Electrostatic Contributions to the Stability of an End-on Cupric Superoxide

Abstract

We recently reported the presence of strong, local electrostatic fields in the secondary coordination sphere of a phosphinimine-decorated CuI complex, [(P3tren)CuI]+ (1). Here, we show that the low-temperature oxygenation of 1 yields a long-lived, three-fold symmetric η1-cupric superoxide complex, [(P3tren)CuII(O2)]+ (2). This latter complex was shown to abstract hydrogen atoms from 2,6-di-tert-butyl-4-methoxy phenol (KIE = 3.0 ± 0.3) and oxidize a cuprous tris(2-pyridylmethyl)amine complex to form a heteroleptic di(cupric)-μ-1,2-peroxide complex (4). The thermal stability of 2 was observed to be uncommonly high for sterically unprotected cupric superoxide complexes in this geometry (t1/2 = 10.4 h at -85 °C). Density functional theory (DFT) calculations implicate a unique electrostatic stabilization of the π*v orbital of the O2 unit, and the thermal stability of 2 is discussed in the context of the CuI/II redox potential of 1, the steric bulk in the complex’s secondary coordination sphere, and intramolecular electrostatic interactions.

Structural distortion by alkali metal cations modulates the redox and electronic properties of Ce3+ imidophosphorane complexes

“…Similar effects of zwitterionic ligands have been reported on Cu redox properties and small molecule activation chemistry. [52][53][54][55] In this imidophosphorane system, optimization of alkali metal binding can be used to tune the potential of anionic metal complexes through the counter cation. This approach could be implemented across the periodic table, and potentially be applied to expand the range of molecular tetravalent lanthanides.…”