Fe Si P to Fe P Si
Transcript of Fe Si P to Fe P Si
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Recombinat ion o f an Fe-Si-P
L inkage to an Fe-P-Si Linkage
through an Iso lab le Intermed iatePhosphasi laferracyclopropane
Peter H.M. Budzelaar
Okazaki, M.; Yoshitomo, T.; Naito, J.; Sato, A.; Komuro, T.; Tobita, H.
J. Am. Chem. Soc.2008, 130, 17674-17675
h
- COFe
OCOC
Si
PPh2
Me2 Fe
OC
Si
P
Me2
Ph2
PhFe
OCOC
P
SiMe2Ph
CO
Fe
OC P SiPh
H Me2
1 2 3
4
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Fe-Si-P to Fe-P-Si2
Recombinat ion ...
What happens ?
synthesis, characterization
How does it happen ?
mechanism
Why is it important ? according to the authors
Evaluation
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Fe-Si-P to Fe-P-Si3
Synthesis and character izat ion
Complex 2 formed from 1 by irradiation in benzene
as reported previously
Now found not to be stable in the presence of CO
so if you do the synthesis, the CO released can react with 2
Procedure for synthesis of 3: Irradiate sample of 1, then let it sitin the dark for a while with added CO
Characterization of 3: Xray, NMR
long Si-P bond, short (and strong) Fe-P bond
h
- COFe
OCOC
Si
PPh2
Me2 Fe
OC
Si
P
Me2
Ph2
PhFe
OCOC
P
SiMe2Ph
CO
1 2 3
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Fe-Si-P to Fe-P-Si4
Synthesis and character izat ion
In the absenceof CO, 2 also rearranges, but now to 4
characterized by NMR only
a possible alternative structure is also mentioned (4', note 7)
but considered less probable
mixture of two isomers (1.7:1)
Fe
OC
Si
P
Me2
Ph22 4
Fe
OC P
SiPhH Me2
Fe
OC
Si
P
HPh
Me2
4'
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Fe-Si-P to Fe-P-Si5
Synthesis and character izat ion
Complex 5, the cyc lohexy lanalogue of 2, is stable in both
absence and presence of CO
characterized by Xray, NMR
Fe
OC
Si
P
Me2
Cy25
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Fe-Si-P to Fe-P-Si6
Mechanism s o f rearrangement
Formation of 2 is straightforward:
For its rearrangement, they draw parallels with silyl(silylene)
chemistry:
the 1,3-migration is unusual, the 1,2-migration can be seen
as 1,1-insertion or as reductive elimination
h
- COFe
OCOC
Si
PPh2
Me2 Fe
OC
Si
P
Me2
Ph21 2
FeOC
Si
PPh2
Me2
M
SiR2
Si RR2
M
Si SiR3
R2
1,2
M
SiR2
Si RR2
1,3
MSiR2
Si RR2
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Mechanism s o f rearrangement
Proposed formation of 3:
FeSiMe2
P PhPh
FeSiMe2Ph
PPh
FeP SiMe2Ph
CO
Ph Ph
FeP SiMe2Ph
CO
FeP
SiMe2
Ph22
3
1,1-deins
1,1-ins
1,3-shift
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Mechanism s o f rearrangement
Proposed formation of 4:
4
Ph Me2
FeP Si
Me2
FeP Si
H
Ph
Fe
P SiPhH
Me2ox add red el
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Difference between Ph and Cy
Cy more bulky, opposes transfer to Si
Ph has "more nucleophilic p-electrons" (whatever that means),
should make transfer easier
There is precedent for transfer of OR from phosphi teto silylene,but this is the first example of transfer from phosphide
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Relevance
Silylenes exhibit relatively high tendencies to group migration
This extends such work to neighbour phosphorus
Migrations of organic groups between non-transition-metal
elements are relatively rare.
Understanding them better can benefit organic synthesis andbuilding of inorganic polymers
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Evaluat ion
Correctness:
Looks OK, X-rays for most structures, in particular for Ph-
migrated structure 3
Where doubt remains (structure of 4), alternative structure
mentioned
No outrageous general claims anywhere
Significance:
Fairly limited, these are exotic combinations of ligand groups
precisely because of their easy rearrangements
Apart from the PSi Ph transfer, not much new chemistry
The idea of metallacyclopropanes reacting as
(phosphide)(silylene) complexes is interesting and perhaps
more general
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Evaluat ion
Presentation
Very clear and to the point
Not speculative at all, maybe too limited
Terrible title!
Is this a JACS paper ?
Notfor its general relevance
Possibly for its nice science
I would have suggested Organometallics