Rotameric transformations in the photochemistry of TpM(CO)2(η3-C3H4R), where Tp = tris(pyrazolyl)borate, M = Mo or W, and R = H or Me

Abstract

Low energy photolysis of TpM(CO)₂(η³-C₃H₄R), where Tp = tris(pyrazolyl)borate, M = Mo or W, and R = 2-H or 2-Me in PVC matrices at 85 K results in exo/gauche isomerism of the allyl ligand. This transformation comes in contrast to the behaviour observed in cyclopentadienyl analogues which undergo exo/endo isomerism. DFT computations reveal an η³ → η¹* → η³ mechanism for the allyl rotameric interconversion where the η¹*-allyl intermediate is generated upon MLCT excitation.