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Recombination of an Fe-Si-P Linkage to an Fe-P-Si Linkage through an Isolable Intermediate Phosphasilaferracyclopropane Peter H.M. Budzelaar Okazaki, M.;

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1 Recombination of an Fe-Si-P Linkage to an Fe-P-Si Linkage through an Isolable Intermediate Phosphasilaferracyclopropane Peter H.M. Budzelaar Okazaki, M.; Yoshitomo, T.; Naito, J.; Sato, A.; Komuro, T.; Tobita, H. J. Am. Chem. Soc. 2008, 130,

2 Fe-Si-P to Fe-P-Si 2 Recombination... What happens ? –synthesis, characterization How does it happen ? –mechanism Why is it important ? –according to the authors Evaluation

3 Fe-Si-P to Fe-P-Si 3 Synthesis and characterization 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 sit in the dark for a while with added CO Characterization of 3: Xray, NMR –long Si-P bond, short (and strong) Fe-P bond

4 Fe-Si-P to Fe-P-Si 4 Synthesis and characterization In the absence of 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)

5 Fe-Si-P to Fe-P-Si 5 Synthesis and characterization Complex 5, the cyclohexyl analogue of 2, is stable in both absence and presence of CO –characterized by Xray, NMR

6 Fe-Si-P to Fe-P-Si 6 Mechanisms of 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

7 Fe-Si-P to Fe-P-Si 7 Mechanisms of rearrangement Proposed formation of 3: 1,1-deins 1,1-ins 1,3-shift

8 Fe-Si-P to Fe-P-Si 8 Mechanisms of rearrangement Proposed formation of 4: ox addred el

9 Fe-Si-P to Fe-P-Si 9 Difference between Ph and Cy Cy more bulky, opposes transfer to Si Ph has "more nucleophilic  -electrons" (whatever that means), should make transfer easier There is precedent for transfer of OR from phosphite to silylene, but this is the first example of transfer from phosphide

10 Fe-Si-P to Fe-P-Si 10 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 and building of inorganic polymers

11 Fe-Si-P to Fe-P-Si 11 Evaluation 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 P→Si Ph transfer, not much new chemistry The idea of metallacyclopropanes reacting as (phosphide)(silylene) complexes is interesting and perhaps more general

12 Fe-Si-P to Fe-P-Si 12 Evaluation Presentation Very clear and to the point Not speculative at all, maybe too limited Terrible title! Is this a JACS paper ? Not for its general relevance Possibly for its nice science I would have suggested Organometallics


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