Metal-Metal Bonds Chapter 15
Metal-Metal Bonds • Single, double, triple, and quadruple bonds are possible in transition metal complexes. • Figure 15-7; [Re3Cl12]3- and [Re2Cl8]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 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 *?
Possible Bonding Interaction in a Complex Containing M-M Bonds • In an actual complex (e.g. [Re2Cl8]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 [Os2Cl8]2-? • Why is it staggered and why does it possess a lower bond order? • Formal shortness ratio. • Table