Boratropic rearrangements in tris(pyrazolyl)borate molybdenum mononitrosyl complexes: effects of co-ligands

Abstract

The complexes [Mo(NO){HB(impz)₃}I(ER)][impz = isopropylmethylpyrazol-1-yl; E = O; R = Prⁱ, Bu^t, CH₂SiMe₃, (CH₂)₄I, Ph or C₆H₄Me-4: E = NH; R = Ph or C₆H₄Me-4] have been prepared from a mixture of isomers of [Mo(NO){HB(impz)₃}I₂]; in the cases where ER = OPh, O(CH₂)₄I or OCH₂SiMe₃ the products could only be obtained as mixtures of isomers, but where ER = OPrⁱ, OBu^t, NHPh or NHC₆H₄Me-4 the products could be thermally converted into compounds containing a single isomer of the ligand HB(impz)₃. Reactions involving REH (E = O; R = Me, Prⁱ or Bu^t; E = NH; R = Et, CH₂Ph or Ph) and a single isomer of [Mo(NO){HB(impz)₃}I₂] produced [Mo(NO){HB(impz)₃}I(ER)] containing a single isomer of the ligand HB(impz)₃ and which did not rearrange on heating. The locations of the methyl and isopropyl groups in the HB(impz)₃ ligand in [Mo(NO){HB(3-Prⁱ-5-Me-C₃N₂H)₃}(OPrⁱ)₂] have been determined by X-ray crystallographic methods.