Synthesis and characterization of two novel tetranuclear sodium ketoiminate complexes;: structural evidence for formation of dative Na•••F and Na-C (olefin) bonding interactions

Treatment of fluorinated beta-ketoiminate ligands MokeimH or AlkeimH with NaH in THF solution afforded the corresponding ketoiminatosodium complexes [Na(Mokeim)](4) 1 and [Na(Alkeim)](4) 2, MokeimH=(CF3)C(=O)CH=C(CF3)NH(CH2CH2OMe) and AlkeimH=(CF3)C(=O)CH=C(CF3)NH(CH2CH=CH2). These new complexes were characterized by spectroscopic methods, elemental analyses and X-ray diffraction studies. Complex 1 consists of a tetrameric Na4O4 cubane core arrangement, of which each sodium atom is surrounded by a tridentate ketoiminato ligand, two oxygen atoms from nearby ketoiminato ligands, and one or two weak Na ... F dative interactions. The core structure of 2 is similar, but with formation of the uncommon allyl to sodium pi interaction. The stabilization of this Na-C (olefin) bonding interaction is as effective as the Na-O (ether) dative bonding in 1 because 2 shows comparable thermal stability and even an enhanced volatility during sublimation.