The 18-electron rule, which is the organometallic equivalent of the octet rule, posits that transition metal complexes with 18 valence electrons achieve enhanced stability corresponding to a noble gas electron configuration.
The claim that transition metal complexes with 18 valence electrons achieve noble gas configuration stability is a well-established foundational concept in coordination chemistry (the 18-electron rule), treated as common knowledge in textbooks and literature. Paper [4] explicitly invokes this rule to explain the stability of its investigated transition metal complexes. No papers refute the general validity of the rule.