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 (C 5 Ph 5 )Cr(CO) 3 reacts with halogens (C 6 H 5 I‚Cl 2 , Br 2 , and I 2 ) in C 6 H 6 to yield the dimeric oxidation products [(C 5 Ph 5 )Cr(µ-X)X] 2 as thermally stable solids. Reactions with other chlorinating agents similarly yield [(C 5 Ph 5 )CrCl 2 ] 2 . An X-ray crystal structure of [(C 5 Ph 5 )Cr(µ-Cl)Cl] 2 was obtained. The magnetic properties of the Cl 2 -bridged dimer have been determined and modeled using the usual isotropic Hamiltonian H ) -2JS ˆ1‚ S ˆ2, which yields J/k ) -30 K. Low-temperature (77 K) Raman spectra of solid [(C 5 Ph 5 )-CrX 2 ] 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 (C 5 Ph 5 )CrX 2 (THF).

Synthesis and X-ray Crystal Structure of [(C5Ph5)CrCl(μ-Cl)2Tl]2: An Example of the Rare M−X−TlI Linkage (X = Halide)

“…In contrast, the angle decreases significantly to ca. 92° in the highly crowded molecule [(C 5 Ph 5 )Cr(μ-Cl)Cl] 2 . All other angles in the three chromium dimers are similar.…”

“… The starting chromium dimer and thallium-containing product are nearly identical in color. While [(C 5 Ph 5 )CrCl(μ-Cl)] 2 possesses extremely low solubility in noncoordinating solvents, 1 dissolves readily in dichloromethane. Thus, the reaction changes from an initial mixture of green and white solids in a nearly colorless solution to a dark green solution with excess solid TlCl present as the reaction progresses.…”