The mechanism of fluxionality of (1,2,7-η3-2-Me-benzyl)(η5-C5H5)Mo(CO)2

It is shown that (1,2,7-η³-2-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits in solution as one isomer which is fluxional, probably via (7-η¹-2-Me-benzyl)((η⁵-C₅H₅)Mo(CO)₂, with ΔG^≠₃₇₀ = 23.6 ± 1.0 kcal mol⁻¹. In contrast, (1,2,7-η³-3-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG^≠ 15.7 kcal mol⁻¹. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.     

Molecular structure of ansa-compound (η5-C5H4)CMe2(η5-C9H6)TiCl2

The structure of a new ansa compound, (⁵-C₅H₄)CMe₂(⁵-C₉H₆)TiCl₂ (1), was studied by X-ray analysis:a = 15.00(1),b =15.500(5),c = 13.032(4) Å, = 92.66°(4),V = 3025.1(1) ų, space groupP2₁/.,R = 0.038. The distorted tetrahedral coordination sphere of the Ti atom is formed by two Cl atoms and two -ligands. It was proposed that the angle () between theC-M direction and the line normal to M-Cp can be considered as one of the geometric parameters characteristic of the structure-properties correlation.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 305–308, February, 1995.     

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.     

η5-cyclopentadienyl-η2-styrenedicarbonylmanganese for initiation of free-radical polymerization of vinyl monomers

The polymerization of styrene, methyl methacrylate, and vinyl chloride catalyzed by η⁵-cyclopentadienyl-η²-styrenedicarbonylmanganese is studied. It is shown that the cyclopentadienyl complex of manganese containing the monomer ligand (styrene) in the coordination sphere can initiate the radical polymerization of vinyl monomers in a mild temperature range. On the basis of the experimental data and the quantum-chemical simulation of the initial stages of the process, schemes describing the initiation of polymerization under the action of the complex under study and the binary initiating system containing carbon tetrachloride are advanced. In the latter case, additional acceleration of the reaction is related to the interaction of carbon tetrachloride with the triplet form of the manganese complex that yields trichloromethyl radicals initiating polymerization.     

Insertion reactions of t-Bu(η5-C5H5)Fe(CO)2

The complex t-Bu(η⁵-C₅H₅)FE(CO)₂ has been treated with triphenylphosphine in refluxing THF to produce t-BuCO(η⁵-C₅H₅)Fe(CO)(PPh₃). The large steric bulk of the t-butyl group suggests that this reaction should be faster than the reaction involving the methyl group, and a kinetic investigation illustrates this to be the case. The same steric bulk predicts that the reaction with SO₂ should be slow, and indeed we have been unable to effect the related SO₂ insertion reaction. Attempts to prepare the corresponding t-Bu(η⁵-C₅H₅)W(CO)₃ led to formation of the related isobutyl complex.     

Syntheses and Anti-inflammatory Action of (η-C_5H_5)_2Ti(Cin)_2 and (η-C_5H_5)_2Ti(Tzea)_2

ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅＫ ｐｆｄｉｓｃｏｖｅｒｅｄｔｈａｔｄｉｃｙｃｌｏｐｅｎｔａｄｉ ｅｎｙｌｔｉｔａｎｉｕｍｄｉｃｈｌｏｒｉｄｅｅｘｈｉｂｉｔｅｄａｎｔｉｔｕｍｏｕｒａｃｔｉｏｎｉｎ1979,1ａｌａｒｇｅｎｕｍｂｅｒｏｆｃｙｃｌｏｐｅｎｔａｄｉｅｎｙｌｔｉｔａｎｉｕｍｃｏｍ ｐｌｅｘｅｓｂｅａｒｉｎｇｄｉｆｆｅｒｅｎｔｓｕｂｓｔｉｔｕｅｎｔｓｈａｖｅｂｅｅｎｓｙｎｔｈｅ ｓｉｚｅｄ .2 ,3Ｔｈｅｅｘｐｅｒｉｍｅｎｔａｌｄａｔａｒｅｖｅａｌｅｄｔｈａｔ (Ｃｐ) 2 ＴｉＸ2(Ｘ =ｈａｌｏｇｅｎ ,ｐ…     

Synthesis and reactions of dicarbonyl (η2-indene)-η5-indenyl complexes of manganese and rhenium

Photochemical reactions of M(CO)₃(⁵-C₉H₇), where M=Mn (1) or Re (2), with indene have produced ²-indene complexes M(CO)₂(²-C₉H₈)(⁵-C₉H₇), where M=Mn (3) or Re (4). Deprotonation of complex3 witht-BuOK in THF at –60 °C gives the anion [Mn(CO)₂(¹-C₉H₇)(⁵-C₉H₇)^– (5), in which there occurs a rapid interchange of the Mn(CO)₂(⁵-C₉H₇) group between positions 1 and 3 in the ¹-indenyl ligand. The reaction of complex4 with Ph₃CPF₆ in CH₂Cl₂ at 0 °C leads to the complex [Re(CO)₂(³-C₉H₇)(⁵-C₉H₇)PF₆, whereas the similar reaction of complex3 gives only decomposition products even at –20 °C.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1280–1285, July, 1993.     

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.     

Application of electron-transfer chain catalysis: preparation of bridged 〚{(η5-C5H5)Fe(CO)2}2(μ-diphosphine)2+〛 complexes without chelated 〚(η5-C5H5)Fe(CO)(η2-diphosphine)+〛 byproducts

The ligand substitution by diphosphine L–L on (η⁵-C₅H₅)Fe(CO)₂I usually results in the chelated 〚(η⁵-C₅H₅)Fe(CO)(η²-L–L)⁺〛〚I^–〛 product exclusively. One could suppress the chelated complexes and selectively prepare the bridged 〚{(η⁵-C₅H₅)Fe(CO)₂}₂(μ-L–L)²⁺〛 complexes by application of the electron-transfer chain catalysis with a chemical initiation. Introducing a catalytic amount of reductant at low temperature to the mixture of 2:1 (η⁵-C₅H₅)Fe(CO)₂I/L–L in THF selectively produces the bridged complexes in 78–93% isolated yields where L–L is Ph₂P(CH₂)_nPPh₂, n = 1–4, or (η⁵-C₅H₄PPh₂)₂Fe.     

Triphospha-Ferrocenes as Ligands. Crystal Structures of [Fe(η5-C5Me5)(η5-C2 TBu2P3)M(CO)5)], (M= Cr,MO, W) and the Novel ruthenium and Nickel Complexes [Fe(η5-C5Me5) (η5-C2 TBu2P3)Ru3(CO)9] and [Fe(η5-C5Me5)(η5-C2 tBu2P3)Ni(Co)2]2

Abstract

Syntheses and structures of penta- and hexaphosphorus analogues of ferrocene have been described recently¹. Unlike their simple ferrocene analogues, these complexes have further ligating potential towards other transition metal centres by virtue of the availability of the ring phosphorus lone-pair electrons that are not involved in the η⁵-coordination. We now describe the first examples of coordination compounds of the triphospha-ferrocene [Fe(η⁵-C₅Me₅) (η⁵-C₂ ^tBu₂P₃]. In the ruthenium complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃) Ru₃(CO)₉] ² two adjacent phosphorus atoms of the η⁵-C₂ ^tBu₂P₃ ring are interlinked by a ruthenium carbonyl cluster in which all three ruthenium atoms interact with the phosphorus atoms. The tetrametallic nickel complex [Fe(η⁵-C₅Me₅)(η⁵-C₂ ^tBu₂P₃)Ni(CO)₂]₂ ³ represents the first example of intermolecular interlinkage of two phospha-ferrocene systems by two metal centres.     

Synthesis and structures of the η5-C5H5Cl(CO)2W-η1,η5-(PPh2)C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3 and MeSi[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)2PPh3]3 complexes

The metallation of the η⁵-C₅H₅(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex with BuⁿLi (THF, ?78 °C) followed by the treatment of the lithium derivative with Ph₂PCl afforded the η⁵-Ph₂PC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ complex. The reaction of the latter with η⁵-C₅H₅(CO)₃WCl in the presence of Me₃NO produced the trinuclear complex η⁵-C₅H₅Cl(CO)₂W-η¹,η⁵-(Ph₂P)C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃. The structure of the latter complex was established by IR, UV, and 1H and ³¹P NMR spectroscopy and X-ray diffraction. The reaction of MeSiCl₃ with three equivalents of LiC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃ gave the hexanuclear complex MeSi[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₂PPh₃]₃.     

The preparation of a series of ring-linked derivatives of [Fe2(η-C5H5)2(CO)2(μ-CO)2] starting from [Fe2η5,η5-C5H4CH(NMe3)CH(NMe2)C5H4}(CO)2(μ-CO)2]+ salts

The salts [Fe₂η⁵,η⁵-C₅H₄CH{NMe₃)CH(NMe₂)C₅H₄}(CO)₂(μ-CO)₂][X] (X = I or SO₃CF₃) are the synthetic precursors to a wide range of [Fe₂(η-C₅H₅)₂(CO)₂(μ-CO)₂] derivatives in which the two cyclopentadienyl ligands are joined by a two-carbon bridge.     

Efficient Diastereoselective Synthesis of Chiral Diferrocenylphosphine‐diamines: X‐ray Crystal Structure of [(η5‐C5H5)Fe{(η5‐C5H3)PPh2CH(CH3) N(CH2)2(CH2)2NCH(CH3)PPh2 (η5‐C5H3)}Fe(η5‐C5H5)]

Abstract

Three novel chiral planar diferrocenylphosphine‐diamines 5 (a–c) were designed and synthesized starting with (s)‐(?)‐N,N‐dimethyl‐1‐ferrocenylethylamine‐1 [(S)‐1]. All new compounds were identified by ¹H NMR and MS. The structure of chiral diferrocenylphosphine‐diamine 5c was determined by X‐ray crystallography. Single crystal X‐ray diffraction analysis reveals that the molecular structure of compound 5c [(η⁵‐C₅H₅)Fe{(η⁵‐C₅H₃)PPh₂CH(CH₃) N(CH₂)₂(CH₂)₂NCH(CH₃)PPh₂‐(η⁵‐C₅H₃)}Fe(η⁵‐C₅H₅)] is enantiomerically pure and crystallizes in the noncentrosymmetric P2(1)2(1)2(1) space group; it maintains “Z” shape and contains a piperazine hexahydrate ring bridge. The piperazine ring adopts a favored chair conformation and the chiral center C₂₃ and C₂₉ substituents in S‐configuration.     

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.     

Preparation and crystal structures of [μ-SbPh2]2[Mo(CO)2(η5-C5H5)]2·CHCl3 and SbPh[Fe(CO)2(η5-C5H5)]2

Antimony is reduced when [SbPh₂BrO]₂ is treated with Na[Mo(CO)₃(η⁵-C₅H₅)] to produce [μ-SbPh₂]₂[Mo(CO)₂(η⁵-C₅H₅)]₂. A structure determination shows diphenylstibido groups bridging between two Mo(CO)₂(η⁵-C₅H₅) moieties giving a central ‘butterfly’ shaped Sb₂Mo₂ ring. The cyclopentadiene rings are trans to each other and Mo–Sb and Sb–Sb separations are both short. An iron analogue could not be obtained from [SbPh₂BrO]₂ and Na[Fe(CO)₂(η⁵-C₅H₅)] but a mixture of SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ and SbPh₂[Fe(CO)₂(η⁵-C₅H₅)] was obtained using SbPh₂Cl. An X-ray structure for SbPh[Fe(CO)₂(η⁵-C₅H₅)]₂ shows an open stibinidine structure.     

The reductive dimerization of [W(NCMe)(MeC2Me)2(η-C5H5)]+: Synthesis and X-ray structure of the novel bis(metallacyclopentadiene) complex [W2(μ-σ,σ,η2,η2-C4Me4)2(η-C5H5)2]

Treatment of [W(CO)(MeC₂Me)₂(-C₅H₅)][PF₆] with ONMe₃ in acetonitrile yields [W(NCMe)(MeC₂Me)₂(-C₅H₅)][PF₆] which undergoes irreversible reduction at a Pt electrode in THF. Sodium amalgam reduction of [W(NCMe) (MeC₂Me)₂(-C₅H₅)][PF₆] gives orange crystals of [W₂(µ-,, ², ²-C₄Me₄)₂ (-C₅H₅)₂] X-ray studies on which reveal pairwise alkyne coupling and a novel bis(metallacyclopentadiene) structure.Dedicated to Professor L. F. Dahl on the occasion of his 65th birthday.     

Structural chemistry of titanium and aluminium bimetallic hydride complexes VI. Molecular structure and physico-chemical properties of (η5-C5 H5) 2Ti(μ2-H)2 Al(Cl) (μ2 -H)2Ti(η5-C5H 5)2, a catalyst-precursor for hydrogenation in the [(η5-C5H5)2TiCl]2-LiAIH4 system

The complex (Cp₂Ti)₂AlH₄Cl has been isolated from the catalytic system (Cp₂TiCl)₂-LiAlH₄, which is a precursor of the catalyst for the hydrogenation and isomerization of olefins. This complex has been studied by X-ray diffraction. The complex forms rhomboidal crystals with unit cell dimensions a = 10.414, b = 11.998, c = 16.008 Å, space group P2₁2₁2₁, Z = 4, and density ϱ_calc = 1.40 g/cm³. The Cp₂Ti moieties are linked to the Al atom via double hydrogen bridges; the Cl atom is bonded to the Al atom. Analysis of the EPR spectral data and some chemical properties of (Cp₂Ti)₂AlH₄Cl solutions has led us to suggest a mechanism for the formation of the catalytically active species upon interaction of this compound with olefins and solvating solvents.     

The crystal and molecular structure of bis(η5-trimethylsilylcyclopentadienyl)titanium(IV) dichloride,Ti(η5-C5H4SiMe 3)2Cl2

Summary The crystal and molecular structure of the titanocene complex Ti(⁵-C₅H₄SiMe ₃)₂Cl₂ has been determined by X-ray diffraction studies. The compound crystallizes in the triclinic crystal system [a=6.747(8),b=12.815(2),c=12.928(4) Å and =67.16(2), =82.29(5), =74.83(4)°] in the space group with 2 formula units in the unit cell. The coordination about the titanium atom formed by the two chlorine atoms and the centroids of the cyclopentadienyl rings is that of a distorted tetrahedron. The Cl-Ti-Cl angle is 91.63° while the (centroid)-Ti-(centroid) angle is 131.02°.

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Die Kristall- und Molekülstruktur von Bis(⁵-trimethylsilylcyclopentadienyl)titan(IV)dichlorid, Ti(⁵-C₅H₄SiMe ₃)₂Cl₂

Zusammenfassung Die Kristall- und Molekülstruktur des Titanocen-Komplexes Ti(⁵-C₅H₄SiMe ₃)₂Cl₂ wurde durch eine Röntgenstrukturanalyse bestimmt. Die Verbindung kristallisiert im triklinen Kristallsystem [a=6.747(8),b=12.815(2),c=12.928(4) Å und =67.16(2), =82.29(5), =74.83(4)°] in der Raumgruppe mit 2 Formeleinheiten pro Elementarzelle. Das Titanatom ist von zwei Chloratomen und den Centroiden der Cyclopentadienylringe umgeben, wobei die Koordination des Titanatoms verzerrt tetraedrisch ist. Die Winkel Cl-Ti-Cl und (Centroid)-Ti-(Centroid) betragen 91.63° bzw. 131.02°.

     

Substitution and insertion reactions of (η5-C5H5)Cr(CO)3C2H5

The complex (η⁵-C₅H₅)Cr(CO)₃Cp42 H₅ has been made and its reactions with σ donor ligands L (L = (MeO)₃P and (EtO)₃P) and with SO₂ studied. The alkyl phosphites give compounds of the composition (η⁵-C₅H₅)Cr(CO)₂LC₂H₅, and sulfur dioxide gives the corresponding S-sulfinato (η⁵-C₅H₅)Cr(CO)₃SO₂C₂H₅.