Synthesis, Structure, and Haptotropic Interconversions of Tungsten Cycloheptatrienyl–Acetonitrile–Carbonyl Complexes

Abstract

Tungsten cycloheptatrienyl complexes (η⁷-C₇H₇)W(CO)₂I (I), [(η³-C₇H₇)W(CO)₂(CH₃CN)₃]PF₆ (II), and [(η⁷-C₇H₇)W(CO)₂(CH₃CN)]PF₆ (III) (CIF files CCDC nos. 1875096 (I), 1875097 (II), 1875098 (III)), characterized earlier only by spectroscopic methods, were prepared and studied by X-ray diffraction. The tris(acetonitrile) complex II can lose two acetonitrile ligands in both coordinating and non-coordinating solvents with the η³ → η⁷ change in the hapticity of the cycloheptatrienyl ring to be converted to III. The reverse ligand attachment process with the η⁷ → η³ change in the hapticity of the cycloheptatrienyl ring takes place upon the dissolution of monoacetonitrile complex III in acetonitrile. The electron-compensating η³ ↔ η⁷ change in the hapticity of the tropylium ligand is reversible.