Volume 41, Issue 10

S 5 N 5 [SnCl 5 (CH 3 CN)] is prepared by the reaction of SnCl 2 with trithiazyl chloride in acetonitrile suspension. The compound is characterized by its IR spectrum, the 119 Sn Mössbauer spectrum and by an X-ray crystal structure determination (1851 observed, independent reflexions, R = 0.024). S 5 N 5 [SnCl 5 (CH 3 CN)] crystallizes in the monoclinic space group P2 1 /n with Z = 4 and the lattice dimensions a = 758.8; b = 1574.6; c = 1429.1 pm; β = 97.65°. The compound consists of planar S 5 N 5 ® cations with the azulene-like structure, and anions [SnCl 5 (CH 3 CN)]e in which the tin atom has a distorted octahedral coordination. The bond angle Sn-N ≡ C (168°) is surprisingly small.

An improved method of synthesis for MoCl 3 (N 3 S 2 ) from molybdenum pentachloride and trithiazylchloride is given. Its reaction with pyridine and tetrahydrofuran in a CH 2 Cl 2 suspension yields the donor-acceptor complexes [MoCl 3 (N 3 S 2 )(C 5 H 5 N)] and [MoCl 3 (N 3 S 2 )(C 4 H 8 O)], respectively. Both are soluble in CH 2 Cl 2 and can be obtained in form of black, moisture sensitive crystals. Their IR spectra are reported and their crystal structures were determined by X-ray diffraction. Both compounds have nearly the same structure (monoclinic, space group P2 1 /c, Z = 4). Lattice constants: [MoCl 3 (N 3 S 2 )(C 5 H 5 N)], a = 1102.2, b = 997.7, c = 1134.9 pm, α = 94.19° (1582 observed, independent reflexions, R = 0.023); [MoCl 3 (N 3 S 2 )(C 4 H 8 O)], a = 1069.7, b = 1002.5, c = 1122.0 pm, β = 93.77° (1440 reflexions, R = 0.024). In the molecules, the Mo atoms are members of nearly planar MoN 3 S 2 rings with MoN bond distances between 178 and 185 pm , which correspond to double bonds. The sixfold coordination of the Mo atoms is completed by three chlorine atoms and the N or O atom of the pyridine or tetrahydrofuran ligand, respectively. The solvate molecules are in trans positions to one of the N atoms and form dihedral angles of 34.0° and 41.4° with the M oN 3 S 2 rings, respectively.

Reaction of py · PS 2 Cl (py = pyridine) with benzyl amine in the presence of NEt 3 yields triethyl-ammonium 1,3-dibenzyl-2,4-dithioxo-1,3-diaza-2λ 5 ,4λ 5 -diphosphetidine-2,4-dithiolate which reacts with MeI to give the corresponding methyl ester. By fractional crystallization from cyclohexane three modifications of the methyl ester were obtained (two trans-(A and A') and one cis-modification (B)). The crystal structure of these modifications have been determined by single crystal X-ray diffraction. Crystal data: A: triclinic, space group P1̄ , Z = 2, a = 7.100(3), b = 10.088(6), c = 17.785(6) Å , α = 99.18(4)°, β = 93.75(5)°, γ = 106.96(4)°, A': monoclinic, P2 1 /c, Z = 2, a = 7.933(3), b = 13.689(3), c = 9.917(4) Å, β = 111.98(3)°; B: orthorhombic, P cab, Z = 8, a = 12.962(6), b = 16.581(6), c = 19.475(7).

By reaction of CS 2 with maleonitrile in presence of sodiumethanolate in ethanol, Na 2 S 2 C 4 N 2 is obtained. SrS 2 C 4 N 2 · 5 H 2 O was synthesized by reaction of Sr(NCS) 2 with Na 2 S 2 C 4 N 2 in ethanol. It crystallizes monoclinically, space group P2 1 /c, with a = 9.201(2), b = 9.990(6), c = 14.605(5) Å, β = 122.3(3)°, Z = 4. The compound is isotypical with CaS 2 C 4 N 2 · 5 H 2 O. A structural model based on equivalent metal positions was refined to R = 0.057. The crystal structure contains layers of nearly planar [S 2 C = C(CN) 2 ] 2- anions held together by interspersed Sr 2+ cations in a tricapped trigonal prismatic surrounding of 6O and 3N atoms. The S atoms of the ligand are not included in the coordination sphere of Sr 2+ but are involved in several O - H···S hydrogen bonds.

Mo(CO) 2 (PPh 3 ) 2 (MeCN)(η 2 -SO 2 ), reacts with a number of unidentate or tridentate phosphines with displacement of both MeCN and PPh 3 . Mixtures of up to three different isomers are obtained the structures of which are assigned by IR , 1 H, 13 C, and 31 PNMR , and in one case by X-ray crystallography. The results support earlier observations concerning the relationship between the disposition of donor and acceptor ligands around the metal and the bonding mode of SO 2 .

Indium trichloride reacts with 2 moles of monothiodibenzoylm ethane (LH) in the presence of sodium acetate to yield In Cl 2 L(LH). According to an X-ray structure analysis the molecule possesses a hexacoordinated indium atom with two chlorine atoms in cis position and two sulfur atoms in trans position. The symmetry of the molecule is C 2 imposed by a crystallographic twofold axis. The unique hydrogen atom , assumed to form an intermolecular hydrogen bridge between oxygen atoms could not be detected in the structure analysis.

Spectra and Crystal Structures of the Adducts C l5Sb • [N(/-C3H 7)C N (i-C3H 7)] and C l4Sn • 2 [N(/-C3H 7)CN(/-C3H 7)j X-Ray, Vibrational Data, Diisopropylcarbodiimide Adducts of SbCl5, SnCl4 Thecarbodiimide adducts Cl5Sb <-(—N (R) = C = N R)(1) and Cl4S n ^ (-N (R) = C = N R) 2(2)(R = /-C3H 7) have been prepared by the reaction o f R —N = C —N — R with SbCl5 in a 1:1 and with SnCl4 in a 2:1 molar ratio, respectively. The vibrational spectra (IR and Raman) of both compounds have been regarded and assigned to the skeleton modes. The X-ray structure determination shows the orthorhombic space group Pna2, with 4 formula units per unit cell for 1. Adduct 2 has a trans-configuration and crystallizes in the triclinic space group P 1 with only one molecule per unit cell.

1,3-Di̲aza-2-s̱ila-4-c̱yclopentenes 1 (DISC), which are electron-rich and easily oxidizable ole­ fins, form strongly coloured, but poorly soluble 1:1 adducts with cuprous halides, while silver trifluoromethylsulfonate oxidizes 1. Much more soluble and again strongly coloured complexes of stoichiometry LPdX 2 , (L) 1.5 PdX 2 and L 2 PdX 2 are formed from 1 and palladium halides. The well-crystallizing adduct (PdCl 2 · L) 2 3a was chosen for an X-ray structure analysis (monoclinic, space group P2/c; a = 10.215(3), b = 14.681(3), c =23.642(5) Å , β = 101.31(2)°; Z = 8 ; R = 0.054), which revealed an almost planar DISC ligand in an oblique η 2 (C=C)-coordination relative to the π-plane. Structural data and rather peculiar spectroscopic properties encourage a comparison of 3a with complexes, in which an electron-rich olefin is split to give a bis(carbene) ligand system. The electronic reasons for the splitting of electron-rich olefins at d 8 metals are discussed under symmetry considerations.

Tripod ligands MeGe(OCH 2 PMe 2 ) 3 (1) and MeSi(OCH 2 PMe 2 ) x (CH 2 CH 2 PMe 2 ) 3-x (x = 0-2) (4-6) have been prepared by reacting MeGeCK and MeSiClxVi 3-x (x = 1. 2). respectively, with Me 2 PCH 2 OH in the presence of a tertiary amine (NEt 3 or NMe 3 ), in case of the resulting vinylsilane derivatives MeSi(OCH 2 PMe 2 ) x Vi 3-x (x = 2: 2; x = 1: 3) and MeSiVi 3 followed by the photochemical addition of Me 2 PH to the vinyl groups. Replacement of the cycloheptatriene ligand in M(CO) 3 CHT compounds (M = Cr. Mo, W) yields the new complexes fac-M(CO) 3 [MeGe(OCH 2 PMe 2 ) 3 ] (7-9) and fac-M(CO) 3 [MeSi(OCH 2 PMe 2 ) x (CH 2 CH 2 PMe 2 ) 3-x ] (10-18). The ligand properties of 1 and 4-6 have been studied by determining the effects of coordination on the spectroscopic data (ν co , 1 H, 31 P NMR).

A series of carbonyl metal complexes with anions of functional α-amino acids has been pre­pared: [M(CO) 3 (L-histidinate)] - (M = Cr. Mo, W), M(CO) 3 (L-histidinate) (M = Mn, Re), [Re(CO) 3 (NO)(L-histidinate)] + PF 6 - ,M(CO) 2 (η 3 -allyl)(L-histidinate) (M = Mo, W), Mo(CO) 2 (NO)(L-histidinate), [Mo(CO)(NO)(η 3 -methallyl)(L-histidinate)]PF 6 , Mo(CO) 2 (η 3 -methallyl)(L-histidineOMe)Cl, [M(CO) 3 ,(cysteinate)] 2- (M = Mo. W), [Mo(CO) 3 (glyglyO)(H 2 O)] - , [Re(CO) 3 (L-ornithinate)(CH 3 CN)] and [Re(CO) 3 (L-lysinate)]. The IR and NMR data of the new complexes are reported.

The syntheses of the hexaquaternary salts 1,1'-bis-[2-(1′-methyl-[4,4'-bipyridinium]-1-yl)-ethyl]-4,4'-bipyridinium hexaperchlorate and 1,1'-bis-[3-(1'-methyl-[4,4'-bipyridinium]-1-yl)-propyl]-4,4'-bipyridinium hexaperchlorate are reported. The salts are reduced in aqueous solution to triradical trications at a potential (E 0 ) of -0.24 V.

The oxidation of imines containing a α-methylene group by selenium dioxide is investigated. The products are shown to be a-imino carbonyl compounds by spectroscopic methods. The reactivity of various imines is discussed.

2-Pyrryl-(3.5-dimethylphenyI)-carbinol, 2-pyrryl-(3,5-di-t-butyl-phenyl)-carbinol and 2-pyrryl- mcsityl-carbinol are cyclised in acidic medium to the corresponding meso-tetraarylporphyrins. The meso-tetraarylporphyrins are transfered to the iron complexes. The reactions of the iron- porphyrins with OH ⊖ and H 3 CO ⊖ are studied and the products of these reactions are character­ised.

We describe the preparation o f 1,3-Benzodioxole-5,6-dicarboxaldehyde (1d) and 1,3-Benzdioxole- 4,5-dicarboxaldehyde (3h). Under especially mild conditions also the synthesis of 4,7- Dimethoxy-1,3-benzodioxole-5,6-dicarboxaldehyde (4g) can be achieved. Its reaction with Hydroxyacetone leads to quinone 9a, which after methylation can be identified with the dim ethylether of Nepenthone-A .

Excitation of the compounds cis -{Pt[P(n-C 4 H 9 ) 3 ] 2 (4-XC 6 H 4 ) 2 } with radiation o f the wavelengths 287.5 and 312.0 nm resulted in the reductive elimination of the substituted biphenyls 4-XC 6 H 4 -C 6 H 4 X-(4) (X=CF 3 ,CH 3 ,C(CH 3 ) 3 ,OCH 3 ), whereas they are photostable towards irradiation of 253.5 nm. It is demonstrated that the elimination is a regiospecific pericyclic reaction at platinum; no free radicals are involved.

9-Cyanoanthraccne, 9,10-dicyanoanthracene and 3,7,9,10-tctracyanoanthraccne photosensitize the oxidation in acetonitrile of toluene, durene. hexamethylbenzene, 1-methyl- and 2-methvl- naphthalene to the corresponding aldehydes, with low yield of the alcohols and. in the case of hexamethylbenzene, of tetramethylphthalidc. In benzene, only hexamethylbenzene reacts through a different pathway involving singlet oxygen. Comparison with fluorescence quenching data and experiments in the presence of good donors, halides or radical traps, as w-ell as the effect of solvents and of oxygen concentration show that the reaction involves electron transfer from the methylaromatic to the singlet excited state of the sensitizer, followed by proton transfer to CA˙̄ or O 2 ˙̄ yielding benzyl radicals, which react with oxygen or can be trapped.

Synthetic methodologies for the preparation of nitroxyl labeled derivatives of D -(+)-glucose, α -D -(+)-m ethylglycoside, 2-amino-2-deoxy-D -(+)-glucose, and D -(+)-glucuronic acid are presented. The spin labels in these compounds are attached variably at the 1, 2, 3, and 6 positions of the glucose framework. These new compounds, being water soluble and producing marked en­hancement of spin-lattice (T ,) and spin-spin (T2) proton relaxation in deionized water and human plasma have potential utility as contrast altering pharmaceuticals for magnetic resonance imaging and as spin probes in biomolecular research. These spin labeled carbohydrates may demonstrate in vivo biodistribution characteristics reflecting tissue-specific differences in glucose metabolism .

The kinetically stabilized cyclobutadiene 2 undergoes [4+2]-cycloaddition reaction at elevated temperature with the acetylenecarboxylate 3 to yield the regioisomeric dewarbenzenes 5 and 6. They are transformed into the prismanes 7 and 8 by a photochemical intramolecular [2+2]- cycloaddition process. Under thermal conditions (150 °C) this isomerization reaction is reversible (7→5, 8→6).

Secondary and primary aliphatic amines 2 form regioselectively N,N '-substituted 1,1-dimethylethylenediamines by reaction with activated 2,2-dimethylaziridines 1. The kind of activation (X in 1), determines the mode of ring opening: X = sulfonyl gives structure 3, X = acyl or 2,4- dinitrophenyl structure 4.

The design, synthesis and preliminary conformational studies of two polypeptides exhibiting βαβ-type folding topologies are presented. In the design of the model peptides the general concept for the construction of new proteins developed in the preceeding paper was applied. According to this strategy, amphiphilic helices and β-sheets are linked together via hydrophilic loops to attain three-dimensional structures of higher order (‘supersecondary structures’). Com­puter-assisted molecular modelling served as a valuable tool for minimizing conformational con­straints within the molecules. The 38-residue peptide MI was synthesized using polyethylene glycol (PEG) as solubilizing polymeric support (‘Liquid-Phase synthesis'). Conformationally in­duced changes in the physico-chemical properties of the growing peptide chain stressed the significance of conformational effects in peptide synthesis reported earlier. Similar observations were made during the solid-phase synthesis of the 35-peptide MII. CD and IR spectroscopic studies revealed a high degree of secondary structure for both folding units. The present data strongly support the adoption of a three-dimensional structure for both models.

The reactions of δ-bromoketones 1 with amines lead to cyclic enamines 6 or secondary δ-am inoketones 3 depending on the nature of the amine used. Amino substituents which increase the nucleophilicity forces the course of the reaction towards cyclisation to 6 , which in turn yields the corresponding iminium salts 5. This pathway can be suppressed by large substituents leading to the formation of ammonium salts 4.