Rotation of the η³‐Propargyl Ligand in [(C₆Me₅H)M(CO)₂(η³‐C₃H₃)]⁺ (M=Cr, Mo, W) Complexes

Abstract

The dynamic behaviour of η3‐propargyl ligand in [(C6Me5H)M(CO)2(η3‐C3H3)]+ (comp : M, M=Cr, Mo, W) complexes was systematically studied using computational chemistry approaches. Two isomerization pathways were assessed: a simple rotation of the propargyl fragment around the metal‐ligand axis and the η3‐η1 hapticity slippage of the propargyl ligand. The former mechanism possesses the activation energies of +25.9 (comp : Cr), +20.7 (comp : Mo), and +20.3 kcal mol−1 (comp : W) and is feasible at near‐room temperatures. The η3‐η1 partial decoordination requires essentially the same energy for comp : Cr (+25.8 kcal mol−1) but is hindered for comp : Mo and comp : W (>+30 kcal mol−1). To analyse the factors that influenced these trends, the binding of analogous comp : M and η3‐allyl complexes was studied using the local energy decomposition method.