New structural motif of 18 valence electron molecules with a planar tetracoordinate heavier group 14 center: Unique stabilization effect of a π‐type skeleton

Proposing new valence electron counting rules and new structural motifs are both very important in chemistry. In this work, we unexpectedly found that by introducing a π‐type skeleton YCCY (Y = Al/Ga/In/Tl), a total of sixteen novel planar tetracoordinate heavier group 14 species, that is, ptM (M = Si/Ge/Sn/Pb) in neutral, can be designed as global minima. The underlying bonding situation contrasts sharply both with the well‐known 18ve‐ptC and the limited 18ve‐ptM, for which there is little multiple bonding character within the skeleton. The fact that each YCCY (Y = Al/Ga/In/Tl) can stabilize all heavier group 14 atoms in a planar tetracoordinate fashion strongly demonstrates the universality of such a π‐type skeleton. The present work firmly demonstrates that introducing the π‐type ligand skeleton can effectively enrich the planar tetracoordinate chemistry with the heavier group atoms.