Addition of Nitriles to Alkaline Earth Metal Complexes of 1,2-Bis[(phenyl)imino]acenaphthenes

• Published in: Chemistry : a European journal 2005-09, Vol.11 (19), p.5749-5757
• Main Authors: Fedushkin, Igor L., Morozov, Alexander G., Rassadin, Oleg V., Fukin, Georgii K.
• Format: Article
• Language: English
• Subjects: alkaline earth metals; iminolization; N ligands; nitriles
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200500330

Compounds [Sr(dpp‐bian)(thf)4] (2), [Ba(dpp‐bian)(dme)2.5] (3) and [Mg(dtb‐bian)(thf)2] (4) (dpp‐bian=1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene; dtb‐bian=1,2‐bis[(2,5‐di‐tert‐butylphenyl)imino]acenaphthene) were prepared by reduction of dpp‐bian and dtb‐bian with an excess of metallic Mg, Sr, or Ba in THF or DME. Reactions of [Mg(dpp‐bian)(thf)3], 3, and 4 with diphenylacetonitrile gave keteniminates [Mg(dpp‐bianH)(NCCPh2)(thf)2] (5), [Mg(dtb‐bianH)(NCCPh2)(thf)2] (6), and [Ba(dpp‐bianH)(NCCPh2)(dme)2] (7), respectively. The reaction of 2 with CH3CN in THF gave [{Sr(dpp‐bianH)[N(H)C(CH3)C(H)CN](thf)}2] (8). The compounds 2, 3, 5–8 were characterized by elemental analysis, and IR and NMR spectroscopy. Molecular structures of 2, 3, 7, and 8 were determined by single‐crystal X‐ray diffraction. In contrast to reactions of alkali‐metal reagents, magnesium amides, or yttriumalkyls with α‐H acidic nitriles, which are accompanied by an amine or an alkane elimination, the reactions of [Mg(dpp‐bian)(thf)3] (1), 2, 3, and 4 with such nitriles proceeded with formation of Mg, Sr, and Ba keteniminates and simultaneous protonation of one nitrogen atom of the bian ligand. The NMR spectroscopic data obtained for complex 5 indicated that in solution the amino hydrogen atom underwent the fast (on the NMR timescale) shuttle transfer between both nitrogen atoms of the dpp‐bianH ligand. Alkaline earth metal complexes of rigid dianionic acenaphthenediimine ligands deprotonate nitriles to give keteniminate species by the uptake of the hydrogen atom from nitriles to a ligand nitrogen atom (see scheme).