Rhodium catalysed hydroformlyation of higher alkenes using amphiphilic ligands: part 2

Preparation of carboxylic arylphosphines by hydrolysis of the trifluoromethyl group

Triarylphosphines substituted with carboxylic and trifluoromethlyl groups have been prepared by the hydrolysis of trifluoromethyl groups using fuming sulfuric acid and boric acid. The reaction has been studied in a set of homoleptic and heteroleptic trifluoromethylated triarylphosphines and offers a new synthetic procedure for the preparation of carboxylic phosphines with a relatively simple methodology. The degree of carboxylation is modulated by the reaction conditions and is sensitive to the substitution pattern of the starting trifluoromethylated phosphines. A pH-dependent procedure based on the amphiphilic character of these phosphines was developed for their separation and purification. The electronic properties of the synthesized carboxylic-trifluoromethylated phosphines have been analyzed by ³¹P NMR of the corresponding selenide derivatives. Finally, the structures of two palladium complexes, containing the para and meta carboxylic-trifluoromethylated phosphines are also described, showing different dimeric structures.

Nonionic Tenside Ligands and its Application in Biphasic Catalysis

This review article mainly surveys our research results of biphasic catalysis with nonionic tenside ligands. Emphasis is given to the synthesis and property of cloud point of the nonionic tenside ligands, the general principles of thermoregulated phase-transfer catalysis (TRPTC) and thermoregulated phase-separable catalysis (TPSC). It also explores the applications of TRPTC and TPSC in the hydroformylation of higher olefins and CO selective reduction of nitroarenes. The introduction of TRPTC to biphasic systemis free from the shortcomings of classical aqueous/organic two-phase catalysis, in which the application scope is restrained by the water solubility of the organic substrate. The biphasic catalysis with nonionic tenside ligands was characterized by homogeneous catalysis coupled with convenient biphasic separation.

Neutral and Cationic Complexes with P-Bonded 2-Pyridylphosphines as N-Donor Ligands toward Rhodium. Electrical Charge vs Steric Hindrance on the Conformational Control

Bimetallic palladium(II)-rhodium(I) and gold(I)-rhodium(I) complexes of the type [(4,4'-Me2-bipy)(C6F5)Pd(mu-PPh(3-n)Pyn)Rh(diene)](BF4)2 and [(C6F5)Au(mu-PPh(3-n)Pyn)Rh(diene)](BF4) (n = 2, 3; Py = 2-pyridyl) have been synthesized. The P donor atom of the bridging ligands (mu-PPh(3-n)Pyn) is coordinated to the Pd or to the Au center. The resulting complexes react with [Rh(diolefin)(solv)2]+ (solv = acetone) in a way similar to pyrazolylborates, affording square-planar or pentacoordinated rhodium complexes with two or the three N-donor ends chelating the Rh atom. The metallacycles formed upon chelation can adopt one of two conformations in the square-planar Rh(I) complexes, either bringing the other metal close to the Rh center or bringing it to a remote position. The first conformation is preferred for the gold P-coordinated complexes and the second for the palladium complexes. The X-ray structures of [(4,4'-Me2-bipy)](C6F5)Pd(mu-PPhPy2)Rh(COD)](BF4)2 (COD = 1,5 cyclooctadiene) and [Au(C6F5)(mu-PPhPy2)Rh(TFB)](BF4) (TFB = 5,6,7,8-tetrafuoro-1,4-dihydro-1,4-etenonaphthalene) are reported.

Anionic Platinum Complexes with 2-Pyridylphosphines as Ligands for Rhodium: Synthesis of Zwitterionic Pt−Rh Organometallic Compounds

Bimetallic zwitterionic platinum(II)-rhodium(I) complexes of the type [(C(6)F(5))(3)Pt(micro-PPy(n)Ph(3)(-)(n)Rh(CO)(2))] and [(C(6)F(5))(3)Pt(micro-PPy(n)Ph(3)(-)(n)())Rh(diene))] (n = 2, 3; Py = 2-pyridyl) have been prepared. The P end of the bridging ligands (micro-PPy(n)Ph(3)(-)(n)) is always coordinated to the Pt center, while the N-donor ends chelate the Rh atom, giving metallacycles comparable to pyrazolylborate-Rh complexes. These metallacycles can adopt two conformations, either with the Pt complex in pseudoaxial position approaching the Rh center or with the Pt complex in a remote position. The preferred conformation depends on the steric hindrance at the rhodium center. In less sterically demanding Rh-carbonyl complexes the Pt moiety gets close to the Rh moiety as this brings closer the opposite charges of the zwitterion. For diene complexes mixtures of conformers are obtained. The X-ray structures of [(C(6)F(5))(3)Pt(micro-PPhPy(2))Rh(COD)] (COD = 1,5-cyclooctadiene) and [(C(6)F(5))(3)Pt(micro-PPhPy(2))Rh(CO)(2)] are reported.

A novel amphiphilic chiral ligand derived from D-glucosamine. Application to palladium-catalyzed asymmetric allylic substitution reaction in an aqueous or an organic medium, allowing for catalyst recycling

A novel amphiphilic phosphinite-oxazoline chiral compound, 2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[4-((diethylamino)methyl)phenyl]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline (1), has been prepared from natural D-glucosamine hydrochloride. The newly prepared complex, [Pd(2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[(4-((diethylmethylammonium)methyl)phenyl)]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline)(eta3-C3H5)]3+ x 3BF4- (3), is soluble in water and an efficient catalyst for asymmetric allylic substitution reaction in water or an aqueous/organic biphasic medium (up to 85% ee). This catalytic system offers an easy separation of the aqueous catalyst phase from the product phase and allows recycling of the catalyst phase. In addition, compound 1 also works as an effective ligand for the palladium-catalyzed reaction under conventional homogeneous conditions in an organic medium, in which the catalyst (Pd-1 complex) can be recovered by simple acid/base extraction and reused in the second reaction.