Twists and Turns of Platinum-Allene Chemistry

Although platinum exhibits similar reactivity to gold in general, there are increasing examples where under similar conditions, these two metals get involved in different reaction pathways and give different products.1
For  example,  we  have  reported  the  Pt-­‐catalysed  dihydroalkoxylation  and  bisindolylation  of  allenes,2  which  give  acetals  or  bisindolyl alkanes with double addition of the nucleophile to the terminal or less substituted double bond of the allene, and complete saturation of the second double bond, instead of the most common allyl derivatives obtained under gold catalysis.3 To explain the different reactivity of the two metals, different mechanisms and metallic intermediates have to be proposed for the two processes.
The  mode  of  coordination  in  metal-­‐allene  complexes  is  crucial  for  the  understanding  of  the  reactivity  of  these  important  systems. Although a lot of attention has been paid to Au-­‐allene complexes,4 studies on Pt-­‐allene complexes are still rare. We are very interested in revealing the secrets behind the divergence reactivity in Pt-­‐allene systems using a POC approach. In this talk our efforts towards this understanding, including the development of a new NMR method (SSTD NMR) to study the fluxional behavior of platinum-­‐allene complexes,5 and examples of the divergent reactivity in Pt-­‐allene chemistry discovered in  our  group  will  be  discussed,6  focussing  on  the  surprises  encountered  in  the  mechanism  of  the  Pt-­‐catalysed  dihydroalkoxylation of allenes, the development of the intra-­‐intermolecular Pt-­‐catalysed bis(indolylation) of allenes, and briefly presenting a novel Pt-­‐catalysed cyclization of bisallenes.

References
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J. M., Spriger Heidleberg Dordrecht London New York (ISSN 0340-­‐1022).
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3. (a) M. P. Muñoz, Org. Biomol. Chem., 2012, 10, 3584; (b) M. P. Muñoz, Chem. Soc. Rev., 2014, 43, 3164; (c) C. Hurtado-­‐Rodrigo, S. Hoehne, M. P. Muñoz,
Chem. Comm., 2014, 50, 1494.
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5. (b) M. T. Quirós, J. Angulo, M. P. Muñoz, Chem. Comm., 2015, 10222; M. T. Quirós, C. Macdonald, J. Angulo, M. P. Muñoz, JoVE 2016, in press; M. T, Quirós, M. P. Muñoz, J. Christensen, S, J. Coles, manuscript in preparation.
6. (a) M. T. Quirós, E. Gomez-­‐Bengoa, M. P. Muñoz, manuscript in preparation; (b) L. Cooper, L. Eagling, H. Newson, S. Herath, C. Thomson, A. Lister, C. Howsham, V. Furminger, B.Cox, manuscript in preparation; C. Hurtado-­‐Rodrigo, M. T. Quirós, M. P. Muñoz, manuscript in preparation.