Volume 48, Issue 9

[TaTe 4 ] 4 [PtI 6 ]I 2 was synthesized from the elements at 680°C. Its crystal structure was determined using single crystal methods. The structure of the quasi one-dimensional compound [TaTe 4 ] 4 [PtI 6 ]I 2 (P1̄, Z = 1, a = 16.831(1), b = 17.740(1), c = 19.018(1)Å, α = 93.57°, β = 94.08°, γ = 102.09°) consists of Ta(Te 2 ) 2 chains separated by PtI 6 groups and I atoms. The formal oxidation state assignment [(Ta 5+ )(Te 2 2- ) 2 ] 4 [(Pt 4+ )(I - ) 6 ](I - ) 2 indicates that semiconducting properties are to be expected for this material.

The reactions of the acids la-4a and 8a with 1,3,5-trimethylhexahydro-1,3,5-triazine furnished compounds 1b-4b and 8b. The IR investigation of 1 b, 4b and 8b revealed P=O ··· H—N interactions. In the unusual reaction of lb with methyl iodide the quaternary ammonium iodide [(H 3 C) 2 P(:O)CH 2 N(CH 3 ) 3 ]+I- 1c was formed. The reaction of 2b with methyl iodide produced the ammonium iodide [(H 3 C) 2 P(:S)CH 2 NH 2 CH 3 ] + I- 2c. The structure of 2c was confirmed by X-ray crystal structure analysis, which showed the expected distorted tetrahedral geometry at phosphorus and revealed N—H ••• I hydrogen bonds. Reaction of 8b with methyl iodide led to the formation of the ammonium iodide 8c by methylation at the nitrogen atom. In the reaction of lb and 2b with HPF 6 the compounds 1 d and 2d were obtained. The compounds 1 d and 2d, due to their instability at room temperature, could be identified only by 1 H and 31 P NMR spectroscopy.

The 10 complex ions of the system [PtF n Cl 6-n ] 2- , n = 0—6, including the three pairs of stereoisomers for n = 2, 3, 4 have been characterized by 195 Pt and 19 F NMR spectroscopy in CD 2 Cl 2 solution. A wide range from 4731 ([PtCl 6 ] 2- ) to 11816 ppm ([PtF 6 ] 2- ) is covered by the clearly separated 195 Pt resonances. The chemical shift δ( 195 Pt) depends nearly linearly on the sum of the electronegativities of the ligands. In accordance with increasing deshielding of the 195 Pt nucleus by increasing coordination with F ligands an averaged major downfield shift of 1181 ppm per substitution of Cl by F is observed, while a minor averaged value of 354 ppm downfield is found for the trans/mer isomers in comparison to the related cis/fac isomers. Coupling with 19 F results in characteristic 195 Pt multiplets, with 1 J(PtF) coupling constants for symmetric F—Pt—F axes of averaged 1890 Hz about 31% larger than 1 J(PtF • ) for asymmetric F • —Pt—Cl′ axes with averaged 1296 Hz. The data reflect the trans influence of the ligands. Highly resolved and expanded 195 Pt spectra reveal clearly separated isotopomer signals with intensities according to the expected statistical ratios given by the natural abundance of 35 Cl and 37 Cl. For [Pt 35 Cl n 37 Cl 6-n ] 2- five distinct signals related to n = 6-2 with 0,18 ppm highfield shift per 37 Cl atom have been reliably assigned. Resolved isotopomer peaks have also been observed for mer-[PtF 3 35 Cl 3 ] 2- /mer-[PtF 3 35 Cl 2 37 Cl] 2- with 0,21 ppm and for [PtF 5 35 Cl] 2 /[PtF 5 37 Cl] 2- with 0,32 ppm highfield shift per 37 Cl atom, respectively. The 19 F resonances of symmetric axes appear at higher field, in the range from —357 to —382 ppm, than those of asymmetric axes, from —266 to —287 ppm. Under high resolution compounds with inequivalent F nuclei show multiplets originating from homonuclear 2 J(FF • ) couplings of about 40 Hz.

Glas forming regions and glass temperatures of the system P 4 S 4 –As 4 S 4 –As 4 Se 4 –P 4 Se 4 have been determined by thermoanalytical and X-ray methods. In the whole system crystalline samples have been obtained by annealing. From the pure phases As 4 S 4 and P 4 Se 4 broad regions of solid solutions extend into the system. In the P 4 S 4 corner the formation of A 4 B 3 (A = P, As; B = S, Se) molecules is observed. As with A 4 B 3 molecules, a stepwise substitution of P by As atoms, and of S by Se atoms is possible. All molecules of the series P 4 _„As„S 4 and As 4 S 4 _„Se„ (n = 0, 1, 2, 3, 4) were detected by 31 P NMR and/or mass spectroscopy.

Crystal and molecular structure analysis of 1,4-diethylquinoxalinium iodide shows a virtually planar quinoxaline ring with 11 conjugated π-electrons. In contrast to the triiodide of the 1,4,6,7-tetramethyl derivative or to the tetraphenylborate salt of 1,4-diethylquinoxalinium cation radical the iodide exhibits π-π-dimerized radical cations in the solid state with synplanar ethyl groups and a rather small intermolecular distance of about 315 pm between the π-planes of the primarily interacting 1,4-diazine rings. Solid state magnetic measurements between 2 and 300 K show considerably diminished magnetic moments due to partial spin-pairing, and UV/VIS spectroscopic measurements in acetonitrile reflect the π—π-interaction in solution through the appearance of a long-wavelength absorption band.

fac-Li 4 [Rh(SO 3 ) 3 (OH 2 ) 3 ](OH) crystallizes in the rhombohedral space group R3-C 3 4 , Z = 1, in trigonal setting a = 807.7(2), c = 1339.0(3) pm, V = 756.6(2)· 10 6 pm 3 , Z = 3. Rh is octahedrally coordinated by three facial S-bonded sulfite groups with Rh—S = 222.6(1) pm and three aqua ligands with Rh—O bonds Rh—O = 217.5(3) pm, elongated by a trans-influence. The average S—O bond length is 148.0(3) pm. All hydrogen atoms have been located. The OH - ion is coordinated exclusively to Li+. The anions are held together by Li + cations in octahedral environment and by hydrogen bonds of medium strength. Alternatively, the structure can be considered to be built of packages of two oxygen nets and a metal layer, stacked in a sequence similar to that in the CdCl 2 -structure.

The pyrolysis of the silacyclobutanes Vi(Me)Si(CH 2 ) 3 (VMS) and Vi 2 Si(CH 2 ) 3 (V2S) at 700-800°C and 10 -1 -l0 -2 mbar leads to the intermediates Vi(Me)Si=CH 2 and Vi 2 Si=CH 2 , which undergo isomerisation to siliranes followed by cleavage to give allene and the corresponding silylenes Me(H)Si: and Vi(H)Si: respectively. Copyrolyses of these silacyclobutanes with dienes (2,3-dimethyl-1,3-butadiene or isoprene) yield silacyclopentene derivatives (4, 14 and 20). The formation of these products supports the proposed mechanism. The simultaneous existence of silaethenes and silylenes in the gas phase is proven by the presence of the disilacyclobutanes 13 and 17, respectively, in the reaction mixtures. Using isoprene as the quenching reagent for Vi(Me)Si=CH 2 the two isomeric silacyclohexenes 15 and 16 are formed in low yield, in addition to almost equal amounts of 13 and 14 (eq. (6)).

Trifluoromethyl-1,3-diphosphane tBu(H)PCF 2 P(H)CF 3 (2) is formed regioselectively in almost quantitative yield by addition of tert-butylphosphane to perfluoro-2-phosphapropene F 3 CP=CF 2 (1) as a 1:1 mixture of two diastereomers 2 a and 2b. 2 reacts with nickel tetracarbonyl to give the binuclear complex [tBu(H)PCF 2 P(H)CF 3 Ni(CO) 2 ] 2 (3) as the only isolable product. The mixture contains four of the eight possible isomers; one of them (3 a) could be isolated in pure form by crystallization from n-pentane solution. Attempts to generate the phosphaalkene tBu(H)PC(F)=PCF 3 or the 1,3-diphosphaallene tBuP=C=PCF 3 by HF elimination from 2 with NEt 3 , HNMe 2 or HNEt 2 lead to complicated mixtures of products. On the other hand, reaction of 3 a with isopropylamine affords the binuclear complex [(CO)Ni(F 3 CP=CFP(H)tBu)Ni(CO) 2 tBu(H)PCFHP(CF 3 )NHiPr] (4) with both a 16 eand an 18 e-nickel(O) fragment and a side-on coordinated F 3 CP=CF group. The new compounds were characterized by spectroscopic investigations, 3 a and 4 by an X-ray diffraction study.

4,6-Dimethoxy-1,3,5-triazine-2-sulfenic acid (1) was prepared by the reaction of 4,6-dimethoxy-1,3,5-triazine-2(1H)-thion (3) with 2-benzenesulfonyl-3-(p-nitrophenyl)-oxaziridine (2) in THF solution and isolated as a stable crystalline solid. The new compound was characterized by analytical and spectroscopic data (IR, 1 H and 13 C NMR, UV, MS) supported by MNDO-PM 3 calculations. UV spectrometry was used for exact determination of the ionization constant of 1(pK a = 5.86 ± 0.02 at 20°C). According to 13 C NMR data and X-ray analysis the sulfenic acid 1 adopts the sulfenyl structure (R—SOH) in the condensed phase. Crystal data of 1 (90 K): a = 8.418(3), b = 21.289(6), c = 4.411(1) Å, Z = 4, P 2 1 2 1 2, R = 0.0304, R w = 0.0354 for 4105 unique reflections and 122 parameters. In the crystal, the molecules form dimers by two strong intermolecular O—H ••• N hydrogen bonds. The 6-membered ring shows alternating C—N bond lengths and is almost planar. The experimental electron deformation density (EDD) decreases in the order C—N > C—O ≈ C—S > S—O and is described in detail for the vicinity of the S atom.

An incident at Chemetall’s pilot plant installation during the distillation of dilute solutions of vinylmagnesium chloride in THF caused us to investigate the thermal stability of this Grignard reagent. The on-set temperature for the exothermic decomposition depends on the concentration of the solution. Experiments under isoperibolic conditions provided further information for the determination of safety rules for work with vinylmagnesium chloride.

Reactions of N-phenyl-S-methyldithiocarbamate (L 1 ) and N,N-dimethyl-S-methyldithio-carbamate (L 2 ) with CuCl 2 , [Cu 2 I 2 (PPh 3 ) 3 ] and HAuCl 4 yield the complexes [CuCl(L 1 ) 3 ] • CH 2 Cl 2 (1), [AuCl(L 1 ) 2 ] (2), [CuI(L 1 )(PPh 3 )] 2 (3) and [Cu 2 I Cu II Cl 4 (L 2 ) 2 ] n (4). Their structures have been determined by single crystal X-ray crystallography. 1 and 2 are monomeric, with Cu(I) tetrahedrally four-coordinate and Au(I) two-coordinate with an S-Au-S angle of 158.2(1)°. 3 is dimeric with a central CuI 2 Cu core, the Cu•••Cu distance of which [314.9(1) pm] is rather large. The mixed valence complex 4 has a chain structure with the identity period Cu II (μ-Cl) 2 Cu I (μ-S) 2 Cu I (μ-Cl) 2 . Cu I is in a tetrahedral, Cu II in a square planar environment. The (μ-S) 2 bridged Cu I ••• Cu I distance is only 259.1(1) pm. The structures of the CuX 2 Cu cores of 3 and 4 are mainly determined by steric interactions of the donor atoms within the coordination spheres of the metal centers.

The reactions of the tridentate ligands (Me 3 Si) 2 NC(4-RC 6 H 4 )NPPh,NSiMe 3 [(1): R=H, (2): R=CF 3 ] with Re 2 O 7 yield the six-membered rings , (4): R=CF 3 ]. The acyclic compound Me 3 SiNC(4-CF 3 C 6 H 4 )NPPh 2 NReO 2 OSiMe 3 (5) has been obtained by reaction of 2 with Me 3 SiOReO 3- 2 reacts quantitatively with TeCl 4 to form the metallacycle . The molecular structures of 4·CH 2 Cl 2 and 6 · pyridine · 0.5 toluene have been determined by X-ray diffraction.

The preparation of CF 3 N(O)H + MF 6 - and CF 3 NH 2 OH + MF 6 - (M = As, Sb) and the crystal structure of CF 3 NH 2 OH + AsF 6 - are reported. CF 3 N(O)H + MF 6 - is prepared by protonation of CF 3 NO in the superacid system HF/MF 5 (M = As, Sb). With an excess of CF 3 NO the cation CF 3 NH 2 OH + MF 6 - is formed. CF 3 NH 2 OH+AsF 6 - crystallizes in the triclinic space group P T with a = 5.071(2), b = 8.297(3), c = 8.882(4) Å, α = 90.93(4)°, β = 95.49(4)°, γ = 102.96(4)° and Z = 2. It is formed by a redox reaction between CF 3 N(O)H+ and excess CF 3 NO.

The anionic phosphine o-(diphenylphosphinomethyl)phenyl L has been used to prepare the sterically crowded cyclic phosphine-boranes BL 3 , tBuBL 2 , and tBu 2 BL by reaction of the lithiated ligand LiL with B(OMe) 3 , tBuB(OMe) 2 , and tBu 2 BOMe, respectively. In the new compounds tBuBL 2 and tBu 2 BL one ligand L is bonded to the boron center by both its carbanionic and its phosphino function with formation of five-membered rings. In solution 11 B and 31 P NMR spectroscopy does not indicate substantial B—P dissociation, i.e., the existence of threecoordinate boron. The steric bulk of L in BL 3 leads to the formation of oligomers in solution, presumably by a bridging coordination mode of L to two boron centers. No conclusive evidence as to the monomeric or oligomeric nature of BL 3 in the solid state can be given, however. Five-membered ring formation is proven for the solid state by X-ray structure determinations of tBuBL 2 and tBu 2 BL which in addition confirm that the steric bulk of L is superior to that of a tert. butyl group.

1-Methoxy-2-methyl-3-aryl-2 H-isoindoles are accessible via an efficient and economical manner starting from 3-aryl-isoindoline-1-ones; the four step synthesis makes use of the ambivalent reactivity of the cyclic carbonamide group. The regiospecific O-methylation and NH-deprotonation is consecuted by the regiospecific N-methylation of the 3-methoxy-1-aryl-1H-isoindoles and the chemoselective CH-deprotonation. The electronic stabilization of these o-quinonoid hetarenes by an aryl group in 3-position is essential for isolation.

Quaternary hexaselenodiphosphates M I M III [P 2 Se 6 ] (MI/MIII = Cu/In, Cu/Cr, Ag/Αl, Ag/In, Ag/V, Ag/Cr) are obtained by reaction of the binary metal halides with Mg 2 [P 2 Se 6 ] followed by cooling from the melt (Tmax = 530°C; cooling rate: 50°C/h): M 1 + M III Cl 3 + Mg 2 [P 2 Se 6 ]⃗⃗ ⃗→ MIMIII[P 2 Se 6 ] + 2 MgCl 2 . This method of preparation was also successfully used for the hitherto unknown quaternary hexaselenodiphosphate CuAl[P 2 Se 6 ]. The crystal structure of CuAl[P 2 Se 6 ] (trig. R 3 (No. 148); a = 627.95(2) pm; c = 1997.13(6) pm; Z = 3) is closely related to that of Fe 2 [P 2 Se 6 ] (trig. R3). Selenium atoms are arranged in hexagonal close packed layers. Cu I , Al III and the P 2 pairs occupy the octahedral sites of every second selenium double layer in such a way that the P 2 pairs are surrounded by Cu 1 and Al III species (random distribution).

Potassium and triethylammonium salts of bis(acetohydroximato)borate and bis(benzohydroximato)borate have been prepared by reaction of boric acid with the corresponding hydroxamic acid and potassium bicarbonate or triethylamine, respectively. The compounds have been characterized by elemental analysis, IR, Raman and NMR spectra ( 1 H and 11 B).

The stability constants of the mixed ligand complexes formed by Cu 2+ , 2,2′-bipyridyl or 1,10-phenanthroline (= Arm), and the dianion of phosphonylmethoxyethane (PME 2- ), ethyl phosphonate (EtP 2- ), methyl phosphonate (MeP 2- ), or D-ribose 5′-monophosphate (RibMP 2 -) (= R–PO 3 2- ) were determined by potentiometric pH titrations in water containing 30 or 50% (v/v) 1,4-dioxane (I = 0.1 M, NaNO 3 ; 25°C). The corresponding results regarding water as solvent were taken from our earlier work. Previous measurements with simple phosphate monoesters, together with the present results for RibMP 2 -, were used to establish log versus straight line plots. With the aid of the equilibrium constants determined for the MeP 2- and EtP 2- systems it is shown that simple phosphonates, i.e., those without an additional binding site, fit also on the same straight lines. Therefore, it could be demonstrated with these reference lines that the Cu(Arm)(PME) complexes in all solvents have a higher stability than expected for a sole phosphonate Cu 2+ coordination. This increased stability is attributed to the formation of 5-membered chelates involving the ether oxygen present in the – CH 2 – O – CH 2 –PO 3 2- residue of PME 2- . The formation degree of the 5-membered chelates in the Cu(Arm)(PME) systems varies only between about 65 and 85% in the three mentioned solvents, despite the fact that the stabilities of the Cu(Arm)(PME) complexes increase by more than 1.8 log units by going from water to 50% dioxane-water. It is concluded that (i) such 5-membered chelates will also be formed in mixed ligand complexes of other metal ions in solvents with a reduced polarity, and (ii), more importantly, that the same interactions will also occur with the parent compound of PME 2 -, i.e. the dianion of 9-(2-phosphonylmethoxyethyl)adenine (PMEA 2 -), a compound which shows antiviral properties and for which the ether oxygen is important.

The preparation of the title compound 4 by electrochemical reduction of 4,4,8,8-tetrachloro-dispiro[2.1.2.1]octane 3 is described. The geometry of the compounds is discussed in terms of quantum chemical calculations and spectroscopic results.

Two dimeric bismethides (10 a, 10 b) with anthracene skeleton are obtained by thermolysis of spiroquinole ethers 8 a and 8b. Both methides represent the thermodynamically stable form in the 9 a/10 a system and yield only traces of the photoreactive furanes 9a and 9 b, resp., on heating.

Based on model experiments it is suggested that the reduction of substrates by nitrogenase occurs at a mononuclear site containing molybdenum, homocitrate and the imidazole component of his-442 of the apoenzyme, generated from the FeMo-co by a reversible dissociation of the Fe 7 S 8 unit from the MoFe 7 S 8 cluster in a redox-linked process.

According to the molecular structure of 2,2-bis(hydroxymethyl)propionic acid (P 3 1 , a = b = 6.051(1), b = 15.118(2) A, V = 479.4 Å 3 ,Z= 3, wR = 0.047) the corresponding carboxylate should be a good anionic oxygen tripod ligand for hard metal ions with a span of the coordinating oxygen atoms of about 2.7 A.

A synthesis of 4-acetoxy-(E)-3-(3-methyl-1,3-butadien-1-yl)-2(1 H)-quinolinone by dehydration of 4-acetoxy-(E)-3-(2-hydroxy-3-methylbuten-1-yl)-2(1 H)-quinolinone is described.

The D-ring expansion of 3 β-hydroxy-5 α-androstan-17-one (epiandrosterone) by the cyanogen azide ring-expansion reaction is described. Epiandrosterone was first converted to 17-methylene-3 β-ydroxy-5 α-androstane by a modification of the Wittig reaction employing methylsulfinyl carbanion-dimethyl sulfoxide. Treatment of the 17-methyleno derivative with cyanogen azide followed by hydrolysis led to 3 β-hydroxy-D-homo-5 α-androstan-17 a-one with migrational selectivity.