successively oxidative addition of the amine borane, reductive elimination of H 2 ,
and activation of the borane–H bond to regenerate 42.
Nishibayashi has described the etherification of propargylic alcohols using
trichloridoheterobimetallic complexes 43 as catalysts (Scheme 29) [96]. The reactions were carried from 1,1-diphenylpropynol and ethanol in the presence of 10 mol%
of bimetallic complexes 43 and 10 mol% of NaB(Ar
F
) 4 at 60
C for 72 h. All three
complexes catalyzed the reaction to give propargylic ether in moderate yields, the
best combination being Ru/Hf complex 43c. Although these results are modest, it is
much better than with the mononuclear complexes [η
5 -(C 5 H 4 PEt 2 ) 2 ZrCl 2 ],
[Cp*RuCl(depe)], or [Cp*RuCl(depf)] (depf¼1,1
0 -bis(diethylphosphino)ferrocene)
Ph
+ N 2 CHCO 2 Et
Ti-Ru cat. (1 mol%)
-N 2
CO 2 Et
Ph
Ph
Ph
+
Catalyst
Cyclopropanation
Metathesis
Yield
trans/cis
TON
60°C, 4.25h
37a
60%
62/38
1
37c
38%
65/35
0
37d
49%
57/43
4
[(p-cymene)RuCl 2 PPh 3 ]
57%
62/38
10
[(p-cymene)RuCl 2 PCy 3 ]
46%
55/45
40
Ti Cl
Cl
P
R' 2
n
Ru
Cl
Cl
37a : n = 0, R' = Ph
37c : n = 2, R = H, R' = Ph
37d : n = 2, R = H, R' = Cy
Scheme 26 Cyclopropanation of styrene catalyzed by Ti/Ru heterobimetallic complexes
CO 2 Me
MeO 2 C
cat. 37 (0.125 mole %)
n
E i Br (0.25 mole %)
16h, 85°C
Catalyst
Yield
M W /Mn
37d
63%
1.25
37e
97%
1.2
37f
66%
1.3
Cy2
P
Ru
Cl
Cl
37d : X = Cl
37e : X = F
37f : X = O 2 CPh
Ti X
X
Scheme 27 ATRP of MMA catalyzed by Ti/Ru heterobimetallic complexes
Zr
Me
PEt 2
PEt 2
M
40: M = Zr
41: M = Hf
Me 2 NH.BH 3
cat. 40 (2 mol%)
or cat. 41 (10 mol%)
toluene, 50°C
H 2 B
Me 2 N BH 2
NMe 2
H 2 + 1/2
(GC yield of H 2 )
cat. 40: 93% after 3h
cat. 41: 25% after 24h
Zr
H
PEt 2
PEt 2
Ru
42
Zr
H 3 BMe 2 N
PEt 2
PEt 2
Ru
H
H
Zr
H 3 BMe 2 N
PEt 2
PEt 2
Ru
Zr
Me 2 N
PEt 2
PEt 2
Ru
H 2 B
H
H 2
Activation
of B-H
Me 2 NH.BH 3
H 2 B
Me2N BH2
NMe 2
Me2N BH2
1/2
Scheme 28 Dehydrogenation of amine boranes catalyzed by Ti/Ru heterobimetallic complexes
and proposed mechanism
156
E. Bodio et al.