Ligand Toolkit

Hey, guys! It’s been forever, hasn’t it? [laughs sadly] I’m back to studying, and this time, I’m putting together a ligand sheet.

I apologize in advanced, because this might not be the most fascinating thing, but I’ll be referencing these a lot in my next posts, and I need to know them anyway, sooo…

(I’m still watching the cat video. ^^)

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Ligand Toolkit

Hydrogen Ligands:

Hydrido: H^–

• Two-electron donor
• No pi accepting ability
• Bonds to soft metals
• Negatively charged

Carbon Ligands:

Carbonyl: CO

• Two-electron sigma donor through carbon
• Pi-accepting into pi antibonding orbitals
• Bonds to soft metals
• Neutral charge

Cyanido: CN^–

• Two-electron sigma donor through carbon
• Pi-accepting into pi antibonding orbitals
• Bonds to hard and soft metals
• Negatively charged

Alkenes

• Two-electron sigma donor through pi orbitals
• Pi-accepting into pi antibonding orbitals
• Bond to soft and hard metals
• Neutral charge

Alkynes

• Two-electron (monodentate) or four-electron (bidentate bridging) sigma donors through pi orbitals
• Pi-accepting into pi antibonding orbitals
• Bond to soft and hard metals
• Neutral charge

Cyclic Aromatic

Benzene: η⁶-C₆H₆

•  Six-electron sigma donor through pi orbitals
• Pi-accepting into pi antibonding orbitals
• Bonds to soft metals
• Neutral charge

Cyclopentadienyl: η⁵-C₅H₅^–

• Six-electron sigma donor through pi orbitals
• Pi-accepting into pi antibonding orbitals
• Bonds to soft and hard metals
• Negatively charged

Carbene

Carbenes: CRR’

• Two-electron sigma donor through sp² on carbon
• Pi-accepting into 2p orbital on carbon
• Bond to soft metals
• Neutral charge

Carbanion

Alkyl and Aryl Carbanions

• Two-electron sigma donor through sp³ on carbon
• Possible pi-accepting on aryl carbanions through pi antibonding orbitals
• Bond to soft and hard metals
• Negatively charged

Acyl

Acyl: C(O)R^–

• Two-electron sigma donor through sp² on carbon
• Possible pi-accepting through pi antibonding orbitals
• Bond to soft metals
• Negatively charged

Allyl

Allyl: η³-C₃H₅^–

• Four-electron sigma donor through pi orbitals
• Pi-accepting through pi antibonding orbitals
• Bonds to soft metals
• Negatively charged

Nitrogen Ligands:

Aliphatic Amines

• Two-electron sigma donor through sp³ on nitrogen
• No pi accepting
• Bond to hard metals
• Neutral charge

Heterocyclic Nitrogen Bases (Pyridine, Imidazole, etc.)

• Two-electron sigma donor through sp² on nitrogen
• Possible pi-accepting into pi antibonding orbitals
• Bonds to soft and hard metals
• Neutral charge

Imines: C=N

• Two-electron sigma donor through sp² on nitrogen
• Pi-accepting into pi antibonding orbitals
• Bonds to soft and hard metals
• Neural charge

Nitrile: R-CN

• Two-electron sigma donor through sp on nitrogen
• Possible pi-accepting into pi antibonding orbitals
• Bonds to soft and hard metals
• Neural charge

Dinitrogen: N₂

• Two-electron sigma donor through sp on nitrogen
• Pi-accepting into pi antibonding orbitals
• Bonds to soft metals
• Neural charge

Nitrosyl: NO

• Has two forms: linear (triple bonded) and bent (double bonded)

Linear Nitrosyl:

• Two-electron sigma donor through sp on nitrogen
• Pi-accepting into pi antibonding orbitals
• Bonds to soft metals
• Positive charge

Bent Nitrosyl:

• Two-electron sigma donor through sp² on nitrogen
• Pi-accepting into pi antibonding orbitals
• Bonds to soft metals
• Negative charge

Phosphorus Ligands:

Phosphine, Phosphite

• Two-electron sigma donor per phosphorus
• Pi-accepting into d orbitals (in phosphite)
• Bonds to soft metals
• Neutral charge

Oxygen Ligands:

Ether, Alcohol, Aqua

• Two-electron sigma donors
• No pi backbonding
• Weaky bond to hard metals
• Neutral charge

Alkoxo an Aryloxo: RO^–

• Two-electron donors
• No pi backbonding
• Strongly bond to hard metals
• Negatively charged

Beta-Diketonato

• Four-electron donors (chelating)
• Pi-accepting through pi antibonding orbitals
• Bond to soft and hard metals
• Negatively charged

Carboxylato

• Two-electron donors per carboxylato group
• No pi-backbonding
• Bond to hard metals
• Negatively charged

Sulfur Ligands:

Thiolato

• Two-electron donors
• No pi-backbonding
• Bond to soft metals
• Negatively charged

Dithiocarbamato

• Four-electron donor (chelating)
• No pi-backbonding
• Negatively charged

Halide Ligands:

Halido

• Either two-electron donor or four-electron bridging

Macrocyclic Ligands:

Porphyrinato, Crown Ethers, Cryptands

• Form more stable complexes than equivalent numbers of nonchelating ligands

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All right! That’s it! I’m done! Now I’m going to watch the Iron Bowl! (Not that I have a choice… I’m basically watching it right now, so…)

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