New Strategies to Phosphino–Phosphonium Cations and Zwitterions

Geier, Stephen J.; Dureen, Meghan A.; Ouyang, Eva Y.; Stephan, Douglas W.

doi:10.1002/chem.200902369

Cited by 60 publications

(39 citation statements)

References 70 publications

(59 reference statements)

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“…In this fashion the di-, tetra-, and pentaphosphines (Ph 2 P) 2 , (CyP) 4 , and (PhP) 5 react with alkyne in the presence of borane to give the species 320-322 (Scheme 101). [166] Use of N-bases in FLP reactions with alkyne was also probed. PhCH 2 NMe 2 with PhCCH and B(C 6 F 5 ) 3 102).…”

Section: Flp Additions To Alkynesmentioning

confidence: 99%

Frustrated Lewis Pair Chemistry: Development and Perspectives

2015

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Frustrated Lewis pairs (FLPs) are combinations of Lewis acids and Lewis bases in solution that are deterred from strong adduct formation by steric and/or electronic factors. This opens pathways to novel cooperative reactions with added substrates. Small-molecule binding and activation by FLPs has led to the discovery of a variety of new reactions through unprecedented pathways. Hydrogen activation and subsequent manipulation in metal-free catalytic hydrogenations is a frequently observed feature of many FLPs. The current state of this young but rapidly expanding field is outlined in this Review and the future directions for its broadening sphere of impact are considered.

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Section: Flp Additions To Alkynesmentioning

confidence: 99%

Frustrated Lewis Pair Chemistry: Development and Perspectives

2015

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“…[2,3] Related alkyl-linked zwitterions, such as Mes 2 P(H)C 2 H 4 B(H)A C H T U N G T R E N N U N G (C 6 F 5 ) 2 , have also been discovered and shown to catalyze the hydrogenation of enamines, [4,9] silylenol ethers, [6] and selected N heterocycles. [10] In addition, new synthetic routes to such zwitterionic derivatives have been developed from the reactions of sterically encumbered frustrated Lewis pairs (FLPs) with a variety of small molecules including olefins, [11][12][13][14] alkynes, [15][16][17][18][19] CO 2 , [20][21][22] and N 2 O. [23,24] In the case of the reactions of FLPs with alkynes, we have shown that a variety of Lewis bases, including phosphines, [15,17] polyphosphines, [16] amines, thioethers, [18] and pyrroles, [19] will effect addition reactions to give alkenyl-linked zwitterionic products.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Reactivity of Alkynyl‐Linked Phosphonium Borates

Zhao

Lough

Stephan

2011

Chemistry A European J

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The phosphine tBu(2 PC[triple bond]CH (1) was reacted with B(C(6)F(5)) to give the zwitterionic species tBu(2)P(H)C[triple bond]CB(C(6)F(5))(3) (2). The analogous species tBu(2)P(Me)C[triple bond]CB(C(6)F(5))(3) (3), tBu(2)P(H)C[triple bond]CB(Cl)(C(6)F(5))(2) (4), tBu(2)P(H)C[triple bond]CB(H)(C(6)F(5))(2) (5), and tBu(2)P(Me)C[triple bond]CB(H)(C(6)F(5))(2) (6) were also prepared. The salt [tBu(2)P(H)C[triple bond]CB(C(6)F(5))(2)(THF)][B(C(6)F(5))(4)] (7) was prepared through abstraction of hydride by [Ph(3)C][B(C(6)F(5))(4)]. Species 5 reacted with the imine tBuN=CHPh to give the borane-amine adduct tBu(2)PC[triple bond]CB[tBuN(H)CH(2)Ph](C(6)F(5))(2) (8). The related phosphine Mes(2)PC[triple bond]CH (9; Mes=C(6)H(2)Me(3)) was used to prepare [tBu(3)PH][Mes(2)PC[triple bond]CB(C(6)F(5))(3)] (10) and generate Mes(2)PC[triple bond]CB(C(6)F(5))(2). The adduct Mes(2)PC[triple bond]CB(NCMe)(C(6)F(5))(2) (11) was isolated. Reaction of Mes(2)PC[triple bond]CB(C(6)F(5))(2) with H(2) gave the zwitterionic product (C(6)F(5))(2)(H)BC(H)=C[P(H)Mes(2)][(C(6)F(5))(2)BC[triple bond]CP(H)Mes(2)] (12). Reaction of tBu(2)PC[triple bond]CB(C(6)F(5))(2), a phosphine-borane generated in situ from 5, with 1-hexene gave the species [tBu(2)PC[triple bond]CB(C(6)F(5))(2)](CH(2)CHnBu)[tBu(2)PC[triple bond]CB(C(6)F(5))(2)] (13) and subsequent reaction with methanol or hexene resulted in the formation of [tBu(2)P(H)C[triple bond]CB(C(6)F(5))(2)](CH(2)CHnBu)[tBu(2)PC[triple bond]CB(C(6)F(5))(2)](OMe) (14) or the macrocycle {[tBu(2)PC[triple bond]CB(C(6)F(5))(2)](CH(2)CH(2)nBu)}(2) (15), respectively. In a related fashion, the reaction of 13 with THF afforded the macrocycle [tBu(2)PC[triple bond]CB(C(6)F(5))(2)](CH(2)CHnBu)[tBu(2)PC[triple bond]CB(C(6)F(5))(2)][O(CH(2))(4)] (16), although treatment of tBu(2)PC[triple bond]CB(C(6)F(5))(2) with THF lead to the formation of {[tBu(2)[triple bond]CB(C(6)F(5))(2)][O(CH(2))(4)]}(2) (17). In a related example, the reaction of Mes(2)PC[triple bond]CB(C(6)F(5))(2) with PhC[triple bond]CH gave {[Mes(2)PC[triple bond]CB(C(6)F(5))(2)](CH[triple bond]CPh)}(2) (18). Compound 5 reacted with AlX(3) (X=Cl, Br) to give addition to the alkynyl unit, affording (C(6)F(5))(2)BC(H)=C[P(H)tBu(2)](AlX(3)) (X=Cl 19, Br 20). In a similar fashion, 5 reacted with [Zn(C(6)F(5))(2)]⋅C(7)H(8), [Al(C(6)F(5))(3)]⋅C(7)H(8), or HB(C(6)F(5))(2) to give (C(6)F(5))(3)BC(H)=C[P(H)tBu(2)][Zn(C(6)F(5))] (21), (C(6)F(5))(3)BC(H)=C[P(H)tBu(2)][Al(C(6)F(5))(2)] (22), or [(C(6)F(5))(2)B](2)HC=CH[P(H)tBu(2)] (23), respectively. The implications of this reactivity are discussed.

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“…[6,11] FLPs have also been exploited to effect the activation of a variety of small molecules including olefins, [17] dienes, [18] alkynes, [19,20] BÀH bonds, [21] disulfides, [22] PhNCO, [3,23,24] CO 2 , [25] and N 2 O. [26] In the case of olefins and alkynes, Stephan and co-workers [17,19,20] showed that sterically encumbered phosphines and boranes or alanes, can effect inter-and intramolecular additions affording zwitterionic phosphonium borates. DFT studies have suggested that such additions to olefins occur via an antarafacial asynchronous concerted addition.…”

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confidence: 99%