Preparation and characterisation of dimolybdenum complexes containing fluorophenylimide ligands

Abstract

The arylimido complexes [Mo₂O₂(µ-NR)(µ-O)(η⁵-C₅ H₄Me)₂] and [{MoO(µ-NR)(η⁵-C₅H₄Me)} ₂] (R = C₆H₄F-2 or C₆H₄CF₃-2) were obtained from the reaction between [{Mo(η⁵-C₅H₄Me)(CO)₃ }₂] and the appropriate nitrobenzene RNO₂. In contrast, the corresponding reaction between O₂NC₆H₃F₂-2,6 and [{Mo(η⁵-C₅H₄Me)(CO)₃ }₂] generated two isomeric bis(imido) complexes [{MoO(µ-NC₆H₃F₂-2,6)(η⁵ -C₅H₄Me)}₂], which were separated by column chromatography. Hydrogen-1 and ¹⁹F NMR spectroscopic studies suggested that [{MoO(µ-NC₆H₄CF₃-2)(η⁵ -C₅H₄Me)}₂] exists in two chemically inseparable isomeric forms. The molecular structures of [Mo₂O₂(µ-NC₆H₄F-2)(µ-O)( η⁵-C₅H₄Me)₂], [Mo₂O₂(µ-NC₆H₄CF₃ -2)(µ-O)(η⁵-C₅H₄Me)₂ ] and the centrosymmetric isomer of [{MoO(µ-NC₆H₄CF₃-2)(η⁵ -C₅H₄Me)}₂] have been determined by single-crystal X-ray diffraction. In each structure the central Mo₂(µ-O)(µ-NR) or Mo₂(µ-NR)₂ core is planar with a trans configuration of methylcyclopentadienyl ligands and a substantial twist angle between the phenyl rings and the metallacycle planes.

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