Chemistry of Ruthenium Polypyridine Complexes: V. Electronic Structure of Ruthenium(II) Bipyridine-Diphosphine Mixed-Ligand Complexes

Comparative analysis of the donor-acceptor capacities of diphosphine ligands in two series of complexes: cis-[Ru(bpy)2(LL)]q+ [LL = 2,2'-bipyridine (bpy), o-benzoquinonediimine (bqdi), cis-1,2-bis(diphenylphosphino)ethane, cis-1,2-bis(diphenylphosphino)ethylene (dppen), (NH3)2, and (CO)2] and [Ru(NH3)4. (LL)]2+ (LL = bpy, dppen, and bqdi), was performed. Diphosphines are the strongest σ donors; they compare in π-acceptor capacity which is associated with phosphorus d orbitals with 2,2'-bipyridine and fall far short of o-benzoquinonediimine and carbonyl.