1094249-98-5Relevant articles and documents
Dihydrogen activation by B(p-C6F4H)3 and phosphines
Ullrich, Matthias,Lough, Alan J.,Stephan, Douglas W.
experimental part, p. 3647 - 3654 (2010/10/04)
The Grignard reagent (p-C6F4H)MgCl was used to prepare (Et2O)B(p-C6F4H)3 (2) and the free borane B(p-C6F4H)3 (1). On the basis of Lewis acidity tests, the borane 1 exhibits ca. 95% of the acidity of B(C 6F5)3. 1 forms classical adducts with ethers and phosphines of the general formula (L)B(p-C6F4H) 3 (L = Et2O (2), THF (3), Me3P (4), Et 3P (5), i-Pr2(H)P (6), Ph3P (7), (3,5-Me 2C6H3)3P (8), t-Bu2(H)P (9), and Cy3P (10)). Compounds 9 and 10 react with 4 atm of H 2 to give the salts [t-Bu2PH2][HB(p-C 6F4H)3] (11) and [Cy3PH][HB(p-C 6F4H)3] (12). The sterically demanding phosphines R3P (R = t-Bu, i-Pr, 2,4,6-Me3C 6H2, and 2-MeC6H4), R 2R′P (R,R′ = t-Bu, i-Pr and t-Bu, Cy), and (Ph 2CH)R2P (R = t-Bu (22), i-Pr (23), Cy (24), and C 5H9 (25)) show no evidence of adduct formation with 1, but react with H2 to give the corresponding salts [R3PH] [HB(p-C6F4H)3] (13-16), [R2R′ PH][HB(p-C6F4H)3] (17-20), and [(Ph 2CH)R2PH][HB(p-C6F4H)3] (26-29), respectively. The [t-Bu2PH2]+ species 11 is stable only under an H2 overpressure, while the [t-Bu 3PH]+ salt 13 cleanly extrudes isobutene and H2 at elevated temperatures to give 9. The [(2-MeC6H4) 3PH]+ derivative 16 readily liberates H2 under vacuum, thus providing a metal-free system capable of reversible H2 uptake and release. Crystallographic data for compounds 1, 5, 8, 9, 10, 13, and 26 are reported.
