The Highly Lewis Acidic Dicationic Phosphonium Salt: [(SIMes)PFPh₂][B(C₆F₅)₄]₂

Abstract

The dicationic imidazolium-phosphonium salt [(SIMes)PFPh 2 ][B(C 6 F 5 ) 4 ] 2 has been prepared and shown to exhibit remarkable Lewis acidity in stoichiometric reactions and acting as an effective Lewis acid catalyst for the hydrodefluorination of fluoroalkanes and the hydrosilylation of olefins.Scheme 1. Preparative route to 5.

Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations

“…We note that hydrosilylation of ketones has been previously reported using the Lewis acid catalyst B(C 6 F 5 ) 3 . Thep reviously reported dicationic phosphonium ion 5 [9] is an effective catalyst for the deoxyge-nation of 10 a and 11 a in the presence of two equivalents of silane,t hus affording quantitative formation of 10 c and 11 c, respectively. Quantitative hydrosilylation of 10 a,thus yielding exclusively 10 b,was observed.…”

“…[5] More recently,wehave focused on enhancing this Lewis acidity by preparing more electrophilic phosphonium cations (EPCs) such as [(C 6 F 5 ) 3 PF] + (1), [(C 6 F 5 ) 2 PhPF] + (2), and [(C 6 F 5 )Ph 2 PF] + (3). [8] Thes cope of these EPCs has been broadened to include dicationic phosphonium species [(SIMes)PPh 2 F] 2+ (5) [9] and bifunctional bis(phosphonium) compounds. [8] In the latter case,t andem transfer hydrogenation can also be effective with concurrent dehydrocoupling reactions.…”

“…[8] In the latter case,t andem transfer hydrogenation can also be effective with concurrent dehydrocoupling reactions. [8] Thes cope of these EPCs has been broadened to include dicationic phosphonium species [(SIMes)PPh 2 F] 2+ (5) [9] and bifunctional bis(phosphonium) compounds. [10] Thea dditional charge is manifested in even greater Lewis acidity.…”

“…Further reduction of the Lewis acidity,f or example in the phosphonium ion [Ph 3 PF] + (4), [10,20] eliminated catalytic activity completely and neither hydrosilylation nor deoxygenation was observed. Thep reviously reported dicationic phosphonium ion 5 [9] is an effective catalyst for the deoxyge-nation of 10 a and 11 a in the presence of two equivalents of silane,t hus affording quantitative formation of 10 c and 11 c, respectively.…”

Establishing the Coordination Chemistry of Antimony(V) Cations: Systematic Assessment of Ph4Sb(OTf) and Ph3Sb(OTf)2 as Lewis Acceptors

“…Structurally characterized complexes featuring cationic Sb V acceptors, however, are rare,8, 9 although spectroscopic characterization has been presented in some cases 10–15. Furthermore, structurally characterized complexes involving prototypical pnictonium cations, that is, [R 4 Pn] + (Pn=N, P, As, Sb, or Bi), as acceptors are rare,8, 14, 16, 17 likely a consequence of steric encumbrance at the pnictogen acceptor, an effect illustrated by the solid‐state structures of [Ph 4 P][X] (X=Cl or Br) (Scheme ) 18. 19 Both compounds present ionic formulations, in which the phosphorus center is tetrahedral in geometry, and the shortest phosphorus–halide contact is greater than the sum of the P–X van der Waals radii (Σ vdW ).…”