Dimethylsulfoxide as a Ligand for Rh I and Ir I Complexes—Isolation, Structure, and Reactivity Towards XH Bonds (X=H, OH, OCH 3 )

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(DM S O) 3 ] ( 1 ) and [IrCl(DM S O) 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 (DM S O) 4 ] ( 3 ) was obtained from 2 . The first example of a square‐planar complex with a bidentate S,O‐bridging DMSO ligand, [(coe)(DM S O)Rh(μ‐Cl)(μ‐DM SO )RhCl(DM S O)] ( 4 ), was obtained by treating [Rh 2 Cl 2 (coe) 4 ] with three equivalents of DMSO. The mixed DMSO–olefin complex [IrCl(cod)(DM S O)] ( 5 , COD=cyclooctadiene) was generated from [Ir 2 Cl 2 (cod) 2 ]. Substitution reactions of these neutral systems afforded the complexes [RhCl(py)(DM S O) 2 ] ( 6 ), [IrCl(py)(DM S O) 2 ] ( 7 ), [IrCl( i Pr 3 P)(DM S O) 2 ] ( 8 ), [RhCl(dmbpy)(DM S O)] ( 9 , dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine), and [IrCl(dmbpy)(DM S O)] ( 10 ). The cationic O‐bound complex [Rh(cod)(DMS O ) 2 ]BF 4 ( 11 ) was synthesized from [Rh(cod) 2 ]BF 4 . Treatment of the cationic complexes [M(coe) 2 (OCMe 2 ) 2 ]PF 6 (M=Rh, Ir) with DMSO gave the mixed S‐ and O‐bound DMSO complexes [M(DM S O) 2 (DMS O ) 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)(DM S O) 2 ]PF 6 ( 13 ) and [Ir(py) 2 (DM S O) 2 ]PF 6 ( 14 ). Oxidative addition of hydrogen to [IrCl(DM S O) 3 ] ( 2 ) gave the kinetic product fac ‐[Ir(H) 2 Cl(DM S O) 3 ] ( 15 ) which was then easily converted to the more thermodynamically stable product mer ‐[Ir(H) 2 Cl(DM S O) 3 ] ( 16 ). Oxidative addition of water to both neutral and cationic Ir I DMSO complexes gave the corresponding hydrido–hydroxo addition products syn ‐[(DM S O) 2 HIr(μ‐OH) 2 (μ‐Cl)IrH(DM S O) 2 ][IrCl 2 (DM S O) 2 ] ( 17 ) and anti ‐[(DM S O) 2 (DMS O )HIr(μ‐OH) 2 IrH(DM S O) 2 (DMS O )][PF 6 ] 2 ( 18 ). The cationic [Ir(DM S O) 2 (DMS O ) 2 ]PF 6 complex (formed in situ from [Ir(coe) 2 (OCMe 2 ) 2 ]PF 6 ) also reacts with methanol to give the hydrido–alkoxo complex syn ‐[(DM S O) 2 HIr(μ‐OCH 3 ) 3 IrH(DM S O) 2 ]PF 6 ( 19 ). Complexes 1, 2, 4, 5, 11, 12, 14, 17, 18 , and 19 were characterized by crystallography.