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)(α-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 π-π stacking of the phenanthroline ligands.