Stereochemistry of cyclic ether formation—II : Intramolecular cyclisation of secondary aliphatic alcohols to tetrahydrofuran-type ethers

The mechanism and stereochemistry of δ-C atom functionalisation in the reactions of secondary straight-chain aliphatic alcohols with lead tetraacetate, ceric ammonium nitrate, and heavy metal (Pb⁴⁺, Hg²⁺, Ag⁺) salts (AcO)^?1, O^2?, CO₃^2?-halogen (I₂, Br₂, Cl₂) combinations are discussed. By demonstrating the intermediacy of 5-bromo-2-hexanol, it was confirmed that the dark silver oxidebromine induced cyclisation of 2-hexanol (and alcohols in general) involves (as the other hypohalite reactions) intramolecular 1,5-hydrogen abstraction by alkoxy radicals and formation of δ-bromohydrins. A novel and simple procedure for obtaining tetrahydrofurans from alcohols by way of the hypochlorite reaction, using silver or mercuric salts and chlorine, is described.     

Metal Complexes of Biologically Important Ligands,CLXXVII. Dichlorido Platinum(II) and Palladium(II) Complexes with Long Chain Amino Acids and Amino Acid Amides

The synthesis of Cl₂Pt[NH₂(CH₂)_nCOOH]₂ (n = 5, 10) and the reactions of their carboxylic groups with H₂N(CH₂)₁₇CH₃, d ‐glucosamine, and (R,R)‐1,2‐diaminocyclohexane to give complexes with amino acid amides as ligands, are reported. Cl₂Pd(histidine) is coupled with amino alcohols to give Cl₂Pd(histidineamide) complexes.     

Glycosylidene Carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides

The syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pK_HA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH₂Cl₂ at room temperature leads to the glycosides 2–5 in yields between 60 and 34% (Scheme 1 and Table 1). At ?70 to ?60°, yields are markedly higher. In CH₂Cl₂, diastereoselectivities are very low. In THF, at ?70 to ?60°, however, glycosidation of i-PrOH leads to α-D -/β-D - 4 in a ratio of 8:92. More strongly acidic alcohols, such as CF₃CH₂OH, (CF₃)₂ CHOH, and (CF₃)₂C(Me)OH, and the highly fluorinated long-chain alcohols CF₃(CF₂)₅(CH₂)₂OH ( 11 ) and CHF₂(CF₂)₉CH₂OH ( 13 ) react (CH₂Cl₂, r.t.) in yields between 73 and 85% and lead mainly to the β-D -glucosides β-D - 6 to β-D - 8 , β-D - 12 , and β-D - 14 (d.e. 14–68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimetoxyethane, or THF are used, as examined for the glycosidation of (CF₃)₂C(Me)OH, yielding (1,2-dimethoxyethane, 25°) 80% of α-D -/ β-D - 8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF₃)₂C(Me)OH yields up to 55% of the imidate 10 . Glycosidation of di-O-isopropylideneglucose 15 leads to 16 (CH₂Cl₂, r.t.; 65%, α-D / β-D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10 , derived from the attack of (CF₃)₂MeCO^? on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α-D - 9 and β-D - 9 , derived by attack of i-PrO^? on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO? C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO^? in the π plane of the (solvated) oxonium ion.     

Thermal Activation of Molecular Tungsten Halide Clusters with the Retention of an Octahedral Metal Framework and the Catalytic Dehydration of Alcohols to Olefins as a Solid Acid Catalyst

When the molecular tungsten halide cluster (H₃O)₂[(W₆Cl₈)Cl₆]·6H₂O, with an octahedral metal framework, is heated to 50 and 150 °C in flowing helium gas, it changes into (H₃O)₂[(W₆Cl₈)Cl₆] and [(W₆Cl₈)Cl₄(H₂O)₂], respectively. Activation at 250 °C yields a poorly crystallized solid state cluster, [W₆Cl₈]Cl₂Cl_4/2, which exhibits catalytic activity for the dehydration of ethanol to yield ethylene and a small amount of ethyl ether and acetal. The activity is attributed to the Br?nsted acidity of the hydroxo ligand that is produced by elimination of hydrogen chloride from the chloro and aqua ligands. The catalytic activity increases with increasing temperature, and reaches a maximum at 300 °C. The catalytic activity then disappears above 350 °C, at which temperature the crystallinity of the cluster improves and the active sites are included in the crystal. In the case of primary alcohols, the reactivity decreases with increasing length of the carbon chain, and secondary alcohols are more reactive than the corresponding primary alcohols. Halide clusters of niobium, molybdenum, and tantalum having the same metal framework are also active catalysts for these reactions.     

Zirconium borohydride piperazine complex, an efficient, air and thermally stable reducing agent

A zirconium borohydride piperazine complex (Ppyz)Zr(BH₄)₂Cl₂, obtained by the reaction of an ethereal solution of ZrCl₄ and LiBH₄ with piperazine is a stable, selective and efficient reducing agent. (Ppyz)Zr(BH₄)₂Cl₂ reduces aldehydes, ketones, silylethers, α,β-unsaturated carbonyl compounds and esters. The reactions were performed in diethyl ether at room temperature or under reflux, and the yields of the corresponding alcohols were excellent. The selective reduction of aldehydes in the presence of ketones and complete regioselectivity in the reduction of α,β-unsaturated carbonyl groups were observed.     

Water-soluble chiral monosulfonamide-cyclohexane-1,2-diamine-RhCp complex and its application in the asymmetric transfer hydrogenation (ATH) of ketones

Monosulfonamide ligands with heteroatom/heterocyclic systems were derived from trans-(1R,2R)-cyclohexane-1,2-diamine and complexed with [Ru(benzene)Cl₂]₂, [Cp^∗RhCl₂]₂ in situ and used in the ATH of aromatic ketones with aqueous sodium formate as the hydrogen source. The chiral secondary alcohols were obtained with >93% enantioselectivity and >89% yield. Reduction in water was faster than in isopropanol/KOH. Addition of surfactants showed little or no effects.     

Compounds with Cluster Cations together with Cluster Anions [(M6X12)(EtOH)6]2+ besides [(Mo6Cl8)Cl4X2]2– (M = Nb,Ta; X = Cl,Br) – Synthesis and Crystal Structures

Compounds consisting of both cluster cations and cluster anions of the composition [(M₆X₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₄X₂] · n EtOH · m Et₂O (M = Nb, Ta; X = Cl, Br) have been prepared by the reaction of (M₆X₁₂)X₂ · 6 EtOH with (Mo₆Cl₈)Cl₄. IR data are given for three compounds. The structures of [(Nb₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 3 EtOH · 3 Et₂O 1 and [(Ta₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 6 EtOH 2 have been solved in the triclinic space group P1 (No. 2). Crystal data: 1 , a = 10.641(2) Å, b = 13.947(2) Å, c = 15.460(3) Å, α = 65.71(2)°, β = 73.61(2)°, γ = 85.11(2)°, V = 2005.1(8) ų and Z = 1; 2 , a = 11.218(2) Å, b = 12.723(3) Å, c = 14.134(3) Å, α = 108.06(2)°, β = 101.13(2)°, γ = 91.18(2)°, V = 1874.8(7) ų and Z = 1. Both structures are built of octahedral [(M₆Cl₁₂)(EtOH)₆]²⁺ cluster cations and [(Mo₆Cl₈)Cl₆]^2– cluster anions, forming distorted CsCl structure types. The Nb–Nb and Ta–Ta bond lengths of 2.904 Å and 2.872 Å (mean values), respectively, are rather short, indicating weak M–O bonds. All O atoms of coordinated EtOH molecules are involved in H bridges. The Mo–Mo distances of 2.603 Å and 2.609 Å (on average) are characteristic for the [(Mo₆Cl₈)Cl₆]^2– anion, but there is a clear correlation between the number of hydrogen bridges to the terminal Cl and the corresponding Mo–Cl distances.     

Gewellt und eben – La6(C2)‐Oktaederschichten in Lanthancarbidchloriden

Sheets of La₆(C₂) Octahedra in Lanthanum Carbide Chlorides – undulated and plane The reaction of Ln, LnCl₃ (Ln = La, Ce) and C yields the hitherto unknown compounds La₈(C₂)₄Cl₅, Ce₈(C₂)₄Cl₅, La₁₄(C₂)₇Cl₉, La₂₀(C₂)₁₀Cl₁₃, La₂₂(C₂)₁₁Cl₁₄, La₃₆(C₂)₁₈Cl₂₃ and La₂(C₂)Cl. The gold‐ resp. bronze‐coloured metallic compounds are sensitive to moisture. The reaction temperatures are 1030 °C, 1000 °C, 970 °C, 1020 °C, 1020 °C, 1080 °C and 1030 °C in the order of compounds given, which mostly crystallize in the monoclinic space group P2₁/c with a = 7.756(1) Å, b = 16.951(1) Å, c = 6.878(1) Å, β = 104.20(1)° (La₈(C₂)₄Cl₅), a = 7.669(2) Å, b = 16.784(3) Å, c = 6.798(1) Å, β = 104.05(1)° (Ce₈(C₂)₄Cl₅), a = 7.669(2) Å, b = 16.784(3) Å, c = 6.789(1) Å, β = 104.05(3)° (La₂₀(C₂)₁₀Cl₁₃), a = 7.770(2) Å, b = 47.038(9) Å, c = 6.901(1) Å, β = 104.28(3)° (La₂₂(C₂)₁₁Cl₁₄) and a = 7.764(2) Å, b = 77.055(15) Å, c = 6.897(1) Å, β = 104.26(3)° (La₃₆(C₂)₁₈Cl₂₃), respectively. La₁₄(C₂)₇Cl₉‐(II) crystallizes in Pc with a = 7.775(2) Å, b = 29.963(6) Å, c = 6.895(1) Å, β = 104.21(3)° and La₂(C₂)Cl in C2/c with a = 14.770(2) Å, b = 4.187(1) Å, c = 6.802(1) Å, β = 101.50(3)°. The crystal structures are composed of distorted C₂ centered La‐octahedra which are condensed into chains via common edges. Three and four such chains join into ribbons, and these are connected into undulated layers with Cl atoms between them. The variations of the structure principle are analyzed systematically.     

Allylstannation III. Synthesis of homoallylic alcohols and 4-chloro-2,6-dialkyl-3-methyltetrahydropyrans by reactions between (E/Z)-2-butenyldichloro-n-butyltin and aldehydes

2-Butenyldichloro-n-butyltin (in various cis/trans isomer ratios) reacts readily with neat RCHO (R = CH₃, C₂H₅, (CH₃)₂CH, and C₆H₅) at 25°C to give (a) linear alcohols, RCH(OH)CH₂CHCHCH₃ in the E and Z forms, (b) branched alcohols, RCH(OH)CH(CH₃)CHCH₂ in the threo and erythro forms, and (c) 2,3,4,6-tetra-substituted tetrahydropyrans (A) as a mixture of cis/trans isomers arising from the CH(CH₃)CHCl bond. The maximum yields of these tetrahydropyrans were obtained

by the use of 3–3.5 molar ratios RCHO/tin compound in the absence of solvent, whereas work-up after reactions in CH₂Cl₂ gave linear, alcohols as the main products. The formation of linear alcohols appears to be stereospecific, as the ratio of _E/_Z isomers obtained is the same as that in the organotin compound. Tetrahydropyrans are formed preferentially as the _trans isomers.     

The reactions of cyclotriphosphazene with 2-(2-hydroxyethylamino)ethanol. Spectroscopic studies of the derived products

Abstract

The reactions of cyclotriphosphazene (1) with 2-(2-hydroxyethylamino)-ethanol (2) were investigated. 2-(2-hydroxyethylamino)-ethanol (2) is a tri-functional reagent consisting of both aliphatic hydroxyl and the secondary amino groups and its nucleophilic substitution reactions with cylotriphosphazene can lead to different product types; open chain, spiro, ansa, bridged and their mixtures. The reactions with one, two and three equimolar ratios of 2-(2-hydroxyethylamino)-ethanol, in the presence of NaH at 0–10?°C and at room temperature gave the following cyclotriphosphazene derivatives: one mono-spiro, N₃P₃Cl₄[O–(CH₂)₂–NH–(CH₂)₂–O] (3, 1:1, r.t.); its isomer mono-ansa (5, 1:1, r.t.); one dispiro, N₃P₃Cl₂[O–(CH₂)₂–NH–(CH₂)₂–O]₂ (4, 1:1, r.t.); its isomer spiro-ansa (6, 1:2, r.t.); and one single-bridged compound with spiro substituted units, N₃P₃Cl₃[O–(CH₂)₂–NH–(CH₂)₂–O]₃N₃P₃Cl₃ (7, 1:3, at 0–10?°C); as well as single-, N₃P₃Cl₅[O–(CH₂)₂–NH–(CH₂)₂–O]N₃P₃Cl₅ (8, 1:2, r.t.), double-, N₃P₃Cl₄[O–(CH₂)₂–NH–(CH₂)₂–O]₂N₃P₃Cl₄ (9, 1:2, r.t.), and tri-bridged, N₃P₃Cl₃[O–(CH₂)₂–NH–(CH₂)₂–O]₃N₃P₃Cl₃ (10, 1:3, at 0–10?°C) derivatives. Triple-bridged derivative is the major product in this system. The structures of the novel-derived compounds were characterized by TLC-MS, FT-IR, elemental analysis, ¹H, and ³¹P NMR spectral.     

The lewis acidic ruthenium-complex-catalyzed addition of beta-diketones to alcohols and styrenes is in fact Brønsted acid catalyzed

The perchlorate salt of the dicationic bipy–ruthenium complex cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂]²⁺ effectively catalyzes addition of β‐diketones to secondary alcohols and styrenes to yield the α‐alkylated β‐diketones. In a catalytic addition reaction of acetylacetone to 1‐phenylethanol, the κ²‐acetylacetonate complex [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ was isolated after the catalysis; this complex is readily synthesized by reacting cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with acetylacetone. [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ is unreactive toward 1‐phenylethanol in the presence of HClO₄; it also fails to catalyze the addition of acetylacetone to 1‐phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of β‐diketones to the secondary alcohols is in fact catalyzed by the Brønsted acid HClO₄, which is generated by the reaction of cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with the β‐diketone.     

Rh(III), Pd(II), Pt(IV) and Au(III) complexes of 2-thiopyrimidine derivatives

Some news thiopyrimidine derivatives and complexes [4-amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidine (TANH), its 2-methylthio derivative (MTH), the ammonium salt ofTANH (sTANH) and six new complexes of formulas: Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃ Pd(TANH)₂Cl₂ and Au(TAN ^–)Cl] have been synthesized and characterized by elemental analysis, IR and¹H-NMR spectroscopy techniques. The thermal behaviour of all compounds has also been studied.

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Rh(III), Pd(II), Pt(IV) und Au(III) Komplexe von 2-Thiopyrimidin Derivaten

Zusammenfassung Es wurden einige neue Thiopyrimidinderivate und deren Komplexe synthetisiert und mittels Elementaranalyse, IR und¹H-NMR charakterisiert: 4-Amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidin (TANH), dessen 2-Methylthio-Derivat (MTH), das Ammoniumsalz vonTANH (sTANH) und sechs neue Komplexe der Formeln Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃, Pd(TANH)₂Cl₂ und Au(TAN ^–)Cl. Das thermische Verhalten der Verbindungen wurde ebenfalls untersucht.

     

RuS4Cl12 und Ru2S6Cl16, zwei neue Ruthenium(II)‐Komplexe mit SCl2‐Liganden

RuS₄Cl₁₂ and Ru₂S₆Cl₁₆, Two New Ruthenium(II) Complexes with SCl₂ Ligands Ru powder was reacted with SCl₂ in closed silika ampoules at 140 °C. From the black solution three compounds RuS₄Cl₁₂ 1 , Ru₂S₆Cl₁₆ 2 , and Ru₂S₄Cl₁₃ 3 could be crystallized and characterized by x ray analysis. Black crystals of 1 (monoclinic, a = 9.853(1) Å, b = 11.63(1) Å, c = 15.495(1) Å, β = 105.23(1)°, space group P2₁/c, z = 4) are identified as Trichlorsulfonium‐tris(dichlorsulfan)trichloro‐ruthenat(II) SCl₃[RuCl₃(SCl₂)₃]. In the structure the complex anions fac‐[RuCl₃(SCl₂)₃]^– and the cations [SCl₃]⁺ are connected to ion pairs by three chlorine bridges. The brown crystals of 2 (triclinic, a = 7.754(2) Å, b = 7.997(2) Å, c = 10.708(2) Å, α = 103.74(3)°, β = 98.44(3)°, γ = 108.58(3)°, space group P‐1, z = 1) contain the binuclear complex Bis‐μ‐chloro‐dichloro‐hexakis(dichlorsulfan)‐diruthenium(II), (SCl₂)₃ClRu(μ‐Cl)₂RuCl(SCl₂)₃ with two fac‐RuCl₃(SCl₂)₃‐units connected by two chlorine bridges. 3 was identifyed as a known mixed valence Ru(II,III) binuclear complex [Cl₂(SCl₂)Ru(μ‐Cl)₃Ru(SCl₂)₃]. The vibrational spectra and the thermal behaviour of the compounds are discussed.     

1,2-Bis-[(5-methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and their PdCl2 complexes

1,2-Bis-[(5-methyl)-2-1H-benzimidazolyl]- (L ¹), 1,2-bis-[(5-chloro)-2-1H-benzimidazolyl]- (L ²), 1,2-bis-[(5-nitro)-2-1H-benzimidazolyl]-1,2-ethanediol (L ³) and their PdCl₂ complexes were synthesized and characterized by elemental analysis, molar conductivity, i.r. and ¹H-n.m.r. spectra. The benzene ring substituents lead to a decrease in melting point. The methyl group reduces the solubility and the acidity of L ¹ and Pd(L ¹)Cl₂, whereas the Cl and NO₂ groups increase the solubility and the acidity of L ², L ³, Pd(L ²)Cl₂ and Pd(L ³)Cl₂. In Pd(L ¹)Cl₂ and Pd(L ²)Cl₂ complexes, the ligands act as a bidentate through two nitrogen atoms. In Pd(L ³)Cl₂, ligand coordination occurs through one OH group oxygen atom and one of the benzimidazole nitrogen atoms.     

Darstellung,Strukturen und EPR-Spektren der Rhenium(II)-Nitrosylkomplexe [Re(NO)Cl2(PPh3)(OPPh3)(OReO3)], [Re(NO)Cl2(OPPh3)2(OReO3)] und [Re(NO)Cl2(OPPh3)3](ReO4)

Synthesis, Structures, and EPR-Spectra of the Rhenium(II) Nitrosyl Complexes [Re(NO)Cl₂(PPh₃)(OPPh₃)(OReO₃)], [Re(NO)Cl₂(OPPh₃)₂(OReO₃)], and [Re(NO)Cl₂(OPPh₃)₃](ReO₄) The paramagnetic rhenium(II) nitrosyl complexes [Re(NO)Cl₂(PPh₃)(OPPh₃)(OReO₃)], [Re(NO)Cl₂(OPPh₃)₂ · (OReO₃)], and [Re(NO)Cl₂(OPPh₃)₃](ReO₄) are formed during the reaction of [ReOCl₃(PPh₃)₂] with NO gas in CH₂Cl₂/EtOH. These and two other Re^II complexes with 5 d⁵ ”︁low-spin”︁”︁-configuration can be observed during the reaction EPR spectroscopically. Crystal structure analysis shows linear coordinated NO ligands (Re–N–O-angles between 171.9 and 177.3°). Three OPPh₃ ligands are meridionally coordinated in the final product of the reaction, [Re(NO)Cl₂(OPPh₃)₃][ReO₄] (monoclinic, P2₁/c, a = 13.47(1), b = 17.56(1), c = 24.69(2) Å, β = 95.12(4)°, Z = 4). [Re(NO)Cl₂(PPh₃)(OPPh₃)(OReO₃)] (triclinic P 1, a = 10.561(6), b = 11.770(4), c = 18.483(8) Å, α = 77.29(3), β = 73.53(3), γ = 64.70(4)°, Z = 2) and [Re(NO)Cl₂ (OPPh₃)₂(OReO₃)] (monoclinic P2₁/c, a = 10.652(1), b = 31.638(4), c = 11.886(1) Å, β = 115.59(1)°), Z = 4) can be isolated at shorter reaction times besides the complexes [Re(NO)Cl₃(Ph₃P)₂], [Re(NO)Cl₃(Ph₃P) · (Ph₃PO)], and [ReCl₄(Ph₃P)₂].     

The effect of chloroalkane/alcohol solvent composition on the photochemical properties of copper(II) dithiocarbamate mixed-ligand complexes. EPR study

The EPR technics has been used to study the effect of solvent composition on the photochemical conversion of Cu(II) dithiocarbamate mixed-ligand complexes Cu(Et₂dtc)X (X=Cl⁻, Br⁻) and Cu(Et₂dtc)⁺…Y⁻ (Y⁻=ClO₄⁻, NO₃⁻) in chloroalkane/alcohol solutions, where chloroalkane=CCl₄, CHCl₃ or CH₂Cl₂ and alcohol=MeOH, EtOH, i-PrOH or i-BuOH. The obtained results allow to get some insight into the behaviour of the mixed-ligand complexes towards the halogen donation power of chloroalkanes and the co-ordination abilities of alcohols. The paper deals with the nature of the complexes obtained as intermediate products of photolysis.     

Crystal Structure,Magnetic Properties,and Electronic Structure of Ni(NCNH2)4Cl2 and Co(NCNH2)4Cl2

The crystal structures of Ni(NCNH₂)₄Cl₂ and Co(NCNH₂)₄Cl₂, the first complexes with cyanamide as a neutral ligand, have been determined from single crystal data (Im3m, Z = 6, a = 1259.3(2) pm, R₁ = 0.0245 for Ni(NCNH₂)₄Cl₂ and a = 1266.3(2) pm, R₁ = 0.0241 for Co(NCNH₂)₄Cl₂; both 329 intensities and 23 parameters). Ni²⁺ and Co²⁺ are octahedrally coordinated by four equatorial H₂NCN molecules and two axial chloride ions, and the 20 and 19 electron octahedral complexes are connected by a network of hydrogen bonds. The cyanamide ligands are slightly bent (166°), and the two N–C distances are 112 and 133 pm. Ni(NCNH₂)₄Cl₂/Co(NCNH₂)₄Cl₂ are Curie paramagnets with two/three unpaired electrons.     

Die darstellung von [(CH3)3PRu(CO)2Cl2]2 und [(Ch3)3P]2Ru(CO)2Cl2; Eine berichtigung zu: Die alkoholyse des triethylsilans katalysiert von [(Ch3)3P]2Ru(CO)2Cl2

The ruthenium(II) complex used as a catalyst in reactions of alcohols and Et₃SiH proved to be the dimer [(CH₃)₃PRu(CO)₂Cl₂]₂ and not the complex [(CH₃)₃P]₂ Ru(CO)₂Cl₂. Both complexes were prepared, characterized and their catalytic properties were compared.     

Highly Efficient Redox Isomerisation of Allylic Alcohols Catalysed by Pyrazole‐Based Ruthenium(IV) Complexes in Water: Mechanisms of Bifunctional Catalysis in Water

The catalytic activity of ruthenium(IV) ([Ru(η³:η³‐C₁₀H₁₆)Cl₂L]; C₁₀H₁₆=2,7‐dimethylocta‐2,6‐diene‐1,8‐diyl, L=pyrazole, 3‐methylpyrazole, 3,5‐dimethylpyrazole, 3‐methyl‐5‐phenylpyrazole, 2‐(1H‐pyrazol‐3‐yl)phenol or indazole) and ruthenium(II) complexes ([Ru(η⁶‐arene)Cl₂(3,5‐dimethylpyrazole)]; arene=C₆H₆, p‐cymene or C₆Me₆) in the redox isomerisation of allylic alcohols into carbonyl compounds in water is reported. The former show much higher catalytic activity than ruthenium(II) complexes. In particular, a variety of allylic alcohols have been quantitatively isomerised by using [Ru(η³:η³‐C₁₀H₁₆)Cl₂(pyrazole)] as a catalyst; the reactions proceeded faster in water than in THF, and in the absence of base. The isomerisations of monosubstituted alcohols take place rapidly (10–60 min, turn‐over frequency=750–3000 h^?1) and, in some cases, at 35 °C in 60 min. The nature of the aqueous species formed in water by this complex has been analysed by ESI‐MS. To analyse how an aqueous medium can influence the mechanism of the bifunctional catalytic process, DFT calculations (B3LYP) including one or two explicit water molecules and using the polarisable continuum model have been carried out and provide a valuable insight into the role of water on the activity of the bifunctional catalyst. Several mechanisms have been considered and imply the formation of aqua complexes and their deprotonated species generated from [Ru(η³:η³‐C₁₀H₁₆)Cl₂(pyrazole)]. Different competitive pathways based on outer‐sphere mechanisms, which imply hydrogen‐transfer processes, have been analysed. The overall isomerisation implies two hydrogen‐transfer steps from the substrate to the catalyst and subsequent transfer back to the substrate. In addition to the conventional Noyori outer‐sphere mechanism, which involves the pyrazolide ligand, a new mechanism with a hydroxopyrazole complex as the active species can be at work in water. The possibility of formation of an enol, which isomerises easily to the keto form in water, also contributes to the efficiency in water.     

Chloroselenate(IV): Darstellung,Struktur und Eigenschaften von [As(C6H5)4]2Se2Cl10 und [As(C6H5)4]Se2Cl9

Chloroselenates(IV): Synthesis, Structure, and Properties of [As(C₆H₅)₄]₂Se₂Cl₁₀ and [As(C₆H₅)₄]Se₂Cl₉ The Se₂Cl₁₀^2? and Se₂Cl₉^? anions were prepared, as the first dinuclear haloselenates(IV), from the reaction of (SeCl₄)₄ with stoichiometric quantities of chloride ions in POCl₃ solutions; they were isolated as yellow crystalline As(C₆H₅)₄⁺ salts. Complete X-ray structural analyses at ?130°C of [As(C₆H₅)₄]₂Se₂Cl₁₀ ( 1 ) (space group P1 , a = 10.296(7), b = 11.271(6), c = 12.375(8) Å, = 74.17(5)°, α = 81.38(5)°, β = 67.69(4)°, V = 1276 ų) and of [As(C₆H₅)₄]Se₂Cl₉ ( 2 ) (space group P2₁/n, a = 12.397(5), b = 17.492(6), c = 14.235(4) Å, α 93.25(3)°, V = 3082 ų) show in both cases two distorted octahedral SeCl₆ groups connected through a common edge in 1 and a common face in 2 . The terminal Se? Cl bonds (average 2.317 Å in 1 , 2.223 Å in 2 ) are much shorter than the Se? Cl bridges (av. 2.661 Å in 1 , 2.652 Å in 2 ). The stereochemical activity of the Se^IV lone electron pair causes severe distortion of the central Se₂Cl₂ ring in the centrosymmetric Se₂Cl₁₀^2? ion. The vibrational spectra of the anions are reported.