Volume 44, Issue 10

[Na-15-crown-5] 2 [ZrF 2 Cl 4 ] has been prepared by the reaction of the amidinato complex [Ph—C(NSiMe 3 ) 2 ZrCl 3 ]2 with sodium fluoride in acetonitrile suspension, as well as by the reaction of ZrCl 4 in acetonitrile, both in the presence of 15-crown-5. On an analogous route (PPh 4 ) 2 [ZrCl 6 ] · 2 CH 2 Cl 2 has been prepared by the reaction of [Ph—C(NSiMe 3 ) 2 ZrCl 3 ] 2 with PPh 4 Cl in CH 2 Cl 2 solution, as well as by the reaction of ZrCl 4 with PPh 4 Cl in CH 2 Cl 2 . The compounds are characterized by their IR spectra and by crystal structure determinations. [Na-15-crown-5] 2 [ZrF 2 Cl 4 ]: Space group Ρ2 1 /a, Z = 4, 6589 observed independent reflexions, R = 0.069. Lattice dimensions at 20°C: a = 1705.0(9), b = 1092.4(6), c = 1906.5(10) pm, β = 113.14(3)°. [Na-15-crown-5] 2 [ZrF 2 Cl 4 ] forms ion triples, in which both sodium ions are sevencoordinate by five oxygen atoms of the crown ether molecules, as well as by a fluorine and a chlorine atom of the cis-[ZrF 2 Cl 4 ] 2- unit. (PPh 4 ) 2 [ZrCl 6 ] · 2 CH 2 Cl 2 : Space group P1̄, Z = 1, 4831 observed independent reflexions, R = 0.041. Lattice dimensions at 20°C: a = 1030.1(5), b = 1124.8(6), c = 1245.6(6) pm, α = 70.81(3), β = 80.61(4), γ = 80.39(4)°. The compound has an ionic structure with ZrCl 6 2- ions of symmetry C i .

The reduction of the tungsten alkyne complexes [WCl 4 (RC≡CR)] 2 (R = Ph, SiMe 3 ) with cobaltocen in THF solutions leads to the complexes [CoCp 2 ] 2 [WCl 4 (RC≡CR)] 2 (R = Ph (1); R = SiMe 3 (2)), as green, oxygen sensitive crystalline powders. Reduction of [WCl 4 (Me 3 SiC=CSiMe 3 )] 2 and of [MoCl 4 (PhC=CPh)] 2 with sodium naphthalide in THF solutions in the presence of 15-crown-5 gives [Na-15-crown-5] 3 [W 2 Cl 9 ], and MoCl 3 (THF) 3 , respectively. All compounds have been characterized by IR spectroscopy, and 1 and 2, in addition, by their EPR spectra. The crystal structure of MoCl 3 (THF) 3 was determined by X-ray methods. Space group P2 1 /c, Z = 4, 2642 observed unique reflexions, R = 0.050. Lattice dimensions at 20 °C: a = 888.4(2), b = 1281.5(3), c = 1535.2(3) pm, β = 92.17(2)°. The compound forms monomeric octahedral molecules with a meridional arrangement of the ligands.

The first pentaorganylcyclopentaphosphane monosulfide (PEt) 5 S (1) has been obtained by the reaction of (PEt) 5 with sulfur under proper conditions, and has been isolated in pure form. According to spectroscopic investigations sulfur is bound exocyclically to the five-membered phosphorus ring. Of the three possible configurational isomers only lb is formed due to steric reasons.

Li[PhS(NSiMe 3 ) 2 ]-0.5 Et 2 O (1) is prepared by treatment of Me 3 SiNSNSiMe 3 with phenyllithium. The lithium salt 1 reacts with UCl 4 , ScCl 3 (THF) 3 and NdCl 3 (THF) 2 to give di-, and trisubstituted complexes containing the chelating [PhS(NSiMe 3 ) 2 ] ligand. [PhS(NSiMe 3 ) 2 ] 2 UCl (2) has been characterized by an X-ray structure determination.

Dimeric (η 6 -hexamethylbenzene)tin(II)bis(tetrachloroaluminate), [(η 6 -C 6 Me 6 )Sn(AlCl 4 ) 2 ] 2 , has been obtained from the reaction of anhydrous SnCl 2 , AlCl 3 , and hexamethylbenzene in the molar ratio of 1:2:1 in benzene as a solvent. The complex, which crystallizes in the triclinic space group PĪ, contains a folded eight-membered ring Al 2 Sn 2 Cl 4 2+ , with the two tin(II) centers linked by two bidentate bridging AICl 4 - counterions. Each tin(II) atom is η 6 -bonded to a hexamethylbenzene ring at a distance of 2.45 Å — the shortest Sn-to-arene distance ever found in the tin(II)/arene system. Each tin(II) atom is further connected to another AICl 4 - anion, also acting as a bidentate ligand, but without contacts to other tin(II) centers. The three crystal benzene molecules show no specific metal contacts.

Reactions of B 2 Cl 4 with 3-hexyne, 2,2-dimethyl-3-butyne, and 2,2,5,5-tetramethyl-3-hexyne lead to the cis-bis(dichloroboryl)alkenes la—c; with bis(trimethylsilyl)acetylene geminai diborylation and Me 3 Si migration occurs to yield (Me 3 Si) 2 C=C(BCl 2 ) 2 (2a). On heating 2a in benzene a Cl/Me exchange with formation of 2b is observed. Me 2 C=C(BCl 2 ) 2 (4a) is obtained from Me 2 C=C(SnMe 3 ) 2 and BCl 3 . In 1a—c, e, 2a, and 4a reaction of one Cl of each BCl 2 group with Me 3 Si—NMe 2 or iPr 2 NH leads to the corresponding bis(chloro-dialkylaminoboryl)ethenes 5c, f—i, 5′a, b, e, 2d, e, and 4b, c, of which 5′a, b, e possess the 1-azonia-2-borata-5-borole structure via an intramolecular donor-acceptor N→B bond. 2,4-Bis(t-butyl)-1,3-bis(dimethylamino)-1,3-dihydro-1,3-diborete (6c) is cleaved with bromine to yield the cis-1,2-diborylethene derivative 5j, as established by an X-ray structure analysis.

With the determination of the crystal structure of (NH 4 ) 2 TeI 6 the list of the descriptions of A 2 TeX 6 structures is further completed. At 293 K three structure types are observed with an antifluorite packing of cations and anions: The cubic K 2 PtCl 6 type structure (space group Fm 3̄ m, Z = 4), the tetragonal Rb 2 TeI 6 type structure (space group P4/mnc, Z = 2), and the monoclinic K 2 TeBr 6 type structure (space group P2 1 /n, Z = 2). The latter type was found for (NH 4 ) 2 TeI 6 with a = 8.0694(7), b = 8.0926(9), c = 11.7498(8) Å and β = 89.605(8)° and refined to a final R w of 0.065. From ionic radii ratios the symmetry of the A 2 MX 6 type structures can be predicted including a prediction of low temperature instability (soft mode condensation). Group-subgroup relationships connect the corresponding space groups and the space groups of the high/low temperature polymorphs.

Solutions of trimethyllead-lithium, [Me 3 Pb]Li (1), in tetrahydrofuran (THF) (-0.5 M) can be obtained from trimethyllead bromide and an excess of lithium at –78°C. 1 H. 13 C and 207 Pb NMR are used for monitoring the formation of the reagent. Extensive decomposition into lead and tetramethyllead is observed at –20°C within minutes. The application of this reagent is demonstrated by the synthesis of trimethyl(trimethylplumbyl)silane (2) and by its stoichiometric 1:1 reaction with BH 3 –THF at –78°C, leading to lithium trimethylplumbyltrihydridoborate [Me 3 PB–BH 3 ]Li (3). The composition of the products in solution follows conclusively from their 1 H, 11 B 13 C, 29 B, 13 C, 29 Si, and 207 Pb NMR data. The silane 2 decomposes slowly at ambient temperature into Me 4 Si, Me 4 Pb and lead. The borate is even less stable, decomposing at temperatures above –30°C mainly into lead, Me 4 Pb, [H 4 B]Li and [Me 4 B]Li.

The electrochemistry of BEDT-TTF + was investigated by means of cyclic voltammetry in solvents most frequently used for the electrocrystallization of radical cations of this donor. It can be shown that the reversibility of redox reactions is decreasing with the scan rate, with a significant influence of solvent. The results presented allow conclusions about the mechanism of electrocrystallization.

Neutron diffraction studies of Li 2 CrCl 4 at 350 °C are presented. The cubic high-temperature polymorph of Li 2 CrCl 4 (space group Fd3̅m, Z = 8, R = 3.26%) crystallizes in an inverse spinel structure (cF56) with large Frenkel disorder of the tetrahedrally coordinated lithium ions. The occupation of the interstitial octahedral 16c sites by lithium ions is 38%, that of the tetrahedral 8a lattice sites only 24%. This large disorder is obviously the reason of the high ionic conductivity of Li 2 CrCl 4 at elevated temperatures. There are some indications of a dynamic Jahn-Teller distortion of the CrCl 6 units.

[(en) 2 Co(H 2 O) 2 ](ClO 4 ) 3 reacts with CuSO 4 ·5H 2 O, K,[PdCl 4 ], or K,[PtCl 4 ] to form the heterometallic complexes [Cu{(OH) 2 Co(en) 2 } 2 ](ClO 4 ) 4 ·2H 2 O (1), [Pd{(OH) 2 Co(en) 2 } 2 ](ClO 4 ) 4 ·2H,O (2), [PdCl 2 {(OH) 2 Co(en) 2 }] 2 [PdCl 4 ] (3) or [PtCl 2 {(OH) 2 Co(en) 2 }] 2 [PtCl 4 ] (4), respectively, containing [(en) 2 Co III (OH) 2 ] + ligands. The central metal(2+) cations in these complexes have a square planar coordination geometry. This has been confirmed by X-ray structure analyses.

1,2,3,4-Tetramethyl-1,4-diboracyclohex-2-ene (1) reacts in THF solution with two equivalents of potassium metal to yield a red solution of the dianion 1 2- . Reactions of 1·2 K with allylnickel bromide dimer, cyclooctadiene-rhodium chloride dimer or bis(ethene)rhodium chloride dimer give the triple-deckers 3, 4, and 5, respectively. The constitution of the diamagnetic (30 VE) triple-deckers is derived from NMR and MS data.

Normal coordinate analyses for all compounds of the two series Cs 2 [PtF„ 35 Cl 6-n ] and Cs 2 [PtF„ 37 Cl 6-n ], n = 0-6, including the geometric isomers for n = 2, 3, 4 have been performed, based on a general valence force field. The excellent agreement of calculated and observed frequencies confirms the assignments of the vibrational spectra. Due to the stronger trans influence of Cl compared to F in all asymmetric F–Pt–Cl axes the Pt–Cl bonds are strengthened and the Pt–F bonds are weakened, as indicated by valence force constants for Pt–Cl approximately 20% higher, for Pt–F 20% lower, compared with the values calculated for symmetric Cl–Pt–Cl and F–Pt–F axes, respectively. The contour of the Raman line ν 2 (E g , O h ) of Cs 2 [PtCl 6 ] is explained by the superposition of the calculated spectra for the six most frequent isotopomers Cs2[Pt 35 Cl n 37 Cl 6-n ] present in mixtures with natural abundance of Cl isotopes (75,53% 35 Cl, 24,47% 37 Cl) by statistical distribution on the octahedron sites.

The mixed chloro-bromo-rhodates(III) [RhCl n Br 6-n ] 3- , n = 1-5, have been separated for the first time by ion exchange chromatography on diethylaminoethyl-cellulose. Due to the stronger trans-effect of Br, as compared with Cl, on treatment of [RhBr 6 ] 3- with conc. HCl nearly pure cis/fac-isomers for n = 2, 3, 4 are formed. The reaction of [RhCl 6 ] 3- with conc. HBr yields mixtures of the cis/trans-isomers for n = 2, 4, which cannot be separated, but mer-[RhCl 3 Br 3 ] 3 is formed stereospecifically. The IR and Raman spectra of all isolated mixed ligand complexes are completely assigned according to point groups O h , D 3d , C 4v , C 3v and C 2v , supported by normal coordinate analyses based on a general valence force field. The good agreement of calculated and observed frequencies confirms the assignments. Due to the stronger trans-influence of Br as compared to Cl, in all asymmetric Cl—Rh—Br axes the Rh—Br bonds are strengthened and the Rh—Cl bonds are weakened, indicated by valence force constants for Rh—Br approximately 14% higher, for Rh—Cl 10% lower, as compared with the values calculated for symmetric Br—Rh—Br and Cl—Rh—Cl axes, respectively.

The new compounds Na 4 HgP 2 , K 4 ZnP 2 and K 4 HgP 2 are isotypic and crystallize in the rhombohedral system, space group R3m, Z = 3, with the lattice constants: Na 4 HgP 2 : a = 500.8(2) pm, c = 2544.7(8) pm, c/a = 5.081; K 4 ZnP 2 : a = 566.4(2) pm, c = 2610.1(8) pm, c/a = 4.608; K 4 HgP 2 : a = 567.1(2) pm, c = 2697.7(8) pm, c/a = 4.757. The crystal structure of the compound K 4 CdP 2 , formerly described in the monoclinic system (space group C2/m), has been revised (R3m, a = 568.1(2) pm, c = 2698.4(8) pm, c/a = 4.750). Linear units [P—T—P] 4- with T = Zn, Cd, Hg, which are isoelectronic to the molecule HgCl 2 , represent the characteristic structure elements. The far infrared spectra are recorded and assigned on the basis of the [P—T—P] 4- anions.

Crystal and molecular structure analysis of N,N′-diethylquinoxalinium tetraphenylborate shows a virtually planar quinoxaline ring with 11 conjugated π electrons and approximately antiperiplanar ethyl groups. In comparison with the benzo-analogous phenazinium systems and the de-benzo derivative N,N′-diethylpyrazinium cation, the quinoxalinium species adopts an intermediate position in terms of intra- and intermolecular structural features. In particular, increasing benzanellation seems to favour a cation/anion approach for electrostatic reasons whereas the N—C bonds to the hyperconjugatively charge delocalizing alkyl groups increase due to peri interactions. Solid state magnetic and ESR measurements are compatible with the crystallographically determined structure.

The melting diagram of the system pyridine-hydrogen chloride was determined by DTA. It reveals the existence of intermediary solid complexes pyridine · xHCl with x = 0.5, 1, 2, 4 and 6. The structures of those with x = 1 (room-temperature phase), 2, 4 and 6 were determined from single-crystal MoKa diffractometer data at low temperatures. Pyridinium and chloride ions and, with the exception of the mono-adduct, hydrogen chloride molecules are hydrogen-bonded into various discrete molecular and complex-ionic structural units. Among these are the first poly-(hydrogen chloride) anions, H n Cl n+1 - or [Cl(HCl) n ] - with n > 1 (viz. n = 2, 4 and 5), characterized by crystal structure analysis.

In order to investigate the coordination ability of quasi square pyramidal complexes, tricarbonyl[η 5:1 -(2-cyclopentadiendiyl)ethyl]molybdenum (1) and -tungsten (2) were reacted photochemically with ethylene (a), propene (b), 1-butene (c), Z-2-butene (d), E-2-butene (e), 2-methyl-propene (f), 2-methyl-2-butene (g), 2,3-dimethyl-2-butene (h), styrene (i), 2,2-dimethylcyclopropene (j), allene (k) and acetylene (I). 1 forms [Μο(η 5:1 -C 5 Η 4 C 2 H 4 )(CO)2(η 2 -olefin)] complexes with a—g, i, and k, 2 the corresponding tungsten complexes with a, g, h, and j as ligands. There is no reaction between 1 or 2 and acetylene. 1g and 2h represent the limits for complexes with sterically demanding olefin ligands and were detected only by IR spectroscopy. Prolongated UV irradiation of 2 and ethylene yields in addition to 2a [W(η 5:1 -C 5 H 4 C 2 H 4 )(CO)(η 2 -C 2 H 4 ) 2 ] (2a′). Hindered olefin rotations around the metal-olefin bonds were detected for 1a—1c, 1e, 1f, 1i, and 2a with barrieres of activation between 50 to 75 kJ · mol -1 .

Diphenylchlorophosphine and diethylchlorophosphite react with acetylacetone to generate intermediate phosphine enolates 3 which are quenched with O-diethylboryl derivatives and then oxidized with hydrogen peroxide to give diphenylphosphinates 4 and diethylphosphates 5.

CNDO/2 and MNDO calculations on pyridine N-oxide (PyO), 4-nitro- (4 NO 2 PyO), 4-methyl-(4 PicO), 4-methoxy- (4 MeOPyO), and 4-N′,N′ -dimethylamine-pyridine N-oxide (4 N′,N′Me 2 PyO) and on their protonated forms have been carried out. Unknown geometries have been obtained by optimization of the MNDO energy. It has been shown that for 4 NO 2 PyO, 4 MeOPyO, and 4 N′,N′Me 2 PyO N-oxide oxygen protonated forms are much more energetically stable than the forms protonated on substituents. The calculated ionization potentials and dipole moments of the compounds studied are in good agreement with the experimental data. Both CNDO/2 and MNDO protonation energies correlate well with the experimental pK a values determined in four different solvents: acetonitrile, propylene carbonate, nitromethane, and water, the slopes being however much less than unity which indicates the important role of the solvation effect. Based on the parameters of the correlations obtained the protolytic and solvation properties of the solvents studied have been discussed.

Bis-aminadducts 9 a/10 a, formed by reaction of piperidine with dimeric naphthoquinones of type 2, cyclize under acidic conditions yielding linear binaphtho[2,3-b;2′,3′-d]furan-5,13;7,12-diquinones 11. The latter are hydrolyzed easily, forming 3,3′-dihydroxylated 2,2′-binaphthoquinones (1) in good yield.

From the root bark of Azadirachta indica A. Juss (neem) two new diterpenes nimbilicin and nimbocidin have been isolated and their structures established through chemical and spectroscopic methods.

The thermal decomposition of the following lichen depsides has been described: lecanoric acid, gyrophoric acid, evernic acid, perlatolic acid, planaic acid, confluentic acid, atranorin, 4-O-de-methylbarbatic acid, and sekikaic acid. Main reaction products are decarboxylated compounds, phenolic units, rearranged depsides, and xanthones. Triethylammonium salts of depside carboxylic acids decompose at reasonably lower temperature than the corresponding free acids.

The preparation and properties of 1-ethyl-2,4,5-triacetylbenzol are discribed. NMR and MS data are given.

Alkylation of tetraisopropylcyclopentadienyllithium (4b) gives a mixture of pentaisopropylcyclopentadiene isomers (1) which on metalation yields 11% pentaisopropylcyclopentadienylsodium (2). The mixture of products obtained on reacting 1,3-di-tert-butylcyclopentadienylsodium (6) with tert-butyliodide can be separated into 80% di-tert-butylcyclopentadiene and 9% 1,3,5-tritert-butylcyclopentadiene (7) by distillation.

4,4-Bis(trifluoromethyl) substituted 1-oxa-3-azabuta-1,3-dienes (1) and alkynes react to give open-chain trifluoromethyl substituted N-propargylic amides (4), 4H-1,3-oxazines (5) and 2-oxazolines (6, 7), respectively. The selectivity of the reaction can be controlled effectively by the reaction conditions used.

A highly water soluble undecagold cluster was prepared using a N-hydroxyethyl-N-acetyl-derivative of 4,4′,4″-phosphinidynetri(benzenemethanamine). Monofunctional clusters were synthesized in high yield by the exchange of ligands with phosphines having one free amino group. The clusters can be used for heavy atom labelling of proteins after introduction of a reactive maleimido group.

A platinum(II) complex with an electroneutral adduct of stannous chloride [Pt(Sn(DPPO)Cl 2 ) 2 Cl 2 ] (DPPO = dimethyl phthalimidomethylphosphine oxide) is synthesized and characterized by infrared and electronic spectra.

The chlorothionitrene complex [Cl 4 Mo(NSCl)] 2 reacts with N,N,N′-tris(trimethylsilyl)benzamidine in THF solution to form the heterocyclic complex [MoCl 2 (NSN) · 2 THF] 2 , which contains the [NSN] 4 -unit. The compound is characterized by IR spectroscopy and by an X-ray structure determination (Space group P2,/c, Z = 2, 1504 observed unique reflexions, R = 0.044. Lattice dimensions at 19°C: a = 1176.0(1), b = 1108.6(4), c = 1227.3(3) pm, β = 118.25(1)°). The compound forms centrosymmetric molecules [(THF) 2 Cl 2 Mo(NSN) 2 MoCl 2 (THF) 2 ], in which the molybdenum atoms are members of a nearly planar Mo(NSN) 2 Mo eight-membered ring with bond lengths MoN 180.2 and 175.2 pm; NS 157.5 and 160.6 pm; the bond angle NSN is 108.3°, corresponding to a NSN 4- unit.

Kinetic evidence is presented which strongly suggests that in the diethyl ether solution the aminolysis of p-nitrophenyl isothiocyanate proceeds via a mechanism involving a 1:1-addition intermediate which undergoes catalyzed prototropic rearrangement to the product (Baker-type mechanism).

The synthesis of mono- and diacetamides starting with o,o′-biphenyldiol is described. From o-hydroxy-biphenyl-o′-oxyacetamide an X-ray structure could be obtained.

The unit cell of [LFe]Br 3 · 4 H 2 O (L = 1,2-bis-(1,4,7-triaza-1-cyclononyl)ethane) is monoclinic, space group P2 1 /c, with a = 9.609(3), b = 17.75(1), c = 14.537(6) Å, β = 104.12(3)°, and Z = 4. The iron center is in a distorted trigonal prismatic environment of six nitrogen atoms.