Reactivity and Spectroscopy of the {Ru(DMAP)₅} Fragment: An {Ru(NH₃)₅} Analogue

Reaction of trans-Ru(DMSO)4Cl2 with DMAP (DMAP = 4-dimethylaminopyridine) yields the yellow [Ru(DMAP)6]2+ cation in good yield. The crystal and molecular structure of [Ru(DMAP)6]Cl2·6CH3CH2OH was determined by X-ray diffraction methods. The complex crystallizes in the trigonal R3̅ space group with a = b = 16.373(1), c = 20.311(1) Å, γ = 120°, and Z = 3 molecules per unit cell. The reaction of [Ru(DMAP)6]2+ in aerobic water gives the red [RuIII(DMAP)5(OH)]2+ cation. This complex shows a chemical behavior similar to [RuIII(NH3)5Cl]2+ and allows the preparation of a family of [Ru(DMAP)5L]n+ complexes. Their electronic properties indicate that the {RuII(DMAP)5} fragment is a weaker π-donor than {RuII(NH3)5}. Our density functional theory (DFT) calculations show that in {RuII(DMAP)5} the DMAP ligands can compete for the π electron density of the ruthenium making the fragment a weaker π-donor.