C–H Activation of Terminal Alkynes by Tris-(3,5-dimethylpyrazolyl)boraterhodiumneopentylisocyanide: New Metal–Carbon Bond Strengths

C–H bond activation of terminal alkynes by [Tp′Rh­(CNneopentyl)] (Tp′ = hydridotris-(3,5-dimethylpyrazolyl)­borate) resulted in the formation of terminal C–H bond activation products Tp′Rh­(CNneopentyl)­(CCR)­H (R = t-Bu, SiMe3, hexyl, CF3, p-MeOC6H4, Ph, and p-CF3C6H4). A combination of kinetic selectivity determined in competition reactions and activation energy for reductive elimination has allowed for the calculation of relative Rh–Calkynyl bond strengths. The bond strengths of Rh–Calkynyl products are noticeably higher than those of Rh–Caryl and Rh–Calkyl analogues. The relationship between M–C and C–H bond strengths showed a linear correlation (slope RM–C/H–C = 1.32), and follows energy correlations previously established for unsubstituted sp2 and sp3 C–H bonds in aliphatic and aromatic hydrocarbons.