Syntheses and molecular structures of 18/16-electron half-sandwich iridium(III) complexes with chelating anilido-imine ligands

A 18-electron complex Cp∗IrCl[o-C6H4N(C6H3-Me-p) (CHdouble bond; length as m-dashNC6H3-Me-p)] (Cp∗ = η5-pentamethylcyclopentadienyl) (1a) was obtained by the reaction of the lithium salt of o-C6H4N (C6H3-Me-p)(CHdouble bond; length as m-dashNHC6H3-Me-p) (L1) with [Cp∗IrCl(μ-Cl)]2 in toluene. However, when bulkier ligands (L2 = o-C6H4N(C6H3-Me-p)(CHdouble bond; length as m-dashNHC6H3-i-Me2-2,6), L3 = o-C6H4N(C6H3-Me-p) (CHdouble bond; length as m-dashNHC6H3-i-Pr2-2,6)) were employed in the same reaction, two 16-electron complexes {Cp∗Ir[o-C6H4N(C6H3-Me-p)(CHdouble bond; length as m-dashNC6H3-i-Me2-2,6)]}+Cl− (2b) and {Cp∗Ir[o-C6H4N(C6H3-Me-p)(CHdouble bond; length as m-dashNC6H3-i-Pr2-2,6)]}+Cl− (3b) were formed. A 16-electron complex {Cp∗Ir [o-C6H4N(C6H3-Me-p) (CHdouble bond; length as m-dashNC6H3-Me-p)]}+SO3 CF−3 (1b) bearing L1 could be achieved by the reaction of 1a with AgSO3CF3 in CH3CN solution. The molecular structures of 1a and 2b were determined by X-ray crystallography. Theoretical calculations of all the 18/16-electron species were performed to study their bonding characters and electronic properties. Electron donating effect of Cp∗ and steric effect of anilido-imine ligand were considered as major factors in the formation of coordinative unsaturated complexes 1b, 2b, 3b.