The reaction between the phosphine-borane-substituted alkene {Prn2P(BH3)}(Me3Si)C![[double bond, length as m-dash]](http://www.rsc.org/images/entities/char_e001.gif)
CH2 and elemental lithium in THF yields the complex [(pmdeta)Li{Prn2P(BH3)}(Me3Si)CCH2]2 (2b) after recrystallisation; an X-ray crystallographic study of 2b reveals that the lithium is bound to the BH3 hydrogens of the ligand, with no Li–C(carbanion) contact.
