Syntheses, structures and flexible coordination of sterically demanding di- and “tri”-lithiated methandiides

Abstract

Lithiation of the sterically demanding bis(iminophosphoranyl)methane H₂C{Ph₂P(NDip)}₂ (Dip = 2,6-iPr₂C₆H₃), H₂L, with alkyllithium reagents afforded the methandiide complexes [(LLi₂)₂] 2, [LLi₂(OEt₂)₂] 4, [LLi₂(THF)₃] 5, [LLi₂(THF)₂] 6, and [LLi₂(PMDTA)] 7 (PMDTA = N,N,N′,N′′,N′′-pentamethyldiethylenetriamine), from various solvents or after the addition of donor molecules. The complex [HC(Ph₂PNDip)(Ph₂P)Li(THF)₂] 3 was further identified as a by-product under certain conditions. Further lithiation of the methandiide in ortho-position of one P-bound phenyl group affords complexes of the trianionic ligand L′³⁻, and the complexes [(L′Li₃)₂] 8 and [L′Li₃(THF)₄] 9 were obtained. Different isomeric forms for the methandiide units investigated in solution and in the solid state are described, and the crystal structures of complexes 2, 3, and 5–9 are reported.