Synthesis and Structural Characterization of New Carboranyl-Indenyl Ligands and Their Lanthanide Complexes

Two new directly attached carboranyl-indenyl compounds, 2-(o-carboranyl)indene (2) and 1-(o-carboranyl)indene (4), were synthesized, and their applications in lanthanide chemistry were explored.
Reactions of 2-indanone or indene epoxide with Li2C2B10H10 followed by dehydration reactions gave 2
or 4, respectively. Treatment of 2 with excess sodium metal afforded presumably {η5:η6-(2-C9H6)(C2B10H11)}{Na3(THF)n}, which reacted with LnCl3 to produce dinuclear complexes [{η5:η6-(2-C9H6)(C2B10H11)Ln(THF)}2(μ-Cl)][Na(THF)6] (Ln = Y (5a), Er (5b)). Compound 4 reacted with excess sodium
metal, yielding [{η5:η6-(1-C9H6)(C2B10H11)}{Na3(THF)5}]2 (6), bearing a six-membered C2B4 open face
and a five-membered C5 bonding face. Reaction of 6 with LnCl3 or Ln(BH4)3(THF)3 gave [{η5:η6-(1-C9H6)(C2B10H11)Ln(THF)}2(μ-Cl)][Na(THF)3] (Ln = Y (7a), Nd (7b), Er (7c)) or {[η5:η6-(1-C9H6)(C2B10H11)Er(THF)]2(μ-BH4)}{Na(THF)2} (8), respectively. Interaction of 8 with excess sodium metal
generated {[η5:η7-(1-C9H6)(C2B10H11)Er(THF)]2}{Na4(THF)8} (9). These new complexes were characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 1−4, 5b,
6, 7a, 7c, 8, and 9 were confirmed by single-crystal X-ray analyses. The results showed that these new
ligands favored the formation of the “metal-bridged” type of dinuclear complexes due to the lack of the
linkage between the indenyl and carboranyl units.