1 Frustrated Lewis Pair Catalysis: An Introduction
9
N
Ph
B(C 6 F 5 ) 2
N
B(C 6 F 5 ) 2
PPh 2
PPh2
/ B(C 6 F 5 ) 3
Fe
PMes 2
B(C6F5)2
Mes 2 P B(C6F5)2 Mes 2 P
B(C6F5)2
H
H
SiMe 3
Mes 2 P
B(C6F5)2
H H
SiMe 3
F
F
B
F
F
F
F
F
F
B
F
F
F
F
F
F
F
P
C 6 F 5
C 6 F 5
C 6 F 5
F
N
Ph
Me 3 Si
Ph
N
N
B
[B(C 6 F 5 ) 4 ]
Me
Me
Cl
Cl
N
N
N
B
[B(C 6 F 5 ) 4 ]
Ph
Ph
N
[B(C 6 H 3 Cl 2 ) 4 ]
N
/
[B(C 6 F 5 ) 4 ]
/
B(C 6 F 5 ) 4
B Ph 2
P
PPh 2
Ru Cl
Ph 2 P K
(Me 3 Si) 2 N K
Scheme 1.5 Examples of FLP catalyst variants
While inter- and intramolecular FLP systems have drawn considerable attention,
a range of other FLP catalysts have been explored, broadening the generality of
the concept. For example, intermolecular FLPs derived from the gallane and indane
Ga(C 6 F 5 ) 3 and In(C 6 F 5 ) 3 also catalyze the hydrogenation of imines [71].
An alternative class of FLP catalysts based on N-heterocyclic carbene (NHC)stabilized borenium cations has been reported. Salts of the form [(NHC)(9BBN)][B(C 6 F 5 ) 4 ] were readily prepared from the borane-NHC adducts and these