Electronic Structure of Molybdenum Imido Complexes

The electronic structures of Molybdenum complexes of the form Mo(NAr)(sap)(OCH3)2 (NAr=2,4,6-trimethylphenylimido), (4), Mo(NAr)(1,2-SC6H4NH)(sap) (5), Mo(NAr)(1,2-OC6H4O)(sap) (6), Mo(NAr)(naphthalene-2,3-diolate)(sap) (7), Mo(NAr)(1,2-SC6H4S)(sap) (8), and Mo(NAr)(1,2-HNC6H4NH)(sap) (9) were optimized using Gaussian 09 Suite of programs with a B3LYP/LANL2DZ and a B3LYP/DGDZVP level of theory. The reaction between the starting material 4 and catechol was optimized using a B3LYP/6-31+G(d) level of theory. Gen NBO 5.0 was used to determine bonding interactions within the complexes. The focus of this research project is to investigate the bonding interactions that are causing complex 8 to bind in an equatorial molecular arrangement namely because the remaining complexes, complexes 5, 6, 7, and 9 prefer to bind axial molecular arrangements as opposed to equatorial. We found that the energy difference between complex 8 in an equatorial arrangement and complex 8 in an axial arrangement was a total of 0.83 kcal/mol.  Complexes 5, 6, 8, 9 have longer bond lengths on the bottom half of the aromatic bidentate ligand. In addition, the equatorial arrangement in 8 can be attributed to weak hydrogen bonding interactions between sulfur and hydrogen as 4 interacts with 1,2-benzenedithiol.