A S=3/2 Cr(III) Complex In A Square-Capping NHC Framework

Abstract

Deprotonation of our pentadentate N-Heterocyclic Carbene (NHC) ligand with lithium diisopropylamine in tetrahydrofuran and subsequent salt metathesis with CrCl3THF3 readily forms the complex PhCC4MeCrCl (1), a S=3/2 species in moderate yield. DFT calculations reveal three singly occupied molecular orbitals with π-backbonding character to the square-capping framework, UV-Vis spectroscopy reveals 3 bands ascribed to d-to-d transitions, and cyclic voltammetry reveals an irreversible and quazi-reversible reduction events as well as an irreversible oxidation event. We attempted to exchange the chloride ligand of 1 through salt-metathesis with lithium phenylacetylide without success, the absence of reactivity is rationalized considering our XRD and DFT results.