Pascale Laurent

COMPLEXATION ON RHODIUM OF BIDENTATE AND POTENTIALLY HEMILABILE PHOSPHOROUS LIGANDS

Abstract Various bifunctional potentially hemilabile ligands bearing phosphorous groups have been prepared and their coordination to rhodium has been studied. Their effect on the hydroformylation of styrene has been assessed.

Rhodium-catalyzed hydroformylation of styrene at low temperature using potentially hemilabile phosphite–phosphonate ligands

Abstract The synthesis and the effect of phosphite–phosphonate ligands in rhodium-catalyzed hydroformylation of styrene are described. Activity and selectivity of the catalyst are improved, at low temperature, by increasing bulkiness of both phosphite and phosphonate moieties.

Synthesis, reactivity of the [(CO)3(L)Fe(CO2R)2] dialkoxycarbonyl carbonyl iron complexes (L = CO or PPh3; R CH3, C2H5), and an easy access to [(CO)5Fe(CO2Me)]+

Abstract The cis -dialkylcarboxytetracarbonyliron complexes [(CO) 4 Fe(CO 2 R) 2 ] were readily obtained from reaction of oxalyl chloride with the corresponding tetracarbonylcarboxyiron anion [(CO) 4 Fe(CO 2 R)] − (R  Me, 1a ; R  Et, 1b ). 1a underwent a clean ligand exchange with triphenylphosphine to give [Fe(CO) 3 (PPh 3 )(CO 2 Me) 2 ] ( 2 ). Neither 1a nor 2 yielded dimethyl oxalate after thermolysis; rather, a mixture of methanol and methyl carbonate was obtained. The mobility of the alkoxy groups on 1 was shown by several exchange experiments. A clean reaction of the tetrafluoroboric acid ether with 1a gave [(CO) 5 Fe(CO 2 Me)] + which was isolated and characterized by IR, 1 H, and 13 C NMR spectroscopy.

Synthesis and reactivity of bis(alkyloxalyl) and alkoxycarbonyl alkyloxalyl iron complexes [Fe(COCO2 R)2(CO)4] and [Fe(CO2R)(COCO2R′)(CO)4] (R, R′= Me or Et): evidence for reductive elimination of oxalate

Abstract The new complexes cis-[Fe(COCO2R)2(CO)4] (R = Me or Et) andcis-[Fe(COCO2R) (CO2R′)(CO)4] (R, R′= Me, Et oriPr) have been synthesized. The bis-(alkyloxalyl) complexes decarbonylate at +12°C to their alkoxycarbonyl alkyloxalyl homologues. The latter decompose at +28°C by to two pathways: further decarbonylation to give the known compound [Fe(CO2R)2(CO)4] or via reductive elimination to give oxalates [RO2CCO2R] and [Fe(CO)5]. Bulky and the more electron-donating R or R′ groups favour the last pathway, and this is the only route observed when the COtrans to the alkyloxalyl is replaced by PPh3. The alkoxy group of the alkoxycarbonyl is easily removed; thus the reaction of HBF4 with [Fe(CO2Me)(COCO2 Me)(CO)4] gives the new cation [Fe(COCO2Me)(CO)5]+.

The mild phase transfer syntheses of the ylide adduct (CO)4F−eCH2P+Ph3, the octacarbonyl(μ-methylene)diiron μ-CH2Fe2(CO)8, and acyl tetracarbonyliron anions RCOFe(CO)4− are consistent with the transient generation of the Fe(CO)42− dianion from Fe(CO)5

Addition of Fe(CO)5 under a nitrogen or carbon monoxide atmosphere to the CH2XY/H2O phase transfer system (X, Y  CL, Br; 1 M NaOH and Bu4N+ HSO4− added) after prior introduction of PPh3, yields the ylide adduct (CO)4F−eCH2P+Ph3 efficiently. In the absence of PPh3, (X  Br, Y  Cl, Br) the methylene bridged complex μ-CH2Fe2(CO)8 is obtained in high yields. In the presence reactive chlorides RCl (R  CH2C6H5, CH2CO2-t-Bu, CH2CN, CH2CHCHC6H5) under CO pressure (10 atm) (X  Y  Cl), the acyltetracarbonyl iron anions RCOFe(CO)4− were obtaiend as tetrabutylammonium salts (soluble in the organic solvent) in high yields. When Fe(CO)5 was replaced by the HFe(CO)4− anion there was no reaction, whereas the products mentioned were formed after introduction of the preformed dianion Fe(CO)42− into the PT system.

Phosphane and Bis(phosphane) Ligands from Phosphinic Acids

The Boyd−Regan methodology allowed for access to various cyclic or benzylic mono- and bis(phosphinic acids) 1−6. The reduction of monophosphinic acids to secondary phosphanes 7−9 was achieved with silanes. On the other hand, reduction of the bis(phosphinic acids) with LiAlH4 led to bis(phosphanes) 12−13. Various cyclic phosphanes and bis(phosphanes) were obtained by the alkylation of these secondary phosphanes (as their borane adducts). The Michael addition of the same borane adducts to vinylic phosphonates led to phosphane−phosphonates which could be hydrolysed to new hydrosoluble phosphanes.

Chain–ring isomerism vs. carbon–carbon coupling on two(tetracarbonyliron)-γ-ketoesters: cis-[Fe(COR)(COCOR′)(CO)4](R = Me, R′= OMe; R = OMe; R′= Me)

Ferra-γ-ketoesters 1 and 2 induce thermally either a carbon–carbon coupling process or a chain–ring isomerization; the orientation of the reaction likely depends on the proximity of the ester group to the metal centre.

CIS OCTAHEDRAL IRON COMPLEXES FE(CO)XR(CO)YR'(CO)4 (X + Y = 0,1,2,3,4) : THERMOLYSIS AND CARBON-CARBON COUPLING : A PERSONAL SURVEY

Abstract The synthesis of a homogeneous series of cis bis substituted iron complexes is described. These complexes which display the [M]{[C(O)] x R}{[C(O)) y R′]} ( x + y =0, 1, 2, 3, 4; x , y ⩽2) pattern are models for the study of carbon–carbon coupling processes including mono- and polycarbonylations. Their reactivity is reviewed and particularly that of bis alkoxycarbonyl, bis carbamoyl and metalla γ ketoester iron compounds.

Effect of the ligand L on the transesterification processes of bismethoxycarbonyl iron complexes: cis Fe(CO2Me)2(CO)3L, L=CO, PMe3, PPh3, P(OEt)3

Abstract The synthesis of the new mer or fac Fe(CO2Me)2(CO)3 (L) (L=PMe3: 2a; L=PPh3: 2b; L=P(Cy)3: 2c; L=P(OEt)3: 2d) complexes of various electron densities has been realized in order to study the transesterification reactions between these methoxycarbonyl complexes and alcohols. The easy formation of [Fe(CO2Me)(CO)4(L)] [BF4] by removing a methoxy group from these complexes clearly indicates that their methoxy group and particularly the one trans to the phosphane ligand are mobile. However whereas the unsubstituted complex Fe(CO2Me)2(CO)4 (1) presents fast exchange reactions with ethanol, 2a and 2b are found unreactive towards the same reagent and 2d (L=P(OEt)3) only undergoes slow transesterification reactions at 28°C. It is proposed an associative mechanism for this transesterification process probably induced by a preliminary nucleophilic addition of an alcohol molecule at a terminal carbonyl ligand prior to the elimination of the methoxy group of a methoxycarbonyl.

Cobalt catalysed carbonylation of reactive chlorides into esters by methyl formate without carbon monoxide and methanol added

Abstract Reactive chlorides ZCH 2 Cl (Z = C 6 H 5 , CH 3 OC(O), CN) are readily carbonylated into esters with methyl formate as the sole source of carbon monoxide and methanol, the tetracarbonyl cobaltate anion as the catalyst and sodium carbonate as the base. The reaction occurs after in situ prior mild decomposition of methyl formate with a catalytic amount of sodium methoxide.