American Chemical Society
om201076f_si_006.cif (27.98 kB)

Reactions of Modified Intermolecular Frustrated P/B Lewis Pairs with Dihydrogen, Ethene, and Carbon Dioxide

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posted on 2012-04-09, 00:00 authored by Marcel Harhausen, Roland Fröhlich, Gerald Kehr, Gerhard Erker
In this contribution, we discuss the reactivity of different phosphanes (XPhos (1a), tBuXPhos (1b), and Mes2PEt (1c)) and tris­(pentafluorophenyl)­borane (and in one case, EtB­(C6F5)2) against small molecules. 1a/B­(C6F5)3, 1b/B­(C6F5)3, and 1c/B­(C6F5)3 split dihydrogen heterolytically to yield the phosphonium borate salts 2a, 2b, and 2c, respectively. Control experiments with D2 gave the respective deuterated phosphonium borates 2a-D2, 2b-D2, and 2c-D2. The FLP systems 1b/B­(C6F5)3 and 1c/B­(C6F5)3 underwent 1,2-addition reactions with ethene, resulting in the generation of the ethylene-bridged phosphonium borates 3b and 3c. As well, the Lewis pair EtB­(C6F5)2 and Mes2PEt reacted with ethene to yield the corresponding 1,2-addition product 3d. At low temperature, the FLP systems 1a/B­(C6F5)3 and 1c/B­(C6F5)3 coordinated carbon dioxide (4a, 4c). The new compounds 2a, 2b, 3b, 3c, 3d, 4a, and 4c were characterized by X-ray crystal structure analyses.