Calcium Complexes of Noninnocent α-Diimine Ligands

A series of calcium compounds with α-diimine ligands, [L−Ca-(μ2-Cl)(THF)2]2 (1, L = LiPr; 2, L = LMes), [(LiPr)2−2CaK2(THF)]n (3), [(LMes)2−Na(THF)2]2Ca (4), and [Ca(LiPr)2−Li(THF)(μ3-Cl)Li(THF)2(μ3-Cl)]2 (5), where LiPr = [(2,6-iPr2C6H3)NC(Me)]2 and LMes = [(2,4,6-Me3C6H2)NC(Me)]2, have been synthesized by the reaction of the lithium, sodium, or potassium salts of the reduced ligands (L− or L2−) with calcium chloride. Single-crystal X-ray diffraction analyses reveal that compounds 1 and 2 are isostructural dinuclear compounds bridged by chloride ions, compound 3 forms a left-handed 21 helical structure, while 4 features a metallocene-like structure, and 5 forms a laddered aggregate. The ligand exists as the doubly reduced dianionic form in 3−5 and appears as the radical anion in compounds 1 and 2. The coordination modes of the alkali metal and calcium ions in these complexes are discussed.