18117-31-2Relevant academic research and scientific papers
Metals in organic syntheses. XI. 31P NMR and reactivity studies on the system trans-[PtCl(CO-n-hexyl)(PPh3)2]/SnCl2, an active intermediate in the catalytic hydroformylation of 1-hexene
Scrivanti,Cavinato,Toniolo,Botteghi
, p. 115 - 120 (1985)
The system trans-[PtCl(CO-n-hexyl)(PPh3)2]/SnCl2 has been investigated by 31P NMR spectroscopy. In CD2Cl2 or acetone-d6 solutions two species (in equilibrium with the starting Pt complex) are observed at low temperature: one set of signals is attributed to the complex trans-[Pt(SnCl3)(CO-n-hexyl)(PPh3)2]; the other set does not show SnP coupling and it is tentatively attributed to a complex having chloride bridging the Pt and Sn metal centers. Formation of the complex trans-[Pt(SnCl3)(CO-n-hexyl)(PPh3)2] is prevented when ethanol is added to the CD3Cl2 are acetone-d6 solutions. Treatment of the CD2Cl2 or acetone-d6 solution with molecular hydrogen give n-heptanal and hydroplatinum species; this reaction does not occur in the presence of ethanol, where only a complex having chloride bridging the Pt and Sn metal centers seems to be present. The result are discussed in connection with the catalytic cycle of olefin hydroformylation promoted by the [PtCl2(PPh3)2]/SnCl2 system.
A Study of the Mechanism of Platinum(II)/Tin(II) Dichloride Mediated Hydrogenation of Alkynes and Alkenes Employing Parahydrogen-Induced Polarization
Deibele, Christina,Permin, Alexei B.,Petrosyan, Valery S.,Bargon, Joachim
, p. 1915 - 1923 (2008/10/08)
The mechanism of hydrogenation of alkynes catalyzed by the [(PR3)2PtHX]/SnX2 system (PR3 = PPh3, PMePh2; X = Cl, Br) has been studied by means of parahydrogen-induced polarization of 1H spectra (PHIP). Dihydride intermediates confirming the stepwise hydrogenation at room temperature were observed when the reaction was run in acetone. The obtained 1H-PHIP spectra, together with NMR data for related species, are consistent with the formulation of these intermediates as cis-[H2Pt(PR3)(SnX 3)(σ-alkenyl)(acetone)], where the σ-alkenyl ligand originates from an insertion reaction of the alkyne (1-phenyl-1-propyne, 1-phenyl-1-butyne, diphenylacetylene, 3,3-dimethylbutyne). At elevated temperatures, the hydrogenation in acetone proceeds as a cis-synchronous transfer of the two hydrogen atoms of parahydrogen to the substrate molecule. A mechanism for this synchronous hydrogenation is suggested.
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.
PLATINUM(II) TRICHLOROSTANNATE CHEMISTRY. ON THE IMPORTANCE OF THE Pt-Sn LINKAGE IN HYDROFORMYLATION CHEMISTRY AND A NOVEL PtC(OSnCl2)R-CARBENE
Ruegg, H. J.,Pregosin, P. S.,Scrivanti, A.,Toniolo, L.,Botteghi, C.
, p. 233 - 242 (2007/10/02)
The reaction of trans-PtCl(COR)(PPh3)2 (1) (R=a, C6H5; b, C6H4-p-NO2; c, C6H4-p-CH3; d, C6H4-p-OCH3; e, CH3; f, Et; g, Prn; h, Hexn; i, CH2CH2Ph; j, But) with SnCl2 and SnCl2 plus H2 are described.The reactions with SnCl2 alone afford a mixture of trans-Pt(SnCl3)(COR)(PPh3)2 (2), and trans-PtCl(PPh3)2 (3) with 3 having a tin-oxygen bond.For 1f, 1h and 1j, reactions with SnCl2 plus H2 give aldehydes and platinum(II) hydride complexes, whereas for 1b and 1d, no aldehydes are obtained.The significance of these results in relation to H2 activation in the hydroformylation reaction is discussed. 31 P, 119 Sn, 195 Pt and, in a few cases, 13 C NMR data are presented.
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.
