| Research Abstract |
Investigations on extended hypervalent m-center n-electron bonds (mc-ne : m 【greater than or equal】 4) are just the beginning. In this project, 4c-6e and 5c-6e are investigated in detail. A new type of extended hypervalent bonds are started to investigate, which we call mc^*-ne (m = 3 and 4). While m atoms in mc-ne must align linearly, as defined, one or more atoms in mc^*-ne need not to align linearly. Instead, orbitals supplied by the m-atoms must overlap in the linear area of the interactions. The proposed ides will explain various interactions in organic compounds containing main group elements.
The reactivity of central Z-Z in the extended hypervalent Z'---Z-Z---Z' 4c-6e in 1-(8-PhZ'C_<10>H_6)ZZ(C_<10>H_6Z'Ph-8')-1' [1 (Z, Z') = (Se, S), 2 (Z, Z') = (S, Se), 3 (Z = Z' = Se), and 4 (Z = Z' = S)] is not controlled by the central Z atoms but by the outside Z' atoms, in the sodium boro-hydride reduction. This must create a new concept of chemistry in near future.
We realize that plain rules are necessary to determine geometric and electronic structures based on the NMR chemical shifts, which are founded in theory and are familiar to experimental chemists, to study such field in more detail. Origin of ^<77>Se NMR chemical shifts are elucidated based on the MO theory : They are clarified for pre-α, α, β, and γ effects, together with the orientational effect on aryl groups. The rules enable us to analyze and understand the geometrical and electronic structures of the compounds.
Quantum chemical calculations are also widely applied to clarify weak interactions, which play an important role in the construction of extended hypervalent bonds. Various weak interactions such as Z---Z, Z---Z=0, and 0=Z---Z=0 interactions are well analyzes, as the applications of our project.
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