This paper describes theoretical studies on the insertion reaction of germynes XC ≡ GeY (X,Y=H, Cl and F) at the carbon site into a C‐H bond of CH4 performed at the QCISD(T)/6–311G*//QCISD/6–31G* level of theory. This work was inspired by the observation by Sakamoto, Kira, and coworkers on the carbene‐like reaction mode for stannyne (RC≡SnR′). Due to the limitation in the computation for the tin atom, the study was carried out on germyne compounds instead. We found that the valence state of the germyne moiety in the transition state and reaction product can be well represented by the triplet germyne. It has a bifunctional electronic structure of a triplet cabene joined to a singlet germylene (Structure 1).
This paper describes theoretical studies of halogen-substituted heteroacetylenes (XCMY, M = Si and Ge; X, Y = H, Cl and F) performed at the QCISD(T)/6-311G//QCISD/6-31G level of theory. The electronegative halogen substituents destabilize the singlet state such that the triplet state tends to become favorable. The triplet state has the bifunctional electronic structure of a triplet carbene joined to a heavy singlet carbene. We found that the substituents effectively reduce the energy of the donor-acceptor interactions (E(D-A)) between the two in-plane lone pairs of electrons of the singlet state; therefore, the remaining pi bond is less favorable energetically than the triplet state with a sigma bond. A related phenomenon occurs for the homonuclear heavy acetylenes in singlets in which the lead compound RPbPbR switches to a Pb-Pb sigma bond from the pi bonds observed for the lighter acetylenes.
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