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The formation of seven types of coordination compounds containning metallacyclobutadienes(MCBS)from chloro-ligated alkylidyne structures of group 4 and 6 transition metals(MCln(C3H3))have been studied using density functional theory calculations at the B3LYP level.We have investigated the structures,stabilities,aromaticities,and Wiberg bond indices of every “edge complex” containing planar tetracoordinate carbon.The results indicate that all of these compounds are situated at the minima on the potential energy surfaces.In addition,the energy gaps between the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)of these molecules are less than 2.50 eV.The HOMO-LUMO energy gaps reduced greatly of these complexes in comparison to their parent molecules.The NICS(0)values showed that the three-membered rings have strong aromaticity.In the molecules,M-Cβ distances are significantly shorter than the sum of the covalent radii of corresponding M and C,suggesting a bonding interaction between the metal and the β-carbon.The Wiberg bond order of the 1,3-MC bond is in a range of 0.15-0.35,and the total WBI values of ptC centers vary between 3.43-5.78.The 1,3-MC-bonded metallacycle exhibits significant plannar tetracoordinate charater of the Cβ atom.The formation of hitherto unknown 1,3-MC-bonded multinuclear edge complexes of polycyclic aromatic hydrocarbons is predicted.Their electronic properties are attractive for the design of optoelectronic materials.