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.     

(η6-Anisole) (η2-benzene) dicarbonylchromium(0): an intermediate in the photochemical carbonyl substitution of (η6-anisole)tricarbonylchromium(0) in benzene

The photochemical carbonyl substitution of (η⁶-anisole)Cr(CO)₃ has been investigated by laser flash photolysis. Both transient spectra and second-order rate constants for the reactions of transients with nucleophiles are found to be extremely variable depending upon solvents used. The coordination of benzene to the transient in cyclohexane forms the transient in benzene, indicating two discrete chemical species: (η⁶-anisole)Cr(CO)₂ and (η⁶-anisole)Cr(CO)₂(η²-benzene). The latter type of transient was observed also for fluorobenzene and mesitylene, leading to the assignment of a weak band in the visible region as η²-arene → Cr charge transfer. The existence of (η⁶-arene)Cr(CO)₂(η²-arene′) may throw light on what have been described as solvent effects in organometallic reactions.     

Bis(trifluormethylisocyanid)-(η-pentamethylcyclopentadienyl)-cobalt. Darstellung und Oxidation zu Trifluormethylisocyanid-(η-pentamethylcyclopentadienyl)-dihalogeno-cobalt

Ligand substitution in Cp^*Co(CO)₂ (Cp^* = C₅(CH₃)₅) by trifluoromethyl isocyanide yields Cp^* Co(CNCF₃)₂. Due to the high electron density at the metal atom,the NC vibrations are shifted to low wavenumbers (1906, 1832 cm⁻¹) compared to the free isocya This compound is rapidly oxidized by halogenes to the corresponding halogeno complexes Cp^* Co(CNCF₃)X₂ (X = Cl, Br,I).     

N-(η5-Cyclopentadienylvanadium)benzenesulfonamide

N-(⁵-Cyclopentadienylvanadium)benzenesulfonamide has been synthesized for the first time by treating benzenesulfonamide orN-(tributylstannyl)benzenesulfonamide with vanadocene.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2107–2109, December, 1993.     

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.     

Reaction of alkyne cluster Os3(μ-CO)(CO)9(μ3-η1:η1:η2-Me3SiC2Me) with HC≡CCOOMe. Molecular and crystal structures of Os3(CO)9{μ3-η1:η1:η2:η2-C(SiMe3)C(Me)C(COOMe)CH× and Os3(CO)8{μ3-η1:η1:η4:η1-C(SiMe3)C(Me)C(H)C(COOMe)CH× complexes

Reaction of the cluster Os₃(μ-CO)(CO)₉(μ₃-η¹:η¹:η²-Me₃SiC₂Me) with HC≡CCOOMe in benzene at 70 °C results in Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(COOMe)CH× (5), Os₃(CO)₉{μ₃-η¹:η¹:η²:η²-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (6), Os₃(CO)₉{μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)CH× (7), and Os₃(CO)_δ{μ₃-η¹:η¹:η⁴:η¹-C(SiMe₃)C(Me)C(H)C(COOMe)× complexes (8), containing an osmacyclopentadiene moiety. Complexes5–8 were characterized by¹H NMR and IR spectroscopy. The structure of clusters5 and8 was confirmed by X-ray analysis. Complex7 is formed from cluster5 as a result of a new intramolecular rearrangement and complex8 is obtained by decarbonylation of compound6. Complex8 adds PPh₃ to give Os₃(CO)_δ(PPh₃){μ-η¹:η¹:η⁴-C(SiMe₃)C(Me)C(H)C(COOMe)×.     

Reaction of Mercury(II) Trifluoroacetate with Deprotonated (η6-Toluene)-, (η6-Diphenylmethane)-, and (η6-Triphenylmethane)(η5-cyclopentadienyl)iron(II) Complexes. Mercuration of Some Cationic (Arene)(cyclopentadienyl)iron(II) Complexes

Treatment with mercury(II) trifluoroacetate of deprotonated (⁶-toluene)- and (⁶-diphenyl- methane)(⁵-cyclopentadienyl)iron(II) complexes gave mono-, di-, and trisubstituted [from (⁶-toluene)(⁵-cyclopentadienyl)iron(II) cation] mercury-containing salts. The reaction of mercury(II) trifluoroacetate with deprotonated (⁶-triphenylmethane)(⁵-cyclopentadienyl)iron(II) afforded only the corresponding sym- metric mercury derivative. The same product was obtained by direct mercuration with mercury(II) trifluoroacetate of (⁶-triphenylmethane)(⁵-cyclopentadienyl)iron(II) on heating the reactants in boiling unhydrous ethanol. Reactions of the resulting mercury-containing compounds with acids, symmetrizing bases, and acylating agents were studied.     

New access to (η(5)-cyclohexadienyl)Mn(CO)3 and cationic (η(6)-arene)Mn(CO)3 complexes by Suzuki-Miyaura reaction

First Suzuki-Miyaura coupling reactions applied to (η(5)-chloro-cyclohexadienyl)Mn(CO)3 complexes are described and lead to the syntheses of (η(5)-aryl-cyclohexadienyl)Mn(CO)3 and of cationic (η(6)-arene)Mn(CO)3 complexes after rearomatization. The structures of two of the new complexes have been investigated by X-ray diffraction study.     

Crystal and molecular structure of (μ-η2,η3-propargyl)- bis(cyclopentadienyl)tetracarbonyldimolybdenum tetrafluoroborate and (μ-η2,η3-1,1-dimethylpropargyl)- bis(cyclopentadienyl)tetracarbonyldimolybdenum tetrafluoroborate

An X-ray study of [(μ-η²,η³-HCCCH₂)Cp₂Mo₂(CO)₄]⁺(BF₄⁻) (1) and [(μ-η²,η³-HCCCMe₂)Cp₂Mo₂(CO)₄]⁺(BF₄⁻) (2) reveals their structures to be similar to the structure of neutral compounds of the series (μ-η²,η²-RCCR)Cp₂Mo₂(CO)₄, the difference between 1 and 2 being mainly due to the markedly different MoC⁺ bond lengths, which accounts for different stability and fluxional behavior of these compounds in solution.     

Mercuration with Mercury(II) Trifluoroacetate of (η6-Aniline)- or (N,N-dimethylaniline)(η5-cyclopentadienyl)iron(II)

The reaction of mercury(II) trifluoroacetate with the hexafluorophosphate of the ⁶-aniline-⁵cyclopentadienyliron(II) cation under reflux in dry ethanol gives rise to N-mono- and N,N-disubstituted mercury-containing salts of this cation. The same mercury-containing salts have been synthesized by the action of mercury(II) trifluoroacetate on the deprotonation product of the (⁶-aniline)(⁵-cyclopentadienyl)iron(II) cation. Direct mercuration of the [⁶-(N,N-dimethylaniline)](⁵-cyclopentadienyl)iron(II) cation into the para position of the benzene ring of the arene ligand has been performed. The reactivity of the compounds obtained has been studied.     

Phosphine-centred resolution of (η4-diene)Fe(CO)3 complexes: (η4-tropone)Fe(CO)2L and (η4-isoprene)Fe(CO)2L [L = (+)-(neomenthyl)PPh2]

(η⁴-Tropone)Fe(CO)₃ and (η⁴-isoprene)Fe(CO)₃ form separable diastereoisomers on substitution of CO by (+)-(neomenthyl)PPh₂. In the tropone complex, diastereoisomer interconversion occurs by a 1,3-metal shift. The absolute configuration of the isoprene complex has been determined crystallographically.     

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.     

Planar chiral (η5-cyclohexadienyl)- and (η6-arene)-tricarbonylmanganese complexes: synthetic routes and application

Planar chiral arenetricarbonylchromium complexes have been intensively investigated and they have been applied as valuable building blocks for asymmetric synthesis and as ligands for asymmetric catalysis. In contrast, in the field of the isoelectronic cationic [(η(6)-arene)Mn(CO)(3)](+) complexes, until these last 10 years, very few studies were published involving nonracemic planar chiral cationic complexes and their potential applications, certainly because of the difficult access to enantiopure starting material. In 2009, however, the discovery of the first resolution of such compounds opened a new area for their application in the field of organic as well as of organometallic enantioselective syntheses. We felt it important to write a review on this subject to give an up-to-date summary of the methodologies used to prepare enantiomerically pure planar chiral neutral [(η(5)-cyclohexadienyl)Mn(CO)(3)] and cationic [(η(6)-arene)Mn(CO)(3)](+) complexes as well as their potential in enantioselective synthesis.     

Crystal structure of twinned (η5-C5(CH3)4CF3) (η5-C5(CH3)5)Ru

The substituted sandwich complex crystallizes in monoclinic space groupP2₁/m withZ=2. Twinning to the (001) direction with the special conditionc ^*/4a ^* = cos ^* causes systematic superposition of the reciprocal lattices of both domains and results in an apparent unit cell with double volume and the reflection condition (2h)kl, l=2n. The structure solution was obtained with the subset of intensity data for the predominant individuum and converged atR = 0.040,R _w =0.046 for 832 independent observations and 122 variables. The molecules show disorder with respect to the crystallographic mirror plane. The structure is closely related to that of decamethylruthenocene.     

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.     

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.     

Reactions of (η6-diphenylacetylene) chromiumtricarbonyl complexes with polynuclear carbonyls I. Synthesis of Cr(CO)3(η6-diphenylacetylene) complex and its reaction with Co2(CO)8. Crystal and molecular structure of Cr(CO)3(η6:η2-diphenylacetylene)Co2(CO)6

The reaction of Cr(CO)₃(NH₃)₃ with diphenylacetylene affords as a main product the complex with Cr(CO)₃ moiety bound to a phenyl ring of diphenylacetylene; Cr(CO)₃(η⁶-PhC₂Ph) (I). Complex I readily reacts with Co₂(CO)₈ yielding the mixed metal complex Cr(CO)₃(η⁶:η²-PhC₂Ph)Co₂(CO)₆ (II). The reaction proceeds with retention of the Cr(CO)₃ (η⁶-arene) structural unit, the Co₂(CO)₆ fragment being bound to the triple bond of diphenylacetylene in μ₂,η²-mode. The structure of II was determined by single crystal X-ray analysis. The complex crystallizes in space group P2₁/c with unit cell parameters a 8.666(3) Å, b 18.046(3) Å, c 15.155(6) Å. β 97.57(3)°, V 2349(2) ų, Z = 4, D_x = 1.70 g/cm³. The structure was solved by direct methods and refined by full-matrix least-squares technique to R and R_w values of 0.032 and 0.034, respectively, for 3655 observed reflections. The data obtained show that two structural units in II, Cr(CO)₃(η⁶-Ph-) and Co₂(CO)₆(μ₂,η²-CC), are distorted due to steric repulsion between these metal carbonyl moieties. The Cr(CO)₃ fragment is shifted from the centre of the phenyl ring and slightly tilted with respect to the phenyl ring plane. The Co₂C₂ tetrahedron in the Co₂(CO)₆(μ₂,η²-CC) moiety is distorted in such a way that two of the four Co_iC_j bonds are elongated.     

Replacement of terminal and bridging oxo groups by phenylimido groups in (η-C5H5)OMo(μ-O)2OMo(η-C5H5) giving (η-C5H5)(NPh)Mo(μ-NPh)2Mo(NPh)(η-C5H5)

The treatment of (η-C₅H₅)OMo(μ-O)₂MoO(η-C₅H₅) with excess phenylisocyanate at reflux in tetrahydrofuran yields the arylimido-substituted complex (η-C₅H₅)(NPh)Mo(η-NPh)₂Mo(NPh)(η-C₅H₅), which has been characterized by elemental analysis, and mass, IR and ¹H NMR spectra.     

(η-Tetraarylcyclobutadiene)(η-formylcyclopentadienyl)cobalt(I) complexes: Facilities to finetune the electron-donating capability in dipolar organometallics

Five different (η⁴-tetraarylcyclobutadiene)(η⁵-formylcyclopentadienyl)cobalt(I) complexes (1a-1e) were synthesized in reasonable yields in a one-pot reaction of CoCl(PPh₃)₃, formylcyclopentadienyl sodium and the appropriate diarylethyne. The aryl groups of the ethyne were modified by various para-substituents X (X = Cl, H, Me, OMe, NMe₂), which were intended to alter the redox potentials of the synthesized cobalt sandwich complexes. A cyclic voltammetry study revealed a linear dependence of the first oxidation potential to the Hammett parameter σ_p. X-ray structure analyses performed for two complexes (X = Me and NMe₂) demonstrate only subtle changes in the solid state structure despite the large differences in electrochemical properties. A theoretical analysis by the density functional theory method has been performed on the geometries and electronic structures of the complex (η⁴-cyclobutadiene)(η⁵-cyclopentadienyl)Co(I), its cation and dication.