72794-37-7Relevant academic research and scientific papers
Stoichiometric model reactions in olefin hydroformylation by platinum-tin systems
Gómez, Montserrat,Muller, Guillermo,Sainz, Daniel,Sales, Joaquim,Solans, Xavier
, p. 4036 - 4045 (2008/10/08)
The three independent steps involved in the hydroformylation process, insertion of the olefin, insertion of carbon monoxide, and hydrogenolysis, have been investigated with use of platinum-tin catalysts and 1-pentene as olefin at low pressure and temperature in CH2Cl2. In the temperature range 198-308 K, the three reactions can be studied consecutively. All the intermediates observed were prepared and characterized separately. The complex trans-[PtH(SnCl3) (PPh3)2] was used as the initial compound for this sequence. The hydrido complex crystallized in the monoclinic space group C2/c, with a = 31.345 (5) ?, b = 12.716 (3) ?, c = 18.135 (3) ?, β = 96.5 (2)°, Z = 8, and R (Rw) = 0.056 (0.060) for 3235 independent reflections having I > 2.56σ(I). The large Pt-Sn bond (2.601 (1) ?) distance correlates satisfactorily with the low 1J(Pt-Sn) value. The Pt-Sn bond is necessary for the insertion of 1-pentene in the hydrido-platinum complex and for the hydrogenolysis of the acyl compounds under these mild conditions. The insertion of 1-pentene was observed at 198 K, giving the cis-alkyl complex; CO insertion took place after isomerization to the trans-alkyl complex. The instability of Pt-Sn and Pt-C bonds in the trans-acyl complex favors easy decarbonylation or loss of SnCl2, so any other platinum complex without tin accepts SnCl2 from the acyl complex. The hydrogenolysis of trans-[Pt(SnCl3) (COC5H11) (PPh3)2] under 1.5 bar of H2-CO (1:1) did not yield n-hexanal quantitatively; only 12% of n-hexanal was formed. Thus, decarbonylation was the main process observed. From the reactions studied, it is possible to propose the following order of Pt-Sn bond stability: trans-[Pt(SnCl3)(COC5H11)(PPh3) 2] 3)(C5H11)(PPh3)2] 3)(PPh3)2] 3)(CO)(PPh3)2] 3)(PPh3)]2 3)(PPh3)]- 2(SnCl3)2]2-. The insertion reactions studied with cis-[PtCl2(olefin)(PR3)] as an olefin carrier and the hydrido-platinum complexes trans-[PtHCl(PPh3)2], trans-[PtH(SnCl3)(PPh3)2], and [PtH(SnCl3)-(CO)(PPh3)2] as hydrogen carriers exclude the participation of intermolecular steps by reaction of two different platinum complexes under the experimental conditions described.
METALS IN ORGANIC SYNTHESIS. XIV. NMR, IR, AND REACTIVITY STUDIES ON THE OLEFIN HYDROFORMYLATION CATALYZED BY Pt-Sn COMPLEXES
Scrivanti, Alberto,Berton, Adriano,Toniolo, Luigi,Botteghi, Carlo
, p. 369 - 384 (2007/10/02)
Among the several hydrides formed when trans- (L=PPh3) reacts with SnCl2, only trans- rapidly inserts ethylene, at -80 deg C, to yield cis-.At -10 deg C, cis- irreversibly rearranges to the trans-isomer, thus indicating that the cis-isomer is the kinetically controlled species, and that the trans-isomer is thermodynamically more stable.At -50 deg C, a mixture of trans- and trans- reacts with ethylene to give cis- and this has been attributed to the catalytic activity of SnCl2 which dissociates from cis- at this temperature.Carbon monoxide promotes the cis-trans isomerization of cis-, which occurs rapidly even at -80 deg C.This rearrangement is followed by a slower reaction leading to the cationic complex trans-(1+)SnCl3(1-).At -80 deg C, this complex does not react further, but when it is kept at room temperature ethyl migration to coordinated carbon monoxide takes place, to give several Pt-acyl complexes, i.e. trans-, trans-, trans-, and trans-(1+)SnCl3(1-).This mixture of Pt-acyl complexes reacts with molecular hydrogen to yield n-propanal and the same complex mixture of platinum hydrides as is obtained by treating trans- with SnCl2.
