Diphosphines with natural bite angles near 120.degree. increase selectivity for n-aldehyde formation in rhodium-catalyzed hydroformylation
| Autor: | Gregory T. Whiteker, Douglas R. Powell, James A. Gavney, Charles P. Casey, Margaret G. Melville, Lori M. Petrovich |
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| Rok vydání: | 1992 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 114:5535-5543 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja00040a008 |
| Popis: | The use of 2,2{prime}-bis[(diphenylphosphino)methyl]1,1{prime}-biphenyl (BISBI, 1), trans-1,2-bis[(diphenylphosphino)-methyl]cyclopropane (T-BDCP, 2), and other diphosphines with large natural bite angles as ligands in rhodium-catalyzed hydroformylation has been studied. The X-ray crystal structure of (BISBI)Rh(PPh{sub 3})(CO)H{center_dot}CH{sub 2}Cl{sub 2} (7{center_dot}CH{sub 2}Cl{sub 2}) indicated a trigonal bipyramidal structure with three phosphorus atoms in the equatorial plane. The P-Rh-P bite angle of the BISBI ligand in 7{center_dot}CH{sub 2}Cl{sub 2} of 124.8{degrees} is much smaller than the 152{degrees}P-Fe-P bite angle found in (BISBI)Fe(CO){sub 3} and indicates that the BISBI ligand is rather flexible. NMR studies indicate that rapid exchange ({Delta}G = 15.5 kcal mol{sup -1}) occurs between the coordinated PPh{sub 3} of 7 and free PPh{sub 3}. 7 reacted with CO to produce (BISBI)Rh(CO){sub 2}H(9), which was shown by IR and NMR studies to have a trigonal bipyramidal structure with BISBI in the equatorial plane and hydride in an apical position. The solution structures of the T-BDCP complexes (T-BDCP)Rh(PPh{sub 3})(CO)H(13) and (T-BDCP)Rh(CO){sub 2}H(14) were shown by spectroscopy to be similar to the related BISBI compounds. A correlation between the size of the natural bite angle of chelating diphosphines and the regioselectivity for formation of straight-chain aldehydes in the rhodium-catalyzed hydroformylation of 1-hexane was observed. 30 refs., 9 figs.,more » 2 tabs.« less |
| Databáze: | OpenAIRE |
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