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Seeking The planar tetracoordinate carbon(ptC)family has witnessed fruitful advances in the past forty years.However,species featuring the planar tetracoordinate heavier group element M(ptM)have been largely limited,which must be ascribed to the deficiency of effective stabilization models for ptM.In the present article,among a series of ternary systems C2X2Yq (X=Ge,Sn,Pb; Y=C,Si,Ge,Sn,Pb; q=+1,0,-1),we newly identified 21 global ptM(M=X/Y)structures with 19,20 and 21 valence electrons(ve)with each containing a π-type ligand skeleton.A construction principle was derived.First,the electronic stabilization of ptM contributes from two sets of π-bonding orbitals that is mainly within the ligand skeleton.Second,the element that forms weaker bonding to carbon can be the ptM center.Finally,the π-delocalization is directed from ligand to M.Thus,the structural and bonding motifs of these new ptMs differ greatly from the classic ptMs with σ-type ligand skeleton,16/17/18ve,and the π-delocalization mainly from center to ligand.Besides the significant broadening of the planar tetracoordinate heavier group 14 family,the present construction principle is expected to be applicable to design species with other planar tetracoordinate centers.