from first principles PP-I-1

OP-III-27Structure of Allylic Intermediates Formed from Olefins on Zinc OxideGabrienko A.A., Stepanov A.G.Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russiastepanov@catalysis.ruZinc oxide is active catalyst for olefin double bond isomerization. π-Allylzinc is generallyconsidered to be the main intermediate of the process [1–3]. However, a number of differentbonding modes are possible for allyl ligand attached to zinc in zinc allyl compounds [4]:σ-allyl (1), σ,π-allyl (2), π-allyl (3). σ-Allylzinc was found to be intermediate of propanearomatization process on ZnO-modified zeolite beta [5]. Thus, the question arises on thestructure of intermediates formed from olefins on zinc oxide. Understanding the structure ofsurface intermediates is the key to reveal the mechanism of the isomerization process.1 Zn2 Zn3ZnZnTo inquire into the structure of the surface allylzinc, the interaction of propene and n-butenewith zinc oxide has been monitored by 13 C solid-state NMR spectroscopy. The data obtainedclearly prove that the surface allylzinc exists in a form of σ,π-allyl rather than exclusivelyπ-allyl complex. Dissociative adsorption of propene on zinc oxide results in formation of twoequilibrium structures: σ,π-allyl and π-allyl, the former being a prevailing species (Figure 1).On the other hand, only σ,π-allyl was detected in case of n-butene adsorption.(a)815129(b) **187178**ZnO81178ZnO29ZnHO51187Zn HO100δ / ppm 0200 δ / ppm 100Figure 1. 13 C MAS NMR spectra of propene-3- 13 C (a) and propene-2- 13 C (b) on ZnO.Acknowledgements. This work was supported by the Russian Foundation for Basic Research (grantno. 10-03-00555).References:[1] A. L. Dent, R. J. Kokes, J. Am. Chem. Soc. 92 (1970) 1092.[2] A. L. Dent, R. J. Kokes, J. Am. Chem. Soc. 92 (1970) 6709.[3] A. A. Kheir, T. Howard, J. F. Haw, J. Am. Chem. Soc. 116 (1994) 10839.[4] R. Benn, H. Grondey, H. Lehmkuhl, H. Nehl, K. Angermund, C. Kruger, Angew. Chem. Int. Ed.26 (1987) 1279.[5] A. A. Gabrienko, S. S. Arzumanov, D. Freude, A. G. Stepanov, J. Phys. Chem. C. 114 (2010)12681.71