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

On the basis of fundamental research on the chemistry of π-electron systems between heavier main group elements, it was found that such π-electron systems should exhibit higher HOMO and lower LUMO as compared with those between second row elements. That is, the π-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 π-electron systems and fundamental research on such π-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-dibromodimetallenes, Ar(Br)E=E(Br)Ar (E = Si, Ge, Ar = bulky aryl group), as a possible building block of a π-bond between heavier group 14 elements, (ii) 1,2-diaryldimetallynes (ArE≡EAr, E = Si, Ge) as a unique and reactive π-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 π-electron systems between heavier group 14 elements should be completely different from those of carbon systems and should be of great interest as unique π-systems. Thus, the compounds obtained here are not only “stable multiple bonds” but also possible candidates for novel material species.