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 {eta(5):eta(6)-(2-C9H6)(C2B10H11)}{Na-3(THF)(n)}, which reacted with LnCl(3) to produce dinuclear complexes [eta(5):eta(6)-(2-C9H6)(C2B10H11)Ln(THF)}(2)(mu-Cl)][Na(THF)(6)] (Ln = Y (5a), Er (5b)). Compound 4 reacted with excess sodium metal, yielding [{eta(5):eta(6)-(1-C9H6)(C2B10H11)}Na-3(THF)(5)}](2) (6), bearing a six-membered C2B4 open face and a five-membered C-5 bonding face. Reaction of 6 with LnCl(3) or Ln(BH4)(3)(THF)(3) gave [eta(5):eta(6)-(1-C9H6)(C2B10H11)Ln(THF)}(2)(mu-Cl)][Na(THF)(3)] (Ln = Y (7a), Nd (7b), Er (7c)) or {[eta(5):eta(6)-(1-C9H6)-(C2B10H11)Er(THF)](2)(mu-BH4)}{Na(THF)(2)} (8), respectively. Interaction of 8 with excess sodium metal generated {[eta(5):eta(7)-(1-C9H6)(C2B10H11)Er(THF)](2)} Na-4(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.