The author has succeeded in synthesizing and isolating novel compounds consisting of elements in various groups and periods without limiting the elements to be studied. Systematic studies on their structures and properties resulted in the verification of the similarities and differences among main group elements. He further expanded his chemistry to the construction of extended π-electron systems, transition metal complexes, and small molecule activation opening new areas including the development of new reactions.

1. New Insights in the Chemistry of Multiple Bonds of Heavier Group 14 Elements
In order to expand the synthetic utility of dimetallenes, he succeeded in the synthesis and isolation of a variety of novel dimetallenes of heavier Group 14 elements having hydro, bromo, alkynyl and metallocenyl groups as substituents which will be useful precursors for unexplored chemical species. In particular, the reduction of bulky 1,2-diaryl-1,2-dibromodimetallenes resulted in the isolation of the corresponding first examples of carbon-substituted disilyne and digermyne, which were found to show unique potentials for small molecule activation based on the extremely low energy level of π^* orbitals of their heavy triple bonds.

2．A Novel Cross-conjugated π-System Containing Heavy Group 15 Elements.
A novel P-containing cross-conjugated π-system, i.e., triphos­pha­[3]­radi­alene was success­fully synthesized and isolated, and its stepwise chemical reduction afforded the corresponding anion radical and dianion species as stable crystalline compounds. Remarkable red shift was found in its electronic spectra due to both cross-conjugation and heavy element effect, leading to the elucidation of the intrinsic nature of a π-electron system containing heavier main group elements.

3．Chemistry of Low-coordinated Aluminum Compounds.
The author found that dialumenes (-Al=Al-) can be generated by the extrusion of a benzene molecule from appropriately designed precursors. Dialumenes thus generated were found to have extremely high Lewis acidity and re­ac­tivity due to their low energy level of π-type LUMO, allowing the reductive cleavage of the H-H bond­ing of H₂ to give the corresponding organo­aluminum hydrides in high yield. In addition, the first alumylene­-Pt complex was also synthesized and isolated to reveal its unique Al­-Pt multiple-bond character and the potential of low-coordinated group 13 element species to be a ligand in transition metal chemistry.

4．The Chemistry of Novel π-Electron Systems Containing Heavier Group 13 Elements.
The first examples of Lewis base-free alumole and gallole, hitherto unexplored heteroles, were successfully synthesized and isolated and their dianions were found to have considerable aromaticity. A stable 1-bromoalumole was also synthesized to show its high reactivity in nucleophilic substitution on the aluminum center as a highly soft Lewis acid. Thus, the reaction of the 1-bromoalumole with 3-hexyne resulted in the for­ma­tion of a novel Al-con­tain­ing 9-memebered heterocycle, i.e., alu­mo­nine, demonstrating the high potential of alumole in small molecule activa­tion.

5．Activation of Molecules Using Weak Interelement Bonds of Heavier Main Group Elements
In the case of heavier interelement bonds, the repulsion of their inner shell electrons results in the bond elongation and the decrease of orbital interaction. This work showed experimentally and theoretically that phosphanylalumanes, i.e., third-row element single-bond compounds between aluminum and phosphorous, have an ambiphilic character of Lewis acid/base due to its weak P-Al bonding nature to activate small molecules such as alkynes and alkenes. Furthermore, it was found that the resulting adducts also serve as activators for small molecules. These results are worthy of note from the viewpoint of a new methodology to utilize the interelement bondings of heavier main group elements in molecular transformation.

6．The Chemistry of "Heavy Aromatics" without the Aid of Steric Protection
Reduction of a germabenzene and a stannabenzene kinetically stabilized with an extremely bulky aryl group using KC₈ was found to afford the corresponding metallabenzenyl anions as stable potassium salts maintaining its "heavy benzene" skeleton. It was revealed that the remarkable stability of these heavy aryl anions is due to the synergetic effects of not only the increasing stability of divalent species of heavier Group 14 elements and the stability as aromatic 6π systems but also the electronic repulsion as anionic species leading to the suppression of their self-oligomerization. This new finding is of great importance from the viewpoint of opening up doors for the general synthetic route towards heavy aryl anions.