XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Comments on the cross-coupling reaction
Shigeyuki AONO
Kanazawa University, Kanazawa, Japan

E-mail address: aonosan2000@ybb.ne.jp
Suzuki and Negishi have investigated the method of cross-coupling reaction which is a kind of catalytic reaction which effectively connect the carbon molecules.
Here we present a brief sketch of this reaction in the respect of chemical reactivity presented by Fukui and Woodward-Hoffmann. Hückel treatment is made simple as possible: the energy levels of unit cell is put zero, the couplings are restricted adjacent and set unity (-1). However the resultant bond order extends all over the molecule. In these simplification, the energy behavior looks as if the bond order ( qij). For butadiene, C4 chain, q14 is obtained negative which suggests the 1-4 sites are repulsive implying the ring closure between them never occurs. On the other hand q16 in the C6 chain is positive is positive, expecting The ring closure (making the benzene ring). Let us turn to the coupling reaction. For the simplest example, the system in which the d-metal connects two C2 molecule (ethylene). The d-orbital is regarded as two p-orbitals, dxz and dyz (called 3 and 4-th). Each ethylene connects the metal to form pz bond and yield as if the molecule of six sites. The chain with six sites make chain, against the case of four members. We thus finished the beginning half of the reaction under consideration. The last half is to separate the metal and left the C4 chain, butadiene. Start from C6 ring, say benzene ring. We have now the ring, then the vertex is pointed 1. We evaluate the bond order q13 vanishing. We now find the 1-3 bond is non-bonding. If any perturbation happens, this bond is breaking and the metal being separates. Our purpose is completed.


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