Abstract: The orbital symmetry principle, a core concept in undergraduate organic chemistry, is primarily covered in chapters on pericyclic reactions and rarely extended to organometallic chemistry. Correspondingly, instruction on elementary reactions in undergraduate organometallic chemistry usually focuses on apparent changes in the oxidation state and coordination number of metal centers, with insufficient attention to orbital symmetry. Taking ground-state concerted reductive elimination as a model system, this paper systematically compares symmetry differences in reaction processes centered on 2p maingroup elements, d-block transition metals, and hypervalent main-group elements. With the aid of visualization tools, we elucidate the unique role of d orbitals in reductive elimination and the underlying origin of reactivity differences between hypervalent main-group compounds and conventional 2p-element compounds. Orbital symmetry analysis serves as a key conceptual bridge between fundamental organic and organometallic chemistry. It deepens students’ understanding of the connections and differences between main-group elements and transition metals, and helps them build a comprehensive knowledge framework of organic chemistry.

Key words: Reductive elimination, Transition metal, Orbital symmetry, Woodward–Hoffmann rules, Hypervalency