Circumambulatory Rearrangement with Characteristics of a 2:1 Covalent Molecular Bevel Gear

anti-W(CO)5-complexed 9-methyl-9-phosphabicyclo[6.1.0]nonatriene represents a covalently interlocked molecular bevel gear. Correlated movement of the phosphorus atom and the eight-membered ring by way of a “walk” rearrangement makes gear slippage impossible. The gearing motion is transferred to the four-toothed W(CO)5 propeller connected to the rotating phosphorus atom, enabling a gearing ratio of 2:1 according to B3LYP and Car−Parrinello Molecular Dynamics calculations. Methyl substitution of the eight-membered ring tempers the gearing process, with the PMeW(CO)5 entity passing the substituted carbon atom only at temperatures above 50 °C