Volume 45, Issue 12

The new molecules P 3 SbS 3 , P 4 S 2 Te und P 4 STe 2 were extracted with CS 2 from mixtures of S. Sb and P 4 S 3 , and P, S and Te samples respectively, which were previously molten and then annealed for several days. In the P 3 SbS 3 molecules the apical phosphorus position of P 4 S 3 is substituted by antimony. In the molecules P 4 STe 2 and P 4 S 2 Te one or two of the sulphur bridges are substituted by tellurium. X-ray and 31 P NMR data of the compounds are given.

MoOCl 4 reacts with two equivalents of tellurium in a sealed evacuated ampoule at 250 C to give Te 4 2+ (MoOCl 4 ) 2 2- in quantitative yield. Te 4 (MoOCl 4 ) 2 forms black crystals which rapidly decompose in moist air. The crystal structure determination (lattice constants a = 1192.9(3), b = 683.7(2), c= 1049.8(2) pm, β = 90.08(2) , Ζ = 2, monoclinic space group P2 1 /n, 1907 unique reflections for 73 parameters, final R = 0.013) shows, that Te 4 (MoOCl 4 ) 2 consists of nearly ideal square Te 4 2+ cations with Te–Te distances of 269.1 and 269.9 pm and dimeric (MoOCl 4 ) 2 2- anions, in which Mo atoms are linked by asymmetric chloro bridges (Mo–Cl = 278.3 and 241.0 pm). The oxygen ligand (Mo–O = 164.7 pm) is located in the trans position to the longer Mo–Cl bond. Close contacts as short as 315.8 pm between chlorine and oxygen to the cation show considerable anion-cation charge-transfer interaction.

Methanestibonic acid is obtained by hydrolysis of tetraalkoxymethylstiborane or by oxidation of dimethoxymethylstibine with H 2 O, in a mixture of methylenchloride and alcohol at 0 °C as a white amorphous powder. Reaction of the acid with 2,3-dimethyl-butane-2,3-diol yields MeSb[OC(Me),C(Me) 2 O] 2 , and with sodium hydroxide a sodium salt Na 2 [MeSb(OH) 3 O] 2 · 6 H 2 O is obtained.

The complexes ′C 4 H 9 N = V(O′C 4 H 9 ) 3-n [SSi(O′C 4 H 9 ) 3 ] n , O = V(O′C 4 H 9 ) 3-n [SSi(O′C 4 H 9 ) 3 ] n , O=V[SSi(O′C 4 H 9 ) 3 ] 2 (9) and VCl[SSi(O′C 4 H 9 ) 3 ] 2 have been prepared by reaction of chlorovanadium compounds with LiSSi(O′C 4 H 9 ) 3 . All complexes are characterized by NMR ( 1 H, 51 V) and ESR spectroscopy. 9 has been found by X-ray diffraction analysis to be a distorted trigonal bipyramidal complex with bidentate thiolate ligands.

The preparation and spectroscopic characterization of the sulfonium salts (CH 3 ) 2 SSCN + AsF 6 -, (CH 3 ) 2 SSeCN + AsF 6 - and (CH 3 ) 2 SNCO + AsF 6 - is reported. The compounds are obtained via halide-pseudohalide exchange reactions with (CH 3 ) 2 SBr + AsF 6 - and the corresponding silver pseudohalide. In addition the crystal structure of (CH 3 ) 2 SSCN+AsF 6 - was determined. The salt crystallizes in the orthorhombic space group Pbca with a = 1048.4(9) pm, b = 1290.2(6) pm, c = 1405.1(12) pm and Z = 8.

The electrochemical oxidation of nickel in pyrimidine-2-thione (pymt H) solution yields a compound of formula [Ni(pymt)2]. When pyridine (py), 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) are added to the solution phase, the product obtained is a complex [Ni(pymt) 2 py 2 ] or [Ni(pymt) 2 L] (L = bipy or phen). The crystal structure of [Ni(pymt) 2 bipy] · H 2 O is monoclinic, space group P 2 1 /c, with a = 726.6(2), b = 1586.2(2), c = 1696.7(4) pm, β = 99.04(4)° and Z = 4. The nickel atom has highly distorted octahedral coordination and the pyrimidine-2-thiolato ligand is bidentate, forming two four-membered chelate rings with a small “bite” angle of ca. 68°. The two sulphur atoms are in a trans arrangement. The vibrational and electronic spectra of the compounds are discussed.

The preparation of the stable compounds [(CH 3 ) 2 SSCl] + SbF 6 - and [(CH 3 ) 2 ,SSSCl] + SbF 6 - from [(CH 3 ) 2 SH] + SbF 6 - and SCl 2 and S 2 Cl 2 , resp., is reported. The isomer [(CH 3 )(Cl)S–SCH 3 ] + SbCl 6 - is prepared from [SCl 3 ]+SbCl 6 - and CH 3 SH in the molar ratio 1:2. For this salt a crystal structure analysis was carried out (Space group P2 1 2 1 2 1 , Z = 4, a = 750.1(4), b = 1133.7(3), c = 1614.8(3) pm).

Methanolothermal reaction of Cs 2 CO 3 with SnSe, in the presence of SnSe at 160 C and 13 bar yields the selenostannates(IV) Cs 4 Sn 2 Se 6 and Cs,Sn 3 Se 7 . The structure of the latter phase was established by X-ray structural analysis. The crystal structure contains polyselenostannate(IV) sheet anions [Sn 3 Se 7 2- ]∞ 2 , for which the basic elements are trigonal SnSe 5 -bipyramids. Six of the seven independent selenium atoms in the asymmetric unit are coordinated by two tin atoms, one by three atoms. Neighbouring anion sheets are so placed that channels are formed which contain two independent cesium cations; these display coordination numbers of, respectively, eight and seven.

Ni(cdt)** reacts with two equivalents of the sterically highly demanding 1,4-diazadiene 2,6- i Pr 2 C 6 H 3 N =CH –CH =NC 6 H 3 -2,6- i Pr, to yield the red-brown, crystalline title compound Ni(2,6- i Pr 2 Ph-dad) 2 (3). The existence of this compound was previously uncertain. 1 H and 13 C NMR, MS, and UV/VIS spectra of 3 are reported. The X-ray structure analysis of 3 revealed a strongly distorted tetrahedral coordination of the nickel center with a dihedral angle of 51 between the planes of the chelate rings and mean bond lengths Ni-Ν 1.965(4) Å and N=CH 1.308(5) Å. The poorly soluble compound appears to be rather unreactive because of the bulk of the ligands.

trans-[Ru(SO 3 H) 2 (NH 3 ) 4 ], monoclinic, space group P2 1 /n, Z =2, a = 619.4(3), b = 701.8(3), c = 1068.6(6) pm, β = 96.32(3)°. In the centrosymmetric octahedral complex the two independent Ru–N bonds are equal within experimental error (average Ru–N 214.0 pm). The rather short Ru–S bonds (227.6 pm) indicate a very weak trans-influence of the – SO 3 H ligand. Caused by the protonation, one of the S–O bonds in the –SO 3 H ligand is long (161.4 pm), the other two are short (mean 148.0 pm). The complex units are linked by pairs of O-H ··· O hydrogen bonds (268.9 pm) to form rods parallel b (symmetry (b) · T), which in turn are held together by N–H ··· O bonds in a pseudo-hexagonal array. A packing coefficient of 0.76 is estimated.

Reaction of Copper(I) halides CuX (X = Cl, Br, I) in methanol with bis(diphenylphosphino)amine (dppa, 1) yields complexes [Cu 3 X 2 (dppa) 3 ]X (X = Cl, Br, I: 2a–c). The derivates [Cu 3 X 2 (dppa) 3 ]PF 6 (2a′–c′) have been synthesized by metatheses of 2a–c with NH 4 PF 6 . The IR, Raman, 31 P{ 1 H} NMR, 1 H{ 31 Ρ} NMR, 13 C{ 1 H} NMR spectra, and FD mass spectra as well as the conductivity data are reported and discussed together with the X-ray crystal structure of 2a · 5 CH 3 OH. The structure consists of the trinuclear cations [Cu 3 Cl 2 (dppa) 3 ] + , distorted tetrahedral anions [Cl( · · · HOCH 3 ) 4 ] - and molecules of methanol of crystallization, hydrogen bridged to the solvated anions. The Cu 3 Cl 2 core of the cations corresponds closely to a trigonal bipyramid with the copper atoms in the equatorial and the chlorine atoms in the axial positions. The colourless prisms of 2a · 5 CH 3 OH crystallize in the triclinic space group P1̅, with the lattice constants a = 1368.0(4); b = 1486.7(4); c = 2036.8(10) pm; α = 74.52(3); β = 74.73(3); γ = 82.26(2)°. Raman and 31 P{ 1 H} NMR data of the complexes [Cu(X)dppm] 4 (dppm = (C 6 H 5 ) 2 PCH 2 P(C 6 H 5 ) 2 ; X = Br, I) described earlier suggest that these compounds should also be formulated as [Cu 3 X 2 (dppm) 3 ]X (4b, c). The Raman spectra of the cations of 2a–c, 2a′–c′ and 4a–c show bands at 165 (X = Cl), 145 (X = Br) and 125 (X = I) cm -1 , which can be assigned to the symmetric (XCu 3 X) stretching mode of the XCu 3 X unit.

1 → 6-, 1 → 3- and 1 → 1-linked α-D-ribopyranosyl disaccharides 2a, 2b, and 5, respectively are prepared with ≥95% stereoselectivities by reacting 3-O-acetyl-2,4-O-phenylboranediylβ-D-ribopyranosyl bromide (1) with the sodium organooxytriethylborates of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, 1,2 : 5,6-di-O-isopropylidene-α-D-glucofuranose and with hexabutyl-distannoxane, respectively. After deboronation and deacetylation 3a, 3b, and 6 are obtained and these are acetylated to give 4a, 4b, and 7.

Several pyrano[2,3-c]pyrazoles were synthesized through a convenient one-pot method in excellent yields. Structure and reaction pathways are also reported and supported by another synthetic route.

1,4-Disilabutane H 3 SiCH 2 CH 2 SiH 3 (1) and n-tetrasilane H 3 SiSiH,SiH 2 SiH 3 were employed as model systems for the preparation of silicon-rich aminosilanes potentially useful for the deposition of silicon nitride Si 3 N 4 . 1 reacts with the appropriate equivalents of diethylamine in an alkane solvent and in the presence of the two-phase catalyst NaNH 2 /18-crown-6 to give the products (Et,N) 2 SiHCH 2 CH 2 SiH 3 , (Et 2 N) 2 SiHCH 2 CH 2 SiH 2 (NEt 2 ), and (Et 2 N) 2 SiHCH 2 CH 2 SiH(NEt 2 ) 2 . By contrast, n-Si 4 H 10 undergoes a cleavage reaction under similar conditions to yield H 3 SiNEt 2 and H 2 Si(NEt 2 ) 2 together with a mixture of polysilanes Si n H 2n+2 , the composition of which is depending on the reaction conditions and the nature of the catalyst (NaH and NaNH 2 ). Diethylaminopolysilanes are also formed, but only in trace quantities. Treatment of n-Si 4 H 10 with pyrrole (C 4 H 5 N) leads to the formation of trisilane accompanied by the pyrrolylsilanes H 2 Si(C 4 H 4 N) 2 , HSi(C 4 H 4 N) 3 , and Si(C 4 H 4 N) 4 . The differences in reactivity suggest excellent leaving group properties of silyl anions in the reaction with amines.

The efficiency of chiral Lewis acids derived from TiCl 4 or Al(Bui) 2 Cl with chiral chelating ligands as catalysts for some enantioselective reactions was evaluated. The Diels-Alder reaction between isoprene and methyl acrylate gave the cyclohexene derivative with up to 32% enantiomeric excess (e. e.). The reaction of 3-methylbutanal with allyltrimethylsilane led to 6-methylhept-1-en-4-ol with up to 36% e. e.

Chiral N-sulfonyl-oxaziridines derived from 8-camphorsulfonic acid and fenchone have been evaluated as asymmetric oxidizing agents for the conversion of sulfides to chiral sulfoxides. There is no correlation between the redox potentials nor the 17 O NMR chemical shifts of the oxaziridines and their relative oxidation rates, nor with the enantiomeric excesses achieved, indicating that steric effects are responsible for their behaviour. The results are consistent with an attack of one sulfur lone pair at the oxaziridine oxygen in such a way that both sulfur lone pairs lie in the plane of the oxaziridine ring. The most efficient oxaziridines, the camphorlactone-sulfonyloxaziridine [(4aS,9 aR)-10,10-dimethyl-6,7-dihydro-4 H-4 a,7-methano-oxazirino[3,2-j]oxepino[3,4-c]isothiazol-9(5H)-one 3,3-dioxide] and the 3-endo-bromocamphorsulfonyloxaziridine [(4aS,8 S,8 aR)-8-bromo-9,9-dimethyl-5,6,7,8-tetrahydro-4 H- 4a,7-methano-oxazirino-2,1-benzisothiazole 3,3-dioxide] allow the preparation of chiral sulfoxides with up to 85% enantiomeric excess.

[3+2] Cycloaddition reactions of 5-azido-4-trifluoromethyl-1,3-azoles with various CC multiple bond systems are described. On reaction of 5-azido-4-trifluoromethylthiazoles 2 with 2,3-dimethylbuta-1,3-diene no [3+2] cycloaddition products could be isolated, 5,6-dihydro-2 H-pyrane 19 was formed exclusively. Photolysis of 1,2,3-triazoles 23, 24, obtained from 2 and electron deficient alkynes, yields imidazo[5,1-b]thiazoles 28. This photoreaction can be interpreted mechanistically as a “Thio-Cornforth-Reaction”.

We want to report on syntheses and test reactions of some ferrocenic compounds which could be used as derivatizing reagents for peptides and proteins in order to detect them electrochemically after an HPLC analysis run. Among the tested compounds we found the 3-ferrocenylpropionic anhydride as the most suitable reagent for this purpose. It is a stable compound which can be prepared with high yields from 3-ferrocenylpropionic acid. Its reaction products with peptides and proteins are highly electroactive which is essential for the sensibility and selectivity of the method.

Cleavage of β-haloalkyl groups can be performed extremely selectively by cobalt(I)phthalocyanine anion under very mild conditions, qualifying it best in the chemistry of highly sensitive β-lactam antibiotics. This is demonstrated in penicillin and cephalosporin semisyntheses.

Thymosine β 11 , a peptide structurally very similar to the known thymosine β 11 , was recently isolated from trout spleen and synthesized by the solid phase method using the p-benzyloxybenzyl alcohol/polystyrene/divinylbenzene resin, N α -Fmoc-amino acids and those with tert-butyl or Boc side chain protection. All couplings are performed with the DCC reagent. The peptide is purified by a combination of gel chromatography and preparative HPLC.

A method for the synthesis of the head group of phospholipids is described. It is formed by ring opening of oxazaphospholanes, either by mild tetrazole mediated hydrolysis of λ 3 -oxazaphospholanes or by methylating ring cleavage of λ 5 -oxazaphospholanes. Oxidation can be performed by means of an oxaziridine.