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

• Published in: Organometallics 2012-04, Vol.31 (7), p.2589-2596
• Main Authors: Zhu, Yinghuai, Jang, Shi Hui Agnes, Tham, Yue Hao, Algin, Oh Biying, Maguire, John A, Hosmane, Narayan S
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om200379c

The reaction of N-pentyl-4-methylpyridinium bromide with Na[7,8-bis(dicyclohexylphosphino)-7,8-dicarba-nido-C2B9H10] led to the formation of a pyridinium salt of the carboranyldiphosphine ligand, [N-pentyl-4-methylpyridinium]+[7,8-bis(dicyclohexylphosphino)-7,8-dicarba-nido-C2B9H10]− (1), in 86% yield. [7,8-bis(dicyclohexylphosphino)-7,8-dicarba-nido-C2B9H10]− 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][CF3SO3]) and was used as a bulky catalyst composite with the ionic liquids [THTdP][DBS] and [HMIM][CF3SO3], with stabilized iridium(0) nanoparticles produced by thermolysis of Ir4(CO)12, or with the iridium complex [Ir(coe)2Cl]2 (coe = cyclooctene) and in the ionic liquid [THTdP][DBS] and [HMIM][CF3SO3] 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.