Hydroboration of Terminal Alkenes and <i>trans</i> ‐1,2‐Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex

A MnI-catalyzed hydroboration of terminal alkenes and a 1,2-diboration alkynes with pinacolborane (HBPin) is described. For alkenes, anti-Markovnikov takes place; for the reaction proceeds excellent trans-1,2-selectivity. The most active pre-catalyst bench-stable alkyl bisphosphine MnI complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. catalytic process initiated by migratory insertion CO ligand into Mn–alkyl bond to yield an acyl intermediate, which undergoes B−H cleavage HBPin (for alkenes) rapid C−H alkynes), forming boryl acetylide catalysts [Mn(dippe)(CO)2(BPin)] [Mn(dippe)(CO)2(C≡CR)], respectively. broad variety aromatic aliphatic was efficiently selectively borylated. Mechanistic insights are provided based on experimental data DFT calculations revealing that acceptorless operating involving dihydrogen release.