Structure and Lewis-base reactivity of bicyclic low-valent germanium and tin complexes bridged by bis(diisopropylphosphino)amine

Lithium bis(diisopropylphosphino)amide LiN[P(i-Pr)2]2 reacts with SnCl2 or GeCl2·dioxane in the presence of excess n-BuLi to produce the bicyclic compounds {MN[P(i-Pr)2]2}2 (M = Sn, Ge) which feature Sn22+ or Ge22+ units bridged by phosphorus. When paired with B(C6F5)3 in THF, the Lewis-basic M22+ complexes participate in a THF ring-opening reaction. Quite surprisingly, in the absence of THF one para-F atom from B(C6F5)3 is activated and displaced to B while a new M–C bond is formed. Each of these complexes, as well as Cl2Sn{N[P(i-Pr)2]2}2 and {ClSnN[P(i-Pr)2]2}2 were characterized by a combination of multi-nuclear NMR spectroscopy and single-crystal X-ray diffraction.