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The 18-electron rule is a chemical rule of thumb used primarily for predicting and rationalizing formulas for stable transition metal complexes, especially organometallic compounds. [1] The rule is based on the fact that the valence orbitals in the electron configuration of transition metals consist of five ( n −1)d orbitals, one n s orbital ...
Tolman's rule states that, in a certain chemical reaction, the steps involve exclusively intermediates of 18- and 16 electron configuration. The rule is an extension of the 18-electron rule . This rule was proposed by American chemist Chadwick A. Tolman . [ 1 ]
In 1972, he proposed the 16 and 18 electron rule, extending Irving Langmuir's 18-Electron rule to include the many examples of stable 16 electron square planar d 8 complexes. [4] Later work focused on the activation of C-H bonds by transition metal complexes [ 5 ] [ 6 ] and free radical oxidation of cyclohexane for the production of adipic acid ...
Many rules in chemistry rely on electron-counting: Octet rule is used with Lewis structures for main group elements, especially the lighter ones such as carbon, nitrogen, and oxygen, 18-electron rule [2] in inorganic chemistry and organometallic chemistry of transition metals, Hückel's rule for the π-electrons of aromatic compounds,
Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reactants or reagents.
From the perspective of the 18-electron rule, the four ligands each provides two electrons, for a total of 16-electrons. As such the compound is coordinatively unsaturated , i.e. susceptible to binding substrates (alkenes and H 2 ).
The cation obeys the 18-electron rule and is considered to be a classic example of an exchange inert metal complex. As a manifestation of its inertness, [Co(NH 3) 6]Cl 3 can be recrystallized unchanged from concentrated hydrochloric acid: the NH 3 is so tightly bound to the Co(III) centers that it does not dissociate to allow its protonation. [1]
The 18-electron rule is the equivalent of the octet rule in main group chemistry and provides a useful guide for predicting the stability of organometallic compounds. [34] It predicts that organometallic species "in which the sum of the metal valence electrons plus the electrons donated by the ligand groups total 18 are likely to be stable."