Expanding the Series of [RE2Ca(OQ)8] Structures: New Heterobimetallic Rare Earth/Alkaline Earth 8-Quinolinolate Complexes

A series of heterobimetallic complexes [RE₂Ca(OQ)₈]·nHOQ(RE = Sm, Gd, Tb, Ho, Tm, Yb, Lu, Y, Sc) and the isostructural [Gd₂Mg(OQ)₈] were synthesised and structurally characterised. They were mainly obtained after direct reactions of the elemental rare earth metals with calcium metal in the presence of 8-hydroxyquinoline (HOQ) and a 1, 3, 5-tri-tert-butyl-benzene (tBuB) flux, and some complexes were synthesised by pseudo solid-state rearrangement reactions between powdered RE(OQ)₃ and AE(OQ)₂ (AE = Mg, Ca) in a 1, 2, 4, 5-tetramethylbenzene (TMB) flux, at elevated temperatures. The linear trinuclear [RE₂Ca(OQ)₈] moieties show a six-coordinate central calcium atom flanked by two eight-coordinate rare earth atoms surrounded by six chelating-bridging OQ and two terminal chelating OQ ligands. The structurally novel [Sc₂Ca(OQ)₈] has a bent Sc-Ca-Sc backbone and exhibits an eight-coordinate central calcium and two seven-coordinate scandium ions.