Synthesis and structural characterization of two cationic dinuclear cymene-ruthenium(II) complexes with thiolato and chloro bridges

Treatment of [(p-cymene)RuCl₂]₂ with HSp-Tol or HSCH₂Ph in the presence of K[PF₆] gave the cationic dinuclear cymene–ruthenium(II) complexes [(p-cymene)₂Ru₂(μ-Cl)(μ-Sp-Tol)₂][PF₆] (1) and [(p-cymene)₂Ru₂(μ-Cl)(μ-SCH₂Ph)₂][PF₆] (2), respectively, which have been characterized by IR, NMR spectroscopies and mass spectrometry along with microanalyses. Their crystal structures were determined by single-crystal X-ray diffraction analyses. The structures of the cationic complexes contain the unusual pseudo-trigonal-bipyramidal Ru₂S₂Cl framework without a ruthenium–ruthenium single bond. The two p-cymene–ruthenium units are held together by two bridging thiolates and one bridging chloride.     

Photochemical substitution of benzene in the iron cyclohexadienyl complex [(η<Superscript>5</Superscript>-C<Subscript>6</Subscript>H<Subscript>7</Subscript>)Fe(η-C<Subscript>6</Subscript>H<Subscript>6</Subscript>)]<Superscript>+</Superscript>

The visible light irradiation of the [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ cation (1) in acetonitrile resulted in the substitution of the benzene ligand to form the labile acetonitrile species [(η⁵-C₆H₇)Fe(MeCN)₃]⁺ (2). The reaction of 1 with Bu^tNC in MeCN produced the stable isonitrile complex [(η⁵-C₆H₇)Fe(Bu^tNC)₃]⁺ (3). The photochemical reaction of cation 1 with pentaphosphaferrocene Cp*Fe(η-cyclo-P₅) afforded the triple-decker cation with the bridging pentaphospholyl ligand, [(η⁵-C₆H₇)Fe(μ-η:η-cyclo-P₅)FeCp*]⁺ (4). The latter complex was also synthesized by the reaction of cation 2 with Cp*Fe(η-cyclo-P₅). The structure of the complex [3]PF₆ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 2007.     

Synthesis and structures of fulvene-bridged diruthenium complexes

Three diruthenium carbonyl complexes, namely (η ³:η ⁵-C₅H₄C(CH₂)₂)Ru₂(CO)₅ (1), (η ³:η ⁵-C₅H₄C(CHCH₂)(C₂H₅))Ru₂(CO)₅ (2), and (η ¹:η ⁵-C₅H₄C₅H₈)Ru₂(CO)₆ (3), were obtained from the reactions of C₅H₄C(Me)₂, C₅H₄C(Et)₂, and C₅H₄C(CH₂)₄, respectively, with Ru₃(CO)₁₂ in refluxing xylene. The complexes were characterized by elemental analysis, IR and ¹H NMR spectra. Single-crystal X-ray diffraction analysis for complexes 1 and 2 revealed that the fulvene ligands bridge two ruthenium atoms in η ³:η ⁵ fashion.     

The First C 3-Symmetric P-Stereogenic Diphosphinomethane Trinuclear Palladium Clusters: Synthesis and Characterization

The enantiomeric ligands (R,R)- and (S,S)-bis(o-anisylphenylphosphino)methane (R,R-14 and S,S-14, respectively) were used to prepare the C ₃-point group clusters [Pd₃(dppm*)₃(CO)(O₂CCF₃)](CF₃CO₂) with dppm* = (R,R)-14 or (S,S)-14. The chiral structure of an enantiomeric clusters (with the chiral R,R-ligand (R,R)-14) was unambiguously demonstrated by both X-ray structure determination and by circular dichroism spectroscopy. This paper is dedicated to Professor C.N.R. Rao.     

Synthesis, Characterization, and Fluxional Behaviour of Binuclear Palladium Complexes with a Half-A-Frame Structure

 Partial removal of chloride anions from the dimer [Pd(η³-2-CH₃*C₃H₄)(μ-Cl)]₂ with AgTf(Tf = CF₃SO₃) followed by addition of dppm affords [Pd₂(η³-Me*C₃H₄)₂(μ-Cl)(μ-dppm)]Tf (1). The substitution of Cl⁻ by X⁻ (X = pz, SC₆F₅, S _py ) using the appropriate salts yields the new derivatives [Pd₂(η³-Me*C₃H₄)₂(μ-X)(μ-dppm)]Tf (2–4). All complexes exhibit a dinuclear half-A-frame structure with two isomers present in solution. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperature ¹H NMR spectroscopy. The molecular structures of 2 and 4 were solved by X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases.     

A convenient synthesis and the mesomorphic properties of new chiral ferroelectric thiobenzoates

A secondary chiral (R)-(?)-2-alcohol underwent the Mitsunobu reaction with triphenylphosphine, diethyl azodicarboxylate and ethyl 4-hydroxybiphenylcarboxylate, resulting in the desired (S)-(+)-product with high enantiomeric purity (>99% ee), with the chiral branched chain attached to the biphenyl. This method is operationally simple and provides the very important chiral precursor in good yields (62% in dry THF and 72% in dry Et₂O). The condensation of the (S)-(+)-acid chloride from this material and a suitable 4-n-alkylthiophenol in toluene in the presence of pyridine or triethylamine furnishes the chiral (S)-(+)-thiobenzoate liquid crystals in good yields (80–83% in pyridine and 65–68% in Et₃N). (S)-(+)-4-(1-Methylheptyloxy)biphenyl 4-alkylthiobenzoates are abbreviated (S)-MHOBSn , where n varies from 4 to 10 and denotes the number of carbon atoms in the alkyl chain. DSC, polarizing microscopy and X-ray diffraction showed that the (S)-MHOBSn series possesses a rich phase polymorphism: two highly ordered tilted phases CrG* and SmI*, as well as the ferroelectric smectic C (SmC*) and chiral nematic (N*) phase. In this series, the seldom observed transition between the chiral phases SmI*–SmC* is seen. All the compounds possess stable enantiotropic SmC* and N* phases. The existence of weak intermolecular hydrogen-bonding in (S)-MHOBSn was confirmed by FTIR spectroscopy.     

Synthesis, Characterization, and Fluxional Behaviour of Binuclear Palladium Complexes with a Half-A-Frame Structure

Summary.  Partial removal of chloride anions from the dimer [Pd(η³-2-CH₃*C₃H₄)(μ-Cl)]₂ with AgTf(Tf = CF₃SO₃) followed by addition of dppm affords [Pd₂(η³-Me*C₃H₄)₂(μ-Cl)(μ-dppm)]Tf (1). The substitution of Cl⁻ by X⁻ (X = pz, SC₆F₅, S _py ) using the appropriate salts yields the new derivatives [Pd₂(η³-Me*C₃H₄)₂(μ-X)(μ-dppm)]Tf (2–4). All complexes exhibit a dinuclear half-A-frame structure with two isomers present in solution. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperature ¹H NMR spectroscopy. The molecular structures of 2 and 4 were solved by X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases. Received June 7, 2000. Accepted June 20, 2000     

Synthesis, Characterization, and Catalytic Activity of Rh(I) Complexes with (S)-BINAPO, an Axially Chiral Inducer Capable of Hemilabile P,O-Heterobidentate Coordination

Summary.  The reaction of dinuclear rhodium(I) derivatives of the formula [Rh(DIOL)X]₂ with the axially chiral phosphinyl phosphane 2-(diphenylphosphinyl)-2′-(diphenylphosphanyl)-1,1′-binaphthalene ((S)-BINAPO, 1) leads to the formation of cationic complexes [(BINAPO)Rh(DIOL)]⁺ where the ligand (S)-BINAPO consistently displays a P,O-chelate coordination which is mantained even in solvents of fair polarity. The mononuclear rhodium(I) complexes (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,5-cyclooctadiene) rhodium tetrafluoroborate (3b) and (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,4-norbornadiene) rhodium tetrafluoroborate (3c) with 1,5-cyclooctadiene (COD) and 2,5-norbornadiene (NBD) as the diolefin were isolated and characterized. Both show a fluxional behaviour in solution which is due to the mobility of the diolefin rather than to a displacement-recombination of the oxygenated arm of the ligand. The mobility of the 1,4-norbornadiene ligand in 3c is extremely pronounced and the coordinated diolefin flexibility could be frozen only at about 200 K. These complexes are active but poorly stereoselective catalysts for the hydrogenation, hydroboration, and hydroformylation of alkenes. Received June 16, 2000. Accepted (revised) July 24, 2000     

Chemiluminescence in the reaction of the RuII trisbipyridyl complex with dimethyldioxirane

The reaction of dimethyldioxirane (1) with the Ru^II trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the rate of its decay increase proportionally with the concentration of Ru^II. The bimolecular rate constant (k ₂) of the reaction of1 with Ru^II was determined. The activation parameters (E _a and logA) for this reaction were calculated from the temperature dependence ofk ₂. The excitation yield of Ru^II* (η _Ru ^* ) was estimated. The quenching of Ru^II* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined. It was suggested that the catalysis of the decomposition of1 and the excitation of Ru^II occurvia a mechanism of chemically initiated electron exchange. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1138–1142, June, 1997.