Daniele Gervais

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.

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.

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.

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.

The role of early transition metal azides as catalysts of the ring-opening reaction of epoxides with trimethylsilylazide

Abstract Complexes of early transition metals (titanium, vanadium, …) catalyse the reaction of epoxides with Me 3 SiN 3 . When an azido complex is used as precursor, the reaction follows an overall second-order law and the rate constant is proportional to the complex concentration. The regioselectivity (α- or β-cleavage of the ring) is compared to that of the stoichiometric reaction of the transition metal azide with epoxides. It is concluded that the catalytic mechanism involves the intermediary formation of a complex resulting from the nucleophilic attack of the epoxide ring by the N 3 group bonded to the transition metal atom.

Metathetical reactions of carbonylate anions with dichlororuthenium complexes: Preparation and characterization of ruthenium—molybdenum and ruthenium—manganese complexes

Abstract The possibility of making metal—metal bonded heterobimetallic species by metathesis of ruthenium dichlorides with anionic carbonylates is demonstrated by the isolation of MoRu(μ-Cl)(μ-CO)(CO) 2 (PPh 3 ) 2 (η-C 5 H 5 ) ( 1 ) and MnRuCl(μ-CO) 2 (CO) 3 (μ-dppm) 2 ( 2 ), obtained by action of [Mo(CO) 3 (η-C 5 H 5 ] − on RuCl 2 (PPh 3 ) 3 and of Mn(CO) 5 − on RuCl 2 (dppm) 2 , respectively. In contrast, reaction of Mn(CO) 5 − with RuCl 2 (PMe 3 ) 4 yielded an ionic species 3 containing the diruthenium cation Ru 2 Cl 3 (PMe 3 ) 6 + . More interestingly, the action of Mn(CO) 5 − on RuCl 2 (PPh 3 ) 3 resulted in the formation of the unexpected complex MnRu(μ-PPh 2 )(CO) 6 (PPh 3 ) 2 ( 4 ) in which the phosphido group PPh 2 bridges the two metals; this process is shown to involve a hydride intermediate, and elimination of a molecule of benzene, both identified in the reaction mixture.

Preparation and properties of some 2,2,2-trifluoroethoxy derivatives of titanium

Abstract The synthesis and characterization of some compounds of titanium(IV) with the formula TiX 4-x (OR f ) x (where x = 2, 3 for X = Cl; x = 1, 2 for X = isopropoxy and OR f = 2,2,2-trifluoroethoxy, OCH 2 CF 3 ) and their adducts with a nitrile (CH 3 CN, C 2 H 5 CN) and the alcohol R f OH are reported. Using an acidity scale based on NMR data, the ligand, 2,2,2-trifluoroethoxy is compared with other ligands such as chlorine and isopropoxy and the following decreasing order of electron donor ability, OR > OR f > Cl is obtained. Attempts to prepare alkylated compounds pounds RTi(OR f ) 3 (R = CH 3 , C 6 H 5 CH 2 ) from TiCl(OR f ) 3 are reported and the cleavage of the titanium carbon bond in these compounds is found to take place readily by action of nucleophilic agents. The reactivity of the titanium oxygen bond of Tiue5f8OR f is tested towards some substitution and insertion reactions.