The square-planar preference of Pd(II) is clearly evident in -di- tert -butyl-2, 11- dia...

The square-planar preference of Pd(II) is clearly evident in -di- tert -butyl-2, 11- diaza[3.3] (2,6)pyridinophane) (J.R. Khusnutdinova, N. P. Rath, L. M. Mirica, J. Am. Chem. Soc. , 2010 , 132 , 7303). Although N4 is a potentially tetradentate ligand, two of the nitrogen atoms point away from the Pd center, yielding a square- lanar coordination geometry. This situation changes upon oxidation to afford a Pd(III) complex with a tetragonal geometry. Sketch the structure of the (N₄)Pd(CH₃)Cl oxidation product, and label the bond lengths with their distances to provide the argument for the Jahn–Teller distortion. Which metal d orbital is believed to contribute the most to the HOMO of the oxidized complex? Without changing any of the donor atoms, how might the ligand be subtly modified to cause this HOMO to increase in energy? Sketch the modified ligand you would introduce and explain the reasoning for your selection in terms of why it might raise the HOMO energy.