Noël Lugan

Skeleton Decoration of NHCs by Amino Groups and its Sequential Booster Effect on the Palladium‐Catalyzed Buchwald–Hartwig Amination

A challenging synthetic modification of PEPPSI-type palladium pre-catalysts consisting of a stepwise incorporation of one and two amino groups onto the NHC skeleton was seen to exert a sequential enhancement of the electronic donor properties. This appears to be positively correlated with the catalytic performances of the corresponding complexes in the Buchwald-Hartwig amination. This is illustrated, for example, by the quantitative amination of 4-chloroanisole by morpholine within 2 h at 25 °C with a 2 mol% catalyst/substrate ratio or by a significant reduction of catalytic loading (down to 0.005 mol%) for the coupling of aryl chlorides with anilines (max TON: 19,600).

Synthesis of a New Potentially Hemilabile Ligand: 1-[2-(Diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole, and Comparison of Its Bonding Properties with the Related 1-[2-(Ethylamino)ethyl]-3,5-dimethylpyrazole Ligand toward RhI

The new ligand 1-[2-(diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole (2) has been prepared by the reaction of 1-(chloroethyl)-3,5-dimethylpyrazole and PPh2Li. The bidentate N,N ligand 1-[2-(ethylamino)ethyl]-3,5-dimethylpyrazole (1) and 2 react with [Rh(COD)(THF)2][BF4] to give [Rh(COD)(1)][BF4] (3) and [Rh(COD)(2)][BF4] (4), respectively. Substitution of 1,5-cyclooctadiene with carbon monoxide in the latter complexes generates [Rh(CO)2(1)][BF4] (5) and

Bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine − A Versatile Ligand for Complexation in RhI Cationic Complexes

The bis[(3,5-dimethyl-1-pyrazolyl)methyl]ethylamine ligand (1) reacts with [Rh(COD)(THF)2][BF4] leading to [Rh(COD)(1)][BF4] ([2][BF4]) in which 1 is κ3 bonded in the solid state. Because of the steric bulk of 1,5-cyclooctadiene, it prefers the κ2 mode of bonding in solution. Substitution of 1,5-cyclooctadiene by carbon monoxide generates [3][BF4] in which 1 is κ3 bonded in solution and solid state. Variable temperature NMR spectroscopic studies give evidence of a κ3 κ2 equilibrium in solution. [3][BF4] is easily decarbonylated to [Rh(CO)(1)][BF4] [4][BF4] in which 1 is κ3 bonded; however on bubbling carbon monoxide through, [3][BF4] is regenerated. The single-crystal X-ray structures of [2][BF4], [3][BPh4], and [4][BPh4] are reported.

Synthesis of Ru(II) complexes of the new 1-[(P-diphenyl)-2-phosphinoethyl]-3,5-dimethylpyrazole ligand and study of their reactivity toward terminal alkynes

Abstract The reaction between [RuCl 2 (PPh 3 ) 3 ] and one or two equivalent amounts of 1-[(P-diphenyl)-2-phosphinoethyl]-3,5-dimethylpyrazole ( 1 ) in dichloromethane gave [RuCl 2 (PPh 3 )( 1 )] ( 2 ) or [RuCl 2 ( 1 ) 2 ] ( 3 ), respectively, in good yields. Activation of propargylic alcohol derivatives by 3 in refluxing dichloromethane and in the presence of NaBPh 4 lead to the new allenylidene ruthenium complexes [RuCl( 1 ) 2 (CCCPhCH 3 )][BPh 4 ] ([ 4 ][BPh 4 ]) and [RuCl( 1 ) 2 (CCCPh 2 )][BPh 4 ] ([ 5 ][BPh 4 ]). The reaction between 3 and phenylacetylene in dichloromethane and in the presence of KPF 6 affords the vinylidene complex [RuCl( 1 ) 2 (CCHPh)][PF 6 ] ([ 6 ][PF 6 ]). The X-ray diffraction studies of 2 , 3 , and [ 5 ][BPh 4 ] are reported.

Study of the bonding properties of the bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ether toward Rh(I): an hemilabile ligand exhibiting κ3N,N,O meridional or facial coordination mode

Abstract The bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]ether ligand ( L 1 ) reacts with [Rh(COD)(THF) 2 ][BF 4 ] generated in situ, giving [Rh(COD)( L 1 -κ 2 N , N )][BF 4 ] ([ 1 ][BF 4 ]). The 1,5-cyclooctadiene ligand is displaced by carbon monoxide to generate [Rh(CO) 2 ( L 1 )][BF 4 ] ([ 2 ][BF 4 ]) in which in the solid state, the ligand L 1 adopts a facial κ 3 N , N , O bonding mode. This is the first example of such a coordination mode for this ligand, which generally prefers a ‘T-shaped’ meridional bonding mode. In solution [ 2 ][BF 4 ] exists as a mixture of two isomers in rapid equilibrium on the NMR time scale, [Rh(CO) 2 ( L 1 -κ 2 N , N )] + ([ 2a ] + ) and the major compound [Rh(CO) 2 ( L 1 -κ 3 N , N , O )] + [ 2b ] + . [ 2 ][BF 4 ] looses easily one molecule of carbon monoxide at room temperature leading to [Rh(CO)( L 1 -κ 3 N , N , O )][BF 4 ] ([ 3 ][BF 4 ]) in which L 1 adopts a ‘T-shaped’ meridional bonding mode. Carbon monoxide addition in solution regenerates rapidly [ 2 ][BF 4 ]. The single-crystal X-ray structures of [ 1 ][BF 4 ], [ 2b ][BF 4 ] and [ 3 ][BF 4 ] are reported.

Protonation of Cp(CO)(PPh3) RuCCPh: Formation of cationnic phenylacetylene and phenylvinylidene complexes and subsequent reaction with ethylene oxide to form the net [2 + 3] cycloadduct [Cp(CO)(PPH3)Ru=CCH(Ph)CH2CH2O]+

Abstract Protonation of the alkynyl complex Cp(CO)(PPh 3 )RuCCPh ( 1 ) at low temperature affords quantitatively the vinylidened complex [Cp(CO)(PPh 3 )RuCCH(Ph)] + ( 3 ), which upon warming to room temperature forms an equilibrium with the η 2 - phenylacetylene complex [Cp(CO)(PPh 3 )Ru( η 2 - HC  CPh )] + ( 4 ), with the latter predominating. Subsequent reaction with ethylene oxide yields the cyclic oxacarbene complex [Cp(CO)(PPH 3 )Ru=CCH(Ph)CH 2 CH 2 O] + ( 5 ), which can be regarded as the result of a net [3+2] cycloaddition reaction between 3 and ethylene oxide. Depronation of 5 affords teh corresponding neutral cyclic vinyl complex [Cp(CO)(PPH 3 )RuC=C(Ph)CH 2 CH 2 O] + ( 6 ), which can in turn be protonated to regenerate 5 in a diastereoselective manner. The structures of complexes 5 and 6 were determined by X-ray crystallography.

Ruthenium Catalysts Supported by Amino‐Substituted N‐Heterocyclic Carbene Ligands for Olefin Metathesis of Challenging Substrates

N-Heterocyclic carbene (NHC) ligands IMesNMe2 and IMes(NMe2)2 derived from the well-known IMes ligand by substituting the carbenic heterocycle with one and two dimethylamino groups, respectively, were employed for the synthesis of second-generation Grubbs- and Grubbs-Hoveyda-type ruthenium metathesis precatalysts. Whereas the stability of the complexes was found to depend on the degree of dimethylamino-substitution and on the type of complex, the backbone-substitution was shown to have a positive impact on their catalytic activity in ring-closing metathesis, with a more pronounced effect in the second-generation Grubbs-type series. The new complexes were successfully implemented in a number of challenging olefin metathesis reactions leading to the formation of tetra-substituted C=C double bonds and/or functionalized compounds.

Ruthenium(II) complexes with new tridentate ligands containing P, N, O donor atoms: highly efficient catalysts for transfer hydrogenation of ketones by propan-2-ol

The complexes [RuCl2(PPh3)(L)] in which L is a tridentate ligand with P, N and O donor atoms are very efficient catalysts for the transfer hydrogenation of cyclic ketones and acetophenone (turnover ⩽ 118 800 h–1) in basic media; when L is optically active, no significant e.e. is observed.

Umpolung of Methylenephosphonium Ions in Their Manganese Half‐Sandwich Complexes and Application to the Synthesis of Chiral Phosphorus‐Containing Ligand Scaffolds

Half-sandwich manganese methylenephosphonium complexes [Cp(CO)2Mn(η(2)-R2P=C(H)Ph)]BF4 were obtained in high yield through a straightforward reaction sequence involving a classical Fischer-type manganese complex and a secondary phosphine as key starting materials. The addition of various nucleophiles (Nu) to these species took place regioselectively at the double-bonded carbon center of the coordinated methylenephosphonium ligand R2P(+)=C(H)Ph to produce the corresponding chiral phosphine complexes [Cp(CO)2Mn(κ(1)-R2P-C(H)(Ph)Nu)], from which the phosphines were ultimately recovered as free entities upon simple irradiation with visible light. The synthetic potential of this umpolung approach is illustrated herein by the preparation of novel chiral pincer-type phosphine-NHC-phosphine ligand architectures.

Synthesis and reactivity of μ-bis(carbene)dimanganese complexes. X-ray structures of {Cp′(CO)2Mn}2{μ-C(OEt)CH2CH2(EtO)C}, (E)-{Cp′(CO)2Mn}2{μ-C(OEt)CHCH(EtO)C} and {Cp′(CO)2Mn}2{μ-H}

The carbene anions resulting from in situ deprotonation of the Fischer-type carbene complexes Cp′(CO) 2 MnC(OEt)CH 2 R ( 1 ; 1a : R=H; 1b : Me) undergo an oxidative coupling in the presence of Cu(I), Cu(II) or Fe(III) salts to produce the corresponding μ-bis(carbene)dimanganese complexes {Cp′(CO) 2 Mn} 2 {μ-C(OEt)CH(R)CH(R)(OEt)C} ( 2 ; 2a : R=H; 2b : Me). Double deprotonation of 2a gives a dianionic species that undergoes an oxidation in the presence of Fe(III) chloride to afford the μ-bis(vinylcarbene)dimanganese complex ( E )-{Cp′(CO) 2 Mn} 2 {μ-C(OEt)CHCH(OEt)C} ( 3 ). The controlled electro-reduction of the latter gives a radical anion whose ESR spectrum is consistent with a type III Mn 0 /Mn I mixed valence complex. When reacted with BCl 3 followed by benzylideneaniline complex 2 afford a mixture of the mixed μ-(alkylalkoxy carbene/azetidinylidene)dimanganese complex {Cp′(CO) 2 Mn} 2 {μ-C(OEt)CH 2 } ( 4 ) and the μ-bis(azetidinylidene)dimanganese complex {Cp′(CO) 2 Mn} 2 {μ- H } ( 5 ). Complex 4 is the product of a net [2+2] cycloaddition reaction between the mixed μ-(alkylalkoxy carbene/carbyne)dimanganese complex {Cp′(CO) 2 Mn} 2 {μ-C(OEt)CH 2 CH 2 C} + [ 6 ] + and the imine, whereas 5 results from a net 2×[2+2] cycloaddition between the μ-bis(carbyne)dimanganese complex {Cp′(CO) 2 Mn} 2 {μ-CCH 2 CH 2 C} 2+ [ 7 ] 2+ and imine. The treatment of complex 4 by BCl 3 followed by reaction with benzylideneaniline afford the mixed μ-(vinylidene/azetidinylidene)dimanganese complex {Cp′(CO) 2 Mn} 2 {μ-CCH } ( 8 ). Finally, the oxidative coupling-type reaction observed from the alkylalkoxy carbene complex 1 could be extended to the azetidinylidene complex [Cp′(CO) 2 MnCN(Ph)CHPhCH 2 ] ( 10 ) to yield 5 in a selective manner.