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

The synthesis and characterization of trinuclear Ge^II and Sn^II chlorides and a trialuminum complex supported by a trinucleating tris­(β-diketiminate) cyclophane ligand (L^3–) 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 Ge^II and Sn^II 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.