Synthesis of Trinuclear Tin(II), Germanium(II), and Aluminum(III) Cyclophane Complexes

The synthesis and characterization of trinuclear GeII and SnII chlorides and a trialuminum complex supported by a trinucleating tris(β-diketiminate) cyclophane ligand (L3–) are reported. The in situ deprotonation of H3L with benzylpotassium and subsequent reaction with GeCl2·dioxane or SnCl2 afforded (GeCl)3L (1) and (SnCl)3L (2) in 42 and 60% yields, respectively. Each GeII and SnII atom is three-coordinate and exhibit pseudotrigonal pyramidal geometry as anticipated for three-coordinate divalent group 14 cations. UV/visible spectra collected on THF solutions of 1 and 2 display a bathochromic shift in the absorption from 1 to 2 (from 361 to 375 nm). Addition of AlMe3 to toluene solutions of H3L resulted in the formation of (AlMe2)2AlMe3HL (3), which possesses two NCCCN chelated AlMe2 moieties. The third β-diketimine arm remains protonated and adopts an atypical trans conformation with an AlMe3 coordinated to the solvent exposed imine N atom.