Volume 53, Issue 8

Treatment of dithiophosphoric acid diesters (RO) 2 P(S)SH with appropriate quantities of tris[(phosphine)gold(I)]oxoniumtetrafluoroborates {[(R′ 3 P)Au] 3 0} + BF4 - in dichloromethane gives di-or trinuclear complexes of the types {(RO) 2 P[SAu(PR 3 )] 2/3 } +/2+ (2) BF4 - as colour­ less, crystalline salts. As determined by single crystal X-ray diffraction studies, in the 1:2 complexes (with R = R′ = Me and R′ = Et, R = Ph and o-Tol), each gold atom is attached to a different sulfur atom, but with short intracationic Au-Au contacts. These cations are associated to form strings through intermolecular Au-Au contacts in the first case (R = Et), but through additional Au-S contacts in the second (R = Ph). For R = o-Tol, the cations are not associated at all owing to steric hindrance. This result is indicative of very small energy differences between the two modes of association. The 1:3 complexes are fluxional in solution and show virtually equivalent R 3 PAU groups in the NMR spectra at 20°C, but at low temperature non-equivalent ligands can be distinguished as shown previously for analogous dithiophosphinate derivatives.

L-Carnitine forms a salt-like 2:1 adduct with L-tartaric acid which crystallizes in the or-thorhombic space group P2 1 2 1 2 1 with Z = 4 formula units in the unit cell. The lattice is composed of an L-tartrate dianion and two crystallographically independent L-carnitinium cations. The two cations show only very minor differences in their conformation. Anions and cations are arranged in separate stacks which are linked via hydrogen bonds. The tartrate anion and the carnitinium cations show standard geometries known from the structures of other salts of these ions, like the L-carnitine component of the R,L-carnitinium chloride or the dianion in alkali tartrates. The title compound has galenic advantages as an L-carnitine drug because of its non-hygroscopic properties. Aqueous solutions have been shown to contain solvated ionic components, i.e. L-tartrate and L-hydrogentartrate anions, L-tartaric acid (15:70:15) and carnitinium cations. The title compound can therefore be classified as a genuine L-carnitinium salt of L-tartaric acid.

Facets of molecular dynamics in organic compounds such as coupled rotations of adjacent substituents are advantageously discussed based on structural data. Within this context, crystal structures of spatially overcrowded ortho-disubstituted benzene derivatives with chloromethyl or methylamino groups are presented together with semiempirical enthalpy hypersurfaces for the substituent rotation. Both compounds, 1 -trichloromethyl-2-dichloromethyl-benzene as well as l-trimethylammonium-2-dimethylamino-benzene exhibit comparable steric overcrowding and their preferred dynamics are predicted to be dominated by the rotation of the threefold substituted group during an approximate standstill of the twofold substituted, mirror-symmetric one. According to known solid state NMR measurements as well as to atom/atom-potential model calculations for the pentachloro ortho-xylene derivative, this molecular dynamic mode is still active in the crystal.

ortho-Benzene derivatives with adjacent bulky propeller substituents are well-suited model compounds to investigate their potentially coupled rotations. To approach the molecular dynamics of 1,2-bis(trimethylsilyl)benzene, a liquid at room temperature and containing heteroelement substituents, an advantageous starting point are the crystal structures of the stereochemically correspondent benzene-1,2-disulfonate dianion salts. For both the rotations of the synperiplanar three-bladed rotor-groups -SO 3 ⊖ and -Si(CH 3 ) 3 , PM3-enthalpy hypersurfaces are presented, which suggest only weak interdentate interaction and, concomitantly, only partly coupled intermolecular substituent rotation dynamics. Additional data from the Cambridge Structural Database for silicon organic compounds fit into the contour lines of the enthalpy surface calculated for 1,2-bis(trimethylsilyl)benzene, and the structure correlation with varying distances Si ···Si between the heteroelement centers can be discussed in more general terms of the substituent propeller blade length vs. thickness ratio.

By reaction of [B 6 H 6 ] 2- with (SCN) 2 in dichloromethane at -80 C° the thiocyanatohexaborate anion is formed and can be isolated by ion exchange chromatography on diethylaminoethyl (DEAE) cellulose. The X-ray structure determination of Cs 2 [B 6 H 5 (SCN)] (orthorhombic, space group Pbca with a = 9.506(5), b = 10.644(5), c = 21.857(5) Å, Z = 8) reveals that the SCN substituent is bonded via the S atom with the B-S distance of 1.885(9) Å and the B-S-C angle of 99.8(5)°. The SCN group is nearly linear (179.9(9)°).

By reaction of [B 6 H 6 H fac ] - with cobaltocene in acetonitrile [(C 5 H 5 )Co(C 5 H 4 )B 6 H 5 H fac ] is formed. Its crystal structure has been determined by single crystal X-ray diffraction analysis (monoclinic, space group P2 1 /n with a = 9.786(2), b = 9.726(2), c = 13.938(2) A, β = 107.2850(3)°, Z = 4). The B 6 octahedron is slightly compressedoin the direction of the B-C bond by about 1%, with B-B bond lengths between 1.69 and 1.87 A. The 11 B NMR spectrum exhibits a 1:4:1 pattern of a monosubstituted B 6 cage. In the IR and Raman spectra characteristic B-H vibrations are observed.

The crystal structures of trans-(Ph 4 P) 2 [OsO 2 (ox) 2 ] (monoclinic, space group P2 1 /n, a = 12.281(2), b = 14.5440(13), c = 13.9810(12) Å, β = 100.000(8)°, Z = 2) and trans- (n-Bu 4 N) 2 [OsO 2 (mal) 2 ] (triclinic, space group P1̄, a = 10.365(4),b = 10.707(3), c - 11.473(5) A, a = 73.00(2), β = 64.44(3), 7 = 82.55(3)°, Z = 1) have been determined by single crystal X-ray diffraction analysis. The IR and Raman spectra of these complexes were measured at room temperature. Based on the molecular parameters of the X-ray determinations normal coordinate analyses have been performed and the vibrations assigned. The valence force constants of [OsO 2 (ox) 2 ] 2- are f d (Os=O) = 6.7, f d (Os-O) = 2.9, f d (C-O) = 5.05, f d (C=O) = 11.2 and f d (C-C) = 4.7 mdyn/Å and of [OsO 2 (mal) 2 ] 2- f d (Os=O) = 6.7, f d (Os-O) = 2.9, f d (C-O) = 4.86, f d (C=O) =11.1 and f d (C-C) = 4.07 mdyn/Å.

By reaction of closo-[B 6 H 5 F] 2- in alkaline solution with excess iodine the monofluoropentaiodo- closo-hexaborate anion [B 6 FI 5 ] 2- is formed in good yield. The crystal structure of (CH 2 Py 2 )[B 6 FI 5 ] has been determined by single crystal X-ray diffraction analysis (orthorhombic, space group Pnma, a = 13.803(2), b = 11.759(2), c = 13.936(2) Å, Z = 4). The B-F-bond length is 1.41 Å, the B-I distances range from 2.13 to 2.17 Å, the B-B distances from 1.69 to 1.76 A. According to the C 4v point symmetry the 11 B NMR spectrum of the anion exhibits three singlets at +3.8,-30.1 and-33.3 ppm with the intensity ratio 1:4:1, the 19 F NMR spectrum one quartet at -247.6 ppm with the coupling constant 1 J ( 19 F, 11 B) = 54 Hz.

1,3,5-Tri(phenylethynyl)benzene 1 obtained by coupling triiodobenzene with phenylacetylene shows an unusual non planar molecular structure.

A new nickel(II) complex with N,N′-tetraethyl-N″-benzoylphosphortriamide (HL = C 6 H 5 C(O)N(H)P(O)(NEt 2 ) 2 ) of composition Ni 4 L 4 (OCH 3 ) 4 ·(HOCH 3 ) 4 (1) has been synthe­ sized. The crystal and molecular structure of 1 has been determined from the X-Ray diffraction data (tetragonal, space group P4̄2 1 c with a = 17.000(2) Å, c = 15.338(3) Å, Z = 2; R = 0.0399 for 1412 unique reflections). The structure is made up of cubane-like tetramers. In the corners of a cube there are 4 atoms of nickel and 4 atoms of oxygen of methoxy groups. The nickel atoms are characterized by a slightly distorted octahedral environment, which consists of three oxygen atoms of methoxy groups, carbonylic and phosphorylic oxygen atoms of the ligand L - , and an oxygen atom of a methanol molecule. The ligands L - coordinate to the metal ion forming a chelate via the oxygen atoms of carbonylic and phosphorylic groups.

The octakis(trimethylsiloxy)calix[4]resorcinarenes, 3 and 4, were synthesized by reaction of 1 and its tetrabromo derivative 2 with hexamethyldisilazane, and were found to exhibit dynamic behaviour in solution. Temperature-dependent NMR investigations confirmed the presence of at least two conformational isomers of 3 in solution. The conformation of 3 in the solid state was determined by an X-ray crystal structure analysis; the calixarene displays a boat conformation. The introduction of the ethoxy group as a spacer into the molecule of 1 was effected via its reaction with ethyl bromoacetate and subsequent reduction with lithium aluminium hydride forming the ethoxy-tethered C-methylcalix[4]resorcinarene 6 in an impure state. Reaction of crude 6 with hexamethyldisilazane furnished the ethoxy-tethered octakis( trimethylsiloxy)calix[4]resorcinarene 7; its hydrolysis led to pure 6.

Keywords The low temperature preparation of the bistrimethylsilylester of carbonic acid is reported. The hydrolysable and thermolabile (Me 3 SiO) 2 CO has been characterized by vibrational and NMR spectroscopic methods. Under inert conditions the (Me 3 SiO) 2 CO is stable at 233 K for several weeks.

The irradiation of [Au(CN) 2 ] - in oxygen-saturated acetonitrile leads to photooxidation of Au(I). In the presence of additional chloride [Au(CN) 2 CL 2 ] - is formed with φ= 0.5 x 10 -4 at λ irr = 254 nm. It is assumed that [Au(CN) 2 ] - in its metal-to-ligand charge transfer state undergoes an excited state electron transfer to oxygen in the primary photochemical step.

Complexes mer-CoH(CO-CR=CR′-O)(PMe 3 ) 3 react with haloalkanes RX (X = Br, I) or with acids HX (X = Cl, Br) under elimination of dihydrogen. In both reactions a change of configu­ration at the metal is brought about by directional steering through the hard/soft (acyl)enolato chelate ligands to form octahedral complexes mer-CoX(CO-CR=CR′-C))(PMe 3 ) 3 or sterically crowded ionic compounds [Co(CO-CR=CR′-O)(PMe 3 ) 4(3) ] + X - (X = ClO 4 ) without opening of the (acyl)enolato chelate ring.

[Co(Bu t 2 PH) 2 I 2 ] (1) reacts with [Ru 3 (CO) 12 ] in refluxing toluene to give a mixture of products including the novel metal clusters [Ru 3 (CO) 6 (μ-H)(μ-I) 2 (μ-PBu t 2 )(Bu t 2 PH)] (2) and [Ru 3 (CO) 7 (μ-H)(μ-I)(μ-PBu t 2 ) 2 ] (3) besides the known complex [Ru 3 (CO) 8 (μ-H) 2 (μ 3 - PBu t )(Bu t 2 PH)] (4). No cluster expansion products could be observed. Thus the cobalt compound acts merely as a phosphine and iodine transfer reagent. The molecular structures of the metal complexes 1 and 2 were determined by single-crystal X-ray structure analyses. 1 crystallizes in the tetragonal space group P4̄2 1 c with a = 13.230(3), b = 13.230(3), c = 14.788(3)Å, V = 2588.4(9)A . 2 crystallizes in the monoclinic space group P2 1 /c with a = 18.161(2), b = 10.292(2), c = 18.381(2)Å, β = 108.73(10)°, V= 3253.7(8)Å 3 .

The crystal structure of the binuclear Cu(II) complex [Cu(mef) 2 DMSO] 2 (mef = deprotonated N-2,3-dimethylphenyl-anthranilic acid; DMSO = dimethylsulfoxide) has been determined by single-crystal X-ray diffractometry. It crystallizes in the triclinic space group P1̄ with Z = 1. IR and electronic spectra of the compound are also discussed briefly.

Tricarbonyl(η 6 -cyclooctatetraene)metal(0) complexes of the group 6 elements were prepared by using the procedures described in the literature with some minor modifications and identi­fied by IR and NMR spectroscopy. Their electrochemical behavior was studied by using cyclic voltammetry in dichloromethane solution containing 0.1 M tetrabutylammonium tetrafiuorob-orate as supporting electrolyte. Their oxidation and reduction potentials were measured and discussed in terms of the frontier energy levels in connection with the UV-Visible electronic ab­ sorption spectral data. In order to elucidate the mechanism of electrooxidation of the complexes, constant potential electrolysis was performed for one representative example, tricarbonyl(η 6 -cyclooctatetraene)chromium(O). The IR monitoring of the reaction showed that it is gradually converted to hexacarbonylchromium(O) upon electrolysis at constant potential.

The 2,3-dihydro-1,3,4,5-tetraalkylimidazol-2-ylidenes 3 (R = Me, iso-Pr) react immediately with pentafluoropyridine to form the 2-tetrafluoropyridylimidazolium salts 4 in good yields. In contrast with the tetramethyl derivative 4a, alkyl fluoride is eliminated from the isopropyl salt 4b to give 1 -isopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazole, which dimerises via hydrogen bridges in the solid state (7). The X-ray structures of 1,3-diisopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazolium chloride (5) and 7 are reported.

The reaction of bis(t-butylamino)dimethylsilane with titanium tetrachloride in dichloromethane solution leads to a mixture of compounds from which the imido complex (H 3 NCMe 3 ) 2 [TiCl 3 (N-CMe 3 )] 2 (1) and by extraction of the residue with acetonitrile the imido complex [TiCl 2 (N-CMe 3 )(H 2 N-CMe 3 )(CH 3 CN)] 2 (2) can be isolated. 1 reacts with acetonitrile to give the ketimido complex [TiCl 3 {NC(Me)N(H)CMe 3 }(CH 3 CN) 2 ] (3). According to crystal structure determinations 2 consists of centrosymmetric dimeric molecules containing TiCl 2 Ti bridges, the N-CMe 3 2- ligands being in equatorial positions with TiN bond lengths of 168.8(4) pm which corresponds to double bonds. In the monomeric complex 3 the chloro ligands are in meridional positions of the distorted octahedrally coordinated titanium atom with a TiN bond length of 175.7(2) pm of the ketimido ligand.

Reaction of the complex [CpRe(NO)(CO) 2 ]BF 4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(i-Pr) 3 }(CO)]BF 4 . The corresponding triphenylphosphite complex [CpRe(NO){P(OPh) 3 }(CO)]BF 4 may be obtained by oxidative CO removal. Reduction of the remaining CO ligand with NaBH 4 furnishes the corresponding methyl com­plexes [CpRe(NO)(L)(CH 3 )]. The structure of [CpRe(NO){P(i-Pr) 3 }(CH 3 )] was determined: triclinic space group P1̄ (No. 2), a = 8.442(4), b = 9.582(5), c -11.820(8) Å, α= 81.81 (4), β = 87.18(4), γ = 63.87(5)°, Z = 2. Reaction of the methyl complexes with HBF 4 in the presence of thiols gives, after chromatographic workup, the thiolate derivatives [CpRe(NO)(L)(SR)] (L = CO, P(OPh) 3 , P(i-Pr) 3 , R = CH 2 Ph, CH 2 (4-C 6 H 4 Cl), CH 2 (4-C 6 H 4 OMe), CH 3 , C 2 H 5 ). The structure of [CpRe(NO){P(i-Pr) 3 }(SCH 3 )] was determined: monoclinic space group P2 1 (No. 3), a = 7.0515(7), b = 17.3469(10), c = 7.9727(7) Å, β = 114.021(7)°, Z = 2. In both structures, a significant opening of the angle N-Re-X (X = C, S) suggests that antibonding interactions between orbitals of the ligand X and the second-highest MO of the [CpRe(NO)(L)] complex fragment are avoided.

Starting from HoSe 2-x powder and holmium metal bright brownish-yellow, plate-like single crystals of Ho 2 Se 3 could be prepared by chemical transport with AlCl 3 . Holmium sesquiselenide crystallizes in the Sc 2 S 3 -type structure, space group Fddd, with lattice constants a = 1140,7(2), b -812,6(1) and c = 2423,9(3) pm.

The stability constants of the 1:1 complexes formed between Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ or Cd 2+ (= M 2+ ) and 5,6-dichloro-l-(β-ᴅ-ribofuranosyl)benzim idazole (DRB) were determined by potentiom etric pH titrations in aqueous solution (25 °C; I = 0.5м, NaNO 3 ). The acidity constant of H(DRB) + , the proton being at N3, was measured by the same method and the result was confirmed via spectrophotometry. Based on previously established [L. E. Kapinos, B. Song, H. Sigel, Inorg. Chim . Acta 280, in press (1998)] log м мʟ versus K ʜ ʜʟ straight-line plots for complexes of imidazole-type ligands it is shown for the Mn(DRB) 2+ and Zn (DRB) 2+ complexes, as examples, that the benzene ring of the benzim idazole residue exerts a steric inhibition for metal ion binding at N3; i.e., the data points for the M(DRB) 2+ complexes fall clearly below the straight lines defined by the imidazole- type ligands.

6-Formyl-7-hydroxy-5-methoxy-2-pentamethylenechromanone (2) was prepared from the naturally occurring “Visnagin” and condensed with benzil, o-phenylenediamine and 3,4-diaminobenzophenone to give the corresponding imidazolylchromanone derivatives 3-5. Knoevenagel reaction of compound 2 with different active methylene compounds afforded benzodipyranone derivatives 12a - c which may be considered as analogues to the naturally occurring “Xanthyletin and Graveolone Compounds”. The structural formula of the new compounds were established by using different methods for their preparation in addition to the instrumental analyses. Some compounds in this study were biologically evaluated for their ability to bind to DNA.

Sulfonium salts [R 2 S-CH 2 -OTf] + OTf - 1a,b are synthetically versatile 1,1-biselectrophiles featuring the sulfonio- and triflato-substituents as leaving groups of differential nucleofugic power. Reactions with a number of neutral nucleophiles |Nu yield a series of novel sulfoniom ethylated onium salts [R 2 S-CH 2 -Nu] 2+ 2OTf - 2 - 8 under very mild conditions. Structures of salts 2a, 5a and 6b were confirm ed by X -ray analysis. With certain N -hetarenes exchange of both nucleofuges in la was achieved, yielding the symmetrical 1,1-bisonium salts 9 and 10. With pyridine(derivatives) selective substitution of the sulfoniofunction in 1,1-bisonium systems 2a and 5a was also realized. These reactions represent typical examples of nucleophilic substitutions at geminally bisonio substituted Csp 3 centers, which we recently have introduced as a novel variant of S ɴ 2 reactivity.

The preparation, crystal structures and optical absorption spectra of [H 3 N(CH 2 ) 6 NH 3 ]BiX 5 (X= I, Cl) and [H 3 N(CH 2 ) 6 NH 3 ]SbX 5 (X =I, Br) are reported. The anions of the compounds consist of MX 6 -octahedra (M =Bi, Sb) sharing cisvertices in one-dimensional zig-zag chains. Because of their one-dimensional character, a blue shift of the excitonic absorption bands, in com parison to those of higher dim ensionality systems (MX 3 ), is observed.