First X-ray crystal study and DFT calculations of anionic λ4-phosphinines

Anionic lambda(4)-phosphinines 3 and 4 were synthesized via the reaction of the corresponding lambda(3)-phosphinines 1 and 2 with MeLi. The X-ray structure of [3][Li(thf)(2)] is reported and shows the eta(5)-coordination of the Li cation to the five carbon atoms of the phosphacyclohexadienyl moiety. Cryptated species [3] [Li [2.2.2]] and [41[Li(thf)(4)]were also synthesized and analyzed by X-ray diffraction methods, allowing direct comparison with noncryptated species. Anion 5 was obtained by the reaction of 2 with t-BuLi. This shows that electronics and sterics can easily be modified on these highly reactive species. The crystal structure of [51 [Li [2.2.2]] is presented. This study was completed by DFT calculations, which showed the negative charge to be essentially localized on the a carbon atoms of these anions.