HYDROFORMYLATION CATALYSIS USING POLYMER-SUPPORTED MULTINUCLEAR RHODIUM CARBONYL CLUSTER CATALYSTS

A series of polymer-supported tetranuclear rhodium carbonyl cluster catalysts were prepared b the reaction of Rh_4(CO)_(12) with several kinds of polymer supports such as crosslinked poly (N-vinylpyrrolidone) (PNVP) and crosslinked poly ( styrene-co-maleic anhydride) (PMAn), and subsequently were used to catalyze the hydroformylation of olefins. The catalysts were characterized by IR, SEM and XPS. The influence of the supports structure and crosslinking, metal's content and particle size of the supports on the catalysts hydroformylation properties was studied. The factors which affect the catalytic conversion were also examined. The experimental results show that the polymer-supported Rh cluster catalysts possess very high catalytic activity and aldehyde selectivity as well as good reproducibility.     

Chemoselective synthesis of multiple epoxy-bridged tetrahydropyranone ring systems

Bis- as well as tris-tetrahydropyranone ring systems were obtained via multiple tandem cyclization-1,3-dipolar cycloaddition reactions of α-diazo ketones with ketone as well as aldehyde functional groups in a chemoselective manner.     

Rhodium-catalyzed addition of arylboron compounds to nitriles, ketones, and imines

The rhodium-catalyzed addition reactions of sodium tetraphenylborate and arylboronic acids to nitriles, ketones, and imines were examined. The reaction of nitriles could be carried out efficiently in the presence of a catalyst system of [RhCl(cod)]₂-dppp and H₂O to give the corresponding monoarylated products selectively. Although unactivated ketones and imines are known to be poor electrophiles for rhodium-catalyzed arylation, the phenylation of them with use of sodium tetraphenylborate proceeded smoothly in the presence of [RhCl(cod)]₂ and Rh(acac)(cod) as catalysts, respectively. The addition of NH₄Cl was found to be crucial to effectively conduct the reaction of ketones and imines.     

A useful procedure for diiodination of carbazoles and subsequent efficient transformation to novel 3,6-bis(triethoxysilyl)carbazoles giving mesoporous materials

Bis(pyridine)iodonium tetrafluoroborate (IPy₂BF₄) was successfully used as a diiodination reagent for carbazole and its derivatives to give 3,6-diiodocarbazoles in excellent yield. Subsequent rhodium-catalyzed disilylation of 3,6-diiodocarbazoles with triethoxysilane gave the corresponding 3,6-bis(triethoxysilyl)carbazoles, which are precursors for sol-gel polymerization, in good yield.     

Atomabsorptionsspektroskopische Bestimmung von Edelmetallen

Zusammenfassung Die atomabsorptionsspektroskopische Palladiumbestimmung wird vom Platin nicht und vom Rhodium nur wenig beeinflußt. Berücksichtigt man, daß ein Zusatz von Uran die Palladiumbestimmung neben Rhodium desaktiviert, so liegen allgemein die günstigsten Bedingungen für die Palladiumbestimmung vor, wenn Lanthan als spektroskopischer Puffer zugesetzt wird. Korrekturgleichungen werden gegeben.

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Determination of noble metals by atomic absorption spectroscopy3. Effect of platinum and rhodium on the determination of palladium

The atomic-absorption determination of Pd is not affected by Pt, but there is a small influence by Rh. The aim of this investigation is to determine these effects quantitatively, furthermore under the releasing effects of uranium and lanthanum. Equations to correct the results are given.

     

Rhodium-catalyzed hydroformylation of C6 alkenes and alkene mixtures - a comparative study in homogeneous and aqueous-biphasic media using PPh3, TPPTS and TPPMS ligands

The complexes RhH(CO)L₃, where L = PPh₃, P(m-C₆H₄SO₃Na)₃ (TPPTS), and (C₆H₅)₂P(m-C₆H₄SO₃Na) (TPPMS) were used as catalyst precursors for a comparative study of the catalytic hydroformylation of several C6 alkenes and alkene mixtures under moderate reaction conditions in homogeneous (PPh₃) and aqueous-biphasic (TPPTS, TPPMS) media. The biphasic systems are efficient for the hydroformylation of hex-1-ene, 2,3-dimethyl-1-butene, styrene, cyclohexene, and mixtures thereof, in water/n-heptane at 80 °C. The main problem associated with these catalysts is their tendency to promote alkene isomerization if the effective syngas concentration in the liquid phases is low, but this side-reaction can be suppressed by using higher CO/H₂ pressures (54 atm). The selectivity of both water-soluble catalysts for linear products of hex-1-ene and for branched products of styrene is modest in comparison with the homogeneous system, which may limit their utility for classical oxo uses, but this is not a disadvantage for other interesting applications related to the hydroformylation of alkene mixtures and particularly to naphtha upgrading where linear and branched products are equally useful. The catalysts can be recycled without significant loss of activity and are resistant to the presence of benzothiophene in the mixture.     

Synthesis and complexation of a new facultative tridentate S2Te donor ligand MeS(CH2)3Te(CH2)3SMe: crystal structures of [Rh(Cp*)(S2Te)][PF6]2 and [PtCl(S2Te)]PF6

The syntheses and spectroscopic characterisation of the new facultative tridentate tellurium containing ligands MeS(CH₂)₃Te(CH₂)₃SMe (S₂Te) and H₂N(CH₂)₃Te(CH₂)₃NH₂ are described. The complexes of the former, fac-[Mn(CO)₃(S₂Te)]CF₃SO₃, [Rh(Cp*)(S₂Te)][PF₆]₂, [MCl(S₂Te)]PF₆ (M=Pd or Pt), [Cu(S₂Te)]BF₄ and [Ag(S₂Te)]CF₃SO₃ have been prepared and characterised by analysis, IR, ¹H-, ¹³C{¹H}-, ¹²⁵Te- and ¹⁹⁵Pt-NMR spectroscopy and mass spectrometry. The X-ray crystal structures of [Rh(Cp*)(S₂Te)][PF₆]₂ and [PtCl(S₂Te)]PF₆ are described. The results are compared with those obtained from complexes of the related tridentates Te{(CH₂)₃TeR}₂, Se{(CH₂)₃SeMe}₂ and S{(CH₂)₃SR}₂.     

Potassium trifluoro(organo)borates in rhodium-catalyzed 1,4-additions to α,β-unsaturated esters

This letter describes an efficient and enantioselective conjugate addition of highly stable potassium trifluoro(organo)borates to α,β-unsaturated esters. This reaction, catalyzed by chiral rhodium(I) complexes, affords Michael adducts with high yields and enantiomeric excesses up to 96%.     

铑配合物催化丁烯氢甲酰化性能的研究

制备了一系列铑配合物,并对其催化丁烯氢甲酰化的催化性能进行了研究.在1-丁烯的反应中,RhCl(PPh3)3和trans-RhCl(CO)(PPh3)2的反应速度很慢,而RhH(CO)(PPh3)3、Rh(CO)2(acac)和 Rh(CO)(acac)(PPh3)三者反应速度都很快.而不同丁烯原料氢甲酰化的反应速度也各不相同,反应速度依次为1-丁烯》2-丁烯》异丁烯.     

Rhodium(I) complexes with 1′-(diphenylphosphino)ferrocenecarboxylic acid as active and recyclable catalysts for 1-hexene hydroformylation

The rhodium complex trans-[Rh(CO)(Hdpf-κP)(dpf-κ²O,P)] (1), (Hdpf = 1′-(diphenylphosphino)ferrocenecarboxylic acid) was used as an efficient and recyclable catalyst for 1-hexene hydroformylation producing ca. 80% of aldehydes at 10 atm CO/H₂ and 80 °C. After the reaction, unchanged complex 1 was separated from the reaction mixture and used again three times with the same catalytic activity. The effect of modifying ligands, phosphines and phosphites, on the reactivity of 1 was investigated. The active catalytic systems containing 1 or trans-[Rh(CO)(L)(dpf-κ²O,P)] (2) were formed in situ from acetylacetonato rhodium(I) precursors [Rh(CO)₂(acac)] (3) or [RhL(CO)(acac)] (4) and Hdpf or Medpf (L = phosphine, Medpf = methyl ester of Hdpf).