Fe Si P to Fe P Si

7/30/2019 Fe Si P to Fe P Si

1/12

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


2/12

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


3/12

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


4/12

Fe-Si-P to Fe-P-Si4


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'


5/12

Fe-Si-P to Fe-P-Si5


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


6/12

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


7/12Fe-Si-P to Fe-P-Si7


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




Proposed formation of 4:

4

Ph Me2

FeP Si

Me2

FeP Si

H

Ph

Fe

P SiPhH

Me2ox add red el



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



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



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



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

Fe Si P to Fe P Si

Documents

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