Platinumolefin bond strength in Pt(PPh3)2(CH2CH2) and Pt(PPh3)2 {C(CN)2C(CN)2}

The enthalpy of the reaction: Pt(PPh₃)₂ (CH₂CH₂)(cryst.) + C(CN)₂C(CN)₂ (g) → Pt(PPh₃)₂ {C(CN)₂C(CN)₂}(cryst.) + CH₂ CH₂ (g) has been determined as ΔH₂₉₈=?155.8±8.0 kJ·mol^?1, from solution calorimetry. The interpretation, that the platinumethylene bond is much weaker than the platinumtetracyanoethylene bond, is contrary to conclusions drawn recently from electron emission spectroscopic studies, but in agreement with available structural data.     

Electrochemical Synthesis of Tricyanomethyl Copper Complexes

The synthesis of tricyanomethyl copper complexes has been achieved by anodic dissolution of a sacrificial copper metal and cathodic reduction of 1, 1, 3, 3‐tetracyanopropane in acetonitrile, in the presence of triphenylphosphane used as coligand. The electrogenerated tetracyanopropyl radical anion is not stable and undergoes a cleavage leading to the tricyanomethyl anion and acrylonitrile which is electropolymerized at the cathode. The reaction solution gives a neutral dimeric binuclear copper(I) complex, bis{(μ‐ tricyanomethanido)bis(triphenylphosphane)copper(I)} [Cu(μ‐C(CN)₃)(PPh₃)₂]₂ ( 1 ). A second product of the synthesis reacts with 1, 10‐phenanthroline to give bis{cis‐(μ‐cyano)bis(triphenylphos‐phane)bis(phenanthroline)dicopper(I)}‐tricyanomethanide‐tetrafluoroborate‐diacetonitrile [cis‐{Cu₂(μ‐CN)(Phen)₂(PPh₃)₂}]₂[C(CN)₃] · BF₄ · 2CH₃CN ( 2 ). The crystal structures of 1 and 2 were determined by X‐ray analysis.     

Halogenid‐Ionen als Katalysator: Metallzentrierte C–C‐Bindungsknüpfung ausgehend von Acetontril

Halide Ions as Catalyst: Metalcentered C–C Bond Formation Proceeded from Acetonitril AlMe₃ reacts at 20 ?C in acetonitrile to the complex [Me₃Al(NCMe)] ( 1 ). By addition of cesium halides (X^– = F^–, Cl^–, Br^–) a trimerisation to the heterocycle [Me₂Al{HNC(Me)}₂C(CN)] ( 2 ) has been observed. The reaction might be carried out under catalytic conditions (1–2 mol% CsX). The gallium complex [Me₂Ga{HNC(Me)}₂ · C(CN)] ( 3 ), generated under similar reaction conditions, can be converted to the silylated compound [Me₂Ga{Me₃SiNC(Me)}₂C(CN)] ( 4 ) by successive treatment with two equivalents n‐butyllithium and Me₃SiCl. 3 reacts under hydrolysis conditions (1 M hydrochloric acid) to the iminium salt [{H₂NC(Me)}₂C(CN)]Cl ( 5 ). A mixture of H₂O, Ph₂PCl and 3 in THF/toluene leads in a unusual conversion to the diphospane derivative [Ph₂P–P(O)(Me₂GaCl)] ( 6 ). 1 , 2 , 4 , 5 and 6 have been characterized by NMR, IR and MS techniques. X‐ray structure analyses were performed with 1 , 2 , 4 and 6 · 0.5 toluene. According this 1 possesses an almost linear axis AlNCC [Al1–N1–C3: 179,5(2)?; N1–C3–C4: 179,7(4)?]. 2 is an AlN₂C₃ six‐membered heterocycle with two iminium fuctions. One N–H group is responsible for a intermolecular chain‐formation through hydrogen bridges to an adjacent nitrile group along the direction [010]. The basic structural motif of the heterocycle 3 has been maintained after silylation to 4 . In 6 · 0.5 toluene an unit Me₂GaCl, originated from 3 , is coordinated to the oxygen atom of the diphosphane oxide Ph₂P–P(O)Ph₂.     

Palladium(II) and Platinum(II) Complexes with Bisphosphanes, [S2C=C(CN)2]2– and [Se2C=C(CN)2]2– as Chelating Ligands

The palladium(II) and platin(II) 1, 1‐dicyanoethylene‐2, 2‐dithiolates [(L–L)M{S₂C=C(CN)₂}] (M = Pd: L–L = dppm, dppe, dcpe, dpmb; M = Pt: dppe, dcpe, dpmb) were prepared either from[(L–L)MCl₂] and K₂[S₂C=C(CN)₂] or from [(PPh₃)₂M{S₂C=C(CN)₂}] and the bisphosphane. Moreover, [(dppe)Pt{S₂C=C(CN)₂}]was obtained from [(1, 5‐C₈H₁₂)Pt{S₂C=C(CN)₂}] and dppeby ligand exchange. The 1, 1‐dicyanoethylene‐2, 2‐diselenolates[(dppe)M{Se₂C=C(CN)₂}] (M = Pd, Pt) were prepared from[(dppe)MCl₂] and K₂[Se₂C=C(CN)₂]. The oxidation potentials of the square‐planar palladium and platinum complexes were determined by cyclic voltammetry. The reaction of [(dcpe)Pd(S₂C=O)] with TCNE led to a ligand fragment exchange and gave the 1, 1‐dicyanoethylene‐2, 2‐dithiolate [(dcpe)Pd{S₂C=C(CN)₂}] in good yield.     

150−230 nm Chemiluminescence from C,CN and CO and observation of C(3P, 1D) in the N/C2F4 and N/O2/C2F4 reactions

Addition of C₂F₄ to a flowing nitrogen afterglow gives rise to CN(E²ΣA²Π, X²Σ), CN(F² ΔA²Π) and C (156.1, 165.5 and 193.0 nm) chemiluminescence. Transitions have been observed from CN(E²Σ) up to ν′ = 2 from which vibrational constants for this state have been recalculated to be ω_eχ_e = 13.8 cm^?1 and ω_e = 1698.4 cm^?1. Ground state and metasrable C(³P, ¹D) have been detected and studied via resonance fluorescence. Addition of O₂ to the N/C₂F₄ reaction system reduces C and CN emission intensities and [C] while giving rise to CO(a³Π-X¹Σ), CO(A¹ΠX¹Σ) and NO(B²ΠX²Π) emission. Probable excitation mechanisms are discussed.     

Reactions of Diazo Compounds with Alkenes Catalysed by [RuCl(cod)(Cp)]: Effect of the Substituents in the Formation of Cyclopropanation or Metathesis Products

The reaction of diazo compounds with alkenes catalysed by complex [RuCl(cod)(Cp)] (cod=1,5‐cyclooctadiene, Cp=cyclopentadienyl) has been studied. The catalytic cycle involves in the first step the decomposition of the diazo derivative to afford the reactive [RuCl(Cp){?C(R¹)R²}] intermediate and a mechanism is proposed for this step based on a kinetic study of the simple coupling reaction of ethyl diazoacetate. The evolution of the Ru–carbene intermediate in the presence of alkenes depends on the nature of the substituents at both the diazo N₂?C(R¹)R² (R¹, R²=Ph, H; Ph, CO₂Me; Ph, Ph; C(R¹)R²=fluorene) and the olefin substrates R³(H)C?C(H)R⁴ (R³, R⁴=CO₂Et, CO₂Et; Ph, Ph; Ph, Me; Ph, H; Me, Br; Me, CN; Ph, CN; H, CN; CN, CN). A remarkable reactivity of the complex was recorded, especially towards unstable aryldiazo compounds and electron‐poor olefins. The results obtained indicate that either cyclopropanation or metathesis products can be formed: the first products are favoured by the presence of a cyano substituent at the double bond and the second ones by a phenyl.     

Crystal Structure of Bis -(2,2′-bipyridine-N,N′)-(dicyanamide-N)-copper(II) Tricyanomethanide. Electronic and Structural Parameters Describing the Shape of Coordination Polyhedra in Five-Coordinated Copper(II) Compounds

 The structure of the new compound [Cu(bpy)₂N(CN)₂]C(CN)₃ (6) is compared with thestructures of six copper(II) coordination compounds with phenanthroline or bipyridine ligands and N-donor pseudohalide anions: [Cu(phen)₂NCS]C(CN)₃ (1), [Cu(bpy)₂NCS]C(CN)₃ (2), [Cu(phen)₂NCS]ONC(CN)₂ (3), [Cu(phen)₂N(CN)₂]C(CN)₃ (4), [Cu(bpy)₂C(CN)₃]C(CN)₃ (5), and [Cu(bpy)₂NCO]C(CN)₃ (7). The Cu(II) atoms in all above compounds are five-coordinated with an N-donor atom of the pseudohalide anion located in the equatorial plane of a deformed trigonal bipyramid. The shape of the coordination polyhedra and the degree of trigonal bipyramidal distortion towards a tetragonal pyramid are discussed and described using one electronic and several structural criteria which are discussed and compared.     

AM1 calculations of parts of the enthalpy surfaces for additions of active methylene nitriles to α β-unsaturated nitriles

The nucleophilic additions of active methylene nitriles (MNs), R₁R₂CH⁻, where R₁=CN and R₂=CN, and CSNH₂, to acetaldehyde and to the resultant α, β-unsaturated nitriles have been studied theoretically by the AM1 semiempirical MO method. The additions of MNs anions to acetaldehyde are found to be endothermic with late productlike transition states (TSs) on the reaction coordinate. Their additions to α,β-unsaturated nitriles may conceivably proceed via two pathways: addition to the C=C double bond and addition to the C≡N triple bond. It has been found that the nucleophilic attack at the &alpha,β-unsaturated linkage is exothermic, while that at the nitrile group is endothermic and has a relatively high enthalpy barrier. Both additions have late productlike transition states. The reactivity of the nucleophilic attack has been discussed in the light of the frontier molecular orbital theory and in terms of the HOMO–LUMO two-electron interaction. The calculations have been compared with experimental results. © 1997 John Wiley & Sons, Inc.     

Cyanoisocyanoacetylene,N≡C−C≡C−N≡C

Vacuum pyrolysis of the precursor complex [(CO)₅Cr(CN−CCl=CF−CN)] resulted in the isolation and structure elucidation by molecular spectroscopy of isomer 1 . According to ab initio calculations 1 is 109 kJ mol⁻¹ less stable than NC−C≡C−CN, which has been known for some time. An accurate equilibrium structure for 1 has been determined with mixed experimental and theoretical methods.     

Über Chalkogenolate. 114. Kristallstruktur von Kalium-N-cyanodithiocarbimat-Monohydrat K2[S2CN ? CN] · H2O

On Chalcogenolates. 114. Crystal Structure of Potassium N-Cyanodithiocarbimate Monohydrate K₂[S₂C?N ? CN] · H₂O The crystal structure of the title compound has been determined and refined to R = 0.0287. K₂[S₂C?N ? CN] · H₂O crystallizes in the orthorhombic space group Pnma with a = 10.336(1) Å, b = 7.862(1) Å, c = 9.882(1) Å Z = 4. The structure is built up from layers of cations and anions. The potassium ion is coordinated by O, N, S atoms. The coordination polyhedron is a quadratic antiprism. ¹³C and ¹⁵N NMR data are reported and discussed.     

The crystal structure of caesium tetracyanodioxoosmate(VI) Cs2[OsO2(CN)4]

Summary The crystal structure of the caesium salt of [OsO₂(CN)₄]^2– has been determined from three-dimensional x-ray diffraction data. The orange crystals are monoclinic, space group C2/m with a=12.125(2), b=8.284(1), c=5.457(1) Å, =102.01(1)° with two molecules per unit cell. The final R value using 778 observed reflections and anisotropic thermal parameters for all atoms was 0.028. The [OsO₂(CN)₄]^2– ion has an octahedral geometry. Bond distances: Os=O=1.750(8)Å and Os–C=2.093(9)Å.     

Methylierung und Oxydation des 1,1-Dicyanoethylen-2,2-oxo-thiolat-Dianions: Präparative und strukturelle Untersuchungen

Methylation and Oxidation of 1,1-Dicyanoethylene-2,2-oxo-thiolate Dianion: Preparative and Structural Investigations The reaction of K₂[S(O)C?C(CN)₂] with CH₃I yields the mono-S-methylproduct. The potassium salt crystallizes in the space group P2₁/c with a = 3.951(1), b = 15.623(3), c = 11.916(2) Å, β = 93.46(3)° and Z = 4. The methyl group is directed towards the oxygen atom. Potassium has a monocapped trigonal prismatic coordination: 5 N and 2 O atoms. The oxidation of 1,1-Dicyanoethylene-2,2-oxo-thiolate yields the dimere [(NC)₂C?C(O)? S? S? (O)C?C(CN)₂]^2? in the first oxidation step. An X-ray crystal structure determination shows that the anion consists of two planar [S(O)C?C(CN)₂] units which are oriented perpendicular within the anion.     

Synthese von Cp(CO)2 MnTCNE aus [Cp(CO)2MnXPh]n (X = S,Se, Te; n = 1,2); Festkörperstruktur und Magnetismus

Cp(CO)₂MnTCNE (1) which was first reported by M. Herberhold et al., has been obtained from the reaction of [Cp(CO)₂MnXPh]_n (X = S, n = 1; X = Se, Te, n = 2) with TCNE. The synthesis of the relevant organometallic sulfur, selenium and tellurium derivatives is described. An X-ray diffraction study of the TCNE compound reveals that two Cp(CO)₂MnNCC(CN)C(CN)₂ (1) molecules form centrosymmetric dimers containing a coordinated centrosymmetric (TCNE)₂^x− pair. The bond lenghts, the v(CN) spectra and a solid state magnetism of μ_eff = 1.1 μ_B (293 K) are all consistent with this structural finding.     

Theoretical study on the gas phase reaction of acrylonitrile with atomic hydrogen

The complex potential energy surface of the H + CH₂=CHCN reaction has been investigated at the BMC-CCSD level based on the geometric parameters optimized at the BHandHLYP/6-311++G(d,p) level. This reaction is revealed to be one of the significant loss processes of acrylonitrile. The BHandHLYP and M05-2X methods are employed to obtain initial geometries. The reaction mechanism confirms that H can attack on the C=C double bond or C and N atom of –CN group to form the chemically activated adducts IM1 (CH₃CHCN), IM2 (CH₂CH₂CN), IM3′ (CH₂=CHCHN) and IM5 (CH₂=CHCNH), and direct H-abstraction paths may also occur. Temperature- and pressure-dependent rate constants have been carried out using Rice–Ramsperger–Kassel–Marcus theory with tunneling correction. IM1 (CH₃CHCN) formed by collisional stabilization is the major product at the 760 Torr pressure of H₂ and in the temperature range (200–1,600 K); whereas the production of IM2 (CH₂CH₂CN) is the main channel at 1,600–3,000 K. The calculated rate constants are in good agreement with the experimental data.     

Endgroups in Copolymers of Acenaphthylene with Methyl Methacrylate Prepared with Azoisobutyronitrile as Initiator

Copolymers of acenaphthylene (ACN) with methyl methacrylate (MMA) have been prepared with azobis(isobutyronitrile-β, β-¹³C₂) as initiator, The endgroups derived from the initiator have been examined by ¹³C-NMR spectroscopy; those attached to ACN units have been distinguished from those attached to MMA units and quantitative comparisons of their numbers have been made. It has been deduced that at 60°C ACN is four times as reactive as MMA toward the (CH₃)₂ C(CN) radical. The marked preference for initiation involving ACN means that, for all copolymers, the ratio of ACN to MMA is appreciably greater for the sites adjacent to the (CH₃)₂ C(CN)– endgroups than for the whole copolymer.     

The silver(I)‐catalyzed exchange of coordinated cyanide in hexacyanoferrate(II) by phenylhydrazine in aqueous medium

The [Ag]⁺‐catalyzed exchange of coordinated cyanide in [Fe(CN)₆]^4? by phenylhydrazine (PhNHNH₂) has been studied spectrophotometrically at 488 nm by monitoring increase in the absorbance for the formation of cherry red colored complex [Fe(CN)₅PhNHNH₂]^3?. The other reaction conditions were pH 2.80±,0.02, temperature = 30.0 ± 0.1^°C, and ionic strength (I) = 0.02 M (KNO₃). The reaction was followed as a function of pH, ionic strength, temperature, [Fe(CN)^4?₆], [PhNHNH₂], [Ag⁺] by varying one variable at a time. The initial rates were evaluated for each variation using the plane mirror method. The initial rates evaluated as a function of [Fe(CN)^4?₆] clearly indicate that the initial rate increases with the increase in [Fe(CN)^4?₆] and finally reaches to a limiting value when [Fe(CN)^4?₆]/[AgNO₃] ? 1000. It indicates the formation of a strong adduct between [Fe(CN)₆]^4? and AgNO₃ prior to the abstraction of CN^?. The variation in initial rates with [PhNHNH₂] also showed limiting values at [Fe(CN)^4?₆]/[PhNHNH₂] ? 8.30. The complex behavior due to pH and [Ag⁺] variations on the rate has been explained in detail. The composition of the final reaction product [Fe(CN)₅PhNHNH₂] formed during the course of reaction has been found to be 1:1 using the mole ratio method. The evaluated values of activation parameters for the catalyzed reaction are E_a = 53.85 kJ mol^?1, Δ H^≠, = 51.33 kJ mol^?1, and Δ S^≠ = ?134.63 J K^?1 mol^?1, which suggest an interchange dissociative mechanism. A most plausible mechanistic scheme has been proposed based on the experimental observations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 447–456, 2007     

Ligand effects in the hydroformylation of acrylonitrile by cobalt carbonyl

The hydroformylation of acrylonitrile (VCN) using Co₂(CO)₈/L (L  HN(CH₂CN)₂, H₂C(CH₂)₃NMe, Me₂N(CH₂)₂NMeH, PPh₃, and PCy₃) has been examined in methanol solvent. Four reaction pathways are observed which are dependent on L. With no L or with L  HN(CH₂CN)₂, the reaction produces the desired acetal (MeO)₂CHCH₂CH₂CN. For the more basic amines the reaction produces ～ 50% yields of hydrodimerization products NCCHMe(CH₂)₂CN/NC(CH₂)₄CN in a 10/1 ratio and an ～ 30% yield of the hydrogenation product CH₃CH₂CN. These reactions are shown to be metal catalyzed. The main reaction for Co₂(CO)₈/PR₃ catalyzed systems appears to be a classical Michael addition reaction of the solvent, methanol, with acrylonitrile to give MeOCH₂CH₂CN. Evidence is given to show that this reaction is catalyzed by phosphine which has dissociated under reaction conditions and not by a ligated cobalt complex.     

The Reactivity of the Pentacyano(η1-Dioxygen)cobaltate(III) Ion in Aqueous Solution

The mononuclear η¹-dioxygen complex [Co(CN)₅O₂]^3? ( A ) decomposes in aqueous solution to the hydroxo-complex [Co(CN)₅OH]^3? ( B ) and the hydroperoxo complex [Co(CN)₅CoO₂N]³ ( C ). The mechanism involves partial dissociation of A to give [Co(CN)₅]^3? ( E ) which binds with unreacted A to give the η¹:η¹-peroxo complex [(CN)₅Co0₂Co(CN)₅]^6? ( F ) which is hydrolysed to B and C . The mechanism is supported by the effects of pH, dioxygen concentration, and ionic strength on the rate of decomposition, and by the trapping of oxidation products of E and F . Complex A reacts readily with reducing agents to give directly the hydroperoxo complex C.     

Catalytic oxidation of 1-hexene with molecular oxygen by iridium nitro complexes

The oxidation of 1-hexene by molecular oxygen catalyzed by iridium(III) complexes, [Ir(CH₃CN)_5−xCl_x(NO₂)]^2−x (x=0, 1, or 2) has been studied in acetonitrile under P(O₂)=1.5 atm and T=100°C. [Ir(CH₃CN)₅(NO₂)](PF₆)₂ oxidizes 1-hexene to 1,2-epoxyhexane. Complex [Ir(CH₃CN)₄Cl(NO₂)]PF₆ oxidizes 1-hexene to 2,3-epoxyhexane only in the presence of [Pd(PhCN)₂(Cl)₂] (an olefin activator). In contrast to the cationic complexes, the neutral complex [Ir(CH₃CN)₄Cl₂(NO₂)] oxidizes 1-hexene to 2-hexanone only in the presence of [Pd(PhCN)₂(Cl)₂].     

Crystal Structure of Bis-(2,2′-bipyridine-N,N′)-(dicyanamide-N)-copper(II) Tricyanomethanide. Electronic and Structural Parameters Describing the Shape of Coordination Polyhedra in Five-Coordinated Copper(II) Compounds

Summary.  The structure of the new compound [Cu(bpy)₂N(CN)₂]C(CN)₃ (6) is compared with thestructures of six copper(II) coordination compounds with phenanthroline or bipyridine ligands and N-donor pseudohalide anions: [Cu(phen)₂NCS]C(CN)₃ (1), [Cu(bpy)₂NCS]C(CN)₃ (2), [Cu(phen)₂NCS]ONC(CN)₂ (3), [Cu(phen)₂N(CN)₂]C(CN)₃ (4), [Cu(bpy)₂C(CN)₃]C(CN)₃ (5), and [Cu(bpy)₂NCO]C(CN)₃ (7). The Cu(II) atoms in all above compounds are five-coordinated with an N-donor atom of the pseudohalide anion located in the equatorial plane of a deformed trigonal bipyramid. The shape of the coordination polyhedra and the degree of trigonal bipyramidal distortion towards a tetragonal pyramid are discussed and described using one electronic and several structural criteria which are discussed and compared. Received July 24, 2000. Accepted October 18,2000