Ge II and Sn II Complexes of [2.2.2]Paracyclophane with Threefold Internal η6 Coordination

SnII is significantly more tightly bound than GeII in the cavity of the [2.2.2]paracyclophane(L), as shown by the structure analyses of the complex cations [LSn(AlCl4)]⊕ and [LGeCl]⊕ 1. In the tin complex the AlCl counterion is loosely coordinated via a Cl atom to the metal (Sn-Cl 3.073 Å) and thus hardly disturbs the expected trigonal-planar coordination, whereas the strong GeCl bond (GeCl 2.224 Å) in 1 leads to a weakening of the Ge-arene interaction and to a preferential tetrahedral environment for the metal.