An Efficient and Recyclable Catalytic System Comprising Nano-Iridium(0) and a Pyridinium Salt of nido-Carboranyldiphosphine for the Synthesis of One-Dimensional Boronate Esters via Hydroboration Reaction

The reaction of N -pentyl-4-methylpyridinium bromide with Na[7,8-bis(dicyclohexylphosphino)-7,8-dicarba- nido -C 2 B 9 H 10 ] led to the formation of a pyridinium salt of the carboranyldiphosphine ligand, [ N -pentyl-4-methylpyridinium] + [7,8-bis(dicyclohexylphosphino)-7,8-dicarba- nido -C 2 B 9 H 10 ] − ( 1 ), in 86% yield. [7,8-bis(dicyclohexylphosphino)-7,8-dicarba- nido -C 2 B 9 H 10 ] − was produced in situ from the decapitation of 1,2-bis(dicyclohexylphosphino)-1,2-dicarba- closo -dodecaborane with sodium hydroxide. Ligand 1 is highly soluble in ionic liquids such as trihexyltetradecylphosphonium dodecylbenzene sulfonate ([THTdP][DBS]) and 1-hexyl-3-methylimidazolium trifluoromethansulfonate ([HMIM][CF 3 SO 3 ]) and was used as a bulky catalyst composite with the ionic liquids [THTdP][DBS] and [HMIM][CF 3 SO 3 ], with stabilized iridium(0) nanoparticles produced by thermolysis of Ir 4 (CO) 12, or with the iridium complex [Ir(coe) 2 Cl] 2 (coe = cyclooctene) and in the ionic liquid [THTdP][DBS] and [HMIM][CF 3 SO 3 ] for the hydroboration of methyl oleate (MO), methyl 10-undecenoate, and 1-hexene. The new Ir(0) catalytic system was found to be efficient, robust, and recyclable so that a number of repetitious hydroborations of MO with high product selectivity could be accomplished.