A New Family of Multiple-Bond Compounds between Heavier Group 14 Elements

On the basis of fundamental research on the chemistry of pi-electron systems between heavier main group elements, it was found that such pi-electron systems should exhibit higher HOMO and lower LUMO as compared with those between second row elements. That is, the pi-electron systems between heavier main group elements are possibly good electron acceptors, good electron donors, and good electron transporters. From the viewpoint of creation of novel pi-electron systems and fundamental research on such pi-electron system of heavier main group elements, a novel type of doubly and triply bonded compounds between heavier group 14 elements was successfully synthesized by taking advantage of kinetic stabilization using bulky substituents. The new family of multiple-bond compounds obtained here are (i) 1,2-dibromorlimetallenes, Ar(Br)E=E(Br)Ar (E = Si, Ge, Ar = bulky aryl group), as a possible building block of a pi-bond between heavier group 14 elements, (ii) 1,2-diaryldimetallynes (ArE EAr, E = Si, Ge) as a unique and reactive pi-bonding, and (iii) 1,2-dihydrodisilenes, Ar(H)Si=Si(H)Ar, as a simple disilene. The fundamental physical and chemical properties of the newly obtained compounds have been revealed, showing that such pi-electron systems between heavier group 14 elements should be completely different from those of carbon systems and should be of great interest as unique pi-systems. Thus, the compounds obtained here are not only stable multiple bonds but also possible candidates for novel material species.