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Dalton Transactions
Page 4 of 7
DOI: 10.1039/C7DT02126G
COMMUNICATION
Journal Name
A plausible mechanism for the dimerization of aldehydes by heterocyclic iminato ligand exhibits a torsional twist resulting in a C2
complex is presented in Scheme 5. symmetry. Both of the ligands with small substituent allow us to
2
In the first step, an aldehyde inserts rapidly into the Th−CH3 access a new class of complexes of type Cp*2Th(L)(CH3), as very
bond via a four-centered transition state, to obtain the active catalyst for the catalytic dimerization of aldehydes.
Acknowledgments
thorium alkoxo intermediate a. A second insertion of an
aldehyde into the Th−O bond results in intermediate b and the
subsequent hydride transfer to an incoming aldehyde, via a
chair like six-membered transition state (c), produces the
catalytically active intermediate d and 1 equiv of the α-
methylated ester. The insertion of an aldehyde into the Th−O
This work was supported by the Israel Science Foundation
administered by the Israel Academy of Science and Humanities
under Contract No. 78/14; and by the PAZY Foundation Fund (2015)
administered by the Israel Atomic Energy Commission.
bond of
d forms the intermediate complex e, which upon
References
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Table 2. Cross-Tishchenko Reaction Catalyzed by Complex 2a
Entry
RCHO
R'CHO
Yield (%)
II
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11
aReaction conditions: catalyst 2/RCHO 1:100, rt, 0.5 mL of C6D6. Yield
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O
O
N
N
N
N
R
H
R
H
N
N
CH3
R
[Th]
O
Me
O
Th
Th CH3
R
O
R
step 2
step 1
(b)
O
R
R
H
(a)
step 3
O
Me
R
O
R
N
N
[Th] =
R
N
H
O
Cp*
Cp*
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R
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R
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R
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O
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H
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O
O
O
R
[Th]
H
[Th]
R
O
H
R
O
(e)
R
(f)
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r.d.s
O
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R
H
Scheme 5. Proposed Mechanism for the Tishchenko Reaction Mediated by Complex 2
In conclusion, here we disclosed the first example of an
organometallic complex with this new family of six and seven
membered N-heterocyclic iminato ligands. The seven-membered N-
(14) Detailed analysis of kinetic rate law can be found in
Supporting Information.
4 | J. Name., 2012, 00, 1-3
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