# List examples of positive and negative ligands?

Aug 23, 2017

Well, metals are electron rich materials.........

#### Explanation:

......and they tend to undergo oxidation, i.e.

$M \rightarrow {M}^{+} + {e}^{-}$

$M \rightarrow {M}^{2 +} + 2 {e}^{-}$

$M \rightarrow {M}^{3 +} + 3 {e}^{-}$

And non-metals, from the right hand side of the Periodic Table, tend to be electron-poor materials, and they tend to be good oxidants....

$\frac{1}{2} {O}_{2} + 2 {e}^{-} \rightarrow {O}^{2 -}$

or......

$\frac{1}{2} {F}_{2} + 2 {e}^{-} \rightarrow {F}^{-}$

Anyway, in most exams you will be issued a standard table of redox potentials, which will give you the possible redox processes.

Aug 23, 2017

Um, not sure for which class, but I can list 12 anions, I suppose... there are hardly any positive ligands. I'm sure you could list more negative ligands than I can think of off the top of my head if you just look at a book.

All of these use the donor pair electron-counting method (Method A in this diagram).

KEY:

• Ligand name (ligand prefix), $\text{formula}$ (side note)

POSITIVE LIGANDS

• Nitrosyl (nitrosyl), ${\text{NO}}^{+}$ (triple-bonded, bonds to metal in a linear configuration)
• Cycloheptatrienyl (heptahaptocycloheptatrienyl), ${\eta}^{7} - {\text{C"_7"H}}_{7}^{+}$ (binds via seven atoms at once)

NEGATIVE LIGANDS

• Nitrosyl (nitrosyl), ${\text{NO}}^{-}$ (double-bonded, bonds to metal in a bent configuration)
• Cyanide (cyano), $\text{^(-)"CN}$
• Chloride (chloro), ${\text{Cl}}^{-}$
• Thiocyanate (thiocyanato), ${\text{S"-"C"-="N}}^{-}$
• Isothiocyanate (isothiocyanato), ${\text{N"="C"="S}}^{-}$
• Superoxide (superoxo), ${\text{O}}_{2}^{-}$ (binds head-on)
• Peroxide (peroxo), ${\text{O}}_{2}^{2 -}$ (binds side-on)
• Oxide (oxo), ${\text{O}}^{2 -}$ (double-bonds usually, may bridge)
• $\pi$-allyl (trihaptoallyl), ${\eta}^{3} - {\text{C"_3"H}}_{5}^{-}$ (binds via three atoms at once)
• Cyclopentadienyl (pentahaptocyclopentadienyl), ${\eta}^{5} - {\text{C"_5"H}}_{5}^{-}$ (binds via five atoms at once)
• Methyl (methyl), ${\text{^(-):"CH}}_{3}$
• Hydroxide (hydroxo), ${\text{HO}}^{-}$

The challenge is, can you keep track of which ones bind using how many electrons?