Design, synthesis, and characterization of a sterically encumbered dioxo molybdenum (VI) core

Dioxo-MoVI complexes of general formula Tp∗MoO2(p-SC6H4Dn) (6a–6c) (where Tp∗ = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate and Dn = dendritic unit) have been synthesized and characterized by spectroscopy and mass spectrometry. 1H NMR spectra of the metal complexes indicate that the Cs local symmetry about the metal core does not change by the incorporation of dendritic functionality at the thiophenolato ring. Electrochemical data show a ∼20 mV change in the redox potential in the complexes with dendritic ligands suggesting a very small perturbation in the redox orbital, which is also supported by small changes in the electronic spectra. The peak-to peak separation (ΔEp) increases from 125 mV in 6(a) to 240 mV in 6(c), suggesting sluggish electron transfer in molecules with larger dendritic ligands.