Hydroformylation studies, 1-butene

To determine whether this isomer distribution was the result of epi-merization, hydroformylation of (Z)-2-phenyl-2-butene was studied. 

As shown by the data of Table I, adding increasing amounts of the three phosphines used in the present studies to tris(tri-phenylphosphine)rhodium(I) carbonyl hydride produces catalyst systems of reduced activity as indicated by the reduced reaction rate. As expected, an increasing excess of triphenylphosphine results in an increased 1-butene hydroformylation selectivity towards the n-... 

As indicated in the introduction, bis-l,3-diphenylphosphino-propane (dppp) and bis-l,2-diphenylphosphinoethane (dppe) were reacted with tris(triphenylphosphine)rhodium(II) carbonyl hydride in toluene-deuterobenzene solution to derive cis-chelate complex hydroformylation catalysts. These complexes were expectedly non-selective terminal hydroformylation catalysts for 1-butene hydroformylation (see Table I) because of their cis-stereochemistry. They were also somewhat less active due to their specific structural features. The structure of these complexes in solution was studied in detail by P-31 NMR spectroscopy. 

The catalysts used in hydroformylation are typically organometallic complexes. Cobalt-based catalysts dominated hydroformylation until 1970s thereafter rhodium-based catalysts were commerciahzed. Synthesized aldehydes are typical intermediates for chemical industry [5]. A typical hydroformylation catalyst is modified with a ligand, e.g., tiiphenylphoshine. In recent years, a lot of effort has been put on the ligand chemistry in order to find new ligands for tailored processes [7-9]. In the present study, phosphine-based rhodium catalysts were used for hydroformylation of 1-butene. Despite intensive research on hydroformylation in the last 50 years, both the reaction mechanisms and kinetics are not in the most cases clear. Both associative and dissociative mechanisms have been proposed [5-6]. The discrepancies in mechanistic speculations have also led to a variety of rate equations for hydroformylation processes. 

A lot of research has been published on hydroformylation of alkenes, but the vast majority of the effort has been focused on the chemistry of various metal-ligand systems. Quantitative kinetic studies including modeling of rates and selectivities are much more scarce. In this work, we present the approach to modeling of hydroformylation kinetics and gas-solubility. Hydroformylation of 1-butene with a rhodium-based catalyst was selected as a case study. 

The synthesis, aggregation behavior, and catalytic activity of Rh complexes of Xantphos derivatives (129) with surface-active pendant groups have been described.416 The complex [HRh(CO)(TPPTS)3] was used as a catalyst precursor in the hydroformylation of 1-butene, 1-octene, and styrene under biphasic reaction conditions 417 The two-phase hydroformylation of buta-1,3-diene with [HRh(CO)(TPPTS)3], with excess TPPPS, gives high yields of C5-monoaldehydes.418 The coordination behavior of the catalytic species HRh(130)(CO)2] was studied by HP NMR spectroscopy which showed the desired bis-equatorial coordination of the ligand to the rhodium center.419... 

Cyclohexene exists only as internal cw-olefin and is moderately reactive. In contrast, -hexene, regardless of whether charged as 1- or internal olefin or a mixture of these, is quickly isomerized to a near-equilibrium mixture containing some 5 to 10% of the isomer with terminal double bond, whose reactivity is about two orders of magnitude higher than those with internal ones. Accordingly, -hexene is more reactive than cyclohexene with only internal double-bond positions. Lastly, neohexene (3,3 -dimethyl-l-butene) has its double bond locked in the terminal position —no double bond can exist adjacent to a quaternary carbon atom—and so should have the highest reactivity if not sterically hindered. (This is an unsubstantiated prediction, as the hydroformylation reactivity of that olefin seems not to have been studied to date.)... 

Frequently, for simphfication of kinetic studies of hydroformylation reactions 3,3-dimethyl-l-butene (neohexene)... 

High-pressure in situ ETIR and polymer matrix techniques were used to study the rhodium-catalyzed hydroformylation of 1-octene, 1-butene, propene, and ethene using Rh(acac)(CO)2 or Rh(acac)(CO)(PPh3) in a polyethylene matrix as the catalyst precursor. The acyl rhodium intermediates, RC(=0)Rh(C0)4 and RC(=0)Rh (CO)3(PPh3), were observed. It was found that the acyl rhodium tetracarbonyl intermediates easily react with ethene to form acyl rhodium tricarbonyl species RC(=0)Rh(C0)3(C2H4) [61]. Deuterioformylation of l-phenyl-l-(n-pyridyl)-ethenes in the presence of a phosphane-modified Rh4(CO)i2 as catalyst precursor was carried out at 100 bar of CO D2 = 1 1 and 80 °C at partial substrate conversion. On basis ofa direct NMR analysis of the crude reaction mixture, it was concluded that the branched alkyl rhodium intermediate is almost exclusively formed [62]. 

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