Versatile Reaction Patterns of Phosphanylhydrosilylalkyne with B(C 6 F 5 ) 3 : A Remarkable Group Substitution Effect

Phosphanylhydrosilylalkynes R 2 HSiCCPAr 2 (R,Ar: Me,4‐ t BuC 6 H 4 1 , Me,Mes 2 , Mes,Ph 3 ; Mes = 2,4,6‐Me 3 C 6 H 2 ) were prepared and the reactions with B(C 6 F 5 ) 3 were studied. Reaction of 1 and B(C 6 F 5 ) 3 produced E ‐alkene {( E )‐(C 6 F 5 ) 3 BCHC[P(4‐ t BuC 6 H 4 ) 2 ]SiMe 2 } 2 ( 4 ) and that of 2 and B(C 6 F 5 ) 3 yielded Z ‐alkene ( Z )‐(C 6 F 5 ) 2 BCHC(PMes 2 )SiMe 2 (C 6 F 5 ) ( 5 ). The former is proposed to go through a key [Me 2 HSi] + for function while the latter via the phosphacyclopropene intermediate, both of which are a result by self‐hydrosilylation. Reaction of 3 and B(C 6 F 5 ) 3 generated at room temperature a P→B coordination compound Mes 2 HSiCCP(Ph 2 )B(C 6 F 5 ) 3 ( 6 ) and at 100 °C the 1,1‐carboboration E ‐alkene ( E )‐Mes 2 HSi(Ph 2 P)CC(C 6 F 5 )B(C 6 F 5 ) 2 ( 7 ). Kinetic study and DFT calculations were accomplished for reaction of 2 and B(C 6 F 5 ) 3 to 5 . The mechanisms of these reactions have been discussed. The reactions of the P/Si + LPs Me 2 Si(Ph 2 P)CCHB(C 6 F 5 ) 3 } 2 ( 3a ) and 4 were also investigated. Compound 4 disassociated H 2 O into {( E )‐(C 6 F 5 ) 3 BCHC[PH‐4‐ t BuC 6 H 4 ) 2 ]Si(Me 2 )} 2 ( µ ‐O) ( 8 ) and ( E )‐(C 6 F 5 ) 3 BCHC[PH(4‐ t Bu‐C 6 H 4 ) 2 ]Si(Me 2 )O(HNC 5 H 5 ) ( 9 ). Compound 3a reacted with t BuNCO by [3+2] dipolar cycloaddition to give a C 2 OPSi‐heterocycle [(C 6 F 5 ) 3 BHC]CSi(Me 2 )P(Ph 2 )OC(N t Bu) ( 10 ). Furthermore, 4 reacted with t BuNCO and then H 2 O to afford ( E )‐(F 5 C 6 ) 3 BHCC[P(4‐ t BuC 6 H 4 ) 2 C(O)NH t Bu][Si(Me 2 )OH(NC 5 H 5 )] ( 11 ) through a C 2 OPSi‐heterocycle intermediate followed by the H 2 O‐disassociation under the C 2 OPSi‐ring opening.