Sulfur-Containing Analogues of the Reactive [CuOH]²⁺ Core

Abstract

With the aim of drawing comparisons to the highly reactive complex LCuOH (L = bis­(2,6-diisopropylphenyl­carboxamido)­pyridine), the complexes [Bu4N]­[LCuSR] (R = H or Ph) were prepared, characterized by spectroscopy and X-ray crystallography, and oxidized at low temperature to generate the species assigned as LCuSR on the basis of spectroscopy and theory. Consistent with the smaller electronegativity of S versus O, redox potentials for the LCuSR–/0 couples were ∼50 mV lower than for LCuOH–/0, and the rates of the proton-coupled electron transfer reactions of LCuSR with anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine at −80 °C were significantly slower (by more than 100 times) than the same reaction of LCuOH. Density functional theory (DFT) and time-dependent DFT calculations on LCuZ (Z = OH, SH, SPh) revealed subtle differences in structural and UV–visible parameters. Further comparison to complexes with Z = F, Cl, and Br using complete active space (CAS) self-consistent field and localized orbital CAS configuration interaction calculations along with a valence-bond-like interpretation of the wave functions showed differences with previously reported results (J. Am. Chem. Soc.20201428514), and argue for a consistent electronic structure across the entire series of complexes, rather than a change in the nature of the ligand field arrangement for Z = F.

Ab Initio Methods in First‐Row Transition Metal Chemistry

“…Very large active spaces making use of DMRG-CASSCF, [74,75] FCIQMC-CASSCF, [76] or selected-CI-CASSCF [77,78] can partly mitigate this problem, [79] but the calculations can be computationally expensive. Nevertheless, CASSCF can provide important information on the character of a complex, [80][81][82][83][84][85][86][87][88] such as the oxidation state of the metal centers or the covalency of the metal-ligand bonds. By analyzing the natural orbital occupation numbers (NOONs) or the weights of leading CSFs, one can determine whether static correlation effects are important.…”

A DMRG/CASPT2 Investigation of Metallocorroles: Quantifying Ligand Noninnocence in Archetypal 3d and 4d Element Derivatives

“…In such a case, the radical character of the corrole is estimated to be half of the total radical character of this pair of orbitals. This approach gives results identical to those obtained in other studies, ,, which employed the equation f = 1 – 0.5­( n + – n – ), where n + and n – are the NOONs of the bonding and antibonding MOs, respectively ( n + + n – ≈ 2).…”

“…As in previous work, [40][41][42]45,50,53,55,105 the GS wave functions can also be characterized in terms of localized molecular orbitals, referred to later as the "valence bond" wave function. To simplify the calculations and interpretations, we used minimal active spaces consisting of singly occupied metal d orbitals (see also Table 1), one corrole(π) orbital, and axial ligand (Cl, Ph, NO) orbitals that mix substantially with the metal d orbitals.…”

“…Values within parentheses were calculated with dichloromethane as the solvent. c See ref 41. to those obtained in other studies,41,104,105 which employed the equation f = 1 − 0.5(n + − n − ), where n + and n − are the NOONs of the bonding and antibonding MOs, respectively (n + + n − ≈ 2).…”

Actinide Arene-Metalates: 2. A Neutral Uranium Bis(Anthracenide) Sandwich Complex and Elucidation of its Electronic Structure

“…These differences in 𝜋 and 𝜋* occupation can be expressed as a change in the radical character of the bond. 23,24 The CASPT2 calculation on the DFT triplet geometry has a bond with only 5% radical character due to partially occupying 𝜋*, while the CASSCF result on the quintet structure has 24.5% radical character. Nevertheless, the CASSCF total spin density for both geometries is uranium-centred and consistent with a 5f 2 configuration (Figure S35).…”