Iridium Phosphane Complexes Containing Arylspiroboronate Esters for the Hydroboration of Alkenes

Iridium phosphane arylspiroboronate esters have been prepared by addition of B(2)cat(3) (cat = 1,2-O2C6H4) to the iridium precursors Ir(acac)(coe)(2)/PR3 (acac = acetylacetonato, coe = cis-cyclooctene) or Ir(acac)(coe)(2)/P-P (chelating bidentate ligands) at elevated temperatures. These novel complexes have been characterized by a number of physical methods including X-ray diffraction studies for the PCy3 (2) and dppp (6, 1,3-diphenylphosphanopropane) derivatives. The arylspiroboronate esters, as seen with the more common rhodium complexes, are bound to the metal centre via one of the benzene catecholato rings. These organometallic complexes can be used as precatalysts for the selective hydroboration of vinylarene derivatives with HBpin (pin = 1,2-O2C2Me4) to give the corresponding linear hydroboration products. Reactions with methyl oleate proceed at elevated temperatures to give the isomerised/hydroboration product selectively along with equal amounts of hydrogenation product.