Halogen Oxidation Reactions of (C₅Ph₅)Cr(CO)₃and Lewis Base Addition to [(C₅Ph₅)Cr(μ-X)X]₂: Electrochemical, Magnetic, and Raman Spectroscopic Characterization of [(C₅Ph₅)CrX₂]₂and (C₅Ph₅)CrX₂(THF) (X = Cl, Br, I) and X-ray Crystal Structure of [(C₅Ph₅)Cr(μ-Cl)Cl]₂

Abstract

The 17-electron complex (C5Ph5)Cr(CO)3 reacts with halogens (C6H5I·Cl2, Br2, and I2) in C6H6 to yield the dimeric oxidation products [(C5Ph5)Cr(μ-X)X]2 as thermally stable solids. Reactions with other chlorinating agents similarly yield [(C5Ph5)CrCl2]2. An X-ray crystal structure of [(C5Ph5)Cr(μ-Cl)Cl]2 was obtained. The magnetic properties of the Cl2-bridged dimer have been determined and modeled using the usual isotropic Hamiltonian H = −2JŜ1·Ŝ2, which yields J/k = −30 K. Low-temperature (77 K) Raman spectra of solid [(C5Ph5)CrX2]2 (X = Cl, I) allow assignments to be made for the metal-ring and metal halogen stretching modes in the low-frequency region (<600 cm-1). Tetrahydrofuran (THF) cleaves these dimers to yield complexes of the form (C5Ph5)CrX2(THF).