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Significance of Intermolecular S...C(π) Interaction Involving M-S and -C=O Centers in Crystal Structures of Metal Thiolate Complexes

Wojciech Bury 1Janusz Lewiński 1Iwona Justyniak 2Janusz S. Lipkowski 2

1. Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, Warszawa 00-664, Poland
2. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland

A plethora of noncovalent interactions account for a number of known binding and structural motifs in biological systems, synthetic catalysis and supramolecular chemistry. In this regard hydrogen bonding plays a dominant role, but many other less conventional noncovalent forces like the CH…π, cation…π, and anion…π interactions, π...π aromatic stacking, halogen bonding or chalcogen-chalcogen interactions have been identified and extensively explored recently. Nevertheless, some structural and functional aspects of biomolecular or catalytic functions remain an active problem which partly results from the fact that less obvious specific forces involving different chemical entities are only rarely encountered.

In recent years we have demonstrated that in the solid state dialkylaluminum chelate complexes have a tendency to form [R2Al(µ-O,O)]2-type adducts with five-coordinate metal centers. As an extension of our previous investigations directed toward relationship between donor-acceptor bonds, hydrogen bonding and other non-covalent interactions we report herein on the structural studies of alkylaluminum compounds derived from methyl thiosalicylate. The structural analysis revealed that the intermolecular S···C(π) interaction between the Al-S thiolate units and the π-surface of the ester functionality can compete with the putative sulfur-aluminum hypercoordinate bond.
There are already more than 100 crystal structures deposited in the CSD and surprisingly the S···C(π) interaction as well its role on the supramolecular structure of various complexes has not been recognized in any case by the original authors.
To the best of our knowledge, this is the first report on the competition of the intermolecular nπ* interaction, involving the thiolate sulfur atom and the electrophilic carbon atom of the ester functionality.


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Presentation: poster at 18th Conference on Physical Organic Chemistry, Posters, by Wojciech Bury
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-06-28 10:02
Revised:   2009-06-07 00:44