μ
2
Àη
1 :η
2 -interaction. Attack of the vinyl group by the amine was proposed to
generate the enaminium intermediate 58, which eliminates the imine product and
coordinates phenylacetylene to complete the catalytic cycle. Unfortunately, only a
limited number of cycles could be promoted using 56 due to its rapid isomerisation
Scheme 20 Ir(III) bi- and monometallic catalysts (54, 55) used for the intramolecular
hydroamination reaction
Ru
Si
Ph
Si
Ru
C
O
Ph
H
CO
OC
Ru
Si
Si
Ru
CH 2
Ph
CO
OC
OC
Ru
Si
Si
Ru
CO
OC
OC
H 2 C
NH 2 R
Ph
Ru
Si
Si
Ru
C
O
CO
OC
Ph
H
H
+
NH 2 R
isomerisation deactivates catalyst
N
R
+ H
+
Ph
Ru
Ru
CH 2
Ph
CO
OC
O
C
No catalysis without m-(SiMe2) bridges
56
60
57
58
59
Scheme 21 Bimetallic Ru (56) catalysed hydroamination reaction mechanism
Alkyne Activation Using Bimetallic Catalysts
127