Mono-, Bi-, and Trinuclear Cu^II-Cl Containing Products Based on the Tris(2-pyridylmethyl)amine Chelate Derived from Copper(I) Complex Dechlorination Reactions of Chloroform

Abstract

The ligand TMPA (tris(2-pyridylmethyl)amine) and its copper complexes have played a prominent role in recent (bio)inorganic chemistry studies; the copper(I) complex [CuI(TMPA)(CH3CN)]+ possesses an extensive dioxygen reactivity, and it is also known to effect the reductive dechlorination of substrates such as dichloromethane and benzyl and allyl chlorides. In this report, we describe a set of new analogues of TMPA, ligand 6TMPAOH, binucleating Iso-DO, and trinucleating SYMM. Copper(I) complexes with these ligands and a previously described binucleating ligand DO react with chloroform, resulting in reductive dechlorination and production of [CuIIx(L)Clx]x+ (x = 1, 2, or 3). X-ray crystal structures of [CuII(6TMPAOH)Cl]PF6, [CuII2(Iso-DO)Cl2](PF6)2, [CuII2(DO)Cl2](PF6)2, and [Cu3(SYMM)Cl3](PF6)3 are presented, and the compounds are also characterized by UV-vis and EPR spectroscopies as well as cyclic voltammetry. The steric influence of a pyridyl 6-substituent (in the complexes with 6TMPAOH, Iso-DO, and SYMM) on the solid state and solution structures and redox potentials are compared and contrasted to those chlorocopper(II) complexes with a pyridyl 5'-substituent (in [CuII2(DO)Cl2](PF6)2 and in [CuII(TMPA)Cl]+). Some insights into the reductive dechlorination process have been obtained by using 2H NMR spectroscopy in following the reaction of [Cu2(Iso-DO)(CH3CN)2](PF6)2 with CDCl3, in the presence or absence of a radical trap, 2,4-di-tert-butylphenol.

Synthesis, structure and dioxygen reactivity of a bis(µ-iodo)dicopper(i) complex supported by the [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine ligand

“…Complex 4 was produced by the reductive dechlorination of chloroform by copper(I) followed by the formation of a chloro-copper(II) species with a Cu-Cl covalent bond. This process is analogous to the dehalogenation reactions mediated by copper(I) complexes described by Lucchese et al 22 except that in our case the redox process was much slower and took place in the presence of dioxygen. Mass-spectrometry data together with low temperature EPR (4 K) have enabled us to deduce that multicopper species exist in the oxygenated solution of 1, and we have proposed an equilibrium between complex 2 and its dimer, namely, tetranuclear (peroxocopper(II)) 2 complex 2 .…”

A rationally designed metal-binding helical peptoid for selective recognition processes

“…EPR measurements of the solid ( Helix HQT i + 3 )Cu complex indicated the presence of Cu 2+ (Fig. 2) and the Hamiltonian parameters obtained from the simulated spectra were g ∥ = 2.23, g ⊥ = 2.070 and A ∥ = 175 G, which are consistent with a square pyramidal coordination geometry 14…”

Metal-binding and redox properties of substituted linear and cyclic ATCUN motifs

“…The EPR parameters obtained for all complexes follow the trend g ∥ > g ⊥ > g e suggesting that all Cu(II)-peptide complexes have a d x 2 – y 2 ground state. This is a characteristic feature of square planar (D 4h ), square pyramidal (C 4v ), or axially elongated tetragonal octahedral geometries with D 4h symmetry [63-65]. Thus, the d–d transitions observed for these complexes is due to the Cu(II) d x 2 – y 2 → d z 2 ransition.…”