Molecular and electronic structure of MM quadruply bonded complexes containing O2CC6H4N(Ph)2 supporting ligands

The complexes trans-M-2((TPB)-P-i)(2)(O2CC6H4-4-NPh2)(2) where M = Mo (I), and M = W (II) were prepared from the reaction between M-2((TPB)-P-i)(4) and the carboxylic acid Ph2N-4-C6H4CO2H (similar to 2 equiv.) in toluene ((TPB)-P-i = 2,4,6-triisopropylbenzoate). The compounds were isolated as microcrystalline powders that are yellow, I or purple II, and are air-sensitive. Compound I was characterized by single-crystal X-ray crystallography and shown to have a centrosymmetric structure and a planar central C6H4-CO2M2O2C-C6H4 unit. Calculations indicate that the HOMO is principally M-2 delta with mixing of the filled pi-orbitals of the N,N-diphenyl-4-aminobenzoate. Oxidation of I and II yield cationic species that have been characterized by EPR and UV-Vis-NIR spectroscopy. The radical cations show EPR spectra characteristic of M-2(5+) centers having the MM configuration sigma(2)pi(4)delta(1) and compound I+ shows a low energy NIR transition assignable to a ligand to metal charge transfer transition. The homoleptic compound Mo-2(O2CC6H4-4-N-Ph-2)(4), III, was prepared from the reaction between Mo(CO)(6) and Ph2N-4-C6H4CO2H in refluxing ortho-dichlorobenzene and is shown to exhibit similar spectroscopic features to those of I. (C) 2013 Elsevier Ltd. All rights reserved.