1229627-69-3Relevant articles and documents
Probing substituent effects on the activation of H2 by phosphorus and boron frustrated Lewis pairs
Neu, Rebecca C.,Ouyang, Eva Y.,Geier, Stephen J.,Zhao, Xiaoxi,Ramos, Alberto,Stephan, Douglas W.
, p. 4285 - 4294 (2010)
The impact of substituent changes on phosphorus and boron-containing frustrated Lewis pairs (FLPs) has been examined. The phosphites (RO) 3P R = Me, Ph form classical Lewis acid-base adducts of the formula (RO)3PB(C6F5)3 R = Me 1; R = Ph 2, whereas P(O-2,4-tBu2C6H3) 3 and P(O-2,6-Me2C6H3)3 generate FLPs. Nonetheless, these latter combinations do not react with H 2. The more basic phosphinite tBu2POR, R = tBu 3 reacts with B(C6F5)3 to give (tBu2(H)PO) B(C6F5)36. The related species tBu 2POR, R = Ph 4; 2,6-Me2C6H35 showed no reaction with B(C6F5)3 but the FLPs react under H2 (4 atm) to give [tBu2P(OR)H][HB(C 6F5)3] R = Ph 7 and 2,6-Me2C 6H38. Similarly, tBu2PCl in combination with B(C6F5)3, generates an FLP that upon addition of H2, gives [tBu2PH2][ClB(C6F 5)3] 9 albeit in low yield. The diborane 1,4-(C 6F5)2B(C6F4)B(C 6F5)2 in combination with either tBu 3P or (C6H2Me3)3P generates FLPs that react with H2 to give [R3PH] 2[1,4-(C6F5)2HB(C6F 4)BH(C6F5)2] (R = tBu 11, C 6H2Me312). Similarly PhB(C6F 5)2 and tBu3P react with H2 giving [tBu3PH][HBPh(C6F5)2] 13. The combination of B(OC6F5)3 and PtBu3 also generate an FLP which reacts with H2 to give [HPtBu 3][B(OC6F5)4] 14, the product of substituent redistribution. The boronic esters, (C6H 4O2)BC6F515, (C6H 3FO2)BC6F516 and (C 6F4O2)BC6F517, and the borate esters B(OC6H3(CF3)2) 318, B(OC6H2F3)319 and B(OC6H4CF3)320 were prepared and shown to generate FLPs with tBu3P or (C6H 2Me3)3P. Nonetheless, no reaction with H 2 was observed for 15-17. Collectively these data suggest that there is a threshold of combined Lewis acidity and basicity that is required to effect the splitting of H2.
