Isolation and Characterization of a Dimeric Ruthenium(II) Complex. An Intermediate in the Ruthenium-Catalyzed Oxygen Oxidation of Thioethers to Sulfoxides

Complexes of the type Ru11X2(MeSO)2 or 3(PR3) are excel1ent catalysts for the selective oxygen oxidation of thioethers to sulfoxides. The complex RuCl2(Me2SO)3(PPh3) is an example of such a catalyst, and its solution chemistry under simulated catalytic conditions reveals that only one detectable complex is present. This presumed catalytic complex has been isolated and characterized by 1H, 13C, and 31P NMR and by an x-ray structure determination to be the chlorotri-μ-chlorotris(dimethyl sulfoxide)bis(triphenylphosphine) diruthenium, 2. Single crystals of 2 are monoclinic with space group P 21/c with a = 16.662(3)Å, b = 16.576(3)Å, c = 19.282(3)Å, and β =98.86(1)°. The structure was refined to R = 0.053(Rw = 0.069) by using 5186 unique reflections. Both Ru centers are coordinated in a distorted octahedral fashion having three μ-bridged chlorine atoms shared between them. RU1 possesses three terminal ligands, one chloride, one triphenylphosphine and a dimethyl sulfoxide. RU2 is terminally bonded to two Me2SO centers and one triphenylphosphine. The μ-bridged chlorine atoms are bonded in an asymmetric fashion due to the differing trans-influences of the Cl−, (CH3)2SO and PPh3 ligands bonded to the metal centers. RU-μCl distances range from 2.436(2)Å to 2.490(2)Å, and Ru-S distances from 2.205(2)Å to 2.269(2)Å.