Robert Choukroun

Synthesis of O-protected azidohydrins catalyzed by titanium and vanadium complexes

Abstract O-protected vicinal azidohydrins are obtained by titanium (or vanadium) complex catalyzed reaction of epoxides on Me 3 SiN 3 via the formation of a transition metal-azide undergoing regio-selective insertion into the oxirane.

μ-Thiolato dirhodium complexes in hydroformylation: study of the low pressure catalytic activity and comparison of Cp2Zr(CH2PPh2)2 a zirconium diphosphine ligand with several classical diphosphines

Abstract Low pressure catalytic hydroformylation of hex-1-ene was performed with a Rh 2 (μ-SBu t ) 2 (CO) 4 precursor by addition of stoichiometric amounts of various diphosphine XXX ligands, including the zirconium species (η 5 -C 5 -H 5 ) 2 Zr(CH 2 PPh 2 ) 2 . In the corresponding substituted complexes Rh 2 (μ-SBu t ) 2 (CO) 2 (XXX) which were isolated, the diphosphine ligand was found to bridge the two rhodium atoms. These complexes were also found to be active as catalyst precursors.

Synthesis and reactivity of substituted cyclopentadienyl diphenylphosphido complexes of zirconium(IV). X-Ray crystal structure of [(C5H4SiMe3)2Zr(PPh2)2]

We thank D. de Montauzon for pertinent discusxad nsions and the Action Integree France-Espagne (Grant No. 106-1989) for generous support to J.C.F. and nA.M.L. and CICYT for financial support to Dept. Q. nInorganica (Project PB 89/0208).

Complexes cationiques bimétalliques rhodium-zirconium et rhodium-titane: caractérisation et activité catalytique

Abstract Treatment of the cationic rhodium species [Rh(COD)(PPh 3 ) 2 ] + (COD = cis,cis -1,5-cyclooctadiene) with the group 4 derivatives Cp 2 M(CH 2 PPh 2 ) 2 (Cp = η 5 -cyclopentadienyl; M = Zr or Ti), affords the new bimetallic cationic complexes, [Cp 2 M(CH 2 PPh 2 ) 2 Rh(COD)] + . In contrast to the previously reported zirconium-rhodium complexes, improvements in the catalytic performance during the hydroformylation of olefins are not observed, when compared with rhodium only precursors. This could be because of cis attachment of the d 0 metal-containing diphosphine to the rhodium and because the d 0 metal is prevented from achieving pentacoordination.

Oxo-titanium and -zirconium diphosphines [(η-C5H5)2M(CH2PPh2]2O (with M = Ti, Az) as building blocks for heterobimetallic complexes

Abstract Oxo-titanium and -zirconium diphosphines [(η-C 5 H 5 ) 2 M(CH 2 PPh 2 )] 2 (with M = Ti, Zr) were synthesized and treated with [Rh(CO) 2 Cl] 2 to give the heterobimetallic d 0 - d 8 species O[(η-C 5 H 5 ) 2 M(CH 2 PPh 2 )] 2 Rh(CO)Cl.

[Cp2V(μ‐η2:η4‐butadiyne)MCp2′] (M=Ti, Zr; Cp′=C5H5, C5H4SiMe3): Heterodimetallic Complexes from a Bis(alkynyl)metallocene and Vanadocene—Unexpected Structure of [Cp2V(μ‐η2:η4‐butadiyne)Zr(C5H4SiMe3)2] Containing Two Planar‐Tetracoordinate Carbon Atoms

Titanium–vanadium and zirconium–vanadiumcomplexes are obtained from the reaction between bis(phenylethynyl)titanocene, or -zirconocene, and vanadocene. The X-ray structure analysis of [Cp2V(μ-η2-η4-butadiyne)Zr(C5H4SiMe3)2] (depicted on the right) reveals that the [Cp2V] metallocene moiety is bonded to a butadiene (or butadiyne) framework through the two internal carbon atoms and that the [(C5H4SiMe3)2Zr] moiety is bonded to this unit through the two internal carbon atoms and the two external carbon atoms. Both internal carbon atoms of the butadiene skeleton are planar-tetracoordinate.

Hydrogenation and isomerization of olefins with diphenylphosphinomethyl hydride zirconium, [Cp2ZrH(CH2PPh2)]n, a selective homogeneous catalyst

Abstract Various linear and cyclic mono- and di-olefins and aromatic substrates have been investigated for catalytic hydrogenation and isomerization with the diphenylphosphinomethyl hydride compound [Cp2ZrH(CH2PPh2)]n. Selective formation of cycloheptene, cyclooctene and 1,2,3,4-tetrahydroanthracene is obtained from cycloheptatriene, cyclooctadiene (1,5- or 1,3-COD) and anthracene, respectively. Catalytic isomerization of 1-hexene to E-2-hexene and 1,5-COD to 1,3-COD occurs rapidly at 80 °C. The kinetic study of the catalytic selective hydrogenation of 1,3-COD to cyclooctene with [Cp2ZrH(CH2PPh2)]n has been investigated. The dependence of the hydrogenation rate as a limiting step and the half order observed for the catalyst in the kinetic law make it possible to propose an active homobimetallic ZrIVZrII species in which both zirconium atoms are bridged by the diphenylphosphinomethyl ligand. A mechanism for the hydrogenation of conjugated diolefins is postulated.

A zirconium-rhodium hydrido complex, Cp2Zr(CH2PPh2)2RhH(PPh3), as catalyst for the hydroformylation of 1-hexene

The early-late transition metal complex Cp2Zr(CH2PPh2)2RhH(PPh3) has been prepared by the reaction of the zirconium diphosphine Cp2Zr(CH2PPh2)2 with the hydride RhH(PPh3)4. Its behaviour as a catalyst for the hydroformylation of 1-hexene under mild conditions is compared with that of related species.

Thermoanalytic studies of the pyrolysis of CpTiCl2N(SiMe3)2 and its use as a precursor for the chemical vapor deposition of titanium carbonitride

Abstract The synthesis and characterization of a triclinic allotropic form of CpTiCl2N(SiMe3)2 is reported. Thermal analysis and simultaneous mass spectroscopy studies carried out under nitrogen and hydrogen show that this complex decomposes to titanium carbonitride at about 350–370°C. The weight loss observed under hydrogen flow is higher than that observed under nitrogen flow. Elemental analyses show that the residue from nitrogen pyrolysis is more carbon rich than the residue from hydrogen pyrolysis, indicating that carbon is more readily removed during pyrolysis in hydrogen. Chemical vapor deposition (CVD) experiments using CpTiCl2N(SiMe3)2 as an organometallic precursor have been carried out on glass, silicon and steel, using a hot wall type CVD reactor. Shiny, bronze—black, metallic thin films have been obtained and characterized as titanium carbonitride by EDS and XPS analyses.

Low pressure catalytic hydroformylation of 1-hexene by the carbonylhydrido-tris(triphenylphosphine)rhodium(I), RhH(CO)(PPh3)3, in association with phosphinomethylzirconium complexes

Abstract Low pressure catalytic hydroformylation of 1-hexene was performed in the presence of RhH(CO)(PPh 3 ) 3 in association with diphenylphosphinomethyl-zirconium complexes such as Cp 2 Zr(CH 2 PPh 2 ) 2 and [Cp 2 Zr(CH 2 PPh 2 )] 2 O or in the presence of bis(diphenylphosphine)butane. An isolated rhodium-zirconium complex, formulated as [Cp 2 Zr(CH 2 PPh 2 ) 2 RhH(CO)PPh 3 ], was found to be catalytically active.