Iso- and Homeostructuralism of Analogous Ph4E and Ph3E−E‘R3 Compounds (E = C, Si, Ge, Sn, Pb; E‘ = Si, Ge, Sn; R = Me, Ph): Crystal Structure of 1,1,1-Trimethyltriphenyldistannane

The Ph3E−E‘Me3 (E = Si, Ge, Sn; E‘ = Si, Ge, Sn) compounds exhibit two morphotropic steps in the crystalline state: a [E = E‘ = Si; E = Si, E‘ = Ge; E = Ge, E‘ = Si, E = E‘ = Ge (space group P3̄)] → b [E = Ge, E‘ = Sn; E = Sn, E‘ = Ge (space group Pna21)] → c [E = E‘ = Sn (space group P3̄)]. Ph3Sn−SnMe3 reverts to group a. Due to the long Sn−Sn bond, it is not isometric, and therefore not isostructural, with the group a compounds; the relaxed relationship is termed as homeostructural.