Schulz J, Sárosi MB, Hey‐Hawkins E. Exploring the Reactivity of B‐Connected Carboranylphosphines in Frustrated Lewis Pair Chemistry: A New Frame for a Classic System.
Chemistry 2022;
28:e202200531. [PMID:
35472172 PMCID:
PMC9320892 DOI:
10.1002/chem.202200531]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Indexed: 11/15/2022]
Abstract
The primary phosphines MesPH2 and tBuPH2 react with 9‐iodo‐m‐carborane yielding B9‐connected secondary carboranylphosphines 1,7‐H2C2B10H9‐9‐PHR (R=2,4,6‐Me3C6H2 (Mes; 1
a), tBu (1
b)). Addition of tris(pentafluorophenyl)borane (BCF) to 1
a, b resulted in the zwitterionic compounds 1,7‐H2C2B10H9‐9‐PHR(p‐C6F4)BF(C6F5)2 (2
a, b) through nucleophilic para substitution of a C6F5 ring followed by fluoride transfer to boron. Further reaction with Me2SiHCl prompted a H−F exchange yielding the zwitterionic compounds 1,7‐H2C2B10H9‐9‐PHR(p‐C6F4)BH(C6F5)2 (3
a, b). The reaction of 2
a, b with one equivalent of R'MgBr (R’=Me, Ph) gave the extremely water‐sensitive frustrated Lewis pairs 1,7‐H2C2B10H9‐9‐PR(p‐C6F4)B(C6F5)2 (4
a, b). Hydrolysis of the B−C6F4 bond in 4
a, b gave the first tertiary B‐carboranyl phosphines with three distinct substituents, 1,7‐H2C2B10H9‐9‐PR(p‐C6F4H) (5
a, b). Deprotonation of the zwitterionic compounds 2
a, b and 3
a, b formed anionic phosphines [1,7‐H2C2B10H9‐9‐PR(p‐C6F4)BX(C6F5)2]−[DMSOH]+ (R=Mes, X=F (6
a), R=tBu, X=F (6
b); R=Mes, X=H (7
a), R=tBu, X=H (7
b)). Reaction of 2
a, b with an excess of Grignard reagents resulted in the addition of R’ at the boron atom yielding the anions [1,7‐H2C2B10H9‐9‐PR(p‐C6F4)BR’(C6F5)2]− (R=Mes, R’=Me (8
a), R=tBu, R’=Me (8
b); R=Mes, R’=Ph (9
a), R=tBu, R’=Ph (9
b)) with [MgBr(Et2O)n]+ as counterion. The ability of the zwitterionic compounds 3
a, b to hydrogenate imines as well as the Brønsted acidity of 3
a were investigated.
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