Metal-Metal Bonds

1
Metal-Metal Bonds

• Chapter 15

2
Metal-Metal Bonds

• Single, double, triple, and quadruple bonds are
  possible in transition metal complexes.
• Figure 15-7 Re3Cl123- and Re2Cl82-
• The metal-metal bond distance in the dimer is 224
  pm. It was the first complex found to have a
  quadruple bond.
• Look at other complexes that have metal-metal
  bonds.

3
Possible Bonding Interaction between Metal d
Orbitals

• Discuss the possible bonding interactions between
  the two metal atoms.
• d orbital interactions.
• The interaction between dx2-y2 and dxy orbitals
  is weak. Why?
• This interactions produces the ? bonding.
• Occupancy of the ? molecular orbitals contributes
  only a small amount to the overall bonding.
• Figure 15.9 in book.
• What about the spacing between ? and ??

4
Possible Bonding Interaction in a Complex
Containing M-M Bonds

• In an actual complex (e.g. Re2Cl82-) the
  ligands interact with the metal orbitals.
• What is the symmetry of this molecule?
• With which orbital combination do the ligands
  interact most strongly?
• LGO treatment (ligands pointing toward the metal
  atoms).
• Interaction occur with multiple orbital
  combinations on the metal but the strongest is
  with the ? MOs (bonding and antibonding)
• Lets look at the IRs.

5
Possible Bonding Interaction in a Complex
Containing M-M Bonds
6
Possible Bonding Interaction in a Complex
Containing M-M Bonds

• New molecular orbitals form when including the
  ligand interactions.
• Simplistic picture showing interaction only
  between the ligands and certain d orbital
  combinations on the metal atoms.
• Why isnt the complex staggered? What will
  rotation do to the energy of the MOs?

7
Possible Bonding Interaction in a Complex
Containing M-M Bonds

• Compounds of the staggered conformation.
• What is the symmetry of Os2Cl82-?
• Why is it staggered and why does it possess a
  lower bond order?
• Formal shortness ratio.
• Table