Metals in organic syntheses: XIV. NMR,IR, and reactivity studies on the olefin hydroformylation catalyzed by Pt-Sn complexes |
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| Institution: | 1. Department of Chemistry, University of Cape Town, Rondebosch, 7701, South Africa;2. Department of Chemistry, University of Johannesburg, PO Box 524, Auckland Park, 2006, South Africa;1. University of Wrocław, Faculty of Chemistry, 14F. Joliot-Curie St., 50-383 Wrocław, Poland;2. Adam Mickiewicz University in Poznań, Faculty of Chemistry, 89b Umultowska St., 61-614 Poznań, Poland;1. A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow, Russian Federation;2. N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation;3. N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation;1. Laboratory of Applied Chemistry (LAC), University of May 8th, 1945, BP 401, 24000, Guelma, Algeria;2. Laboratory of Applied Organic Chemistry, Faculty of Chemistry (LAOC), USTHB, BP 32, El-Alia, 16111, Bab-Ezzouar, Algiers, Algeria;1. N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation;2. Department of Crystallography, St. Petersburg State University, 199034 St. Petersburg, Russian Federation;3. I. M. Gubkin Russian State University of Oil and Gas, 119991 Moscow, Russian Federation |
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| Abstract: | Among the several hydrides formed when trans-PtHClL2] (L = PPh3) reacts with Sncl2, only trans-PtH(SnCl3)L2] rapidly inserts ethylene, at −80°C, to yield cis-PtEt(SnCl3)L2]. At −10°C, cis-PtEt(SnCl3)L2] 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°C, a mixture of trans-PtHClL2] and transPtH(SnCl3)L2] reacts with ethylene to give cis-PtEtClL2] and cis-PtEt(SnCl3)L2] and this has been attributed to the catalytic activity of SnCl2 which dissociates from cis-PtEt(SnCl3)L2] at this temperature.Carbon monoxide promotes the cis-trans isomerization of cisPtEt(SnCl3)L2], which occurs rapidly even at −80°C. This rearrangement is followed by a slower reaction leading to the cationic complex trans-PtEt(CO)L2]+ SnCl3−. At −80°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-PtCl(COEt)L2], trans-Pt(SnCl3)(COEt)L2], trans-PtCl(COEt)l2 · SnCl2], and trans-Pt(COEt)(CO)L2]+ SnCl3−. 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-PtHClL2] with SnCl2.Trans-PtH(SnCl3)L2] reacts with carbon monoxide to yield the five-coordinate complex PtH(SnCl3)(CO)2L2], which has been characterized by NMR and Ir spectroscopy; ethylene does not insert into the PtH bond of this complex at low temperature. At room temperature, trans-PtH(SnCl3)L2] reacts with a mixture of CO and ethylene to yield the same mixture of Pt-acyl species as is obtained when trans-PtEt(SnCl3)L2] is allowed to react with CO.The role of a PtSn bond in these reactions is discussed in relation to the catalytic cycle for the hydroformylation of olefins. |
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