The formation,crystal and molecular structures of bis(η5-indenyl)dicarbonyltitanium and bis(η5-indenyl)dicarbonylzirconium

Bis(η⁵-indenyl)dicarbonyltitanium has been produced in 47% yield by reduction of bis(η⁵-indenyl)dichlorotitanium with activated aluminum in THF solution under a carbon monoxide atmosphere. Bis(η⁵-indenyl)dicarbonylzirconium can similarly be prepared in 45% yield by the reductive carbonylation of bis(η⁵-indenyl)dichlorozirconium using activated magnesium turnings. IR spectral evidence has been obtained for the corresponding hafnium analog, although it could not be isolated. Detailed syntheses for the precursors (η⁵-indenyl)₂MCl₂ (M = Ti, Zr, Hf) have been developed. Bis(η⁵-indenyl)dicarbonyltitanium crystallizes in the monoclinic space group C2/c with unit cell parameters a 30.435(8), b 7.357(5), c 28.279(8) Å and β 90.93(5)°. Refinement of 3530 observed reflections lead to final agreement indices of R = 0.052 and R_w = 0.049. Bis(η⁵-indenyl)dicarbonylzirconium crystallizes in the monoclinic space group P2₁/n with unit cel parameters of a 7.288(5), b 14.398(8), c 15.273(7) Å and β 89.84(5)°. Refinement of 2253 observed reflections lead to final agreement indices of R = 0.049 and R₂ = 0.055.     

Structural study of bis(η-cyclopentadienyl)dicarbonyliron (p-tolyl)tin(IV) bromide

The compound, [η-C₅H₅Fe(CO)₂]₂(p-CH₃C₆H₄)SnBr, crystallizes in the monoclinic space group P2₁/c with a 9.643, b 12.016, c 19.205 Å, β 98.68°, V 2225.9 ų, and Z = 4. The crystal and molecular structures have been solved by use of the Patterson method. A full-matrix least-squares refinement led to a final R value of 0.036 for 3260 independent observed reflections. The electronic structure was calculated by use of the EHMO quantum chemical method. The molecular features and the influence on the coordinate geometry, and the nature of the bonding of the central tin atom are discussed.     

The first complex of C60 fullerene with bis(ethylenedithio)tetrathiafulvalene radical cation: C60·(BEDT-TTF·I3)

The complex of C₆₀ fullerene containing the radical cation of the organic donor,viz., C₆₀·(BEDT-TTF·I₃), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, was synthesized for the first time. Single crystals of the complex were grown in benzonitrile. The crystals of this compound belong to the monoclinic system with a base-centered lattice. The unit cell parameters are as follows:a=17.419(6),b=9.997(4),c=13.499(1) Å, β=99.00 (1)^o. The IR and electronic spectra of single crystals of the complex have absorption bands characteristic of the BEDT-TTF^.+ radical cation and neutral C₆₀. The ESR spectrum has a signal withg=2.0074 and δH _pp=23 G belonging to BEDT-TTF^.+. The position of the 13d_5/2 peak in the X-ray photoelectron spectrum confirms the formation of the I₃ ^? anion.     

The thermodynamic parameters of complex formation between the copper(II) Ion and β-alanine in aqueous solution

The heats of formation of β-alanine complexes with the doubly charged copper(II) ion were determined calorimetrically. The heat effects of interaction of a solution of the amino acid with a solution of copper(II) were measured at 288.15, 298.15, and 308.15 K and ionic strengths of 0.50, 0.75, and 1.00 against the background of KNO₃. The heats of dilution of a solution of copper nitrate with solutions of the background electrolyte were also determined for the introduction of the corresponding corrections. The standard thermodynamic characteristics of complex formation were calculated. The influence of temperature on the thermal effects of complex formation in the β-alanine-copper(II) ions system were considered. The standard enthalpies of formation of CuAla⁺ and CuAla₂ complex particles in aqueous solution were calculated.     

Gas-phase reactions of the bis(η-cyclopentadienyl)methylzirconium cation with imines

The reactions of the bis(η⁵-cyclopentadienyl)methylzirconium cation (1) with four imines have been studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. Reactivity of the bis(η⁵-cyclopentadienyl)methylzirconium cation is governed by the availability of a labile hydrogen in the corresponding imine. The products observed differ from those that might be expected in analogy with earlier work on ketones, aldehydes and alkenes (e.g., zirconocene η³-enolate and η³-allyl complexes): azomethyne/benzylidene species are found instead of enamines; however, the general reaction mechanism resembles that proposed for ketones and alkenes. An elimination reaction leading to final products was shown to be preceded by a fast migratory insertion/deinsertion equilibrium for alkyl-substituted imines. Such an equilibrium is not possible for aryl-substituted imines due to lack of lability of the aryl groups and thus only methane elimination was observed for these imines.     

Kinetics of η6→η5 isomerization of (η6-fluorenyl)(η5-cyclopentadienyl)iron

The kinetics of the reversible isomerization of the zwitterionic complex [(⁶-C₁₃H₉)Fe(⁵-C₅H₅)] (1) into dibenzoferrocene (2) was studied by electronic spectroscopy in the temperature range from 70 to 103 °C. The activation parameters of the reaction 1 2 were determined, E _a = 22.5 kcal mol^–1.     

Vapor-phase electronic absorption spectrum of (η5-cyclopentadienyl)(η5-cycloheptatrienyl)chromium

The UV and visible absorption spectra of (Cp)(Ch)Cr (Cp = η⁵-C₅H₅, Ch = η⁷-C₇H₇) vapor show surprisingly well-resolved Rydberg structure. The first ionization potential (5.603 ± 0.007 eV) has been determined as a convergence limit of three Rydberg series. (Cp)(Ch)Cr is the first sandwich complex in which the lowest Rydberg transitions terminating at ns and np(σ) orbitals have vibrational structure.     

Transition metal catalyzed Fe–C coupling reactions in synthesis of dicarbonyl(2-thienylethynyl)(η5-cyclopentadienyl)iron complex: Spectroscopic,structure and electrochemical study

Transition Metal Chemistry - The new σ-alkynyl iron(II) complex Cp(CO)2Fe-C≡C-(2-C4H3S) was synthesized with application of several known approaches based on the transition metal...     

Effect of solution pH on complex formation between epi-type catechin and β-cyclodextrin

Journal of Thermal Analysis and Calorimetry - The effect of solution pH on the formation of an inclusion complex between (?)-epigallocatechin gallate (EGCg: pKa?=?7.5) and...     

Carbonium ion stabilization by (η5-cyclopentadienyl)dicarbonylnitrosylchromium; a 1H and 13C NMR study

the ¹H and ¹³C NMR spectra of a series of (η⁵-cyclopentadienyl)dicarbonylnitrosylchromium-substituted carbonium ions have been determined. These data suggest that the same mechanism is responsible for the stabilization of carbonium ions by (η⁵-cyclopentadienyl)dicarbonylnitrosylchromium as is operational in the analogous ferrocene and cymantrene complexes.     

Synthesis and molecular structure of (η-pentamethyl-cyclopentadienyl) (η-cyclopentadienyl) hexacarbonyl molybdenum tungsten

The metathesis reaction of Cp*(CO)₃MoBr and NaW(CO)₃Cp produced Cp*(CO)₃Mo-W(CO)₃Cp (1), featuring an unsupported Mo-W bond. Exposure of solutions of 1 to light leads to the quantitative formation of the corresponding homometallic dimers. In the solid state, the title complex exhibits an anti-arrangement of the η⁵-cyclopentadienyl and the η⁵-pentamethyl-cyclopentadienyl ligands and six terminal carbonyls. Comparison to corresponding complexes of molybdenum and tungsten reveals that the Mo-W distance is dictated by the presence of a Cp and a Cp* ligand. This is the first time that an unsupported Mo-W single bond distance is reported.     

μ-[Bis(η5-cyclopentadienyl)dimethylsilyl]bis(tricarbonylwolfram), ein über cyclopentadienylliganden verbrücktes bis(η5-cyclopentadienyltricarbonylwolfram)

The reaction of W(CO)₃(EtCN)₃ with (C₅H₅)₂Si(CH₃)₂ leads to the Cp-bridged, binuclear hydrido complex [W(CO)₃H]₂-μ-[(η⁵-C₅H₄)₂Si(CH₃)₂] as the main product, whereas only [W(CO)₃]₂-μ-(η⁵-C₅H₄)₂Si(CH₃)₂] (I) is formed as the minor product. Much better yields of I can be obtained in the reaction of W(CO)₃(EtCN)₃ with the lithium salt Li₂[(C₅H₄)₂Si(CH₃)₂] and subsequent oxidation. As pointed out by X-ray structure analysis complex I has a cis-configuration with C₂-symmetry due to the linked Cp ligands. In the chiral complex a topomerism can be proved by temperature-dependent NMR spectroscopy.     

Nature of low-lying electron excited states of (η5-cyclopentadienyl) (η7-cycloheptatrienyl)niobium

Electron absorption spectra of (⁵-cyclopentadienyl)(⁷-cycloheptatrienyl)niobium in solution and in the vapor phase have been measured for the first time. Possible variants of the band assignment for the spectrum of the complex in a solution have been considered. In the spectrum of the vaporous compound the bands at 29570, 31730, and 34630 cm^–1 correspond to the electron transitions from the 4d(⁺) orbital to the lowest Rydberg p- and d-levels. The values of Rydberg transition terms and symmetry of p-states have been determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 634–638, April, 1994.The author is grateful to I. L. Fedyushkin for the synthesis of complex 1.     

Molecular complex of C60 fullerene with an organic π-donor,bis(methylenedithiotetrathiafulvalene): synthesis,crystal structures,and properties

A new molecular complex based on [60]fullerene, namely, (BMDT-TTF)·C₆₀·2CS₂ (1) (where BMDT-TTF is bis(methylenedithiotetrathiafulvalene)) was synthesized. The molecular and crystal structures of 1 were established by X-ray diffraction analysis. Complex 1 has a layered structure, layers of C₆₀ molecules alternating with those formed by BMDT-TTF molecules and CS₂ molecules located between them. In complex 1, there are short contacts between C₆₀ and the donor molecules, which results in a changed BMDT-TTF geometry. The donor molecules in 1 form in addition short S...S contacts. The data of IR spectroscopy indicate that the charge transfer to the fullerene molecule is insignificant if at all present. The conductivity of a single crystal of 1 measured at 20 °C using a four-contact method is 2·10^–5 ( cm)^–1.     

Synthesis and characterization of the first transition-metal fullerene complexes containing bis(η-benzene)chromium moieties

While photochemical reaction of C₆₀ with an equimolar amount of Mo(CO)₄(η⁶-Ph₂PC₆H₅)₂Cr (1) in toluene at room temperature produced bimetallic Mo/Cr fullerene complex fac/mer-(η²-C₆₀)Mo(CO)₃[(η⁶-Ph₂PC₆H₅)₂Cr] (2) in 87% yield, the thermal reaction of an equimolar mixture of C₆₀, M(dba)₂ (M = Pd, Pt; dba = dibenzylideneacetone) and (η⁶-Ph₂PC₆H₅)₂Cr (3) in toluene at room temperature afforded bimetallic M/Cr fullerene complexes (η²-C₆₀)M[(η⁶-Ph₂PC₆H₅)₂Cr] (4, M = Pd; 5, M = Pt) in 88% and 92% yields, respectively. Products 2, 4 and 5 are the first transition-metal fullerene complexes containing bis(η⁶-benzene)chromium moieties. While 2, 4 and 5 were characterized by elemental analysis and spectroscopy, the crystal molecular structures of 4 along with the starting materials 1 and 3 have been determined by X-ray diffraction techniques.     

Gas phase ion molecule chemistry of tetracarbonyl (η5-cyclopentadienyl) vanadium by Fourier transform ion cyclotron resonance

The kinetics of the reactions between the CpV(CO)₄ molecule and its fragment cations and anions have been examined using Fourier transform ion cyclotron resonance (FTICR) techniques. With 25 eV electron impact ionization the fragment cations V⁺ and CpV(CO)_n=0–4⁺ react principally by charge exchange or by condensation with the parent neutral molecule. Rate constants for these pathways have been determined along with kinetic evidence for the existence of excited state cations. Some of the product cations show unexpected stability despite their large formal electron deficiency. Exchange of carbonyl ligands was also observed. Under 2.5 eV electron impact, only two anions are produced: CpV(CO)_n=2,3⁻, both of which are unreactive with the parent neutral.     

Regiocontrol switching in CC bond formation during decomplexation of a tricarbonyl(η4-cyclohexadiene)iron complex

A study has been made of additions of nucleophiles to the tricarbonyl(η⁴-cyclohexadiene)iron complex 1 and subsequently reaction of the resulting anions with several electrophiles in the presence of added ligands. Carbonyl insertion to form a functionalised cyclohexene ring is assisted by the addition of phosphines. Depending on the electrophilic reagent, an unusual phosphine-controlled switch in regiochemistry (PhCH₂Br), and interruption of the process prior to loss of the metal (CH₂=CHCH₂Br), have been observed.     

ESR study of reactivity of the complex (η2-C60)Os(CO)(PPh3)2(CNBut) toward free radicals

Addition of the ^·P(O)(OPrⁱ)₂, Me^·, Et^·, ^·Bu^t, and Cl₃C^· radicals to the (ν²-C₆₀)Os(CO)-(PPh₃)₂(CNBu^t) complex (1) was studied by ESR spectroscopy. The spectral parameters of the spin-adducts of these radicals with complex 1 were determined. The predominant direction of the attack by the ^·P(O)(OPrⁱ)₂, ^·Bu^t, and Cl₃C^· radicals are the cis-1 and cis-2 bonds of the fullerene molecule. The stability of the spin-adducts depends substantially on the nature of the added radical. The addition rate constants of the ^·P(O)(OPrⁱ)₂, ^·But, and Cl₃C^· radicals to complex 1 and the dimerization rate constants for these spin-adducts were determined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 301–307, February, 2008.     

Structure and reactivity of substituted di-η5-cyclopentadienyl metal dihalides. Crystal structure of dichlorobis(η5-t-butylcyclopentadienyl)zirconium(IV)

A new approach to the synthesis of t-butylcyclopentadienyl and related anions, via the addition of methyl- or other alkyl-lithium compounds to dimethylfulvene, is reported and details are given for the preparation of (η⁵-t-BuCp)₂ZrCl₂ and (η⁵-t-BuCp)₂TiCl₂. The zirconium compound is orthorhombic, P2₁2₁2, a 13.003(17), b 10.761(10), c 6.703(8) Å. A crystal structure determination (R = 0.037, 980 reflections) shows that the t-butyl groups are directed away from each other on opposite sides of the molecule: this structure appears to be adopted only in molecules in which the substituent groups are too bulky to be accommodated directly above and below the MCl₂ group.