Band 46, Heft 3

Tricyansulfonium hexafluoroarsenate S(CN) 3 + AsF 6 - is prepared by halide-pseudohalide exchange with SBr 3 + AsF 6 - and AgCN. The cyandimethylsulfonium salts (CH 3 ) 2 SCN + AsF 6 - and SbF 6 - are obtained via reactions of CH 3 SCN with CH 3 OSO+MF 6 - (M = As, Sb) in liquid SO 2 . The compounds are characterized by Raman, IR and NMR spectroscopy.

Bis(triphenyllead) compounds (Ph 3 Pb) 2 A [H 2 A = H 2 Ser (= L-serine), H 2 Tyr (= L-tyrosine), H 2 Phoser (= phosphorylserine)], R 3 PbAcSer (HAcSer = O-acetylserine; R = Ph, Me) and Ph 3 SnAcSer have been prepared from R 3 MOH and the appropriate amino acids. From IR data it is inferred that all compounds are polymeric, and that (Ph 3 Pb) 2 A (A = Ser, Tyr) and Me 3 PbAcSer contain unsymmetrically bridging carboxylate groups and coordinating NH 2 . For (Ph 3 Pb) 2 Phoser a structure with a monodentate carboxylate group and intermolecular coordination of Pb by an NH 2 - and a P=O-group is proposed. The molecules of Ph 3 MAcSer (M = Pb, Sn) containing monodentate carboxylate groups are bridged by acetyl-C=O groups.

(Acetoxymethyl)methylphenylgermane [PhMeGe(H)CH 2 OAc, lc] was synthesized by a five-step synthesis starting from trichloro(chloromethyl)germane [Cl 3 GeCH 2 Cl → PhCl 2 GeCH 2 Cl → PhMeGe(Cl)CH 2 Cl → PhMeGe(OAc)CH 2 OAc → PhMeGe(H)CH 2 OH → PhMeGe(H)CH 2 OAc]. The germane le and its carbon analogue PhMeC(H)CH 2 OAc (la) are thermally stable (solutions in C 6 D 6 ; 160 °C, 48 h), whereas the structurally analogous silane PhMeSi(H)CH 2 OAc (lb) undergoes a rearrangement upon heating (formation of the silane PhMe 2 SiOAc; half-life in C 6 D 6 at 135 °C: 7.7 h). By analogy to the perfume la (hydratropyl acetate) and its silicon analogue lb (sila-hydratropyl acetate), the germane lc (germa-hydra-tropyl acetate) exhibits a sweet-floral odor. Despite of some differences, the olfactoric properties of the C/Si/Ge-analogues la/lb/lc are mainly characterized by analogies.

The 2,3,4,5-tetramethylpyrrolyl phosphanes (pyr) n PCl 3-n (2-4, pyr = C 4 Me 4 N; n = 1-3) are obtained by the reaction of PCl 3 with lithiated 2,3,4,5-tetramethylpyrrole 1, 2 and 3 react with Mg to give the cyclotetraphosphane (pyrP) 4 7 and the diphosphane pyr 2 P—Ppyr 2 8, respectively. Spectroscopic and chemical properties indicate the pyrrolyl ligand to be co-ordinated by a single P—N bond not essentially influenced by π-bonding.

The crystal and molecular structure of Bis(pentafluorophenyl)mercury, Hg(C 6 F 5 ) 2 , was redetermined from diffractometer data yielding greatly improved structural parameters. The geometry at mercury is virtually linear (C—Hg—C 178.8(3)°), with mercury carbon bond lengths of 2.047(6) and 2.052(6) Å.

The new compound TaI 2 Cl 2 is formed from the reaction of TaCl 5 with Tal 5 and Ta powder in sealed Ta containers at 450 °C. The crystal structure contains quasi one-dimensional chains of TaI 4/2 Cl 2 octahedra, sharing opposite edges (orthorhombic, Immm, a = 831.5(5) pm, b = 993.7(4) pm, c = 748.5(4) pm; R = 0.037 for 297 independent intensities). Each chain has two Ta bridging iodine bonds alternating in length along the chain direction yielding short (314.9(2) pm) and long (433.6(3) pm) Ta-Ta distances. The electronic structure indicates a Peierls-type stabilization.

The title compound which was prepared by Dilthey already in 1903 has been investigated by X-ray crystallography. The complex cation has the expected octahedral tris-chelate structure with the ligands in a meridional arrangement. The complex crystallizes as a racemate. The Cl · · · Cl distance in the [HCl 2 ] - anion is 3.145(4) A.

The reactions of C(NMe 2 ) 4 (1) with Mn 2 (CO) 10 or Co 2 (CO) 8 in THF yield [C(NMe 2 ) 3 ][Co(CO) 4 ] (3) and [C(NMe 2 ) 3 ][Mn(CO) 5 ] (4), respectively. The compounds Co(CO) 4 NMe 2 (5) and Mn(CO) 5 NMe 2 (6) could not be found. With CH 2 Cl 2 4 is quantitatively converted into [C(NMe 2 ) 3 ][Mn(CO) 4 Cl 2 ] (7) as shown by IR and 13 C NMR investigations. 3 and 4 were characterized by an X-ray structure determination. 3: Space group Pnma, Z = 4, a = 7.435(2), b = 10.79(2), c = 20.299(5)Å. 4: Space group C2/c, Z = 4, a = 11.378(2), b = 10.165(1), c = 14.533(1) Å; β = 103.37(1)°. The compounds form independent ions with no bonding interactions between cation and anion; the central CN 3 unit of the [C(NMe 2 )3 ]+ cation in 3 and 4 is disordered.

The monocation [Ru(′S 6 ′–CH=CH 2 )] + , [2] + , (′S 6 ′–CH=CH 2 - = 2.3.11.12-dibenzo-1.4.7.10.13.16-hexathiaoctadec-17-ene(1–)) forms under normal conditions by S–C bond cleavage in an irreversible and selective reaction on treating salts of the dication [Ru(bzo 2 -18S6)] 2+ , [1] 2+ , (bzo 2 -18S6 = 2.3.11.12-dibenzo-1.4.7.10.13.16-hexathiacyclooctadecane) with one equivalent of base. This reaction demonstrates the drastic S–C activation in coordinated thioethers and should be taken into consideration when cofactors are isolated from metal sulfur enzymes.

NaSi reacts with MoCl 5 and 15-crown-5 in toluene with reduction of Mo(V) to Mo(IV). Work-up in DME yields MoCl 4 (DME)· 15-crown-5 (1). MoCl 4 (DME) (2) is prepared more conveniently from MoCl 5 /DME. 1 and 2 were characterized spectroscopically and by X-ray structure determination. Crystal data: 1, space group P2 1 2 1 2 1 (No. 19), Z = 4, 2765 observed independent reflexions, R = 0.026, cell dimensions (110 K): a = 16.292(4), b = 12.884(3), c = 10.452(2) Å. 2, space group I4̄2d (No. 122), Z = 8, 558 observed independent reflexions, R = 0.037, cell dimensions (292 K): a = b = 9.562(2), c = 23.777(6)Å. The MoCl 4 (DME) molecule of 1 and 2 forms a distorted octahedron. There are four non-coordinating 15-crown-5 molecules present in the unit cell of 1. The UV/VIS spectrum and the magnetic properties of 2 are discussed.

The title compound was obtained on reduction of R 2 S 4 N 3 + Cl - via dismutation. Its crystal structure was determined by X-ray diffraction. (CH 3 -C 6 H 4 ) 2 -S 5 N 4 : The conformation of the SN chain closely resembles that of (SN) x ; however, the bond-distances are in accordance with the assumption of alternating S(II) and S(IV) atoms.

Stereoselective reaction mass spectrometry in the chemical ionization (isobutane) mode has been used to detect the absolute configuration of enantiomerically pure cyclic α-amino acids. Thus, an enantiomerically pure cyclic α-amino acid was allowed to react on a micromole level with both enantiomers of a chiral selector and the mass spectra were detected. The relative abundances of characteristic ions formed by the diastereoselective reaction between the α-amino acid and the chiral selector of the same configuration were much higher than those ions formed by the α-amino acid and the chiral selector of a different configuration. The absolute configuration of the α-amino acid may be predicted by careful examination of the two stereoselective reaction mass spectra of the α-amino acid measured with both, the chiral (R)-and (S)-selector respectively. Various (R)- and (S)-carboxylic acids and (R)- and (S)-α-phenylethyl amine have been used as chiral selectors.

The redox behaviour of aza-substituted naphtho- and anthraquinones, which offer O=C–C=N– chelate tongs for an advantageous five-membered ring metal cation complexation, is investigated by a combination of cyclovoltammetric and ESR/ENDOR spectroscopic measurements. The formation of paramagnetic contact ion pairs like [(quinoline-5,8-semiquinone)· ⊖ Me ⨁ ]·, with Me ⨁ = Li ⨁ , Na ⨁ , Tl ⨁ , or of triple ion radical cations like [(1,4-diazo-9,10-anthrasemiquinone) e Me ⨁ ]· ⨁ , with Me ⨁ = Li⨁, Na ⨁ is corroborated both by shifts of the second reduction potential of up to 0,67 V for e.g. quinoline 5,8-quinone upon addition of Li ⨁ [B(C 6 H 5 ) 4 ] ⊖ to its DMF solution and by the observation of ESR/ENDOR metal couplings.

Highly lipophilic and chromophoric ferrocenylmethyl [Fem] residue is applied to syntheses of peptides hexaglycine and Leu-enkephalin, masking therein all –Gly bonds. Thereby Fem groups influence properties of Fem-peptide derivatives advantageously both in chemosyntheses and cleaning operations, leading to constantly high yields et each step. Despite of its volumous dimension the Fem residue can be introduced into each peptide bond of oligoglycine by succeeding one another of building blocks of H–Fem–Gly–OMe. Strong alkaline conditions during the hydrolyses of methyl esters occurring several times in peptide derivatives do not influence the Gly–Gly-bond at all. Total protected derivatives BOC–(Fem–Gly–) 6 OMe and BOC–Tyr(tBu)–(Fem–Gly–) 2 Phe–Leu–OtBu even are soluble in hexane/ethylacetate (1:1).

Redoxproperties and UV/VIS/NIR-spectra of radical anions and dianions of 3,6-dimethylthieno[3,2-b]thiophen-2,5-dion and 2,5-bis(cyanimino)-2,5-dihydro-thieno[2,3-b]thiophene derivatives are compared.

New synthetic pathways to 3,3,3-trifluoroalanine, 2-deutero-3,3,3-trifluoroalanine, their esters, amides, and thioamides are described, starting from hexafluoroacetone, and trifluoropyruvates, respectively.

Model reactions of the hardening of gelatin with 13 C labeled formaldehyde were monitored by 13 C NMR spectroscopy in solution and in the solid state. In solution primary attack of formaldehyde first forms methylols of lysine residues and later of arginine residues, which react to a lysine-arginine crosslink. During the drying process of hardened gelatin, in addition to the lysine-arginine crosslink an arginine-arginine crosslink is formed. The rate of crosslink formation is strongly influenced by humidity.

An apparent discrepancy between the kinetics reported for the alcoholysis of ketenes is resolved by examining conditions under which third-order kinetic behaviour can be mistaken for secondorder behaviour.

Na 3 PO 4 and Na 2 CO 3 form solid solutions with the high-temperature Na 3 PO 4 structure and a maximum content of nearly 25 mole-% Na 2 CO 3 at 873 K and 15 mole-% at room temperature. The sodium ion conduction is enhanced due to the creation of sodium vacancies. In contrast to pure Na 3 PO 4 there is a second order transition into the highly ionic conducting state. As a result of rotational disorder of the anions the activation energy is lowered.

Single crystals of [(CH 3 ) 4 N]FeF 4 ·H 2 O have been prepared from aqueous HF solution. The crystal structure was determined by X-ray diffraction: space group P1̄, Z = 2 (or 1 dimeric unit), a = 705.7(5), b = 818.5(8), c = 915.2(12) pm, α = 65.46(10)°, β = 82.90(9)°, γ = 72.76(7)°, R/wR = 0.047/0.021. The structure consists of centrosymmetrical dimeric anions [Fe 2 F 8 (H 2 O) 2 ] 2- with fluorine double bridges and is isotypic with [(CH 3 ) 4 N]VOF 3 · H 2 O. Intramolecular H-bonds are found between the axial water and fluoride ligands. By additional strong intermolecular H-bonds (O ··· F 258 pm) the anions are connected to form infinite parallel chains between which the TMA cations are located. [(CH 3 ) 4 N]AlF 4 · H 2 O is shown to be isotypic.

Mono and polyhalogenated dibenzofurans and dibenzo-p-dioxins are electrochemically reduced in a divided cell in technical methanol at a lead cathode.