Unprecedented metathesis of metal–carbon and carbon–carbon bonds in α-agostic n-alkyl niobium alkyne complexes

Abstract

The α-agostic n-ethyl and n-propyl niobium alkyne complexes [NbL(Cl)(µ-H–CHR)(PhCCR′)][L = hydridotris-(3,5-dimethylpyrazolyl)borate; R = Me, Et; R′= Me, Et, Prⁿ] undergo a thermolytic exchange of the niobium and alkyne-bound alkyl groups to give [NbL(Cl)(R′)(PhCCCH₂R]; first-order kinetic parameters have been obtained when R = R′= Me (ΔH‡= 113 kJ mol^–1, ΔS‡= 4 J K^–1 mol^–1).