Photochemical Synthesis and Reactivity of New Chloro-Bridged Complexes with Tungstenocene (η5-C5H5)(η5-C5H4PPh2)WClX (X = H, Cl) and Tetracarbonylmetal (Cr, W) Units

Chloro-bridged bimetallic complexes (η5-C5H5)[η5-C5H4PPh2M′(CO)4]W(μ-Cl)X [X = Cl (3), × = H (4); M′ = Cr, W] were prepared by photochemical irradiation of (η5-C5H5)[η5-C5H4PPh2M′(CO)5]WClX [X = Cl (1), × = H (2); M′ = Cr, W]. The reactivity of the chloro-bridged complexes towards Lewis bases was studied; by exposure to CO or phosphanes, a facile cleavage of the chloro bridge accompanied by regio- and stereospecific coordination at M′ occurs. The X-ray structure of complex 3 (M′ = W) is reported.

The synthesis of metallocene-labelled drugs for biological assays

Several drugs (amphetamine, desipramine, nortriptyline, phenobarbital) have been labelled with metallocenic fragments in order to develop a new immunoassay method. The metallocenic fragments are cymantrenic or benchrotrenic derivatives: the linkage between the organic and organometallic moieties has been achieved by reactions between amino and acidic functional groups. All the products (metallohaptens), purified by different chromatography techniques, have been fully characterized by IR and 1H NMR spectroscopy and their mass spectra.

Formation and Reactivity of a Tantalocene Trihydride Containing an Aminoethyl‐Functionalised Ligand

The complex [Cp*{C5H4(CH2CH2NMe2)}TaCl2] (1) was synthesised by reaction of the lithium salt LiC5H4(CH2CH2NMe2) with the tantalum compound [Cp*TaCl3(PMe3)]. Reduction of 1 with NaAl(H)2(OCH2CH2OMe)2 leads to the trihydride derivative [Cp*{C5H4(CH2CH2NMe2)}TaH3] (2). The oxidation of 2 in THF with ferrocenium ion leads to a cationic dihydride intermediate [Cp*{C5H4(CH2CH2NMe2)}TaH2]PF6 (3) with an intramolecular stabilization by the aminoethyl side-chain of the cyclopentadienyl ligand. The hemilabile character of the functionalised cyclopentadienyl ligand was checked by treating 3 with electron-donating ligands (e.g. phosphanes, sulfides, anions); in all cases, no displacement of the amino g…

Oxo and Hydroxo Tantalocene Complexes:  Synthesis and Reactivity. X-ray Molecular Structures of [(η5-Cp*)TaCl(OH)(η5-C5H4SiMe3)]+Cl-, (η5-Cp*)TaCl(O)(η5-C5H4SiMe3), and [(η5-Cp*)TaCl2(η5-C5H4SiMe3)]+PF6-

Exposure of a THF solution of tantalocene dichloride complexes (η 5 -Cp*)TaCl 2 (η 5 -C 5 H 4 -SiMe 3 ) (1) and (η 5 -Cp*)TaCl 2 (η 5 -C 5 H 5 ) (2) to the ambient atmosphere for 12 h leads to the formation of new tantalum(V) cationic hydroxo complexes [(η 5 -Cp*)TaCl(OH)(η 5 -C 5 H 4 SiMe 3 )] + -Cl- (3) and [(η 5 -Cp*)TaCl(OH)(η 5 -C 5 H 5 )]+Cl - (4). This oxidation reaction is more rapid under oxygen atmosphere since the hydroxo complexes are obtained in better yields within only 15 min. The hydroxo complexes are easily deprotonated by base to generate oxo complexes 5 and 6, which, in turn, react with trimethylsilyl triflate, giving the corresponding cationic silylated complexes 7 and 8…

Tantalocenehydridephosphorus chemistry.

Abstract The aim of this paper is to look for a better knowledge of the behaviour of bent tantalocenes that bear hydrides, phosphorus PR2X (R=Me, Ph; X=H, lone pair) and cyclopentadienyl (Cp=C5H5, Cp′=C5H2tBu(Me)2, Cp*=C5Me5) ligands. An orbital control of regioselectivity of insertion of the PR2 phosphide fragment of chlorophosphines PR2Cl into the central TaH bond of trihydrides Cp2TaH3 leading to the formation of metallophosphonium cations is discussed. Neutralisation of cationic complexes with strong bases leads either to the Ta(V)–phosphide or to the Ta(III)–phosphine species depending on the nature of the cyclopentadienyl ligand; good electron donor Cp′ and Cp* rings favour the forma…

The use of metallocenic esters of n-hydroxysuccinimide for metallohapten synthesis

Different organometallic markers have been described in a new technique for the labelling of many drugs. Thus metallocenic esters of [M = (;CO)3CrC6H5; (;CO)3CrC6H5(;CH2)3; η-C5H5FeC5H4; (;CO)3MnηC5H4; (;CO)3MnηC5H4COCH2CH2; ηC5H4(;ηC5H5)Co+PF−6] react with primary or secondary amine drugs [DRUGNHR] for a psychostimulant drug: amphetamine; tricyclic antidepressants—desipramine and nortriptyline; a vasodilator—histamine; an adrenergic substance—norfenefrine; and for a central stimulant—meth-amphetamine, to give the metallohaptens MCON(;R)—DRUG. All these compounds have been fully characterized by different analytical methods and have potentialities for biological assays. This synthetic route…

Bimetallic complexes with ruthenium and tantalocene moieties: Synthesis and use in a catalytic cyclopropanation reaction

Abstract The reaction of the tantalocene dichloride monophosphines ( 1 – 2 ) with the binuclear complex [( p -cymene)RuCl 2 ] 2 gives the heterobimetallic compounds ( p -cymene)[(η 5 -C 5 H 5 )(μ-η 5 :η 1 -C 5 H 4 (CH 2 ) 2 PR 2 )TaCl 2 ]RuCl 2 ( 3 – 4 ). The air oxidation of these bimetallic species 3 – 4 , leads to the cationic hydroxo tantalum ruthenium derivatives 5 – 6 . The last ones are easily deprotonated by a base to afford the oxo analogues 7 – 8 . A preliminary assessment in catalytic cyclopropanation of styrene with tantalum ruthenium bimetallic complexes 3 – 8 as precatalysts revealed a cooperative effect with a subtle role of the early metal fragment.

Metallocenes of Nb and Ta with η2-Se2H, SeH, and Se Ligands – Crystal Structures of [Cp′2Ta(SeH)H2] and [Cp′2Ta(=Se)H·W(CO)5] (Cp′ =tBuC5H4)

The reactions of [Cp#2NbBH4] (1) [Cp# = C5Me5 (Cp*) or C5Me4Et] and [Cp′2TaH3] (Cp′ = tBuC5H4) with elemental selenium give complexes of the general composition [Cp2MSe2H]. These exist in three isomeric forms, A–C, depending on the metal and the chalcogen. [Cp#2NbSe2H] (2) incorporates the novel η2-Se2H ligand (C), which is labile when exposed to light. Solutions of 2(Cp*) can be converted into [Cp*2NbSe2H] (3), which exists in two isomeric forms A or B, along with [Cp*2NbSe3H] (4) and [Cp*2NbO2H] (5). [Cp′2Ta(η2-Se2)H] (6) is the only isomer found for the Ta system. Se abstraction by means of P(OEt)3 gives [Cp′2Ta(=Se)H] (7). Complex 7 can be reduced with Na/Hg and subsequently hydrolysed …

Investigation into the reactivity of oxoniobocene complexes [Cp*2Nb(O)R] (Cp*=η5-C5Me5; R=H, OH, OMe) towards heterocumulenes: formation of carbamato and thiocarbamato complexes and catalytic cyclization of PhNCO

Abstract The reaction of [Cp*2NbCl2] (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp*2Nb(O)H] (1), the new compound [Cp*2Nb(O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp*2Nb(O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp*2Nb(O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either η1-S-thiocarbamato (3) or η1-O-carbamato ligand (4) along with a terminal NbO group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp*2NbH{OC(O)NPh}] (5) along with so…

Desulfurization and ring opening of thiirane induced by tantalocene trihydride complexes: Synthesis, reactivity and X-ray structure of Cp′2Ta(=S)(S-iPr) with Cp′=η5-C5H4tBu

The reaction of the tantalocene trihydride complexes Cp′ 2 TaH 3 1 (Cp′= η 5 -C 5 H 4 t Bu) or Cp″CpTaH 3 1′ (Cp″= η 5 -C 5 H 2 -1,2-Me 2 -4- t Bu) with propylene sulfide was found to proceed via an unprecedented sulfur transfer and regioselective ring opening reaction at once to yield sulfido-thiolato tantalocene complexes Cp′ 2 Ta(S)(S- i Pr) 2a whose structure has been determined by X-ray crystallography or Cp″CpTa(S)(S- i Pr) 2′a . Complex 1 reacts with ethylene sulfide to give Cp′ 2 Ta(S)(S–Et) 2b . The reactivity of 2a towards a variety of electrophilic moities has been investigated: protonation (with HBF 4 ) and alkylation (with MeI) reactions occur at the terminal sulfur ligand, …

Organochromium complexes - labelled aminoglycoside antibiotics derived from kanamycin A and tobramycin. Synthesis, structural characterization and use as metallotracers for immunoassays.

Abstract The synthesis of metallocenic derivatives of aminoglycoside antibiotics, i. e. kanamycin A and tobramycin, is described. The organometallic-labelled compounds have been obtained from the reaction between the polyaminodrugs and organochromium esters of N-hydroxysuccinimide. The reaction proceeded selectively at the 6′-N position, as might be deduced both from the mass and the pH-dependent 13 C-NMR spectra. The procedure could be regarded as generally useful for the metallolabelling of aminoglycoside antibiotics. As an example of application a competitive immunoassay based on the use of these labels is proposed.

Syntheses and reactivity of oxo niobocene complexes Cp*2Nb(O)X (X=H, OCH3) and crystal structures of [Cp*2Nb(OH)F]BF4 and Cp*2Nb(O)OC(O)H (Cp*=η5-C5Me5)

Abstract Reaction of Cp*2NbCl2 (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF forms the complexes Cp*2Nb(O)X (X=Cl: 2, H: 3). The ratio of 2 and 3 depends on the stoichiometry. If NaOMe is added or MeOH in solution Cp*2Nb(O)OMe 4 is formed in good yields. Reactivity studies with 3 and 4 show that the NbO as well as the Nb–X unit behave as chemically active sites. Protonation of 3 or 4 with HBF4 is followed by an attack of fluoride (from BF4− anion) to give [Cp*2Nb(OH)F]BF4 6 and [Cp*2NbF2]BF4 7. In contrast the reaction of 3 or 4 with HCO2H results in an exchange of X− by formate to give Cp*2Nb(O)OC(O)H 8. The crystal structures of 6 and 8 are reported. Electrochemical investigations of…

Memory effects in functionalized conducting polymer films: titanocene derivatized polypyrrole in contact with THF solutions

Abstract Films with a polypyrrole matrix and pendant titanocene dichloride centers, p(Tc3Py), have been obtained by potentiostatic electropolymerization of the titanocene-pyrrolyl derivative, Tc3Py=Tc(CH 2 ) 3 NC 4 H 4 (Tc=Cl 2 TiCpCp′, Cp=C 5 H 5 , Cp′=C 5 H 4 ), in acetonitrile (AN) solutions on a Pt surface. The redox activity has been studied after the transfer of the film-coated electrode into the monomer-free solution of the same electrolyte, TBAPF 6 , in THF. Contrary to the case of AN or dichloromethane solutions, one can achieve a stable redox activity of the immobilized Tc centers in THF solutions during a series of cycles. A parallel between the redox properties of the Tc complex…

Mono- and di-bridged heterobimetallic systems from group 5 hydride phosphido and hydride phosphino metalloligands. Crystal structure of Cp2Ta(H)( μ-H)( μ-PMe2)Cr(CO)4

Abstract The trihydrides Cp2MH3 (M  Nb, Ta) react with chlorophosphines PR2Cl (R  Me, Ph) affording phosphonium salts [Cp2MH2(PR2H)]+, Cl− (2 (a, b) 2′ (a, b)). Depending on the metal (Nb or Ta) and on the nature of the phosphine substituent (Me or Ph), deprotonation of these salts leads to hydride phosphino Cp2MH(PR2H) (3 (a, b) 3′a) or hydrided phosphido Cp2 TaH2(PPh2) (4′b) metalloligands. These two kinds of complexes are able to bind [M′(CO)5] or [M′(CO)4] (M′  Cr, Mo, W) organometallic fragments to give mono- or di-bridged heterobimetallic systems. The crystallographic analysis of Cp2Ta(H)(μ-H)(μ-PMe2)Cr(CO)4 (7′aCr) is reported and discussed.

New insights into the reactivity of the tantalocene hydride Cp′2TaH3 (Cp′=η5-tBuC5H4). Synthesis and characterisation of cationic Ta(V) complexes with 0,0 and S,N chelating ligands

Abstract Reaction of various neutral LXH bidentate ligands (2-aminobenzoic acid, acetylacetone, dibenzoylmethan and 2-aminobenzenethiol) with [Cp′2TaH2]+, obtained in situ from Cp′2TaH3 treated with triphenylmethan cation, affords after dihydrogen elimination the corresponding cationic species [Cp′2Ta(H)(LX)]+ in BF4 or PF6 salts. Complexes [Cp′2TaH(η2-O2CC6H4-o-NH2O,O′)]PF6 (3), {Cp′2Ta[η2-OC(Me)CHC(Me)OO,O′]}BF4 (4a), {Cp′2TaH[η2-OC(Ph)CHC(Ph)OO,O′]}BF4 (4b) and [Cp′2TaH(η2-SC6H4-o-NH2S,N)]PF6 (5) are characterised by analytical and spectroscopic methods. With thiopyridine, the kinetic (6) and the thermodynamic (6′) isomers [Cp′2TaH(η2-2-SC5H4NS,N)]PF6 are identified. Crystal struc…

Ti–Ru bimetallic complexes: catalysts for ring-closing metathesis

The reaction of the titanocene monophosphanes ( 1 – 4 ) with the dimer [( p -cymene)RuCl 2 ] 2 gives the heterobimetallic compounds ( p -cymene)[(η 5 -C 5 H 5 )(μ-η 5 :η 1 -C 5 H 4 (CR 2 ) n PR′ 2 )TiCl 2 ]RuCl 2 ( 5 – 8 ). The structure of 8 , determined by X-ray diffraction, is reported here. A preliminary assessment of the performance of these complexes in ring-closing metathesis (RCM) revealed an excellent Ti–Ru–allenylidene pre-catalyst 12 .

Synthesis of enol esters catalysed by 'early–late' Ti–Ru complexes

Abstract The titane–ruthenium heterobimetallic compounds ( p -cymene)[(η 5 -C 5 H 5 )(μ-η 5 :η 1 -C 5 H 4 (CH 2 ) m PR 2 )TiCl 2 ]RuCl 2 4 – 6 have been revealed to be quite good catalysts for the addition of formic acid to 1-hexyne and phenylacetylene. These preliminary results led us to synthesize new tetrametallic complexes 10 – 12 via the reaction of the titanocene phosphanes 1 – 3 with the polymer [Ru(CO) 2 (μ-O 2 CH)] n . Their catalytic ability for the enol esters formation has been studied.

Formation and Reactivity of the [Cp‘2Ta(H)2]+ Cation (Cp‘ = η5-tBuC5H4)

The complex Cp‘2Ta(H)(OCOCF3)2 (2) is synthesized by the acidolysis of Cp‘2TaH3 (1) (Cp‘ = η5-tBuC5H4) in the presence of an excess of trifluoroacetic acid. 1 undergoes a loss of H- upon the reacti...

Synthesis, X-ray crystal structure, NMR characterization and theoretical calculations on [Cp2Ta(η2-H2)(CO)]+, the first thermally stable group 5 dihydrogen complex

Protonation of Cp2TaH(CO) (Cp  =  C5H5, 1a; C5H4But, 1b) by HBF4·Et2O at −78 °C in CH2Cl2 affords [Cp2TaH2(CO)]BF4 (2, 3) as mixtures of 2 isomers. The minor ones (2a, 2b) contain the known trans-dihydride [Cp2TaH2(CO)]+ cations whereas the major ones (3a, 3b) are [Cp2Ta(η2-H2)(CO)]BF4, the first group 5 dihydrogen complexes. The crystal structure of the analogous complex 3a·BArf4 recorded at 120 K confirms the presence of the coordinated dihydrogen ligand, which displays an H–H separation of 1.09(2) A in agreement with distances calculated from NMR data. Protonation of Cp2TaH2(SiMe2Ph) by (Et2O)2 ·HBArf4 does not lead to an analogous silane derivative but to the new dinuclear complex [(Cp2…

Reactivity of bimetallic dibridged complexes Cp2Ta(H)(μ-H)(μ-PMe2)M′(CO)4 (M′ = Cr, Mo, W) toward two-electron donor ligands L (L = PR3, Me2P(CH2)nPMe2). Synthesis of linear trinuclear chain complexes Cp2Ta(H)2(μ-PMe2)M′(CO)4(Me2P(CH2)2PMe2)Cr(CO)5 (M′ = Mo, W)

Abstract The reaction of the heterobimetallic phosphido- and hydrido-bridged complexes Cp 2 TaH(μ-H)(μ-PMe 2 )M′(CO) 4 (M′ = Cr, Mo, W) ( 1–3 ) with phosphines (L = PPh 2 Me, PMe 2 Ph) or diphosphines (L = dmpm, dmpe) leads to Cp 2 Ta(H) 2 (μ-PMe 2 )M′(CO) 4 (L) ( 1a, 1b, c, d-3b, c, d ) with L regiospecifically coordinated to M′. Except for L = PPh 2 Me, the reaction is stereospecific, since a cis arrangement (with respect to the PMe 2 bridge) on the M′ site is obtained. The new compounds Cp 2 Ta(H) 2 (μ-PMe 2 )M′ (CO) 4 (Me 2 P(CH 2 ) 2 PMe 2 ) (M′ = Mo, W) are able to bind [Cr(CO) 5 ] fragments affording the linear trinuclear chain compounds Cp 2 Ta(H) 2 (μ-PMe 2 )M′(CO) 4 (Me 2 P(CH 5 )…

ChemInform Abstract: First Titanium-Catalyzed 1,4-Hydrophosphination of 1,3-Dienes.

[TiPHOS(Rh)]+:  A Fortuitous Coordination Mode and an Effective Hydrosilylation Bimetallic Catalyst

The reaction of the titanocene diphosphine {(η5-C5H5)[η5-C5Me3-1,2-(PPh2)2]TiCl2} (TiPHOS; 1) with [Rh(COD)2](OTf) led to the new early−late heterobimetallic complex [(TiPHOS)Rh(COD)](OTf) (2), who...

Tetracarbonyltungsten(0)-bis(μ-dimethylphosphido)-bis[dicyclopentadienylhydridomolybdenum(IV)]

The title trinuclear WMo2 compound, [Mo2WH2(C5H5)4(C2H6P)2(CO)4], was obtained by opening of the hydride bridge in the dinuclear dibridged (μ-PMe2,H){(C5H5)2Mo}{W(CO)4} complex (MoIV) upon the action of (C5H5)2Mo(PMe2H) (MoII) in THF solution. This involves the formal conversion of MoII to MoIV.

Evidence of intramolecular electron transfer between two metallic atoms in a bimetallic complex by electrochemical methods

The electrochemical properties of the monomeric complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2] 1 and the heterobimetallic complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2][RuCl2(C6H4(CH3)(C3H7))] 2 have been studied by cyclic voltammetry, controlled potential electrolysis and rotating disk electrode voltammetry. An unexpected electron transfer between the two heterobimetallic atoms has been observed. This transfer takes place via an intramolecular interaction, hence via a chloride bridge. Electrochemical simulation has been carried out to verify experimental results and to obtain the kinetic constant of the proposed square scheme.

DETECTION LIMITS FOR NATURAL CIRCULAR-DICHROISM OF CHIRAL COMPLEXES IN THE X-RAY RANGE

Whereas both Magnetic Circular Dichroism and Faraday Rotation studies have been successfully carried out at the K-, L- and M-absorption edges of metal atoms in ferromagnetic systems, Natural optical activity of chiral complexes has not yet been detected quite unambiguously in the X-ray range. We review a number of theoretical arguments which confirm that the optical asymmetry factor gσ should be very small in the X-ray range for unoriented powdered samples, especially at the K-absorption edges. This stimulating challenge prompted us to start an intensive programme of measurements aimed at detecting natural circular dichroism in both the soft and “firm” X-ray ranges. Although some of our ex…

Reactivity of the ansa-Bridged Metallocene Dichlorides [X(η5-C5H4)2]MCl2 (X = SiMe2, CMe2; M = Mo, W) toward Metallophosphide Anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). Formation of Heterobimetallic Complexes by Nucleophilic Substitution on a Cyclopentadienyl Ligand or on the Metal M

Two kinds of ansa derivatives, [SiMe2(η5-C5H4)2]MCl2 and [CMe2(η5-C5H4)2]MCl2 (M = Mo, W), are reacted with metallophosphide anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). The silicon-bridged derivatives give the bimetallic systems [SiMe2(η5-C5H4)(η5-C5H3PPh2M‘(CO)x)]M(H)(Cl), which result from a regioselective substitution at the 3-position on the cyclopentadienyl ligand. In contrast, with the CMe2-bridged compounds, the substitution reaction occurs at the metallic center, giving μ-phosphido bimetallic complexes [CMe2(η5-C5H4)2]M(Cl)(μ-PPh2)M‘(CO)x. The solid-state structure of the bimetallic complex [CMe2(η5-C5H4)2]W(Cl)(μ-PPh2)Fe(CO)4 (7d) is reported.

Synthesis and Complexation of the Metalloligand {(η5-C5H5)[η5-C5Me3-1,2-(PPh2)2]TiCl2} (TiPHOS): The First Example of a 1,2-Bis(diphenylphosphanyl)titanocene Derivative

The reaction of lithium 1,2-bis(diphenylphosphanyl)trimethylcyclopentadienide (1) with CpTiCl3 leads to the formation of the titanocene diphosphane {(η5-C5H5)[η5-C5Me3-1,2-(PPh2)2]TiCl2} (TiPHOS, 2). This metalloligand reacts readily with (NBD)Cr(CO)4 and W(CO)5(THF) to give, in both cases, the bimetallic chelate complexes (TiPHOS)Cr(CO)4 (3) and (TiPHOS)W(CO)4 (4). The structure of 4 has been determined by X-ray diffraction. The synthesis of a new early-late heterobimetallic complex (TiPHOS)Rh(CO)Cl (5) is reported.

Synthesis and structural studies of TiRu polymetallic systems

Abstract The reaction of the titanocene monophosphines 1 and 2 with the dimer [( p -cymene)RuCl 2 ] 2 give the heterobimetallic compounds ( p -cymene)[(η 5 -C 5 H 4 )(μ-η 5 :η 1 -C 5 H 4 PPh 2 )TiCl 2 ]RuCl 2 and ( p -cymene)[(η 5 -C 5 H 4 )(μ-η 5 :η 1 -C 5 H 4 CH 2 CH 2 PPh 2 )TiCl 2 ]RuCl 2 , respectively. Both structures have been confirmed by X-ray diffraction. By using same procedure, the synthesis of a trimetallic complex RuTiRu has been achieved.

Tantalocene complexes as bidentate métalloligands: (C5Me5)(C5H4X)Ta(H2)(PPh2) (C5Me5) (C5H4X)Ta(CO) (PPh2) (X = PPh2, CH2CH2NMe2)

Abstract The synthesis of new bidentate metalloligands derived from tantalocene (C5Me5)(C5H4X)Ta(H2)(PPh2) (X = PPh2, 2P; X = CH2CH2NMe22N) and (C5Me5)(C5H4X)Ta(CO)(PPh2) 4(P,N) is described. When opposed to chromium unsaturated fragments the phosphino functionalised complexes 2P and 4P act as chelating bidentate ligands affording Ta(V) (C5Me5)(C5H4PPh2)Ta(CH2) (μ-PPh2)Cr(CO)4 or Ta(III) (C5Me5)(C5H4PPh2)Ta(CO)(μ-PPh2)Cr(CO)4 bimetallic complexes. The same reaction carried out starting from 2N gives rise to a μ-phosphido, μ-hydrido dibridged complex Cp*(C5H4CH2CH2NMe2)TaH(μ-H)(μ-PPh2)Cr(CO)4.

ChemInform Abstract: nBuLi-Mediated Hydrophosphination: A Simple Route to Valuable Organophosphorus Compounds.

A straightforward synthesis of homoallyl- and allylphosphanes has been developed using nBuLi-mediated hydrophosphination of conjugated dienes. In all the cases the phosphorus atom of the reacting phosphane attacked the sterically less demanding side of the diene exclusively. In addition, high regioselectivities towards 1,2- or 1,4-addition products were observed depending on the nature of the dienes. This hydrophosphination reaction was extended to a variety of substrates such as styrene derivatives, alkynes and 1,3,5-cycloheptatriene. The structures of three hydrophosphination products were confirmed by X-ray diffraction studies.

Redox properties of titanocene-pyrrole derivative and its electropolymerization

A new titanocene dichloride derivative in which one cyclopentadienyl ligand (Cp) is functionalized with a pyrrolyl ring, Tc3Py (Cl2TiCpC5H4(CH2)3NC4H4), has been synthesized and characterized with NMR. Its redox properties have been studied by CV in acetonitrile (AN), tetrahydrofurane (THF) and dichloromethane (DCM), in comparison with unsubstituted titanocene dichloride (Tc) and pyrrole. Ti(IV/III) transition observed within the negative potential range is a quasi-reversible reaction in THF and DCM (but without a complete recuperation of the initial reagent in the back scan) while the reoxidation peak in AN is strongly shifted in the positive direction. These results are interpreted within…

Mechanism of redox transformation of titanocene dichloride centers immobilized inside a polypyrrole matrix—EQCM and XPS evidences

Abstract We report electrochemical quartz crystal microbalance (EQCM) results for electrodeposition of titanocene derivatized polypyrrole p(Tc3Py) films and redox transformation of polypyrrole matrix and titanocene centers immobilized in the film. Films of p(Tc3Py), Tc3Py = Tc(CH 2 ) 3 NC 4 H 4 (Tc = Cl 2 TiCpCp′, Cp = C 5 H 5 , Cp′ = C 5 H 4 ) were obtained from acetonitrile solutions of monomer on a Pt disc or thin Au layer evaporated on 10 MHz quartz crystals. Polymerization efficiency, derived from the slope of the change of resonant frequency as a function of the deposition charge ranged from 54% to 75%. A gradual loss of redox activity of Tc centers during consecutive redox cycles of …

Ruthenium titanocene and ruthenium titanium half-sandwich bimetallic complexes in catalytic cyclopropanation

Abstract The reaction of the phosphine functionalised titanium half-sandwich complexes 7, 9 and 10 with the binuclear complex [(p-cymene)RuCl2]2 allowed the access to three new early-late bimetallic complexes (p-cymene)[(μ-η5:η1-C5H4(CH2)nPR2)TiX3]RuCl2 (11–13). The structure of 11 (n = 0, X = Cl) has been confirmed by X-ray diffraction. The ruthenium titanium half-sandwich bimetallic complexes so formed and the ruthenium titanocene analogues 4–6 catalyse the addition of ethyl diazoacetate to styrene with high selectivity toward cyclopropanation versus metathesis contrary to the monometallic complexes (p-cymene)RuCl2PR3.

Complexes hétéronucléaires Cp2MM′(Cp)(CO)3 (M  Nb, Ta; M′  Mo, W) avec groupes carbonyles pontants et semi-pontants: synthèse et comportement dynamique

Abstract Heteronuclear structures Cp 2 MM′(Cp)(CO) 3 (M  Nb, Ta; M′  Mo, W) are obtained by heating Cp 2 MH 3 (M  Nb, Ta) with Cp 2 M′ 2 (CO) 6 (M′  Mo, W) or starting from Cp 2 M(CO)H and Cp 2 M′ 2 (CO) 4 . These heterobimetallic complexes show three CO coordination modes: terminal, semi-bridging and bridging. The two cyclopentadienyl groups of the Cp 2 M moiety are anisochronous owing to molecular rigidity; rotation barriers around the MM′ bond have been estimated and are greatest with tantalum derivatives.

First titanium-catalyzed 1,4-hydrophosphination of 1,3-dienes

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Réactivité d'hydrures de tantalocène : insertion du soufre dans la liaison tantale-hydrogène

Resume La recherche entreprise sur la reactivite des hydrures de tantalocene avec le soufre elementaire nous amene a la synthese de complexes monosoufres par une reaction d'insertion du soufre dans la liaison Ta-H. Des informations sont apportees sur le mecanisme de la formation de complexes a ligand (η2-S2) et la synthese du complexe Cp′2Ta(CO)(SH) est decrite.

First Titanium-Catalyzed anti-1,4-Hydrosilylation of Dienes

1,4-Hydrosilylation of dienes catalyzed by late transition metals constitutes a straightforward access to allylsilanes. However, when unsymmetric dienes are used, it generally leads to a mixture of regioisomers (tail or head products) via Z-specific 1,4-addition. Here we describe the first catalytic anti-1,4-hydrosilylation of dienes using the cheap and stable Cp2TiF2 complex as catalyst. It affords E-allylsilanes in good to excellent yields with an unprecedented regio- and diastereoselectivity. Dehydrogenative double silylation of dienes can be selectively obtained by simply changing the activation protocol of the precatalyst.

Towards a Library of “Early‐Late” Ti–Ru Bimetallic Complexes

A series of new titanocene phosphanes 3–6 have been prepared by replacing both chloride atoms at the titanium atom of the complexes [TiCl2(η5-C5H5){η5-C5H4(CH2)2PR2}] (1: R = Ph; 2: R = Cy) by sodium fluoride or sodium benzoate in two-phase systems. Treatment of these new metalloligands with the binuclear complex [(p-cymene)RuCl2]2 affords the targeted titanocene difluoride and titanocene dibenzoate bimetallic ruthenium complexes 8–11. The first chiral Ti–Ru bimetallic complex 12 bearing a binaphthyloxy ligand at the titanium centre has been synthesised in this way. In each series, an X-ray crystal structure has been determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, …

ATRP of methyl methacrylate catalysed by novel homo- and heterobimetallic ruthenium complexes

nBuLi-Mediated hydrophosphination: a simple route to valuable organophosphorus compounds

A straightforward synthesis of homoallyl- and allylphosphanes has been developed using nBuLi-mediated hydrophosphination of conjugated dienes. In all the cases the phosphorus atom of the reacting phosphane attacked the sterically less demanding side of the diene exclusively. In addition, high regioselectivities towards 1,2- or 1,4-addition products were observed depending on the nature of the dienes. This hydrophosphination reaction was extended to a variety of substrates such as styrene derivatives, alkynes and 1,3,5-cycloheptatriene. The structures of three hydrophosphination products were confirmed by X-ray diffraction studies.

ATRP of Methacrylates Catalysed by Homo- and Heterobimetallic Ruthenium Complexes

The catalytic activity of a series of ruthenium-based homo-and heterobimetallic complexes was determined by investigating the atom transfer radical polymerisation of methyl methacrylate. The complexes under investigation were [(arene)Ru(μ-Cl) 3 RuCl(C 2 H 4 )-(L)] (L = PCy 3 or a N-heterocyclic carbene ligand), [(p-cymene )-Ru(/l-Cl) 3 RuCl(=C=CHR)(PCy 3 )] (R = Ph or t-Bu), and [RuCl 2 -(p-cymene) {PCy 2 (CH2) 2 (n 5 -C 5 H 4 )TiX 2 (n 5 -C 5 H 5 )}] (X = Cl, F, and OBz). The catalytic activity of a variety of related [(p-cymene)-ClRu(μ-Cl) 2 Ru(O/\N)(=CHPh)] complexes (O^N is a Schiff base ligand) is also reported. The results clearly demonstrate that the ligands strongly affect the abili…

Metallocene sulfide chemistry of niobium and tantalum: new insights into the formation of niobium-polysulfido complexes and synthesis, structure, and reactivity of Cp2'Ta(.eta.2-S2)H (Cp' = tert-BuC5H4)

The previously described reaction of Cp'2NbH3 (Cp' = t-BuC5H4) with S8 was investigated with regard to the kinetic stabilization of as yet elusive intermediates during the formation of the polysulfide complex Cp'4Nb2S9 (1). Therefore, the permethylated complex Cp*2NbS3H (2; Cp* = C5Me5) and the Ta complex Cp'2TaS2H (3) were synthesized in a related reaction and structurally investigated. Despite the problematic localization of the hydride atom during X-ray crystallographic studies, the molecules can be described in a proper manner: Characteristic of 2 and 3 are M(eta(2)-S2) cores to which either an SH (2) or a H (3) ligand is attached. Complex 3 is the first known tantalocene sulfide. It re…

Regio- and Stereochemical Aspects of the Substitution Reaction between the Molybdenocene and Tungstenocene Dichlorides (η5-C5H4-R)2MCl2 (R = CMe3, SiMe3; M = Mo, W) and Metallophosphide Anions [(CO)5M‘PPh2]Li (M‘ = Mo, W)

High pressure liquid chromatography resolution of racemic mixtures of chiral tricarbonyl arene chromium(0) and cyclopentadienyl-titanium(IV) complexes

Abstract Enantiomers of chiral tricarbonyl arene chromium(0) and cyclopentadienyl-titanium(IV) complexes have been separated by high pressure liquid chromatography employing a Chiralcel OD (Daicel) column, eluting with hexane/2-propanol mixtures. The capacity factors ( k ) and selectivity factors ( α ) concerning the separation of these compounds have been determined. The resolution of tricarbonyl( η 6 -methyl o -acetylbenzoate)chromium ( IV ), was carried out on semipreparative scale: a comparison of the CD spectra of the enantiomers IVa and IVb with that reported in the literature for a similar complex allowed to establish the absolute configuration [( 1R )] for the most retained enantiom…

Electrosynthesis and properties of poly(3,4-ethylenedioxythiophene) films functionalized with titanocene dichloride complex

Synthesis of a titanocene dichloride derivative functionalized with 3,4-etylenedioxythiophene group, Tc1EDOT (Cl 2TiCpC5H4(CH2) (3,4ethylenedioxythiophene)) has been described. Redox behavior of the monomer in tetrahydrofuran (THF), dichloromethane (DCM) and acetonitrile (AN) at different scan rates has been discussed in terms of different ability of these solvents to coordination with the reduced titanocene (Tc) complex and the solvation of Cl − anions. Electrooxidation of Tc1EDOT to get a conducting polymer film with immobilized titanocene dichloride centers and electrochemical properties of its polymer matrix in background acetonitrile solution have been compared with those of non-substi…