Homogeneously catalyzed high-pressure syntheses of chemicals using small molecules such as carbon monoxide, hydrogen, carbon dioxide, nitrogen, alkenes, or alkynes as reagents

Piero Frediani 

Organic Chemistry Department, via della lastruccia, 13, Sesto Fiorentino (Firenze) 50019, Italy

Abstract

The group has investigated the following homogeneously catalyzed reactions

1) Selective hydrogenations

a) Alkyne were selectively hydrogenated by an active Pd(bian)(ma) catalyst or in aqueous/organic biphasic systems with a Ru(mtppms) catalyst.

b) The ruthenium(II) dihydro complexes hydrogenate/hydrogenolyse organic substrates containing single or multiple C-N, N=N, N(O)=N or NO2 bonds. A benzonitrile conversion of 76.5 % was achieved after 24 h at 393 K. In the same conditions N-benzylidenaniline is hydrogenated with a 92.1 % conversion.

c) [{RuCl2(mtppms)2}2] reacts with hydrogen in aqueous solutions giving cis-[RuH2(H2)(mtppms)3] and trans-[RuH2(mtppms)4].

d) Water-soluble Rh(I)-and Ru(II)-complexes containing an N-heterocyclic carbene ligand derived from 1-butyl-3-methylimidazolium (bmim) salts were prepared and used as catalysts in olefin hydrogenation and redox isomerization of allylic alcohols.

e) Aqueous suspensions of calcium carbonate were hydrogenated to yield calcium formate under a gas phase containing both H2 and CO2. A rhodium(I)-complex of monosulfonated triphenylphosphine (mtppms), [RhCl(mtppms)3] was used as catalyst. Interestingly, at 50°C and 100 bar total pressure the yield of formate was 143% (based on CaCO3) which implies the formation of free formic acid from the CO2 present in the gas phase.

2) Hydroformylation of olefins

a) Catalytic hydroformylation of olefins has shown that using the Rh catalyst a different behaviour was noticed between a terminal (hex-1-ene) and an internal alkene (cyclohexene) and different rate-determining steps of the catalytic cycle. The presence of an additional gas (nitrogen or argon) in the reaction medium decreases the rate of the aldehyde formation.

b) Platinum(II) methyl complexes bearing bis-phosphanyl monosulfides (P^PS) in association with tin(II) chloride has been used for the hydroformylation of 1-octene evidencing that chelation of the P^PS ligand is retained during catalysis; and the role of SnCl2.

3) Oligomerization or polymerization of olefins

a) New functional ligands, neutral and anionic ones, are used to chelate Ni(II) and Pd(I) centres in order to evaluate their reactivity, the insertion of ethylene into the M-carbon bond and investigate the role of cocatalysts towards selective oligomerization. The Ni(II) and Pd(II) organometallic complexes catalyze the coupling of ethylene/CO/polar monomer, such as methylacrylate.

b) A variety of branched polyethylenes, spanning from semicrystalline LLDPE to completely amorphous, rubbery PE, was obtained from ethylene by homogeneous tandem catalysis using combinations of a Co and a Ti catalysts in the presence of MAO at 30 °C.The productivity reached a maximum of 4 570 kg PE (mol Ti*h)-1 yielding a rubbery material.

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Related papers
  1. Final report of WG1

Presentation: Oral at COST action D30 Mid term evaluation meeting, by Piero Frediani
See On-line Journal of COST action D30 Mid term evaluation meeting

Submitted: 2006-02-08 14:38
Revised:   2009-06-07 00:44
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