Volume 42, Issue 3

The reaction of MOCl 4 (C 2 H 5 CN) 2 with (CH 3 ) 3 SiN 3 and subsequent addition of Na[HB(3,5-Me 2 pyz) 3 ] yields the nitrido azido complexes MoN(N 3 ) 2 [HB(3,5-Me 2 pyz) 3 ] and MoN(N 3 )Cl[HB(3,5-Me 2 pyz) 3 ]. The two complexes crystallize from toluene as mixed crystals (space group P2 1 /n, a = 1630.6, b = 878.0, c = 1675.5 pm, β = 112.67°, Z = 4). Crystallographic equivalent positions are occupied in a 4:1 ratio by diazido and monoazido monochloro complexes. The central Mo atom exhibits a sixfold coordination in form of a distorted octahedron with the nitrido ligand and one of the three pyrazol rings in axial positions. The triply bonded nitrido nitrogen atom (Mo≡N 164.2 pm) causes a strong trans effect, resulting in a long Mo-N6 bond (245 pm) to the trans positioned pyrazole nitrogen atom. The Mo-N distances in the equatorial plane are Mo-N2 215 and Mo-N4 216 pm, respectively. The nitrido complexes are remarkably stable against hydrolysis, probably due to steric shielding by the [HB(3,5-Me 2 pyz) 3 ] - ligand. ν(Mo≡N) is observed at 1025 cm -1

Preparation and properties of the title compound 4, [N(CH 3 ) 2 ] 2 PF 2 -(CH 2 ) 2 -PF 2 [N(CH 3 ) 2 ] 2 (2), and [N(CH 3 ) 2 ] 2 + PF-(CH 2 ) 2 - - PF 5 (3), are described. The 1 H, 19 F, 31 P, and 13 C NMR spectra in double and triple resonance mode of 4 are recorded and discussed in detail. A 7 J(HF) long-range coupling could be identified. 300 MHz- 1 H spectra show hindered rotation around the P-N bonds at room temperature

Bis(2-amino-1-ammonioethan)hexasulfide has been synthesized from ethylendiamine, sulfur and hydrogensulfide in ethanolic solution. It consists of unbranched chains S 6 2- (helical all-trans-conformation) and monoprotonated ethylenediamine cations; the latter show the uncommon synclinical conformation. A remarkable system of N - H···S-bridges links the S 6 2- chains to form an infinite array. It crystallizes in the space group P1̄ with a = 9.203(4) Å, b = 9.921(4) Å, c = 15.583(5) Å, α = 93.03(3)°, β = 90.04(3)°, γ = 79.07(3)°

Preparation and crystal structures of the two title compounds are reported. Both of them can be obtained by reaction of K 2 S 5 , sulfur and (crypt-2.2.2) in ethylenediamine (en). [K(crypt-2.2.2)] 2 S 7 · en is monoclinic, S. G. P2 1 /c, with a = 14.347(5) Å, b = 13.148(5) Å, c = 29.42(2) Å, β = 92.84(3)°. [K(crypt-2.2.2)] 2 S 6 is monoclinic, S. G. P2 1 /c, with a = 30.23(2) Å, b = 8.513(5) Å, c = 22.37(2) Å, β = 116.16(2)°. The anionic parts of the lattices consist of unbranched chains S 7 2- and S 6 2- , respectively. The characteristic features of the cations [K(crypt-2.2.2)] + in some polysulfides are briefly discussed

The crystal structure of the monohydroperchlorate of N,N',N"-trimethyl-1,4,7-triazacyclo-nonane, [C 9 H 22 N 3 ](ClO 4 ), has been determined by single crystal X-ray diffraction. The acidic proton of the cation is bonded to one amine nitrogen and it forms hydrogen bonds to the other two N-atoms in agreement with a proposed model, which has been invoked to interpret successive protonation constants of cyclic triamines. The salt [Me 6 [9]aneN 3 ](BF 4 ) 3 has also been prepared

Through carefully controlled treatment of Na 2 B 6 H 6 with halogens in aqueous alkaline solution, or with halogenosuccinimides, mixtures of the halogenohydrohexaborates X n B 6 H 6-n 2- , X = Cl, Br, I, n = 1-6, are formed. In der cases with X = Cl, Br, for n = 2-4 both stereoisomers are generated simultaneously in different amounts, whereas with X = I only the trans/mer compounds are formed. All species including the pure isomers have been separated by ion exchange chromatography on diethylaminoethyl cellulose. The composition has been confirmed by chemical analysis. The colourless crystalline tetrabutylammonium salts are fairly stable at room temperature

The point symmetries of the halogenohydrohexaborates within the nearly complete series X n B 6 H 6-n 2- , X = Cl, Br, I; n = 1-5, are determined from the 11 B and 11 B{ 1 H} NMR spectra, which show characteristic features for homologous isostructural compounds related to the electronegativity of the substituents. The chemical shifts are mainly influenced by -I, +M, and in the case of X = I by the heavy atom effect. Along with a strong antipodal effect a slight vicinal influence between neighbours in the B 6 cage is observed, increasing with the number of substituted atoms

The IR and Raman spectra of 20 different halogenohydrohexaborates, including pairs of geometric isomers of the series X n B 6 H 6-n 2- , X = Cl, Br, I; n = 1-5, have been assigned according to their point groups D 4h , C 4v , C 3v and C 2v determined previously by NMR studies. Due to weak coupling, the vibrations are treated separately to a first approximation in terms of internal B 6 -cage modes on one hand and modes of the substituents against the cage entity on the other hand. Disregarding the splitting by lowered symmetry, depending on the degree of halogenation, all internal modes of the B 6 cluster are observed at nearly unchanged positions in the range of 450-1250 cm -1 . The B 6 -X stretching vibrations, however, exhibit significant shifts to lower energy with increasing mass of substituents

The HCl elimination from β-chloroethyl azide (1-azido-2-chloroethane) over potassium tert. butanolate at 350 K in a low pressure flow system is optimized using PE spectroscopic real-time gas analysis. The highly explosive vinyl azide formed can be purified by cool-trapping the by-products. Its subsequent and virtually hazard-free pyrolysis yields 2H-azirine, which can be isolated at temperatures below 240 K. In contrast, the direct pyrolysis of β-chloroethyl azide requires temperatures above 710 K and results in a simultaneous split-off of both HCl and N 2 , yielding acetonitrile as the main thermolysis product. No intermediates such as β-chloroethanimine or ketenimine are observed, a result which is interpreted in terms of chemical activation

Trifluoromethyl azide decomposes in a low-pressure flow system at rather high temperatures by splitting off N 2 . The nature of the resulting products depends largely on the wall material of the pyrolysis tube: using molybdenum above 1120 K, FCN is observed exclusively. Neither F 2 C=NF nor F 3 C-N=N-CF 3 can be detected as intermediates by comparing their PE spectra with those continuously recorded while increasing the temperature. F 3 C-N = N - CF 3 fragments already at 870 K to give N 2 and F 3 C-CF 3 . The PE spectra of F 3 CN 3 and F 2 C=NF are assigned based on MNDO calculations

The photoelectron spectra of tricyanomethane derivatives X-C(CN) 3 with substituents X = H, CH 3 , Br and C 6 H 5 have been recorded and are assigned based on MNDO calculations as well as on radical cation state comparison with the iso(valence)electronic P(CN) 3 , within the series of cyanomethanes H 4-n C(CN) n , and with each other. For HC(CN) 3 , no traces of the isomeric dicyano, ketimine HN = C=C(CN) 2 are detected in the gas phase. Tricyanomethylbenzene, H 5 C 6 -C(CN) 3 , exhibiting the highest first ionization energy of any known singly acceptor substituted phenyl derivative, demonstrates the tremendous electron withdrawing effect of the -C(CN) 3 group

Reaction of Ph 6 Ge 2 with liquid HCl under pressure leads to di-, tri-and tetrachloro phenyldigermanes. The yield of higher chlorinated products increases with increasing pressure. The analogous reaction of Ph 4 Ge yields Ph 2 GeCl 2 quantitatively. The Ge-Ge bond is most unstable in the case of Ph 3 Ge 2 Cl 3 both chemically and thermally. The crystal structure of Ph 2 Ge 2 Cl 4 has been determined (R = 0.057), Ge-Ge 241.3(1) pm

In the reaction of white phosphorus with sodium in liquid ammonia the hitherto unknown 1,3- diaminotriphosphane(5) (1) is formed besides other products. The composition and the structure of 1, which is only stable in liquid ammonia, have been elucidated by 31 P NMR spectroscopy. Of the three possible diastereomers only the erythro,erythro-isomer 1a with transoid-oriented NH 2 groups is present

Disodium hexadecaphosphide has been prepared as a solvent adduct by reacting white phosphorus with sodium (atomic ratio 3 :1) in boiling tetrahydrofuran or monoglyme in the presence of 18-crown-6

[CuCl 2 (CH 3 CN)] 2 · (μ-S 2 N 2 ) is prepared by the reaction of trithiazyl chloride with CuCl in acetonitrile solution. Thermolysis at 120 °C yields [CuCl 2 ] 2 -(μ-S 2 N 2 ). The complexes are characterized by their IR, EPR, and electronic spectra

The reaction of [Ru(NO) 2 (PPh 3 ) 2 ], [RuCl(NO) 2 (PPh 3 ) 2 ]PF 6 or [RuCl 3 (NO)(PPh 3 ) 2 ] with 1,2- benzenedithiolate(-2), C 6 H 4 S 2 2- , leads to the 16e - -complex [Ru(NO)(S 2 C 6 H 4 ) 2 ] - , which was isolated as the NBu 4 + salt (1). The square pyramidal anion in [NBu 4 )[Ru(NO)(S 2 C 6 H 4 ) 2 ] coordinates PMe 3 with rearrangement of the sulfur ligands to give the six-coordinate cis- [NBu 4 ][Ru(NO)(PMe 3 )(S 2 ChH 4 ) 2 ] (3); the rearrangement of the C 6 H 4 S 2 2- -Iigands from trans to cis coordination is proved by 13 C NMR spectroscopy. [Ru(NO)(S 2 C 6 H 4 ) 2 ] - is rapidly reduced even under mild conditions. Reaction of 1 with NaBH 4 in MeOH leads to the reduction of NO to a nitrido ligand and the concomitant oxidation of (formal) Ru(III) to Ru(VI) yielding [NBu 4 ][Ru(N)(S 2 C 6 H 4 ) 2 ] (2). This compound is also formed when the nitrosyl complex is reacted withSiMe 3 N 3 . [Ru(NO) 2 (PPh 3 ) 2 ] and [RuCl(NO) 2 (PPh 3 ) 2 ]PF are denitrosylated by dttd 2- (dttd 2- = 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane(-2)) to give [Ru(dttd)(PPh 3 ) 2 ]

Chain branched Cimetidine analogous thioethers, promising building blocks for the preparation of H 2 -histaminergic compounds, were synthetized from chiral aminoalkanethiols. Enantiomerically pure amino acids or aminoalcohols were used as starting materials. In one case, a resolution via neutral and acid di-O-(4-toluoyl)tartrates was achieved in good yields and satisfying enantiomeric excess. The absolute configuration of an ethyl branched compound was determined using X-ray diffraction and anomalous dispersion

The synthesis of 5-cyanomethoxy-2-thiouracil (5b) is described. The acid catalysed ethanolysis of 5b leads to 5-ethoxycarbonylmethoxy-2-thiouracil (5a). Condensations of 5-methoxy-2-thiouracil (5) and 5a with the sugar component 7 using the “silyl method” yield peracylated 5-methoxy-2-thiouridine (8) and 5-ethoxycarbonylmethoxy-2-thiouridine (8a), which under treatment with sodium methanolate/methanol afford title 5-methoxy-2-thiouridine (1) (s 2 mo 5 U) and 5-methoxycarbonylmethoxy-2-thiouridine (2) (s 2 mcmo 5 U), respectively

2′,3′-O-Isopropylidene-5-[(N-trifluoroacetyI)methoxycarbonylmethylaminomethyl]uridine (5) and 2′,3′-0-isopropylidene-5-ethoxycarbonylmethoxyuridine (6) have been prepared using as the substrates 2′,3′-O-isopropylidene-5-chloromethyluridine (11) and 2′,3′-O-isopropylidene- 5-hydroxyuridine (8). respectively. The transformation of 5 and 6 into respective 2,5′-anhydro-nucleosides 16 and 10 followed by treatment of 16 and 10 with liquid hydrogen sulphide/pyridine system produces 2′,3′-O-isopropylidene-5-[(N-trifluoroacetyl)methoxycarbonylmethylamino- methyl]-2-thiouridine (17) and 2′,3′-O-isopropylidene-5-ethoxycarbonylmethoxy-2-thiouridine (18). The acid catalysed methanolysis of 6 and 18 yields 5-methoxycarbonylmethoxyuridine (4) and its 2-thioanalogue 4a, while refluxing of 5 and 17 with 50% acetic acid gives 5-[(N-tri-fluoroacetyl)methoxycarbonylmethylaminomethyl]uridine (2) and its 2-thioanalogue 2a

A comparative X-ray structure determination was performed to elucidate possible conformational differences between penicillins and penicillin sulfoxides. Penicillin-G-acetoxy-methylester and its β-oxide were used as model substances, because the only chemical difference between both compounds resides in the thiazolidine ring sulfur oxidation. On the basis of the X-ray data as well as of infrared measurements it is discussed that the drastically reduced biological activity of the penicillin-G-sulfoxide might be related to conformational differences in thiazolidine ring puckering or, even more simply, to the geometric position of the sulfoxide oxygen atom, both of which may hamper the proper reaction of the sulfoxide with its target enzyme(s)

Sodium complexes 3 and 5 of the spin labeled monoazacrown ethers 2,2,15,15-tetramethyl-1-aza- 4,7,10,13-tetraoxacyclopentadecane-1-oxyl (2) and 1,4,7,10-tetraoxa-13-(2′,2′,6′,6′-tetramethyl-piperidine-1′-oxyl-4′-yl)azacyclopentadecane (4) were synthesized and studied by EPR and ENDOR spectroscopies. The hyperfine splitting parameter and the g value of the complex 5, containing the exocyclic nitroxyl moiety, were identical to the parent complexon 4, i.e., a N = 15.6 G. g = 2.0060 ± 0.0001. In contrast, the data for the complex 3, containing the endocyclic nitroxyl moiety were different. Thus, the spectrum of the complex 3 was a triplet of quartets with a N = 15.7 G. a Na = 2.47 G, g = 2.0062 ± 0.0001, whereas the spectrum of the parent complexon 2 was a triplet with a N = 15.5 G, g = 2.0059 ± 0.0001. The interaction between the sodium cation and the nitroxyl moiety in 3 was further confirmed by the sodium ENDOR transition at 7.27 MHz