Synthesis, Structure, and Reactivity of Rare-Earth Metal Carboryne Complexes

Rare-earth metal carboryne complexes LRE(C2B10H10)(thf)n [n = 2, RE = Y (1a), Er (1b); n = 1, RE = Y (2); L = 2-(2,5-Me2C4H2N)C6H4NC(Ph)N(2,6-iPr2C6H3)] were synthesized in good yields via either an alkane elimination reaction of rare-earth metal dialkyls LRE(CH2SiMe3)2 with 1 equiv of o-carborane (o-C2B10H12) in THF or a salt metathesis reaction of yttrium dichloride LYCl2(thf)3 with 1 equiv of Li2C2B10H10 in toluene. They could be viewed as a class of three-membered rare-earth metallacyclopropanes. Their molecular structures were confirmed by single-crystal X-ray analyses, supporting the formation of a unique (RE)CC three-membered ring between the rare-earth metal and two cage C atoms of the carboryne moiety. They underwent ring-expansion (mono-insertion) reactions with many unsaturated organic compounds such as aldehyde, ketone, nitrile, carbodiimide, isocyanate, and thioisocyanate to give exclusively five-membered metallacycles, where the ring-strain plays an important role.