This is analogous to the process of ligand insertion in coordination chemistry.
This reaction might also be imagined to proceed by adsorption of C2H4
followed by ligand migration (an associative surface reaction).
PAC, 1976, 46, 71. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis' on page 84 (https://doi.org/10.1351/pac197646010071)