List examples of positive and negative ligands?

2 Answers
anor277
Aug 23, 2017

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

Explanation:

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

M→M++e−

M→M2++2e−

M→M3++3e−

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....

12O2+2e−→O2−

or......

12F2+2e−→F−

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

Truong-Son N.
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), formula (side note)

POSITIVE LIGANDS

  • Nitrosyl (nitrosyl), NO+ (triple-bonded, bonds to metal in a linear configuration)
  • Cycloheptatrienyl (heptahaptocycloheptatrienyl), η7−C7H+7 (binds via seven atoms at once)

NEGATIVE LIGANDS

  • Nitrosyl (nitrosyl), NO− (double-bonded, bonds to metal in a bent configuration)
  • Cyanide (cyano), −CN
  • Chloride (chloro), Cl−
  • Thiocyanate (thiocyanato), S−C≡N−
  • Isothiocyanate (isothiocyanato), N=C=S−
  • Superoxide (superoxo), O−2 (binds head-on)
  • Peroxide (peroxo), O2−2 (binds side-on)
  • Oxide (oxo), O2− (double-bonds usually, may bridge)
  • π-allyl (trihaptoallyl), η3−C3H−5 (binds via three atoms at once)
  • Cyclopentadienyl (pentahaptocyclopentadienyl), η5−C5H−5 (binds via five atoms at once)
  • Methyl (methyl), −:CH3
  • Hydroxide (hydroxo), HO−

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

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