Dimethylsulfoxide as a ligand for RhI and IrI complexes--isolation, structure, and reactivity towards X-H bonds (X=H, OH, OCH3)

Novel neutral and cationic Rh(I) and Ir(I) complexes that contain only DMSO molecules as dative ligands with S-, O-, and bridging S,O-binding modes were isolated and characterized. The neutral derivatives RhCl(DMSO)(3)] (1) and IrCl(DMSO)(3)] (2) were synthesized from the dimeric precursors M(2)Cl(2)(coe)(4)] (M=Rh, Ir; COE=cyclooctene). The dimeric Ir(I) compound Ir(2)Cl(2)(DMSO)(4)] (3) was obtained from 2. The first example of a square-planar complex with a bidentate S,O-bridging DMSO ligand, (coe)(DMSO)Rh(micro-Cl)(micro-DMSO)RhCl(DMSO)] (4), was obtained by treating Rh(2)Cl(2)(coe)(4)] with three equivalents of DMSO. The mixed DMSO-olefin complex IrCl(cod)(DMSO)] (5, COD=cyclooctadiene) was generated from Ir(2)Cl(2)(cod)(2)]. Substitution reactions of these neutral systems afforded the complexes RhCl(py)(DMSO)(2)] (6), IrCl(py)(DMSO)(2)] (7), IrCl(iPr(3)P)(DMSO)(2)] (8), RhCl(dmbpy)(DMSO)] (9, dmbpy=4,4'-dimethyl-2,2'-bipyridine), and IrCl(dmbpy)(DMSO)] (10). The cationic O-bound complex Rh(cod)(DMSO)(2)]BF(4) (11) was synthesized from Rh(cod)(2)]BF(4). Treatment of the cationic complexes M(coe)(2)(O=CMe(2))(2)]PF(6) (M=Rh, Ir) with DMSO gave the mixed S- and O-bound DMSO complexes M(DMSO)(2)(DMSO)(2)]PF(6) (Rh=12; Ir=in situ characterization). Substitution of the O-bound DMSO ligands with dmbpy or pyridine resulted in the isolation of Rh(dmbpy)(DMSO)(2)]PF(6) (13) and Ir(py)(2)(DMSO)(2)]PF(6) (14). Oxidative addition of hydrogen to IrCl(DMSO)(3)] (2) gave the kinetic product fac-Ir(H)(2)Cl(DMSO)(3)] (15) which was then easily converted to the more thermodynamically stable product mer-Ir(H)(2)Cl(DMSO)(3)] (16). Oxidative addition of water to both neutral and cationic Ir(I) DMSO complexes gave the corresponding hydrido-hydroxo addition products syn-(DMSO)(2)HIr(micro-OH)(2)(micro-Cl)IrH(DMSO)(2)]IrCl(2)(DMSO)(2)] (17) and anti-(DMSO)(2)(DMSO)HIr(micro-OH)(2)IrH(DMSO)(2)(DMSO)]PF(6)](2) (18). The cationic Ir(DMSO)(2)(DMSO)(2)]PF(6) complex (formed in situ from Ir(coe)(2)(O=CMe(2))(2)]PF(6)) also reacts with methanol to give the hydrido-alkoxo complex syn-(DMSO)(2)HIr(micro-OCH(3))(3)IrH(DMSO)(2)]PF(6) (19). Complexes 1, 2, 4, 5, 11, 12, 14, 17, 18, and 19 were characterized by crystallography.