Pseudotetrahedral manganese complexes supported by the anionic tris(phosphino)borate ligand [PhBP^iPr₃]

This paper presents aspects of the coordination chemistry of mono- and divalent manganese complexes supported by the anionic tris(phosphino)borate ligand, [PhBP^iPr₃] (where [PhBP^iPr₃] = [PhB(CH₂PⁱPr₂)₃]^-). The Mn(II) halide complexes, [PhBP^iPr₃]MnCl (1) and [PhBP^iPr₃]Mnl (2), have been characterized by X-ray diffraction, SQUID magnetometry, and EPR spectroscopy. Compound 2 serves as a precursor to a series of Mn azide, alkyl, and amide species: [PhBP ^iPr₃]Mn(N₃) (3), [PhBP^iPr ₃]Mn(CH₂Ph) (4), [PhBP^iPr₃]Mn(Me) (5), [PhBP^iPr₃]Mn(NH(2,6-ⁱPr₂-C ₆H₃)) (6), [PhBP^iPr₃]Mn(dbabh) (7), and [PhBP^iPr₃]Mn(1-Ph(isoindolate)) (8). The complexes 2-8 feature a divalent-metal center and are pseudotetrahedral. They collectively represent an uncommon structural motif for low-coordinate, polyphosphine- supported Mn complexes. Two Mn(I) species have also been prepared. These include the Tl-Mn adduct [PhBP^iPr₃]Tl-MnBr(CO)₄ (9) and the octahedral complex [PhBP^iPr₃]Mn(CN ^tBu)₃ (10). Some of our initial synthetic efforts to generate [PhBP^iPr₃]Mn=N_x species are briefly described, as are DFT studies that probe the electronic viability of these types of multiply bonded target structures.