Reactivity of cyclopentadienyl transition metal(ii) complexes with borate ligands: structural characterization of the toluene-activated molybdenum complex [Cp*Mo(CO)2(η3-CH2C6H5)]

Reactions of cyclopentadienyl transition-metal halide complexes [Cp*Mo(CO)₃Cl], 1, and [CpFe(CO)₂I], 2, (Cp = C₅H₅; Cp* = η⁵-C₅Me₅) with borate ligands are reported. Treatment of 1 with [NaBt₂] (Bt₂ = dihydrobis(2-mercapto-benzothiazolyl)borate) in toluene yielded [Cp*Mo(CO)₂(C₇H₄S₂N)], 3, and [Cp*Mo(CO)₂(η³-CH₂C₆H₅)], 4, with a selective binding of toluene through C-H activation followed by orthometallation. Note that compound 4 is a structurally characterized toluene-activated molecule in which the metal is in η³-coordination mode. Under similar reaction conditions, [NaPy₂] (Py₂ = dihydrobis(2-mercaptopyridyl)borate) produced only the mercaptopyridyl molybdenum complex [Cp*Mo(CO)₂(C₅H₄SN)], 5, in good yield. On the other hand, when compound 2 was treated individually with [NaBt] (Bt = trihydro(2-mercapto-benzothiazolyl)borate) and [NaPy₂] in THF, formation of the η¹-coordinated complexes [CpFe(CO)₂(C₇H₄S₂N)], 6, and [CpFe(CO)₂(C₅H₄SN)], 7, was observed. The solid-state molecular structures of compounds 3, 4, 6, and 7 have been established by single-crystal X-ray crystallographic analyses.