The mechanism of fluxionality of (1,2,7-η 3-2-Me-benzyl)(η 5-C 5H 5)Mo(CO) 2

Abstract

It is shown that (1,2,7-η 3-2-Me-benzyl)(η 5-C 5H 5)Mo(CO) 2 exits in solution as one isomer which is fluxional, probably via (7-η 1-2-Me-benzyl)((η 5-C 5H 5)Mo(CO) 2, with Δ G ≠ 370 = 23.6 ± 1.0 kcal mol −1. In contrast, (1,2,7-η 3-3-Me-benzyl)(η 5-C 5H 5)Mo(CO) 2 exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG ≠ 15.7 kcal mol −1. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.