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Dibenzyl and diallyl 2,6-bisiminopyridinezinc (II) complexes: selective alkyl migration to the pyridine ring leads to remarkably stable dihydropyridinates


John J. Sandoval, Pilar Palma, Eleuterio Álvarez, Antonio Rodríguez-Delgado* and Juan Cámpora*. Chemical Communications 2013, Vol. 0, DOI: 10.1039/c3cc42798f

Transition metal complexes stabilized by Bis(Imine)Pyridine (BIP) ligands are very attractive species due to their high activity and selectivity towards diverse catalytic reactions such as organic hydrosilylation and hydrogenation, or olygomerisation and polymerisation of olefins, among others. Some of the studies developed by our research group consist of exploring the syntheses of novel BIP complexes, having in mind to achieve the rationalization of their chemical behaviour. We expect that this will lead us to reveal their full potential in the above-mentioned processes and other to pursue.

The research described in this communication is based on the expansion of our studies on BIP complexes, traditionally based on first row transition metal such as iron or cobalt to main group metals like zinc. Literature reports on the chemistry of main group alkyl derivatives, e. g., alkylzinc compounds, describe peculiar reactivity patterns that are often 2 in striking contrast with those of similar organotransition metal complexes. In this communication we show that these differences are in part due to the different choice of alkyl groups, and we describe for the first time i) the experimental detection of the transient metal dialkyl species (never observed before for any other metal except for stable beta-silylalkyl derivatives), and ii) the full characterization of the resulting 4-alkyl-1,4-dihydropyridinate complex. These latter species are remarkably stable under inert atmosphere. These results contribute to clarify the chemistry of organometallic complexes with BIP ligands and open new perspectives for the application of these compounds in catalysis.