The First Structurally Characterized Salen-Indium Complexes

In this manuscript are reported the synthesis and characterization of the first complexes of indium incorporating the acen and salen classes of ligands. This includes the compounds of formula LInMe (where L = acen (1) (N,N'-ethylenebis(2-hydroxy-α-methylbenzylidenimine)), salen (2) (N,N'-ethylenebis(2-hydroxybenzylideneimine)), salophen (3) (N,N'-(1,2-phenylene)bis(2-hydroxybenzylidenimine)), salomphen (4) (N,N'-(4,5-dimethyl-1,2-phenylene)bis(2-hydroxybenzylidenimine)). Attempts to prepare the derivatives, [In(R)(salpen)] (salpen = N,N'-propylenebis(2-hydroxybenzylidenimine), R = Me, Et) led to the formation of the bimetallic complexes, [(InMe₂)₂(salpen)] (5) and [In(Et₂)₂(salpen)] (6). Dissolution of 5 and 6 in MeOH causes the formation of three unusual products. They are the ligand bridged compounds [{In(μ-OMe)(μ-salpen)}₂] (7), [(In(salpen)}₂(μ-salpen)] (8) and the methoxy-only bridged complex, [{In(salpen)(μ-OMe)}₂] (9). Compounds 7-9 are the first structurally characterized indium-salen complexes. For purposes of comparison, the structure of [{Al(salen)(μ-OMe)}₂] (10) will also be described.