Low oxidation state ruthenium chemistry : IV. The reactions of M(CO)2(PPh3)3 complexes (M = Fe,Ru) and the hydrogenation and isomerization of alkenes catalyzed by RuL(CO)2(PPh3)2 (L = H2, PPh3)

The complexes M(CO)₂(PPh₃)₃ (I, M = Fe; II, M = Ru) readily react with H₂ at room temperature and atmospheric pressure to give cis-M(H)₂(CO)₂(PPh₃)₂ (III, M = Fe;IV,M = Ru). I reacts with O₂ to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis-Ru(O₂)(CO)₂(PPh₃)₂(V). Even compound IV reacts with O₂ to give V with displacement of H₂; this reaction has been shown to be reversible and this is the first case where the displacement of H₂ by O₂ and that of O₂ by H₂ at a metal center has been observed. III and IV are reduced to M(CO)₃(PPh₃)₂ by CO with displacement of H₂; Ru(CO)₃- (PPh₃)₂ is also formed by treatment of IV with CO₂, but under higher pressure. Compounds II and IV react with CH₂CHCN to give Ru(CH₂CHCN)(CO)₂- (PPh₃)₂(VI) which reacts with H₂ to reform the hydride IV.cis-Ru(H)₂(CO)₂(PPh₃)₂(IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H₂ and O₂ on the “Ru(CO)₂(PPh₃)₂” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO)₂(PPh₃)₃(II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere.     

Metallocenylborane III. Darstellung und eigenschaften von ferrocenyl- und cymantrenylboranen

Ferrocene, cymantrene and methylcymantrene react with BI₃, BBr₃, C₆H₅BI₂ and CH₃BI₂ in boiling CS₂ or C₆H₁₂ forming air-sensitive metallocenylhaloboranes. The direct dichloroborylation is only possible with ferrocene. Starting from metallocenyliodoboranes the corresponding substituted metallocenylboranes are obtained by halogen exchange with AsF₃ or AsCl₃, by methylation with Sn(CH₃)₄, by ether cleavage of (C₂H₅)₂O, by redox reaction with (CH₃S)₂ and by reaction with R₂NH. ¹H and ¹³C NMR spectra indicate that in contrast to cymantrenylhaloboranes, in ferrocenylhaloboranes the 3,4-protons are more deshielded than the 2,5-protons. The metallocenylboranes, isoelectronic with α-metallocenylcarbenium ions, are weaker Lewis acids than phenylboranes; they form donor-acceptor compounds with pyridine and dimethylsulfane, respectively.     

Synthese und Kristallstrukturen der Phosphanimin-Komplexe [Cu(μ-HNPEt3)]4(O3S–CF3)4 und [Pt2Me6(μ-I)2(μ-HNPMe3)]

Synthesis and Crystal Structures of the Phosphaneimine Complexes [Cu(μ-HNPEt₃)]₄(O₃S–CF₃)₄ and [Pt₂Me₆(μ-I)₂(μ-HNPMe₃)] The title compounds have been prepared by the reaction of copper(I)triflate with [NiBr(NPEt₃)]₄ in CH₂Cl₂ suspension in the presence of water, and by the reaction of [PtMe₃I]₄ with Me₃SiNPMe₃ in boiling toluene in the presence of cesium fluoride, respectively. According to the crystal structure determinations the cation of the copper complex forms tetrameric units [Cu(HNPEt₃)]₄⁴⁺ with S₄ symmetry with Cu–N bond lengths of 191.6 and 192.1 pm. In the platinum complex the platinum atoms are linked by two μ-I bridging atoms as well as by the μ-N atom of the HNPMe₃ ligand with Pt–N bond lengths of 228.1 and 229.5 pm.     

Entanglement networks of 1,2-polybutadiene crosslinked in states of strain. VII. Stress-birefringence relations

Crosslinks are introduced by γ irradiation into 1,2-polybutadiene while strained in uniaxial extension near T_g with stretch ratio λ₀, thereby trapping a proportion of the entanglements originally present. The stress at any subsequent strain λ is accurately given by the sum σ_N + σ_x, where σ_N is the stress contributed by a trapped entanglement network with λ = 1 as reference and a Mooney–Rivlin stress-strain relation, and σ_x is that contributed by a crosslink network with λ = λ₀ as reference and neo-Hookean stress-strain relation. The birefringence is accurately given as δn = ?_Nσ_N + ?_xσ_x, where the ?'s are the respective stress-optical coefficients. From measurements at λ = λ₀ where σ_x = 0, ?_N can be determined separately. For polymer with 88% 1,2 microstructure, ?_N and ?_x are nearly equal and independent of irradiation dose, though strongly dependent on temperature. For polymer with (95–96)% 1,2, ?_N and ?_x are different (even opposite in sign) and dependent on dose. This behavior is associated with a side reaction of cyclization by the γ irradiation, which is inhibited by the 1,4 moiety in the polymer with lesser 1,2 content. It is responsible for residual birefringence in the state of ease (λ = λ_s) where σ_N = –σ_x and the stress is zero.     

Synthesis and x-ray crystal structure of the TiMgCl5(OOCCH2Cl) · (ClCH2COOC2H5)3 Adduct

The synthesis of the TiMgCl₅(OOCCH₂Cl) · (ClCH₂COOC₂H₅)₃ adduct, obtained by reacting TiCl₄ with a solution of MgCl₂ in dry ClCH₂COOC₂H₅, is reported together with its molecular and crystal structure as determined by x-ray diffraction. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.057 for 1318 independent observed reflections. Crystals are monoclinic, space-group P2₁/c, with 4 formula units in a unit-cell of dimensions a = 10.480(4), b = 19.641(9), c = 16.597(6) Å, β = 120.21(5)°. The titanium(IV) atom is octahedrally coordinated by five chlorine atoms and an oxygen atom of a OOCCH₂Cl residue. The magnesium atom is similarly coordinated by two chlorine atoms, the carbonyl oxygen atoms of three ClCH₂COOC₂H₅ molecules and an oxygen atom of the OOCCH₂Cl residue. The two octahedra share an edge by a double chlorine bridge between the magnesium and the titanium atoms and are also connected by the COO group of the OOCCH₂Cl residue. Changes in the configurations and dimensions with respect to the free acceptor and donor molecules are discussed.     

New routes to pentafluorophenyl derivatives with germanium-chalcogen bonds

Tris(pentafluorophenyl)germanethiol, (C₆F₅)₃GeSH (Ia), was obtained in good yield by heating the tris(pentafluorophenyl)germane with elemental sulphur or by the exchange between Et₃GeSH and (C₆F₅)₃GeBr. The reaction between sulphur and (C₆F₅)₂GeH₂ or C₆F₅GeH₃ gives heterocyclic products with chains of alternating germanium and sulphur atoms in the cycles. The compounds [(C₆F₅)₃Ge]₂X (X = S, Se) were prepared by exchange reaction of (Et₃Ge)₂X with tris(pentafluorophenyl)germanium bromide and by reaction of chalcogens (S₈, Se₈) with hexakis(pentafluorophenyl)digermane. Ia reacts with diethylmercury affording (C₆F₅)₃GeSHgEt. Insertion of elemental sulphur into the GeHg bond of bis[tris(pentafluorophenyl)germyl]mercury led to the thermally stable (C₆F₅)₃GeSHgGe(C₆F₅)₃.     

Methylmetall-bis(trimethylsilyl)amidoderivate des Aluminiums,Galliums und Arsens

Methyl Metal Bis(trimethylsilyl)amido Derivatives of Aluminium, Gallium, and Arsenic MeAl[N(SiMe₃)₂]₂ (Me ? CH₃) has been prepared by the reaction of AlMe₃ with HN(SiMe₃)₂ in a 1:2 molar ratio. The homologue Gallium compound (as well as the Aluminium derivative) is formed in good yields by the interaction of MeMcl₂ (M = Al, Ga) with Li- and Na[N(SiMe₃)₂], respectively. MeAs[N(SiMe₃)₂]₂ is formed by the reaction of AsCl₃ and Na[N(SiMe₃)₂] in a 1:3 molar ratio. These colourless amido derivatives are monomeric in solution, they have been characterized by analyses, mass, n.m.r. (¹H and ¹³C), and especially by i.r. and Raman spectra.     

Synthesis, single crystal X-ray analysis, and TEM for a single-sized Au11 cluster stabilized by SR ligands: The interface between molecules and particles

An SR-modified Au cluster with a sub-nanometer size, Au₁₁(S-4-NC₅H₄)₃(PPh₃)₇ (1), has been synthesized by NaBH₄ reduction of Au(S-py)(PPh₃) or by reacting [Au₉(PPh₃)₈](NO₃)₃ with HS-4-py in good yield. Its molecular structure has been elucidated by single crystal X-ray diffraction, and TEM observation has been achieved for the first time for this size of SR-modified Au clusters. The core structure is best described in terms of an incomplete icosahedron. CV measurements in CH₂Cl₂ have suggested that the cluster does not coagulate in solution with significant concentration.     

Limitations of low resolution mass spectrometry in the electron capture negative ionization mode for the analysis of short- and medium-chain chlorinated paraffins

The analysis of complex mixtures of chlorinated paraffins (CPs) with short (SCCPs, C₁₀–C₁₃) and medium (MCCPs, C₁₄–C₁₇) chain lengths can be disturbed by mass overlap, if low resolution mass spectrometry (LRMS) in the electron capture negative ionization mode is employed. This is caused by CP congeners with the same nominal mass, but with five carbon atoms more and two chlorine atoms less; for example C₁₁H₁₇³⁷Cl³⁵Cl₆ (m/z 395.9) and C₁₆H₂₉³⁵Cl₅ (m/z 396.1). This can lead to an overestimation of congener group quantity and/or of total CP concentration. The magnitude of this interference was studied by evaluating the change after mixing a SCCP standard and a MCCP standard 1+1 (S+MCCP mixture) and comparing it to the single standards. A quantification of the less abundant C₁₆ and C₁₇ congeners present in the MCCP standard was not possible due to interference from the major C₁₁ and C₁₂ congeners in the SCCPs. Also, signals for SCCPs (C₁₀–C₁₂) with nine and ten chlorine atoms were mimicked by MCCPs (C₁₅–C₁₇) with seven and eight chlorine atoms (for instance C₁₀H₁₂Cl₁₀ by C₁₅H₂₄Cl₈). A similar observation was made for signals from C₁₅–C₁₇ CPs with four and five chlorine atoms resulting from SCCPs (C₁₀–C₁₂) with six and seven chlorine atoms (such as C₁₅H₂₈Cl₄ by C₁₀H₁₆Cl₆) in the S+MCCP mixture. It could be shown that the quantification of the most abundant congeners (C₁₁–C₁₄) is not affected by any interference. The determination of C₁₀ and C₁₅ congeners is partly disturbed, but this can be detected by investigating isotope ratios, retention time ranges and the shapes of the CP signals. Also, lower chlorinated compounds forming [M+Cl]^– as the most abundant ion instead of [M-Cl]^– are especially sensitive to systematic errors caused by superposition of ions of different composition and the same nominal mass.     

Hydrogen Peroxide Formation by Electric Discharge with Fine Bubbles

Pulsed discharge plasma is typical oxidation technology for disposing organic compounds in aqueous solutions. When this electrical discharge plasma was applied in water, it may produce hydrogen peroxide (H₂O₂) without any catalyst or chemical agent. In order to increase H₂O₂ production by electrical discharge plasma in water, fine bubbles were introduced into the electrical discharge plasma in this experiment. Bipolar pulsed voltages were applied to cylindrical electrodes in the water while Ar or O₂ bubbles were introduced, generating a pulsed discharge plasma. The introduction of the bubbles seemed to enhance the dissociation of water molecules and increased H₂O₂ formation, especially with O₂ bubbling. Dissolved oxygen in the water contributed to H₂O₂ formation by pulsed discharge plasma with the bubbles, while dissociation of water molecules was the cause of H₂O₂ formation by pulsed discharge plasma without bubbles. More H₂O₂ was formed by pulsed discharge plasma with O₂ bubbles, because the amount of dissolved oxygen in the water increased upon bubbling with O₂.     

Ti7Cl16 und Ti7Br16 sowie weitere Untersuchungen mit Titanhalogeniden. Al2X6 als Komplexbildner

Ti₇Cl₁₆ and Ti₇Br₁₆ and Further Investigations with Titanium Halides. Al₂X₆ as a Complex Forming Agent TiCl_3,s can be transported with Al₂Cl₆ via TiAlCl_6,g in a temperature gradient. The equilibrium of this reaction was studied by mass spectroscopy. There is no indication of the existence of a TiAl₂Cl₉ molecule as assumed in the literature. β-TiBr₃ was prepared from the elements in the presence of the transporting agent Al₂Br_6,g. The transport of TiCl₂ with Al₂Cl_6,g involves, as an important step, the disproportionation which is favoured by the reaction of Ti with the glass wall. If the disproportionation is made impossible by addition of Ti the novel compound Ti₇Cl₁₆ is obtained. Independent of Ti₇Cl₁₆, a phase TiCl_{(2 + x)} with a broad range of homogeneity exists. The compound Ti₇Br₁₆, being isostructural with Ti₇Cl₁₆, was also prepared. Results of magnetic measurements and observations on the thermal decomposition of the compounds are reported.     

Computer-assisted study of characteristics of water clusters in the presence of nitrogen dioxide

The interaction of IR radiation with water clusters that have absorbed NO₂ molecules is studied by the molecular dynamics method in terms of the polarizable model. Induced dipole moments of H₂O and NO₂ molecules diminish during the addition of one to six NO₂ molecules to (H₂O)₅₀ cluster. The integral intensity of IR absorption by a system consisting of (NO₂) _i (H₂O)₅₀ heteroclusters with 1 ≤ i ≤ 6 decreases, whereas the power of heat emission rises as compared with an (H₂O) _n system. The decrease in the IR absorption and the increase in the IR emission by water clusters with the capture of NO₂ molecules are nonmonotonic. The absorption of NO₂ molecules by water clusters causes a noticeable reduction in the intensity of the first peak and the confluence of the fourth and fifth peaks in the Raman spectrum.     

Endo- and Exocyclic Substitutions in α-P4S3I2

Two isomers each of α-P₄S₂SeX₂ and α-P₄SSe₂X₂ (X=Cl, Br) have been identified by ³¹P-NMR spectroscopy in mixtures obtained from thermal reaction of PX₃ and P₄S_1.4Se_1.6. Systematic changes in chemical shifts and coupling constants with electronegativity of the ligand by exocyclic substitution and with alteration of the molecular geometry by the replacement of sulfur by selenium are reported.     

Synthesen von Verbindungen mit M–N‐Bindungen (M = Li,Ga, In)

Syntheses of Compounds with M–N Bonds (M = Li, Ga, In) The adducts [GaCl₃(HNⁱPr₂)] ( 1 ) and [InCl₃{HN(CH₂Ph)₂}₂] ( 2 ) can be obtained by the reactions of the corresponding metal(III) halides with the amines. The In amide In(N^cHex₂)₃ ( 3 ) can be formed by treatment of InCl₃ with three equivalents of LiN^cHex₂. Reaction with four equivalents of LiN^cHex₂ leads to the same product. However, the treatment of InCl₃ with four equivalents of LiN(CH₂Ph)₂ gives the desired metalate [Li(THF)₄][In{N(CH₂Ph)₂}₄] ( 4 ). From the corresponding reaction of InCl₃ with LiNⁱPr₂ no In‐containing product could be identified. Instead, the aggregate of LiCl with three units of LiNⁱPr₂, [Li₄(NⁱPr₂)₃(THF)₄Cl] ( 5 ), was isolated. 1 – 4 were characterized by NMR, IR and MS techniques as well as by X‐ray structure determinations. According to them, 1 possesses a tetrahedrally coordinated Ga atom, at which two units of 1 are connected by hydrogen bridges to centrosymmetrical dimers. The In atoms in 2 have a trigonal‐bipyramidal coordination sphere; the amine molecules occupy the apical positions. The central metal atom in 3 and the anion of 4 exhibit trigonal‐planar and distorted tetrahedral environments, respectively. The novel structural motif in 5 is the Cl^– ion, only partly surrounded by Li⁺ ions in a strongly distorted trigonal‐bipyramidal fashion. The dominating angle amounts to 165.2(2)°.     

Crystal structure of Cs8[α-BW12O40][RhCl6]·5·5H2O double salt

By heating in the air [HBW₁₁O₃₉]⁸⁻ with [Rh₂(CH₃COO)₄(H₂O)₂] in the excess of tungstate followed by crystallization in the presence of CsCl, a double salt of Cs₈[6h-BW₁₂O₄₀][RhCl₆]·5.5H₂O is obtained and structurally characterized. Its crystal structure is determined by single crystal X-ray diffraction. The structure is ionic with Cs⁺ cations, [BW₁₂O₄₀]⁵ anions with the Keggin structure, and [RhCl₆]³ octahedral anions.     

Synthese und Kristallstrukturen der Phosphanimin-Komplexe MCl2(Me3SiNPMe3)2 mit M = Zn und Co,und CoCl2(HNPMe3)2

Syntheses and Crystal Structures of the Phosphaneimine Complexes MCl₂(Me₃SiNPMe₃)₂ with M = Zn and Co, and CoCl₂(HNPMe₃)₂ The molecular complexes MCl₂(Me₃SiNPMe₃)₂ (M = Zn, Co) have been prepared by the reaction of the dichlorides of zinc and cobalt with Me₃SiNPMe₃ in CH₃CN and CH₂Cl₂, respectively, whereas the complex CoCl₂(HNPMe₃)₂ has been prepared by the reaction of CoCl₂ with NaF in boiling acetonitrile in the presence of Me₃SiNPMe₃. All complexes were characterized by IR spectroscopy and by crystal structure determinations. The complexes MCl₂(Me₃SiNPMe₃)₂ crystallize isotypically. ZnCl₂(Me₃SiNPMe₃)₂: Space group P2₁2₁2₁, Z = 4, 2677 observed unique reflections, R = 0.024. Lattice dimensions at ?70°C: a = 1243.6; b = 1319.0; c = 1464.7 pm. CoCl₂(Me₃SiNPMe₃)₂: Space group P2₁2₁2₁, Z = 4, 3963 observed unique reflections, R = 0,071. Lattice dimensions at ?80°C: a = 1236.3; b = 1317.4; c = 1457.6 pm. CoCl₂(HNPMe₃)₂ · CH₂Cl₂: Space group Pbca, Z = 8, 1354 observed unique reflections, R = 0.055. Lattice dimensions at ?80°C: a = 1247.3; b = 998.4; c = 2882.4 pm. All complexes have monomeric molecular structures, in which the metal atoms are coordinated in a distorted tetrahedral fashion by the two chlorine atoms and by the nitrogen atoms of the phosphaneimine molecules.     

Zinc Hydrazides and Alkoxyhydrazides: Organometallic Compounds with Novel Zn4N8, Zn4N6O and Zn4N4O2 Cage Structures

Tetrameric [{RZn(NHNMe₂)}₄] (R = Me, Et), the first organometallic zinc hydrazides to be described, have been prepared by alkane elimination from dialkylzinc solutions and N,N‐dimethylhydrazine. They were characterised by ¹H and ¹³C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X‐ray crystallography. The compounds form asymmetric aggregates containing the novel Zn₄N₈ core; tetrahedra of Zn atoms bear the alkyl groups at Zn, with the triangular faces bridged by NHNMe₂ substituents. The NH groups are connected to two Zn atoms, and the NMe₂ groups to one. Hydrolysis of the compounds with water gives [(RZn)₄(OH)(NHNMe₂)₃] as products, which also were characterised as described above. Higher yields of these hydroxo clusters were achieved in one‐pot syntheses by reaction of dialkylzinc solutions with mixtures of N,N‐dimethylhydrazine and water. They contain Zn₄N₆O cages, in which one hydroxide in the tetrameric hydrazides described above replaces one NHNMe₂ group. Similar products can be prepared with alkoxy instead of hydroxy groups, in analogous one‐pot syntheses with alcohols. Alcoholysis of [EtZn(NHNMe₂)]₄ with methanol or ethanol gave zinc trishydrazide monoalkoxides, [(EtZn)₄(OR)(NHNMe₂)₃] (R = Me, Et), which have constitutions analogous to the monohydroxides. The organozinc bishydrazide bisalkoxides [(MeZn)₄(NHNMe₂)₂(OEt)₂] and [(EtZn)₄(NHNMe₂)₂(OEt)₂] were obtained in one‐pot reactions from dialkylzinc solutions with mixtures of the hydrazine and alcohol, and their crystal structures, confirmed by spectroscopic methods in solution, show an unsymmetrical aggregation with the novel Zn₄N₄O₂ cage structure.     

Synthesis,characterization and structure of oxorhenium(V) complexes with 2-methylmercaptobenzamide

The neutral, mononuclear complex [ReO(mta)₂Cl] (1) [Hmta?=?2-(methylmercapto)aniline] was prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of Hmta in methanol. The oxo-bridged dimer (μ-O)[ReO(mta)₂]₂ (2) was synthesized by reacting [ReOCl₃(PPh₃)₂] with a twofold excess of Hmta in a 9?:?1 acetone/water mixture. The compounds were characterized by spectroscopy and complex 1 also by X-ray crystallography. Complex 1 has a distorted octahedral geometry with the chloride coordinated trans to the oxo group, and with the chelating ligands in the equatorial plane in a cis-N cis-S configuration.     

A Mechanistic Dichotomy in Two-Electron Reduction of Dioxygen Catalyzed by N,N’-Dimethylated Porphyrin Isomers

Selective two-electron reduction of dioxygen (O₂) to hydrogen peroxide (H₂O₂) has been achieved by two saddle-distorted N,N’-dimethylated porphyrin isomers, an N21,N’22-dimethylated porphyrin ( anti -Me₂P ) and an N21,N’23-dimethylated porphyrin ( syn -Me₂P ) as catalysts and ferrocene derivatives as electron donors in the presence of protic acids in acetonitrile. The higher catalytic performance in an oxygen reduction reaction (ORR) was achieved by anti -Me₂P with higher turnover number (TON=250 for 30 min) than that by syn -Me₂P (TON=218 for 60 min). The reactive intermediates in the catalytic ORR were confirmed to be the corresponding isophlorins ( anti -Me₂Iph or syn -Me₂Iph ) by spectroscopic measurements. The rate-determining step in the catalytic ORRs was concluded to be proton-coupled electron-transfer reduction of O₂ with isophlorins based on kinetic analysis. The ORR rate by anti -Me₂Iph was accelerated by external protons, judging from the dependence of the observed initial rates on acid concentrations. In contrast, no acceleration of the ORR rate with syn -Me₂Iph by external protons was observed. The different mechanisms in the O₂ reduction by the two isomers should be derived from that of the arrangement of hydrogen bonding of a O₂ with inner NH protons of the isophlorins.     

Reaction of pentaammine(urea-O)cobalt(III) cation with chlorine and hypochlorous acid in aqueous solution

Summary The Co(NH₃)₅[OC(NH₂)₂]³⁺ cation in aqueous acid reacts with chlorine and hypochlorous acid, with two sequential steps observed in each case. Rate constants for both steps show a first-order dependence on [oxidant], with k₁/k₂ always <20, but varying with the choice of reactant and acid. Rate constants with Cl₂ as reactant are faster than with HOCl, possibly related to preferential attack by Cl⁺ compared with OCl^– on the bound urea. Competition by ions (HSO ₄ ^– , Cl^– or NO ₃ ^– ) measured by product analysis of reactions conducted in 1 M acid produced competition ratios R (R=[CoX]/[CoOH₂][X]) which are similar to values determined with a range of leaving groups previously, indicating a mechanistic constancy. No formation of Co(NH₃)₅Cl²⁺ was observed in reactions conducted in H₂SO₄ or HNO₃, implying that free Cl^– is not generated at the reaction site and captured by the metal ion. Electronic and vibrational spectra of the intermediate formed in the two stage reaction is indicative of a change from an O-bound to an N-bound ligand in forming that intermediate, although it cannot be a simple isomerization due to the dependence on [oxidant]. A possible mechanism is discussed.