Substitution at boron in molybdaborane frameworks: Synthesis and characterization of isomeric (η⁵-C₅Me₅Mo)₂B₅H_nX_m (when X = Cl: n = 5, 7, 8; m = 4, 2, 1 and X = Me: n = 6, 7; m = 3, 2)

Abstract

Reaction of (η⁵-C₅Me₅)MoCl₄ with 6-fold excess of LiBH₄·thf followed by pyrolysis with BHCl₂·SMe₂ in toluene at 90 °C yielded known (η⁵-C₅Me₅Mo)₂B₅H₉ (1) and B-Cl inserted (η⁵-C₅Me₅Mo)₂B₅H₈Cl (2), (η⁵-C₅Me₅Mo)₂B₅H₇Cl₂ (3–5, three isomers) and (η⁵-C₅Me₅Mo)₂B₅H₅Cl₄ (6). In addition, reaction of (η⁵-C₅Me₅Mo)₂B₅H₉ with 5-fold excess of n-BuLi followed by excess of MeI in THF yielded B-Me inserted metallaboranes (η⁵-C₅Me₅Mo)₂B₅H₇ (CH₃)₂ (7, 8 two isomers) and (η⁵-C₅Me₅Mo)₂B₅H₆(CH₃)₃ (9, 10 two isomers). Isolated yields of 2–6 are poor but 7–10 are modest to good. Compounds 2–10 can be viewed as bicapped closo trigonal bipyramidal geometry. All the new compounds have been characterized in solution by IR, ¹H, ¹¹B, ¹³C NMR and mass spectroscopy as simple substitution derivatives of (η⁵-C₅Me₅Mo)₂B₅H₉ and the structural types were unequivocally established by crystallographic analysis of compounds 2, 3, 5 and 6.