Volume 48, Issue 10

Selenium diimides R(NSeN)R [R = t Bu (1a), t Oct (1b)], the eight-membered heterocycle t BuN(SeSeSe) 2 N t Bu (2) and the aminoselenanes of the type [R(Cl 3 Si)N] 2 Se (4a,b) and [(Me 3 Si) 2 N] 2 Se (5) were studied by multinuclear NMR with emphasis on 15 N NMR for detection of coupling constants J( 77 Se 15 N). The selenium diimides possess the largest values of 1 J( 77 Se 15 N) observed so far (1a: 158.4 and 163.5 Hz; 1 b: 158.6 and 162.8 Hz). Compound 1 b was found to be much more stable than 1a, the heterocycle 2 being the major decomposition product of 1a. The selenium diimides (1a,b) react readily with hexachlorodisilane to give the bis[alkyl(trichlorosilyl)amino]selenanes 4a,b. The solid state 13 C, 15 N, 29 Si and 77 Se CP/MAS NMR spectra of bis[bis(trimethylsilyl)amino]selenane (5) gave results in accord with the known crystal structure, and there is agreement with the solution state NMR data

The reaction of organoindium halides RInCl 2 with tBu 2 PSiMe 3 leads to compounds of the type [{RIn(μ-tBu 2 P)Cl} 2 ] (R = iPr: 1, Me 3 SiCH 2 : 2). According to the crystal structure determinations 1 and 2 contain planar In 2 P 2 rings. The In atoms are coordinated to two bridging tBu 2 P groups, a terminal alkyl group and a terminal Cl atom

The direct synthesis of a number complexes with general composition Cu 4 OCl 6 - n(CH 3 ) 2 NH · mSolv, where n = 4, m = 0-2 and Solv = CH 3 OH, DMSO, is reported. It is shown by X-ray structure investigation, that in Cu 4 OCl 6 .4 (CH 3 ) 2 NH the copper atoms are linked by μ 4 -oxygen and μ 2 -chlorine bridging atoms, while molecules of (CH 3 ) 2 NH are attached to the metal atoms via nitrogen ones

The system tert-butanol-water has been confirmed by X-ray powder diffraction and singlecrystal structure analysis to contain two hydrates, a dihydrate and a higher hydrate. The composition of the latter, contradictory in the literature, could be resolved in favor of the new one of a heptahydrate. The dihydrate (m.p. 0.7°C) is monoclinic with space group P2 1 and Z = 2 formula units per unit cell of dimensions a = 6.017, b = 6.055, c = 10.377 Å and β = 106.60° at -150°C. The heptahydrate (m.p. -6°C, dec.) is orthorhombic with space group Pnma, Z = 4, a = 12.589, b = 15.251 and c = 6.645 Å at -150°C. Both hydrates contain characteristic layers of hydrogen-bonded O atoms, which in the heptahydrate are further linked into a three-dimensional semi-clathrate structure

The ionic crown ether complexes [Tl(12-crown-4) 2 ][SbCl 6 ] (1) and [In(12-crown-4)2][SbCl 6 ] 3 ·3 CH 3 CN (3) have been prepared by reaction of T1C1 and InCl 3 , respectively, with SbCl 5 in the presence of 12-crown-4 in acetonitrile solution. The lead complex [Pb(15-crown-5) 2 ][SbCl 6 ] 2 · [SbCl 3 (15-crown-5)] (2) has been obtained from the reaction of Pb(CH 3 ) 2 Cl 2 with SbCl 5 in the presence of 15-crown-5 in acetonitrile solution. 1-3 were characterized by crystal structure determinations. [Tl(12-crown-4) 2 ][SbCl 6 ] (1): Space group C2/c, Z = 4, 2306 observed unique reflections, R = 0.051. Lattice dimensions at -70°C: a = 2360.9(5), b = 1189.6(2), c = 1080.4(3) pm, β = 111.14(2)°. 1 contains cations [Tl(12-crown-4) 2 ] + , in which the Tl+ ion is coordinated sandwichlike by the eight oxygen atoms of the two crown ether molecules. The lone pair at the thallium ion shows steric activity. [Pb(15-crown-5) 2 ][SbCl 6 ] 2 ·[SbCl 3 (15-crown-5)] (2): Space group Pna2(1), Z = 4, 4631 observed unique reflections, R = 0.048. Lattice dimensions at -70°C: a = 2972.5(3), b = 1481.9(5), c = 1305.5(1) pm. 2 consists of [Pb(15-crown-5)2] 2+ ions, in which the lead ion is coordinated sandwich-like by the ten oxygen atoms of the two crown ether molecules without steric activity of the lone pair of Pb 2+ , of SbCl 6 - ions, and of molecules [SbCl 3 (15-crown-5)], which are already known. [In(12-crown-4) 2 ][SbCl 6 ] 3 ·3CH 3 CN (3): Space group P1̅, Z = 2, 5530 observed unique reflections, R = 0.059. Lattice dimensions at -70°C: a = 1041.8(8), b = 1052(1), c = 1543(2) pm, α = 103.62(9)°, β=108.68(8)°, γ = 99.48(8)°. 3 consists of [In(12-crown-4) 2 ] 3+ ions, SbCl 6 - anions, and crystal CH 3 CN molecules. The In 3+ ion is coordinated sandwich-like by the eight oxygen atoms of the two crown ether molecules, which are disordered in two positions

The title compound has been prepared by the reduction of N,N′-dimethyl-4,4′-bipyridinium dichloride with dilithium tritelluride in dimethylformamide solution. It forms deep blue crystal needles, which were characterized by a crystal structure determination. Space group Pna 2 1 ,Z = 8,3450 observed unique reflections, R = 0.045. Lattice dimensions at -70°C: a =1707.6(8), b = 2323.9(11), c = 664.6(3) pm. The N,N′-dimethyl-4,4′-bipyridinium radical cations are planar and form ion pairs in the lattice. The chloride ions together with the water molecules form an infinite network of hydrogen bridges along the crystallographic a-axis. The structural parameters of the radical cation are in excellent agreement with ab initio calculations.

Density Functional Theory (DFT) within the Local Density Approximation (LDA) was employed to calculate the reaction of OF 2 with the metal fragment Cr(CO) 5 . It is demonstrated that OF 2 does not show simple ligand behavior but reacts with the transition metal fragment under oxidative addition, leading to a chromium oxo-complex and transforming two cis CO into fluoroformyl ligands. We calculated this reaction to proceed without any major activation barrier and to be exothermic by about 100 kcal/mol. A possible mechanism for this reaction is discussed

The complexes [K(18-crown-6)][N(SO 2 CH 3 ) 2 ] and [K(dibenzo-18-crown-6)][N(SO 2 CH 3 ) 2 ] are obtained as white solids from equimolar methanolic solutions of KN(SO 2 CH 3 ) 2 and the appropriate crown ether. The former complex crystallizes at -25°C from methanol as a labile (1/2) solvate (title compound). The crystallographic data of the solvate at -95°C are: orthorhombic, space group P 2 1 2 1 2 1 , a = 848.2(4), b = 1233.2(4), c = 2496.6(10) pm, V = 2.612 nm 3 , Z = 4, D x , = 1.373 Mg m- 3 . The structure in the solid state consists of ion pairs. The potassium cation is coordinated by the six oxygen atoms of the crown ether and two oxygen atoms belonging to different sulfonyl groups of the anion. The bond distances are K - O(crown) 274.2-297.1 (mean value 288.7), K-O(sulfonyl) 283.8 and 284.5 pm. The potassium ion lies 74 pm out of the best plane of the crown ether oxygen atoms. One methanol molecule acts as a hydrogen-bond donor towards the nitrogen atom of the anion and as a hydrogen-bond acceptor towards the second methanol molecule. The coronand displays the frequently observed symmetry D 3d

The structure of the cobaloximatic acid, hydro-trans-diiodobis(ethanedioximato(1-)-N,N′)cobaltate(III), has been determined by X-ray diffraction. Crystal data: C 4 H 7 CoI 2 N 4 O 4 , M r = 487.87; monoclinic space group P2 1 /a (C 2h 5 ); a = 10.795(7), b = 9.003(7), c = 11.881(6) Å; β = 97.29(6)°; V = 1145.35 Å 3 ; Z = 4; d c = 2.83 Mg m -3 . R w (R) = 3.6 (3.9)% for 3064 observed independent reflections and 148 parameters. The coordination geometry around Co III is a distorted (4 + 2) octahedron of four chelating equatorial N atoms and two apical iodides. The compound is most adequately formulated as a monovalent strong acid: H(Co(GH) 2 I 2 ) (GH- = ethanedioximate or glyoximate). The H atoms of the oxime groups are involved in the usual intramolecular, as well as in much stronger intermolecular O-H-O bridgings (O ••• O intramol = 2.613-2.631, O ••• O intramol = 2.454 A). The “acidic” H atom of each molecule participates in the intermolecular bridging which extends throughout the structure, and propagates nearly parallel to the [101] crystallographic direction. The redox properties of the present compound were examined by cyclic voltammetry in acetonitrile solution at room temperature. Redox waves attributed to the reduction of Co III and to the oxidation of I - were observed, along with a wave which may be linked to the reduction of the “acidic” proton

A simple method is described which allows the growth of large transparent single crystals of tris[bis(trimethylsilyl)amido]lanthanide(III) complexes (lanthanide = Pr, Nd, Sm, Eu, Er, Tm, Yb). We have used these single crystals as starting material for a number of chemical reactions and detected no contamination with THF containing by-products. The superior quality of the crystals grown is demonstrated by optical polarization experiments. From the spectra a large negative crystal field parameter B 2 0 could be concluded

The structure of (5H)-2-Amino-3-hydroxy-5-phenyl-furan-4-one (lb) was determined by NMR-spectroscopy in solution and in the solid state. The structure of its oxidation product, 3,4-Dihydro-3,3,4,4-tetrahydroxy-5-phenyl-furan-2(5H)-one (7), given in the literature as 5-Phenyl-2,3,4-(5H)-furan-trione, was determined by NMR spectroscopy and crystal structure analysis. The solid state NMR spectrum of 7 was compared to the spectrum of dehydroascorbic acid

Reactions of the organometallic phosphinimine Ph 3 P=N-SiMe 3 (1), with aqueous ReO 4 - and 188 ReO 4 - yield the ion pairs Ph 3 P=NH 2 + MO 4 - (M=Re (2); 188 Re (4)). The ion pairs undergo dehydration upon heating to produce the neutral Re(VII) species: Ph 3 P=N-MO 3 (M=Re (3); 188 Re (5)). The solid state structure of Ph 3 P=NH 2 + ReO 4 - (2) shows the presence of hydrogen bonding between the iminato hydrogen and the rhenium oxo center. The relevance of such reactions for the design of new radiopharmaceuticals is discussed

Ν,N′,N″,N‴-Tetraaryl-oxalic amidines react with N-trimethylsilyldiethylamine to yield the activated and open chained derivatives 3a, b. By the use of diorganyldichlorosilanes the new 1,3-diaza-2-sila-cyclopentanes 5a-d were obtained. Cycloacylations of 3a with geminal dichlorides are leading to different kinds of heterocyclic compounds

The treatment of salicylaldehyde 1 and derivatives 2-4 with triethyl phosphonoacetate 5 in refluxing toluene using piperidine acetate and β-alanine affords 3-diethyl phosphonocoumarins 6-9. By hydrogenation of the compounds 6-9, 3-diethylphosphono-3,4-dihydrocoumarins 10-13 have been obtained. The compounds 10-13 react with the aromatic aldehydes 14-18, under Wittig-Horner conditions, to give 3-alkyl-coumarins 19-24 in satisfactory yields. The reaction of 3-diethyl-phosphonolactones 25, 26 with isatin 27 and 5-bromoisatin 28, under similar reaction conditions, leads to 3-alkyl-α,β-unsaturated δ-lactones 29-31

Kaempferol-3-O-rutinoside-7-O-sophoroside and kaempferol-3-O-(6-O-malonylgluco-side)-7-O-glucoside were isolated from Equisetum palustre and Equisetum x litorale, respectively. Their structures are prooved

Synthesis and properties of various 4,4′-binaphthylidene-1,1′-diones are described. The UV spectra of the deep red to purple diones may be calculated on the base of substituent increments. The experimental values of the analyzed substituents can be reproduced using PPP calculations with satisfying accuracy, which makes it possible to predict also absorption maxima of hitherto unknown 4,4′-binaphthylidene-1,1′-diones

The organic extract from Oceanapia bartschi has been shown to contain the antibiotic diterpene Ambliol A (1) and three indole derivatives, 3-bromoindole (2), 6-bromo-3-indolecarboxyaldehyde (3), and 6-bromo-5-hydroxy-3-indolecarboxyaldehyde (4). The structure of the novel compound 4 has been established from its spectroscopic ( 1 H and 13 C NMR, UV, IR, and MS) data

The 2,5-bis(2-arylvinyl)-1,4-benzoquinones 1a-1e are formed from hydrolysis of their corresponding ketals 5 which are generated by anodic oxidation of the corresponding 1,4-dimethoxybenzene derivatives 4. The crystal structures of the quinone compounds 1a, 1d and 1e have been determined by X-ray analyses. The bond lengths of the quinone system are influenced by polar resonance structures. An α-type packing mode is observed for the three crystal structures of compounds 1. The vinylic double bonds have short intermolecular distances (1a: 4.417(5), 1d: 3.653(2), 1e: 4.224(5) Å). Only the crystals of 1d with the shortest contacts are photoreactive

A CD conformational analysis has been performed on CCK-peptides elongated at the N-terminus in sequence mode beyond the naturally occurring CCK-8 up to the pentadecapeptide sequence. By extending N-terminally the CCK-8 sequence an intramolecular salt bridge between the tyrosine-O-sulfate and the arginine guanido function is allowed to be established. However, this intramolecular electrostatic interaction was not found to affect the bioactivities of the CCK-peptides indicating that induction of such salt bridge at the level of the ligand molecule does not prevent a similar interaction at receptor level by exchange of the counterion partner. As expected for unconstrained short linear peptides the dichroic properties in aqueous solution were indicative of predominantly random coil structure. Conversely, in aqueous TFE the CD spectra were consistent with the presence of γ-type turns similarly to what has been observed under identical conditions for small size peptides related to the homologuous gastrin hormone. In surfactant solutions the CCK-peptides were found to assume β-type structures by inserting at least the C-terminal portion of the bioactive core into more hydrophobic compartments of the surfactant micelles, whereas the hydrophilic charged N-termini of the CCK-pep-tides of increasing chain length are exposed to the water phase in random coil structures as suggested by the CD spectra. This contrasts previous findings related to the homologuous gastrin peptides, where identical CD spectra were recorded in aqueous TFE and in presence of micelles. This observation strongly suggests that gastrin and CCK related peptides exhibit distinct conformational preferences, despite their high degree of sequence homology, and fully agrees with the ability of CCK to interact specifically with different receptors

The complexes M(CO) 5 (CH 3 CN) (M: Cr, Mo, W) were obtained from the substitution of THF in M(CO) 5 (THF) which has been generated by photolysis of M(CO) 6 in THF and characterized by using IR, 1 H NMR and 13 C NMR spectroscopies. The acetonitrile ligand is found to be N-bonded to the M(CO) 5 -moiety with a local C 4v -symmetry. The effect of the acetonitrile ligand on the metal-carbonyl bonding was discussed in terms of 13 C NMR chemical shifts.

Coupling constants 2 J( 15 N 13 C R ) and n J( 15 N 1 H R ) in 2-substituted pyridines [R = Me (1), CH=CH 2 (2), C≡CH (3), C(O)H (4), C(O)Me (5)] have been measured by using Hahn-echo extended (HEED) pulse sequences for one- (1 D) and two-dimensional (2D) 13 C/ 1 H NMR (HEED-INEPT, HEED-HETCOR). The magnitude of | 2 J( 15 N 13 C R )| is hardly affected by the hybridization of 13 C R . 15 N NMR spectra, measured under conditions of ultra high resolution (UHR) confirm the values 2 J( 15 N 13 C R ). 2D 13 C/ 1 H HEED-HETCOR experiments show that the sign of 3 J( 15 Ν 1 H R ) is negative in 1, whereas the coupling constants 3 J( 15 N 1 H R ) in 4 and 4 J( 15 N 1 H R ) in 3 have a positive sign