Base- and Additive-Free Carbon Dioxide Hydroboration to Methoxyboranes Catalyzed by Non-Pincer-Type Mn(I) Complexes

[Image: see text] Well-defined, bench stable Mn(I) non-pincer-type complexes were tested as earth-abundant transition metal catalysts for the selective reduction of CO(2) to boryl-protected MeOH in the presence of pinacolborane (HBpin). Essentially, quantitative yields were obtained under mild reaction conditions (1 bar CO(2), 60 °C), without the need of any base or additives, in the presence of the alkylcarbonyl Mn(I) bis(phosphine) complexes fac-[Mn(CH(2)CH(2)CH(3))(dippe)(CO)(3)] [Mn1, dippe = 1,2-bis(diisopropylphosphino)ethane] and [Mn(dippe)(CO)(2){(μ-H)(2)(Bpin)}] (Mn4), that is obtained by reaction of the bench-stable precatalyst Mn1 with HBpin via elimination of butanal. Preliminary mechanistic details were obtained by a combination of NMR experiments and monitoring of the catalytic reactions.