A series of noninnocent vanadium(V) catechol complexes were investigated by 51V solid-state magic angle spinning NMR spectroscopy to explore the electronic environments of such compounds. Our findings demonstrate the sensitivity of the anisotropic NMR parameters to both the variations in the ancillary ligand and the catecholate environment in the vicinity of vanadium. Different 51V NMR observables such as quadrupolar and chemical shift anisotropies are shown to be associated with the size of the HOMO-LUMO gap in these complexes and hence provide insights on the interaction between vanadium and ligand. Substituting the catechol ligand with electron donating groups results in an increase in the HOMO-LUMO gap and can be directly followed by an upfield isotropic shift for the vanadium catechol complex. In contrast, substitution of the catechol ligand with electron withdrawing groups results in a decrease in the HOMO-LUMO gap and can directly be followed by a downfield shift for the complex. We find a linear correlation of 51V NMR isotropic solution and solid-state chemical shifts of complexes containing noninnocent ligands. Protonation of the catechol ligand as in [VO(gsal)(HCat)] changes the redox non-innocent complex to a redox innocent and we demonstrated the changes in electronic properties in this compound by solid-state 51V NMR technique. Modification of the ancillary ligand from H2shed to Hensal does not impact the observed trend between complexes ranging from catechols with electron rich to electron poor substituents. However, the ancillary ligand affects quantitatively the independent parameters describing the EFG and CSA tensors and suggests that these two series of compounds differ by how readily they undergo electron transfer reactions

Application of solid state <sup>51</sup>V NMR spectroscopy to characterize compounds with electronically ambiguous structures

244th National Meeting (2012)

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Application of solid state 51V NMR spectroscopy to characterize compounds with electronically ambiguous structures

Application of solid state ⁵¹V NMR spectroscopy to characterize compounds with electronically ambiguous structures