Substitution at boron in molybdaborane frameworks: Synthesis and characterization of isomeric (η5-C5Me5Mo)2B5HnXm (when X = Cl: n = 5, 7, 8; m = 4, 2, 1 and X = Me: n = 6, 7; m = 3, 2)

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.

Reaction of (η5-C5Me5)MoCl4 with excess of LiBH4thf followed by pyrolysis with BHCl2SMe2 yielded B-Cl inserted (η5-C5Me5Mo)2B5HnClm, 2–6 (n = 5, 7, 8; m = 4, 2, 1). In addition, exo-cluster substitution at B-H in (η5-C5Me5Mo)2B5H9 was achieved using BuLi/MeI reagents which afforded (η5-C5Me5Mo)2B5HnMem (7–10) (n = 6, 7; m = 3, 2).Figure optionsDownload as PowerPoint slide