Bimetallic mixed-metal complexes of the salen(^tBu) ligands

The Salen(^tBu) ligands, Salen(^tBu), (N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine) and Salpen(^tBu), (N,N′-propylenebis(3,5-di-tert-butylsalicylideneimine) can be combined with GaEt₃ to prepare the 'open' monometallic compounds, Salen(^tBu)H(GaEt₂) (1) and Salpen(^tBu)(GaEt₂) (2). These, in turn, can be converted to the bimetallic derivatives, Salen(^tBu)(GaEt₂)₂ (3) and Salpen(^tBu)(GaEt₂)₂ (4) by addition of GaEt₃. Alternatively, 3 and 4 can be made by the addition of two moles of GaEt₃ to the appropriate ligand. This was the method used to prepare Salben(^tBu)(GaEt₂)₂ (5) (Salben(^tBu) = N,N′-butylenebis(3,5-di-tert-butylsalicylideneimine) and Salhen(^tBu)(GaEt₂)₀ (6) [Salhen(^tBu) = N,N′-hexylenebis(3,5-di-tert-butylsalicylideneimine]. Compounds 1 and 2 can be utilized to form the unique mixed-metal derivatives L(GaEt₂) (MR₂) (where L = Salen(^tBu), M : R = Al, Me (7) ; Al, Et (9) ; and L = Salpen(^tBu), M : R = Al, Me (8) ; Al, Et (10). At ambient temperatures in non-polar solvents, 7-12 do not undergo exchange of either the alkyl or MR₂ groups. All of the compounds were characterized by Mp, analyses, ¹H NMR, IR and, in the case of 1 and 3-6, by X-ray crystallography.