPh 3 distances (231.6 and 232.1 pm) are longer than the terminal Fe-S bonds in RS coordinated [Fe 4 S 4 ] clusters. The Fe-I bonds are found at 251.6 and 251.8 pm. respectively.

[(F 3 CC 6 H 4 NNNC 6 H 4 CF 3 )Cu] 4 (1) and [(F 3 CC 6 H 4 NNNC 6 H 4 CF 3 )Ag] n (2) are obtained by the addition of a solution of CuCl or AgNO, in CH 3 CN to a solution of Na(F 3 CC 6 H 4 NNNC 6 H 4 CF 3 ) in THF. Recrystallization of 1 in toluene/n-hexane yields air-stable orange crystals (tetragonal space group P4̄2 1 c, lattice constants a - 1527.7(5), c = 1281.3(4) pm, Z = 2). Complex 1 forms tetrameric units of symmetry S 4 with the four Cu atoms forming a slightly folded rhombus. The triazenido ligands bridge the Cu atoms alternatingly above and below the rhombic Cu 4 ring resulting in short Cu -Cu interactions of 257.9 pm. Complex 2 crystallizes from pyridine/methanol in form of yellow, air-stable crystals exhibiting a weak temperature independent paramagnetism of 0.64 B.M. per Ag atom at room temperature. The lattice constants are a = 2943(2), b = 475.8(5), c = 2280(1) pm. β = 111.99(6)°. Z = 8 for the monoclinic space group P2 1 /c. The Ag atoms form zigzag chains with short Ag-Ag distances of 283.4 and 284.0 pm and angles Ag-Ag-Ag of 113.7 and 114.1°. The bridging triazenide ligands are arranged alternatingly above and below the Ag-Ag chain. Two symmetry independent zigzag chains are found in the unit cell.

Vinyl cations I + , I + b , I + c of the structure R′ 2 C=CR″ (I + a : R′ = R″ = anisyl; I + b R′ = phenyl.R″ = anisyl. I + c : R′ - methyl.R″ = anisyl) were generated by flash photolysis of corresponding bromides. Lifetime measurements yielded the following: substitution of aromatic groups in 2-position by methyl groups largely improved the electrophilicity of the vinyl cations. The nucleophilicity of typical compounds (ketone, ester, alcohol, olefin) was measured.

Low-valent trimethylphosphine cobalt compounds are oxidized by tellurium, selenium, or sulfur to give the title compounds. Several high-yield syntheses are described. The crystal and molecular structures of (Me 3 P) 3 CoX 3 Co(PMe 3 ) 3 (1: X = Te. 2: X = Se. 3: X = S) have been determined by single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P2 1 /n; a = 933.8(6) pm. b = 1488.3(6) pm. c = 1257.9(6) pm. β = 92.82(6)°. Z = 2. Complex 2 crystallizes in the triclinic space group P1, a = 1785.6(7) pm. b = 1599.7(7) pm. c = 928.9(5) pm. α = 87.8(1)°. β = 85.2(1)°. γ = 73.3(1)°. Z = 3. Complex 3 crystallizes in the monoclinic space group P2 1 /c; a = 952.6(5) pm. b = 1868.7(8) pm. c - 1893.1(8) pm. β = 90.19(6)°. Z = 4. All three structures contain centrosymmetric molecules with planar Co 2 X 2 rings. In solution dissociation of phosphine ligands occurs followed by slow decomposition to produce [(Me 3 P) 2 Co(PMe 2 )] 2 among other products. 1 reacts with carbon monoxide to afford a ditelluride [(Me 3 P) 2 (CO) 2 Co] 2 Te 2 . but no corresponding derivatives of 2 or 3 were obtained.

The sandwich type product CpCoL (1c) and the carbonyl species (OC) 3 FeL (2c), (OC) 4 CrL (3e), (OC) 4 MOL (4b), and (OC) 4 WL (5b) were prepared with diazadiboretidines (RBNR′) : (L) as tetra-hapto ligands (a-d: R = Me, Et, Pr. Bu; R′ = tBu; e: R = R′ = iPr). The ligand (iPrBNiPr) 2 , prepared by a novel catalytic cyclodimerisation of iPrB≡NiPr, undergoes subsequent cyclodimerisation to the eight-membered ring (iPrBNiPr) 4 at ambient temperature, where-as the corresponding cycloreversion occurs at 100 °C. The structure of the complexes (OC) x ML is discussed by means of IR and NMR data and the structures of crystalline 2c and 5d were determined by X-ray crystallography.

The cis-isomer of the silazane H 2 L (1) (L = [N t Bu][Me]Si(N t Bu) 2 Si[Me][N t Bu]) has been used as a ligand to main group metals. By displacing the hydrogen atoms of 1 the compounds L(MgMe) 2 (4), L(MgCl) 2 (5) and L(Li)(InMe 2 ) (6) have been obtained. According to the 1 H NMR spectra the structures of 4-6 are very similar: a polycyclic, cubane-like Si 2 N 4 M 2 framework results from the special atomic arrangements and from intramolecular Lewis acid-base interactions between the metals M and the nitrogen atoms. Divalent metals and metal-centered groups can also be incorporated into 1. In the latter case a seco norcubane-like polycycle Si 2 N 4 M is produced as confirmed by X-ray structure determinations of LGaMe (8) and LSb + InCl 4 - (11). LInMe (7) and LSn (9) seem to adopt the same tricyclic structure as 8, although the 1 H NMR spectra are not consistent with a rigid molecule (low symmetry), but rather with a fluxional behaviour (high symmetry). When 5 is allowed to react with sodium/naphthalene in THF part of the magnesium is reduced and LMg(THF) 2 (12) is formed. An X-ray structure determination of 12 reveals the compound to be only bicyclic with the magnesium atom coordinated by two nitrogen and two THF oxygen atoms.

Reaction of SiCl 4 with NMe 4 NCSe or NEt 4 NCSe in cold acetonitrile leads to the corresponding crystalline salts of the new hexa-coordinate silicon complex anion [Si(NCSe) 6 ] 2- (1 ] ; . Their crystallographic data were determined: [NMe 4 ] 2 [Si(NCSe) 6 ]: rhombohedral. R3̄. a = 897 pm. a = 84.1°. Z = 1. [NEt 4 ] 2 [Si(NCSe) 6 ], tetragonal modification (from pure acetonitrile): P4 2 /m, a = 1056 pm. c - 1580 pm. Z = 2. [NEt 4 ] 2 [Si(NCSe) 6 ]. orthorhombic modification (from acetonitrile containing NEt 4 Cl): a = 1704 pm. b = 1986 pm. c = 1028 pm. Z = 4. N-bonding of the NCSe groups in [Si(NCSe) 6 ] 2 is proved by the X-ray structure analysis of [NMe 4 ] 2 [Si(NCSe) 6 ] and by IR spectra. The concentration dependence of the molar conductance of an acetonitrile solution of [NMe 4 ] 2 [Si(NCSe) 6 ] was studied. At low concentrations partial dissociation of the hexa-isoselenocyanatosilicate ion is observed.

Preparation of cross-linked isonitrile-functionalized polystyrene resins of the type ⓟ-C 6 H 5 (CH 2 ) n NC (n = 1,2) is described. The polymers extract a variety of normal oxidation state metals from aqueous tetrahydrofuran and anhydrous metal salts and organometallic complexes from tetrahydrofuran and toluene. Structures of the complexes species are assigned on the basis of analyses and infrared spectra.

The influence of the size of the substituents at N-7 is of great importance to the stereochemistry of 3-oxa-7-azabicyclo[3.3.1]nonanones. The conformational and configurational isomers I-III are isolated and MNDO calculations of these isomers are done.

S,S-dialkyl acetals of hexanal and numerous aldoses, tripodal in structure, have been synthesized, characterized and investigated by optical microscopy and D.S.C. Most of these geminal dithioacetals show a complicated melting behaviour and are thermotropic liquid crystal-line, exhibiting only one smectic-like phase of identical type. This mesophase is not miscible with the S Ad -Phase of other amphiphilic sugar-based liquid crystals. As shown in a homologues series of D-glucose S,S-dialkylacetal derivatives clearing points are rising as function of growing number n of carbon atoms in their S-alkyl chains. With constant n given a similar trend is observed by varying the length of the polar, hydrophilic sugar units. Regarding stereochemistry the dithioderivatives 5 and 12 of the pentose or hexose series, respectively, with a configuration related to that of D-mannose exhibit relatively the most stable mesophase. However, the most stable mesophase of all investigated sugar dithioderivatives is exhibited by the heptose S,S-dialkylacetal 13. Surprisingly, derivative 10 of L-rhamnose (6-desoxy-L-mannose) - the terminal hydroxyl group in the sugar chain of mannose is missing! -showed to be non-mesomorphic, demonstrating that a terminal hydroxyl group of these sugar derivatives seems to be essential for exhibiting a mesophase. On the other hand, as shown with the dithioderivative 9 of 2-desoxy-D-glucose in comparison to the derivative 8e and 12 of D-glucose or D-mannose, respectively, their clearing points seem to be less, although differently effected if an internal hydroxyl group - for instance here at C-2 - has been stripped off. Melting behaviour as well as thermomesogenic properties of the presented amphiphilic carbo-hydrate liquid crystals in relationship to their molecular structure are discussed in detail.

The syntheses of 1.2-, 1.3- and 1,4-distyrylbenzenes with four or six dodecyloxy chains (1→5a, b, c, 6→13). and the structural conditions for the generation of liquid crystalline states are discussed. 5c forms a thermotropic smectic phase, which is degradated by light and renewed in the dark.

Claisen condensation of 2-acetyl-1,3-indandione (1) with ethyl acetate afforded the 2-acetoacetyl-1,3-indandione (2) which upon treatment with benzylamine and paraformaldehyde in a molar ratio of (1:1:2) and (1:2:4) afforded the piperidinone and the diazabicyclic derivative (4) and (5) respectively. On the other hand, Claisen condensation of 1 with diethyl oxalate yielded two products (6) and (9). The behaviour of 6 towards phenyl hydrazine, and of 9 towards selenium dioxide and double Mannich reaction were also investigated.

Methyl 5-hydroxy-3,11-di-2-pyridyl-4,5-dihydro-1H,3H-2,6-methano-6-benz[c]azocinecarb-oxylate (-)-3 is synthesized by oxidative cyclization of an N-benzyl-4-piperidone, reduction and resolution with (-)-camphanic acid chloride. The structures of C 24 H 23 N 3 O 3 (-)-3 and of the corresponding camphanic acid ester C 34 H 35 N 3 O 6 (-)-5 are orthorhombic and monoclinic with space groups P2 1 2 1 2 1 ((-)-3) and P2 1 ((-)-5). The respective cell parameters are a = 9.758(3), b = 12.815(2), c = 16.584(4) Å, Z = 4 and D x = 1.29 g cm -3 ((-)-3) and a = 11.189(1), b = 10.591(1), c -12.84(1) Å, β = 92.53(1)°, Z = 2, D x = 1.27 g cm -3 ((-)-5). They were refined to R (unweighed) -0.037 ((-)-3), 0.069 ((-)-5) and R (weighed) = 0.035 ((-)-3), 0.061 ((-)-5) using 965, 1722 non-equivalent reflections, respectively. The absolute configuration of (-)-3 was determined as 2S, 3R. 5R, 6R, 11 R.

A new eudesmane sesquiterpene, argutinin (1) has been isolated from Pluchea arguta Boiss. Its structure has been elucidated by spectroscopic methods.

(o-Trimethylsilylbenzyl)diphenylphosphine (1) crystallizes in the monoclinic space group P2 1 /n with a = 14.088(2), b = 8.712(1), c = 16.481(2)Å, β = 101.63(1)°, V -1981.3 Å 3 Z = 4. There is no P-Si interaction in the solid state which is also found for the solution ( 31 P NMR, 13 C NMR).

A phase transfer reaction between the title ketones, sodium trichloroacetate, and an alkyl halide leads to 2a, b, 4, or 5. Whereas these com-pounds are fragmented by NaOH, sodium meth-oxide/methylmalonate/methanol give compound 8 from 5 in a complex series of consecutive rearrange-ments.

1,3-Dioxin-4-ones from Ketones Onium salt and acid catalyzed addition of di-ketene to (-)-menthone gives improved yields of 2 and 3. Excess of diketene leads to diastereomeric mixtures of compounds 4 and 6 from menthone and menthol, respectively.

The values 1 J( 15 N≡ 13 C) from 15 N satellites in the 13 C NMR spectra for two nitriles [C 6 H 5 -C≡N, (CH 3 ) 2 CH-C≡N] have been determined and δ( 15 N) for trimethylsilylcyanide has been con- firmed. This completed a set of NMR parameters in order to compare phosphaalkynes and nitriles. Linear relationships emerged for the following NMR parameters of phosphaalkynes and nitriles: δ( 31 P p≡c )/δ( 15 N N≡C ), δ( 13 C P≡C )/δ( 13 C N≡C ) and 1 J( 31 P= 13 C)/ 1 J( 15 N≡ 13 C). On the basis of the latter relationship a positive sign for 1 J( 31 P≡ 13 C) has been proposed. This is also corroborated by the sub- stituent-induced changes in the magnitude of 1 J( 13 C≡ 13 C) in corresponding alkynes.