Organometallic Chemistry: 18-Electron Rule

The ______ rule, also known as the 18-electron rule, suggests that stable organometallic compounds should have 18 electrons in their outermost shell.

The 18-electron rule was first proposed by ______ and later extended by Bailey.

The 18 electrons in the valence shell of the metal occupy ns, np, and (n-1)d orbitals, a total of ______ orbitals.

If there are less than 18 electrons in the valence shell of the metal, an empty low-lying orbital will be available, leading to ______ upon slight heating.

If there are more than 18 electrons, the excess electron will move to the ______ orbitals, reducing the stability by decreasing the bond order.

The 18-electron rule helps predict the stability of organometallic complexes and the ______ structure of newly synthesized complexes.

The application of the 18-electron rule involves determining the electrons in the valence shell of the metal in the ______ oxidation state.

If the complex is positively charged, the ______ electron must be removed or deducted from the total electrons.

The ______ rule is used to determine the number of electrons that surround a transition metal in a coordination complex.

A ______ ligand contributes two electrons to the metal center.

The metal in the complex [Re(CH3)(CO)2(PR3)2(H2C=CH2)] has a +1 ______ state.

When a metal has a +1 oxidation state, it has a ______ electron count.

The ______ ligand in the complex [Re(CH3)(CO)2(PR3)2(H2C=CH2)] contributes two electrons.

The ______ of a molecule indicates if all its orbitals are filled.

The 18-electron rule can be used to identify an unknown ______ in a compound.

In the complex [Co(CO)5]z, the unknown charge z is determined to be +1 using the ______ rule.

If the compound or complex has 18 electrons in the valence shell of the metal, it is considered ______ and on heating such complex it will not decompose at relatively low temperature.

However, if the number of electrons in the valence shell of a metal is less than or greater than 18, the complex is ______ and may decompose on heating except those that have a special stability associated with 16-electron Square planar complexes.

Note that the second row and third row transition metals under these groups will have the same number of valence electrons: nickel, palladium and platinum will have 10 valence electrons in zero ______ state.

The number of electrons donated by the ligands depends on the nature of the ligand and the nature of the ______ below are some examples:

Generally, the early transition metals (group 3 to 5) could have an electron count of 16 or less. Middle transition metals (group 6 to group 8) commonly have 18 electron count while late transition metals (group 9 to group 11) generally have 16 or ______ electron count.

When a structure has less than an 18 electron count, it is considered electron-deficient or ______ unsaturated.

If a structure has "too many electrons," that means that not all of the bonds are covalent bonds, and thus some has to be ______ bonds.

Two methods are commonly employed for electron counting: Neutral atom method: Metal is taken as in zero ______ state for counting purpose

The 18-electron rule allows one to predict the reactivity of a certain ______.

A molecule with an electron count less than 18 will most likely undergo an ______ reaction.

Compounds like CH3TiCl3 have an effective atomic number of ______ in their valence shell.

The geometry adopted by stable complexes that do not follow the 18-electron rule is ______ planner.

The bulkiness of bonded ligands imposes a ______ effect on the approach of incoming ligands.