Metal-Metal Bonds Chapter 15

Metal-Metal Bonds Single, double, triple, and quadruple bonds are possible in transition metal complexes. –Figure 15-7; [Re 3 Cl 12 ] 3- and [Re 2 Cl 8 ] 2- –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.

Possible Bonding Interaction between Metal d Orbitals Discuss the possible bonding interactions between the two metal atoms. –d orbital interactions. The interaction between d x2-y2 and d xy 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  *?

Possible Bonding Interaction in a Complex Containing M-M Bonds In an actual complex (e.g. [Re 2 Cl 8 ] 2- ) 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  MO’s (bonding and antibonding) –Let’s look at the IR’s.

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 isn’t the complex staggered? What will rotation do to the energy of the MO’s?

Possible Bonding Interaction in a Complex Containing M-M Bonds Compounds of the staggered conformation. –What is the symmetry of [Os 2 Cl 8 ] 2- ? –Why is it staggered and why does it possess a lower bond order? Formal shortness ratio. –Table