Replacement of the Common Chromium Source CrCl 3 (thf) 3 with Well-Defined [CrCl 2 (μ-Cl)(thf) 2 ] 2 .

CrCl ₃ (thf) ₃ is a common starting material in the synthesis of organometallic and coordination compounds of Cr. Deposited as an irregular solid with no possibility of recrystallization, it is not a purity guaranteed chemical, causing problems in some cases. In this work, we disclose a well-defined form of the THF adduct of CrCl ₃ ([CrCl ₂ (μ-Cl)(thf) ₂ ] ₂ ), a crystalline solid, that enables structure determination by X-ray crystallography. The EA data and XRD pattern of the bulk agreed with the revealed structure. Moreover, its preparation procedure is facile: evacuation of CrCl ₃ ·6H ₂ O at 100 °C, treatment with 6 equivalents of Me ₃ SiCl in a minimal amount of THF, and crystallization from CH ₂ Cl ₂ . The ethylene tetramerization catalyst [iPrN{P(C ₆ H ₄ - p -Si(nBu) ₃ ) ₂ } ₂ CrCl ₂ ] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- prepared using well-defined [CrCl ₂ (μ-Cl)(thf) ₂ ] ₂ as a starting material exhibited a reliably high activity (6600 kg/g-Cr/h; 1-octene selectivity at 40 °C, 75%), while that of the one prepared using the impure CrCl ₃ (thf) ₃ was inconsistent and relatively low (~3000 kg/g-Cr/h). By using well-defined [CrCl ₂ (μ-Cl)(thf) ₂ ] ₂ as a Cr source, single crystals of [(CH ₃ CN) ₄ CrCl ₂ ] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- and [{Et(Cl)Al(N(iPr) ₂ ) ₂ }Cr(μ-Cl)] ₂ were obtained, allowing structure determination by X-ray crystallography, which had been unsuccessful when the previously known CrCl ₃ (thf) ₃ was used as the Cr source.