Synthesis, structure, and reactivity of rhodium and iridium complexes of the chelating bis-sulfoxide tBuSOC2H4SOtBu. Selective O-H activation of 2-hydroxy-isopropyl-pyridine

The chloro-bridged rhodium and iridium complexes M2(BTSE)2Cl2] (M = Rh 1, Ir 2) bearing the chelating bis-sulfoxide tBuSOC2H4SOtBu (BTSE) were prepared by the reaction of M2(COE)4Cl2] (M = Rh, Ir; COE = cyclooctene) with an excess of a racemic mixture of the ligand. The cationic compounds M(BTSE)2]PF6] (M = Rh 3, Ir 4), bearing one S- and one O-bonded sulfoxide, were also obtained in good yields. The chloro-bridges in 2 can be cleaved with 2-methyl-6-pyridinemethanol and 2-aminomethyl pyridine, resulting in the iridium(I) complexes Ir(BTSE)(Py)(Cl)] (Py = 2-methyl-6-pyridinemethanol 5, 2-aminomethyl-pyridine 6). In case of the bulky 2-hydroxy- isopropyl-pyridine, selective OH oxidative addition took place, forming the Ir(III)-hydride Ir(BTSE)(2-isopropoxy-pyridine)(H)(Cl)] 7, with no competition from the six properly oriented C-H bonds. The cationic rhodium(I) and iridium(I) compounds M(BTSE)(2-aminomethyl-pyridine)]X] (M = Rh 8, Ir 10), Rh(BTSE)(2-hydroxy- isopropyl-pyridine)]X] 9(stabilized by intramolecular hydrogen bonding), Ir(BTSE)(pyridine)2]PF6] 12, Ir(BTSE)(alpha-picoline)2]PF6] 13, and Rh(BTSE)(1,10-phenanthroline)]PF6] 14 were prepared either by chloride abstraction from the dimeric precursors or by replacement of the labile oxygen bonded sulfoxide in 3 or 4. Complex 14 exhibits a dimeric structure in the solid state by pi-pi stacking of the phenanthroline ligands.