Reactivity and spectroscopy of the {Ru(DMAP)5) fragment:: An {Ru(NH3)5} analogue

Reaction of trans-Ru(DMSO)(4)Cl-2 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)]Cl-2.6CH(3)CH(2)OH was determined by X-ray diffraction methods. The complex crystallizes in the trigonal R3 space group with a = b = 16.373(1), c = 20.311 (1) angstrom, gamma = 120 degrees, and Z = 3 molecules per unit cell, The reaction of [Ru(DMAP)(6)](2+) in aerobic water gives the red [Ru-III(DMAP)(5)(OH)](2+) cation. This complex shows a chemical behavior similar to [Ru-III(NH3)(5)Cl](2+) and allows the preparation of a family of [Ru(DMAP)(5)L](n+) complexes. Their electronic properties indicate that the (Ru-II(DMAP)5) fragment is a weaker pi-donor than {Ru-II(NH3)(5)}. Our density functional theory (DFT) calculations show that in {Ru-II(DMAP)(5)} the DMAP ligands can compete for the pi electron density of the ruthenium making the fragment a weaker pi-donor.