Abstract: 

The utilization of uncommon ligands for the stabilization of rare-earth metal complexes in unusual oxidation states (rare-earth metal = Y, Sc, and the lanthanides) has been under-explored.  Discussed here are the syntheses and spectroscopic and crystallographic characterization of complexes of these ligands and an evaluation of their value in stabilizing unusual oxidation states. Reduction chemistry of the lanthanides is explored with the hexa-iso-propyl-terphenylthiolate (SAr^iPr6)^1–, di(mesityl)boroxide (OBMes₂)^1–, di-tert-butylmethylsilanide (Si^tBu₂Me)^1–, and tris(2-oxo-1-tert-butylimidazolyl)hydroborato (TpO^tBu)^1– ligands. The synthesis of many lanthanide coordination complexes are reported, including a La^II(SAr^iPr6)₂ complex which exhibits a very small hyperfine coupling of 67.3 MHz, an Sm^II₄(OBMes₂)₄(μ₄-O) cluster with an encapsulated O^2– ion, the heteroleptic Ce^IV complex Ce(OBMes₂)₂(N(TMS)₂) the first crystallographically characterized coordination complex with three Y–Si bonds, and a homoleptic Yb(II) complex Yb(TpO^tBu)₂.