A theoretical study on the mechanisms of intermolecular hydroacylation of aldehyde catalyzed by neutral and cationic rhodium complexes

In this paper, we used density functional theory(DFT) computations to study the mechanisms of the hydroacylation reaction of an aldehyde with an alkene catalyzed by Wilkinson's catalyst and an organic catalyst 2-amino-3-picoline in cationic and neutral systems. An aldehyde's hydroacylation includes three stages: the C–H activation to form rhodium hydride(stage I), the alkene insertion into the Rh–H bond to give the Rh-alkyl complex(stage II), and the C–C bond formation(stage III). Possible pathways for the hydroacylation originated from the trans and cis isomers of the catalytic cycle. In this paper, we discussed the neutral and cationic pathways. The rate-determining step is the C–H activation step in neutral system but the reductive elimination step in the cationic system. Meanwhile, the alkyl group migration-phosphine ligand coordination pathway is more favorable than the phosphine ligand coordination-alkyl group migration pathway in the C–C formation stage. Furthermore, the calculated results imply that an electron-withdrawing group may decrease the energy barrier of the C–H activation in the benzaldehyde hydroacylation.

A new class of rhodium complexes containing free donor atoms and their intramolecular substitution reaction

A new class of rhodium complexes with high catalytic activity as well as excellent stability, which was used as catalyst for carbonylation of methanol to acetic acid, is reported. It contains free donor (namely un-coordinated donor) atoms which enable to improve its stability by intramolecular substitution reaction. Its synthesis, characteristic and catalytic reaction were discussed here.

Rhodium-catalyzed selective[2+2+2]cyclizations of 1,6-diynes with monoynes leading to isoindolines and isobenzofurans

A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.

Hydrosilylation of olefins over rhodium complex anchored over thioether-functionalized MCM-41

The hydrosilylation of alkenes with triethoxysilane has been achieved at 120 C in the presence of 0.01 mol%of thioetherfunctionalized MCM-41 anchored rhodium complex,affording the corresponding addition products in 68-91%yields.This supported rhodium complex can be reused several times without noticeable loss of activity.Our system not only solves the basic problems of catalyst separation and recovery,but also avoids the use of phosphine ligands.

The Performance of Rhodium Complex-diphosphine Systems in the Hydroformylation of 1-Dodecene

The catalytic performances of four HRh(CO)(PPh3)3-diphosphine (BISBI,BDPX, BDNA and BINAP) systems in 1-dodecene hydroformylation were investigated and compared with HRh(CO)(PPh3)3-PPh3 system. The catalyst system HRh(CO)(PPh3)3-BISBI exhibited very high regioselectivity for the formation of linear aldehyde.

Hydroaminomethylation of 1-Dodecene Catalyzed by Water-soluble Rhodium Complex

The hydroaminomethylation of 1-dodecene catalyzed by water soluble rhodium complex RhCl(CO)(TPPTS)2 in the presence of surfactant CTAB was investigated. High reactivity and selectivity for tertiary amine were achieved under relatively mild conditions.

Methanol as hydrogen source: Chemoselective transfer hydrogenation of α,β-unsaturated ketones with a rhodacycle

Methanol is a safe, economic and easy-to-handle hydrogen source. It has rarely been used in transfer hydrogenation reactions, however. We herein report that a cyclometalated rhodium complex, rhodacycle, catalyzes highly chemoselective hydrogenation of α,β-unsaturated ketones with methanol as the hydrogen source. A wide variety of chalcones, styryl methyl ketones and vinyl methyl ketones, including sterically demanding ones, were reduced to the saturated ketones in refluxing methanol in a short reaction time, with no need for inter gas protection, and no reduction of the carbonyl moieties was observed. The catalysis described provides a practically easy and operationally safe method for the reduction of olefinic bonds in α,β-unsaturated ketone compounds.

Synthesis, Crystal Structure and Hydrogenation Catalysis of a CF_3-BINAP(O)-Rh-COD Complex

The complex [（CF3-BINAP（O））Rh（COD）][ClO4]·Et2O （2, CFa-BINAP（O） = 2- {bis[3,5-bis（trifluoromethyl）phenyl]phosphino } -2 ＇- {bis [3,5-bis（trifluoromethyl）phenyl]phosphinyl } -1,1、-binaphthyl, COD = 1,5-cyclooctadiene） was obtained directly from the reaction of CF3- BINAP（O） ligand with [Rh（COD）][C104]. Complex 2 has been characterized by single-crystal X-ray diffraction. The crystal adopts space group P21/n with a = 19.0727（4）, b = 15.6275（4）, c = 22.3039（6） A, fl = 112.3570（10）°, V= 6148.2（3） A3, Z = 4, Dc = 1.693 g/cm3, F（000） = 3144, μ（MoKa） = 0.500 mm-1, the final R = 0.0947 and wR = 0.2501. Structural studies reveal that Rh（I） is coordinated by one oxygen and one phosphorus in the same ligand. Asymmetric hydrogenation of acetami- docinnamic acid with compound 2 was also evaluated.

Synthesis and Liquid Crystal Behaviors of 2,4-Dioxo-3-pentyl 4-decyloxy Cinnamate Rhodium(I) Complexes

The title complexes have been synthesized by the reaction of [RhCl(CO)_2]_2 or _2 (COD=1,5-cyclooctadiene) with the organic ligand 2,4-dioxo-3-pentyl 4-decyloxy cinnamate 2. The complex 3 based on dicarbonylrhodium(I) shows nematic phase,while the complex 4 containing rhodium(I) bound to a COD ligand is a nonmesogen. The relationship between molecular structures and liquid crystal behavior has also been discussed by means of computer-aided molecular modeling.

Ab initio study on the mechanism of rhodium-complex-catalyzed carbonylation of methanol to acetic acid

The whole catalytic cycle of the carbonylation of methanol to acetic acid catalyzed by Rh complex is theoretically studied. All structural geometries of reactant, intermediates, transition states and product are optimized at HF/LANL2DZ level under the ECP approximation. The potential energy profiles for elementary reactions of carbonylation are calculated respectively. The transition states are further confirmed by having one and only one imaginary vibrational frequency. The results indicate that the activation energy values of CHin3I oxidative addition, carbonyl insertion and CH3COI reductive elimination fundamental steps are 216.03, 128.10 and 126.55 kJ/mol, respectively; and that the CH3I oxidative addition step is predicted to be the rate-determining one.

Oligo(p-phenylenevinylene)-rhodium complex as intracellular catalyst for enhancing biosynthesis of polyhydroxybutyrate biomaterials

Microbial synthesis utilizes sustainable resources to produce valuable chemicals,as a potential alternative to petroleum-based chemical industry.Although metabolic engineering is an efficient method to enhance the biosynthesis efficacy of microorganisms,it requires complicated biological procedures.Herein,we report a facile intracellular catalysis system for augmenting the production of bio-based material in microorganism.Covalent linking of oligo(p-phenylenevinylene)(OPV)and cyclopentadienyl rhodium(Ⅲ)bipyridine offers intracellular metal catalyst(OPV-Rh).The OPV-Rh complex displayed certain resistance to toxic biomolecules,which guaranteed its catalytic activity in complicated biological systems.With uptake by Gramnegative bacterium Ralstonia eutropha H16(R.eutropha H16),the OPV-Rh complex promotes the transformation of intracellular NADP+to NADPH,which further enhances the biosynthesis of polyhydroxybutyrate(PHB)by this microorganism.This work demonstrates that synthetic metal catalyst can be employed for regulating microbial biosynthesis intracellularly.

Asymmetric Hydroformylation of Olefins Catalyzed by a Chiral Diphosphite-Rhodium Complex

A C2-symmetrical aryl diphosphite derived from chiral binaphthol was prepared and its rhodium complex was used as catalysts in the asymmetric hydroformylation of olefins. High catalytic activity and good regioselectivity were observed. Up to 31.2% ee and 38.1% ee were achieved for the hydroformylation of 4-fluoro-styrene and vinyl acetate respectively. The influences of ligand-to-metal ratio, reaction temperature and the pressure of syn-gas on the enantioselectivity and regioselectivity were also studied.

Coordination chemistry of organometallic polydentate ligand Reactive chemistry of the tridentate ligand trans-Fe(Ph_2PQu-P)_2- (CO)_3 [Ph_2PQu=2-diphenyl-phosphino-4-methylquinoline] and molecular structure of [Fe(CO)_3(μ-Ph_2PQu)_2HgI]^+[HgI_3]

Reaction of a new type of bidentate ligand PhPQu [ PhPQu = 2-diphenylphosphino-4-methylquinoline] with Fe(CO)5 in bu-tanol gave trans-Fe(PhPQu-P)(CO)3 (1).Compound 1,which can act as a neutral tridentate organometallic ligand,was reacted with I B,II B metal compounds and a rhodium complex to give six binuclear complexes with Fe-M bonds,Fe(CO)3(u-Ph2PQu)MXn(2-7) [M=Zn(Ⅰ),Cd(Ⅱ),Hg(Ⅱ),Cu(Ⅰ),Ag(Ⅰ),Rh(Ⅰ)],and an ion-pair complex [Fe(CO)3(n-Ph2PQu)2HgI][HgI3]- (8).The structure of 8 was determined by X-ray crystallography.Complex 8 crystallizes in the space group P-1 with a=1.0758(3),b= 1.6210(4),c = 1.7155(4) nm; a = 75.60(2)β=71.81(2),Y = 81.78(2) and Z = 2 and its structure was refined to give agreement factors of R =0.050 and Rw = 0.057.The Fe-Hg bond distance is 0.2536 nm.