Versatile Reaction Patterns of Phosphanylhydrosilylalkyne with B(C6F5)3: A Remarkable Group Substitution Effect

Abstract

Phosphanylhydrosilylalkynes R2HSiCCPAr2 (R,Ar: Me,4‐tBuC6H4 1, Me,Mes 2, Mes,Ph 3; Mes = 2,4,6‐Me3C6H2) were prepared and the reactions with B(C6F5)3 were studied. Reaction of 1 and B(C6F5)3 produced E‐alkene {(E)‐(C6F5)3BCHC[P(4‐tBuC6H4)2]SiMe2}2 (4) and that of 2 and B(C6F5)3 yielded Z‐alkene (Z)‐(C6F5)2BCHC(PMes2)SiMe2(C6F5) (5). The former is proposed to go through a key [Me2HSi]+ for function while the latter via the phosphacyclopropene intermediate, both of which are a result by self‐hydrosilylation. Reaction of 3 and B(C6F5)3 generated at room temperature a P→B coordination compound Mes2HSiCCP(Ph2)B(C6F5)3 (6) and at 100 °C the 1,1‐carboboration E‐alkene (E)‐Mes2HSi(Ph2P)CC(C6F5)B(C6F5)2 (7). Kinetic study and DFT calculations were accomplished for reaction of 2 and B(C6F5)3 to 5. The mechanisms of these reactions have been discussed. The reactions of the P/Si+ LPs Me2Si(Ph2P)CCHB(C6F5)3}2 (3a) and 4 were also investigated. Compound 4 disassociated H2O into {(E)‐(C6F5)3BCHC[PH‐4‐tBuC6H4)2]Si(Me2)}2(µ‐O) (8) and (E)‐(C6F5)3BCHC[PH(4‐tBu‐C6H4)2]Si(Me2)O(HNC5H5) (9). Compound 3a reacted with tBuNCO by [3+2] dipolar cycloaddition to give a C2OPSi‐heterocycle [(C6F5)3BHC]CSi(Me2)P(Ph2)OC(NtBu) (10). Furthermore, 4 reacted with tBuNCO and then H2O to afford (E)‐(F5C6)3BHCC[P(4‐tBuC6H4)2C(O)NHtBu][Si(Me2)OH(NC5H5)] (11) through a C2OPSi‐heterocycle intermediate followed by the H2O‐disassociation under the C2OPSi‐ring opening.