Nickel-Catalyzed Reductive Hydroesterification of Styrenes Using CO2 and MeOH

Complexes [(dippe)Ni(μ-H)] 2 ( A ) (dippe = 1,2-bis-di-isopropylphosphino)ethane) and [(dtbpe)Ni(μ-H)] 2 ( B ) (dtbpe = 1,2-bis-di- tert -butylphospino)ethane) catalyze the reductive hydroesterification of styrenes with the use of CO 2 and MeOH. The latter acts as a hydrogen source and as an esterificating agent, to yield the corresponding branched and linear esters in moderate to good yields. In all of the studied reactions the linear esters were obtained in higher amounts than the branched ones. When the hydroesterification reaction was carried out using a stoichiometric metal/substrate ratio, the complexes [(P–P)Ni(CO) 2 ] and [(P–P)Ni(CO 3 )] (P–P = dippe or dtbpe) were isolated and characterized by standard spectroscopic methods. Compounds [(dtbpe)Ni(CO) 2 ] and [(dtbpe)Ni(CO 3 )] were also fully characterized by single-crystal X-ray diffraction.