Oxidation of isomeric η6- and η5-fluorenylchromiumtricarbonyl anions

The oxidation of the carbon-centered [(⁶-C₁₃H₉)Cr(CO)₃]^– anion (1 ^–) results in formation of (-⁶:⁶-9,9-bifluorenyl)bis-chromiumtricarbonyl (3) due to coupling of the intermediate carbon-centered radical (1^.). The oxidation of the metal-centered anion [(⁵-C₁₃H₉)Cr(CO)₃]^– (2 ^–), which is isomeric to the 1^– anion, gives an equilibrium mixture of the chromium-centered radical {(⁵-C₁₃H₉)Cr(CO)₃}^. (2 ^.) and its dimer [(⁵-C₁₃H₉)Cr(CO)₃]₂ (6). Radical2 ^. readily reacts with MeI and the solvent (THF); the resulting derivatives, (⁵-C₁₃H₉)Cr(CO)₃R (R=Me (10); R=H (7)), undergo fast ricochet inter-ring ⁵⁶ rearrangements into (⁶-9R-C₁₃H₉)Cr(CO)₃ (R=CH₃ (9); R=H (4)).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1354–1358, July, 1995.The authors are grateful to D. V. Zagorevskii who recorded the mass spectra. This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-05209) and the International Science Foundation (Grant Nos. MQ 4000 and REV 000).     

The interconversion of η5 and η3 hapticities in cycloheptadienyl complexes of molybdenum and tungsten

[Mo(CO)₄(η⁵-C₇H₉)]⁺ (1) reacts with acetonitrile to give [Mo(CO)₂(NCMe)₃(η³-C₇H₉)]⁺ (3), which is precursor of a wide reange of η⁵-cycloheptadienyl complexes [Mo(CO)₂L₂(η⁵-C₇H₉)]⁺ [6, L = PPH₃; 7, L₂ = Ph₂PCH₂PPh₂; 8, L₂ = 1,3-cyclohexadiene; 9, L₂ = 2,2′-dipyridyl]; 9 reacts reversibly with NCMe to give [Mo(CO)₂(NCMe)(dipy)(η³-C₇H₉)]⁺ (10).     

Acyclic boron-containing π-ligand complexes: η2- and η3-coordination modes

Cyclic boron-containing π-ligands such as boratabenzenes and borollides are well established, in particular as supporting ligands. By contrast, the chemistry of acyclic boron-containing π-ligands has remained relatively unexplored, presumably in part due to the higher reactivity of acyclic π-ligands relative to cyclic analogues. This perspective is focused on the synthesis, structures and reactivity of isolated transition metal complexes bearing η(n)-coordinated (n = 2 or 3) acyclic boron-containing ligands. Both monometallic and multimetallic compounds are included, and are discussed with an emphasis on metal-ligand and intraligand bonding and parallels with hydrocarbon π-ligand complexes.     

Acetylation and benzoylation of η5,η5-fulvalenedimanganesehexacarbonyl

⁵,⁵-Fulvalenedimanganesehexacarbonyl (dicymantrenyl) was acetylated and benzoylated by RC(O)Cl+AlCl₃ in CH₂Cl₂, under conditions of the Friedel-Crafts reaction. The reaction involves both nonequivalent positions of the cyclopentadienyl rings to give mixtures of two isomeric ketones. When using an excess of the acetylating mixture, diacetyl derivatives of dicymantrenyl were obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2017–2020, October, 1995.The authors are grateful to P. V. Petrovsky and E. V. Vorontsov (the NMR laboratory of the Institute of Organoelement Compounds, Russian Academy of Sciences) for recording¹H NMR spectra.     

Fullerene C60 as a η5- and η6-ligand in sandwich-type π-complexes with transition metals

The molecular and electronic structures of some hypothetical sandwich-type -complexes of transition metals with fullerene C₆₀ were modeled. The M-C₆₀ bonds in ⁵-C₆₀MCp⁺ complexes (M = Fe, Ru, Os) are less strong than the M-Cp bonds in ferrocene, ruthenocene, and osmocene, respectively. The ⁶-C₆₀MC₆H₆ complexes (M = Cr, Mo, W) should be less stable than their classical analogs (C₆H₆)M(C₆H₆). The coordination of a metal atom with the fullerene at its pentagonal face is more energetically favorable than at a hexagonal face.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 598–601, April, 1994.We are grateful to V. I. Sokolov for discussion of the results obtained. This study was supported by the Russian Foundation for Basic Research (grants 93-03-4101 and 93-03-18725).     

Syntheses and characterization of cyano-bridged homo and hetero bimetallic complexes containing η and η-cyclic hydrocarbons

The reactions of [(ind)Ru(PPh₃)₂CN] (ind = η⁵-C₉H₇) (1) and [CpRu(PPh₃)₂CN] (Cp = η⁵-C₅H₅) (2) with [(η⁶-p-cymene)Ru(bipy)Cl]Cl (bipy = 2,2′-bipyridine) (3) in the presence of AgNO₃/NH₄BF₄ in methanol, respectively, yielded dicationic cyano-bridged complexes of the type [(ind)(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (4) and [Cp(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (5). The reaction of [CpRu(PPh₃)₂CN] (2), [CpOs(PPh₃)₂CN] (6) and [CpRu(dppe)CN] (7) with the corresponding halide complexes and [(η⁶-p-cymene)RuCl₂]₂ formed the monocationic cyano-bridge complexes [Cp(PPh₃)₂Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (8), [Cp(PPh₃)₂Os(μ- CN)Ru(PPh₃)₂Cp](BF₄) (9) and [Cp(dppe)Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (10) along with the neutral complexes [Cp(PPh₃)₂Ru(μ-CN)Ru (η⁶-p-cymene)Cl₂] (11), [Cp(PPh₃)₂Os(μ-CN)Ru(η⁶-p-cymene)Cl₂] (12), and [Cp(dppe) Ru(μ-CN)Ru(η⁶-p-cymene)Cl₂] (13). These complexes were characterized by FT IR, ¹H NMR, ³¹P{¹H} NMR spectroscopy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies.     

Redox-induced η5 ⇔ η3 haptotropy of the fluorenyl ligand in 9-substituted η5-fluorenylmanganesetricarbonyl complexes

It has been shown by cyclic voltammetry in THF within the –90 to 40 °C temperature range that fluorenyl (⁵-9-R-C₁₃H₈)Mn(CO)₃ complexes (R=Bu^t (3) and Ph (4)) undergo two-electron reduction to form allyl type [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– dianions as final products. At low temperatures complexes3 and4 are reduced in two one-electron steps according to the EEC-scheme. The first step is reversible and corresponds to the formation of 19-radical anions 3^–. and 4^–.. TheE ⁰ values for redox pairs3 ^0/–. and4 ^0/–. are –1.88 and –1.73 V, respectively. The further reduction of radical anions3 ^–. and4 ^–. at more negative potentials is accompanied by fast ^{5 3} haptocoordination of the fluorenyl ligand to form 18-dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2–. These dianions obtained by the reduction of complexes3 and4 by the radical anion of pyrene are stable at –80 °C and are characterized by their IR spectra. At room temperature the ^{5 3} hapticity change is a fast and reversible process occurring at the step of 19-radical anions3 ^–. and4 ^–. and leading to the electron deficient 17-species [(³-9-R-C₁₃H₈)Mn(CO)₃]^–., which are reduced easier than the initial complexes. As a result, complexes3 and4 are reduced to the corresponding dianions [(³-9-R-C₁₃H₈)Mn(CO)₃]^2– at room temperature in one reversible two-electron step according to the ECE-scheme. Reactivities of 19e^–-species of the isomeric ⁵- and ⁶-fluorenylmanganesetricarbonyl complexes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1347–1353, July, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 93-03-05209) and the International Science Foundation (Grant No. REV 000).     

Fulleride-metal η5 sandwich and multi-decker sandwich complexes: A DFT prediction

The (C₆₀CN)⁻ formed by the reaction of CN⁻ with fullerene shows high electron rich character, very similar to C₆₀˙⁻, and it behaves as a large anion. Similar to Cp⁻, the bulky anion, (C₆₀CN)⁻, acts as a strong η⁵ ligand towards transition metal centers. Previous studies on η⁵ coordination of fullerene cage are reported for pseudo fullerenes whereas the present study deals with sandwich complexes of (C₆₀CN)⁻ with Fe(II), Ru(II), Cr(II), Mo(II), and Ni(II) and multi-decker sandwich complexes of CN–fullerides with Fe(II). The structural parameters of these complexes and the corresponding Cp⁻ complexes showed very close resemblance. Analysis of the metal-to-carbon bonding molecular orbitals showed that sandwich complex [Fe(η⁵-(C₆₀CN)⁻)₂] exhibit bonding features very similar to that of ferrocene. Also, a 6-fold decrease in the band gap energy is observed for [Fe(η⁵-(C₆₀CN)⁻)₂] compared to ferrocene. The energy of dissociation (ΔE) of the ligand (C₆₀CN)⁻ from [Fe(η⁵-(C₆₀CN)⁻)₂] is slightly lower than the ΔE of a Cp* ligand from a ferrocene derivative wherein each cyclopentadienyl unit is substituted with four tertiary butyl groups. The (C₆₀CN)⁻ ligand behaved as one of the bulkiest ligands in the chemistry of sandwich complexes. Further, the coordinating ability of the dianion, (C₆₀(CN)₂)²⁻ is evaluated which showed strong coordination ability simultaneously with two metal centers leading to the formation of multi-decker sandwich and pearl-necklace type polymeric structures.     

Intramolecular dehydrofluorinative coupling of η-arene and fluoroarylphosphine ligands in ruthenium complexes

NMR studies of reactions between a series of arene ruthenium(II) fluoroarylphosphine complexes and Proton Sponge have revealed the necessary conditions for intramolecular dehydrofluorinative ligand coupling. The complex must be cationic, and the phosphine need have only one fluoroaryl substituent. The reaction is rapid and clean for [(η⁶-toluene)RuCl(dfppe)]BF₄, [(η⁶-mesitylene)RuCl{(C₆F₅)₂PC₆H₄SMe}]BF₄ and the diastereomer of [(η⁶-toluene)RuCl{Ph₂PC₂H₄PPh(C₅F₄N-4)}]BF₄ in which the tetrafluoropyridyl substituent is close to the η⁶-arene. [(η⁶-p-cymene)RuCl(dfppe)]BF₄ reacts in the presence of Proton Sponge to give a mixture of unidentified compounds. The neutral complex [(η⁶-toluene)RuCl₂{Ph₂P(C₆F₅)}] and the diastereomer of [(η⁶-toluene)RuCl{Ph₂PC₂H₄PPh(C₅F₄N-4)}]BF₄ in which the tetrafluoropyridyl substituent is distant to the η⁶-arene do not undergo reaction.     

Hydroxylation of azomethine carbon: isolation of complexes of η5 and η6-cyclic hydrocarbon platinum group metals with a new Schiff-base ligand

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η⁶-arene)Ru(µ-Cl)Cl]₂ and [Cp*M(µ-Cl)Cl]₂ (M = Rh and Ir) with one equivalent of L in the presence of NH₄PF₆ in methanol yielded dinuclear complexes, [(η⁶-arene)₂Ru₂(L-OH)Cl](PF₆)₂ {arene = C₆H₆ (1), p-ⁱPrC₆H₄Me (p-cymene) (2) and C₆Me₆ (3)}, and [Cp*₂M₂(L-OH)Cl](PF₆)₂ [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF₆]₂ and N(3) for 4[PF₆]₂}. The complexes have been characterized by various spectroscopic methods including infrared and ¹H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies.     

Baseninduzierte CC-Kupplungsreaktionen an η2-Thiocarbenliganden - Synthese von η3-Thioketencomplexen des Wolframs

Dicarbonyl(η⁵-cyclopentadienyl)[η²-aryl(methylthio)carbene]tungsten tetrafluoroborate reacts with trimethylphosphine to give first an intermediate cationic η³-thioketene complex which adds trimethylphosphine to yield a cationic tungsta-oxa-thia-cyclopentene ring system.     

Synthesis and catalytic activity of rhodium diene complexes bearing indenyl-type fullerene η-ligand

Rhodium η⁵-complexes bearing an indenyl-type fullerene ligand, Rh[C₆₀(PhCH₂)₂Ph](cod) (2), Rh[C₆₀(PhCH₂)₂Ph](nbd) (3) and Rh(C₇₀Ph₃)(cod) (4), have been synthesized from the corresponding fullerene tri-adducts in 93-96% yields. X-ray crystallographic analysis of 4 indicated that the structure of 4 is similar to that of Rh(Ind)(cod). The rhodium complex 2 catalyzes alkyne trimerization reactions and hydroboration reactions.     

The First Rotational Isomers of Stable Selenobenzaldehydes and their η1-Tungsten Complexes

The first rotational isomers of stable selenoaldehydes are synthesized by deselenation of cyclic polyselenides having an efficient steric protection group, 2, 4, 6-tris[bis(trimetylsilyl)methyl]phenyl (Tbt). Reactions of these selenoaldehydes with W(CO)₅.THF gives the corresponding η¹-selenoaldehyde tungsten complexes, the structures of which are established by X-ray crystallography.     

Study of η5-(1-chloro-4-methylcyclohexadienyl) and η5-(1-methyl-4-chlorocyclohexadienyl)tricarbonylmanganese complexes in solution and in the solid state

The spectroscopic studies of neutral η⁵-(1-chloro-4-methylcyclohexadienyl) and η⁵-(1-methyl-4-chlorocyclohexadienyl) tricarbonylmanganese complexes have been realized in solution by ¹H NMR spectroscopy as well as in the solid state. The structures showed a dihedral angle of the sp³ carbon of 33.2° and 36.6° with respect to the cyclohexadienyl ring. To cite this article: F. Rose-Munch et al., C. R. Chimie 6 (2003).     

1,3-Dipolar cycloaddition reaction of nitrone η6-(arene)chromium tricarbonyl complexes with styrene and η6-(styrene)chromium tricarbonyl

The products of 1,3-dipolar cycloaddition of the nitrone-type η⁶-(arene)chromium tricarbonyl complexes (CO)₃CrC₆H₅CH=N⁺(O^?)R, where R = Me, Ph, Bu^t, with styrene and η⁶-(styrene)chromium tricarbonyl were obtained and characterized by a combination of physicochemical methods. This type of reactions proceeded with very high regio- and stereoselectivity to exclusively form cis-2,3,5-tri-substituted isoxazolidines.     

Mono- and di-nuclear azido η6-p-cymene ruthenium(II) complexes; synthesis,reactivity, and structures

The azide bridge complex [(η⁶-p-cymene)Ru(µ-N₃)Cl]₂ (2) was prepared from the reaction of sodium azide with [(η⁶-p-cymene)RuCl]₂ in ethanol. The molecular structures and spectroscopic properties of the various azido ruthenium complexes so obtained from the reaction with monodentate and bidentate ligands are described.     

P-Functionalized η1-P Phosphole Tungsten Complex as Intermediates for Cycloaddition Reactions and Phosphinidene Formation

Abstract

The reaction of 3,4-dimethylphospholyl anion 1 with W(CO)₆ yields the η¹ complexed anion 2 which reacts with electrophiles to give the new-P-functionalized complexes 3. Their ability to give Cycloaddition reactions has been compared.