Inorganic Chemistry, Vol.51, No.3, 1480-1488, 2012
A Sterically Demanding Iminopyridine Ligand Affords Redox-Active Complexes of Aluminum(III) and Gallium(III)
The combination of an electrophilic metal center with a redox active ligand set has the potential to provide reactivity unique from transition metal redox chemistry. In this report, substituted iminopyridine complexes containing monoanionic and dianionic (IPMes)-I-Me ligands have been characterized structurally and electronically. Green ((IPMes-)-I-Me)AlCl2 (1), ((IPMes-)-I-Me)AlMe2 (2), and ((IPMes-)-I-Me)GaCl2 (5) have a doublet spin state which results from the anion radical form of (IPMes)-I-Me. Purple ((IPMes2-)-I-Me)AlCl(OEt2) (3), ((IPMes2-)-I-Me)AlMe(OEt2) (4), and ((IPMes2-)-I-Me)GaCl(OEt2) (6) are each diamagnetic. We have also investigated the solvent dependence of the decomposition of the (IPMes)-I-Me anion radical. Complexes 1 and 2 can be obtained from benzene and hexanes whereas the use of ether solvents results in the formation of undesirable ((IPMes-)-I-CH2)AlCl2 (1a) and ((IPMes-)-I-CH2)AlCl2 (2a) formed by loss of a hydrogen atom from the (IPMes-)-I-Me ligand. Electrochemical measurements indicate that 1, 2, and 5 are redox active.