Copper(I) Ethylene Adducts and Aziridination Catalysts Based on Fluorinated Tris(pyrazolyl)borates [HB(3-(CF₃),5-(R)Pz)₃]^- (where R = CF₃, C₆H₅, H; Pz = pyrazolyl)

Abstract

The ethylene adducts of copper(I) tris(pyrazolyl)borates, [HB(3,5-(CF 3 ) 2 Pz) 3 ]Cu(C 2 H 4 ), ),5-(C 6 H 5 )Pz) 3 ]Cu(C 2 H 4 ), and [HB(3-(CF 3 )Pz) 3 ]Cu(C 2 H 4 ), have been prepared by reacting the corresponding sodium derivative with CF 3 SO 3 Cu in the presence of ethylene. They were characterized both in the solid state and in solution using 1 H, 13 C, and 19 F NMR and IR spectroscopy and by X-ray crystallography. Solid samples of these nonionic copper complexes featuring fluorinated tris(pyrazolyl)borate ligands display notably high stability toward air oxidation and ethylene loss. The 1 H NMR chemical shifts of the copper(I)-bonded ethylene protons appear in the 4.8-5.2 ppm region. The 13 C signal of copper-coordinated ethylene shows an upfield shift of about 35 ppm, whereas the 1 J C-H shows a minor change (an increase of about 2-5 Hz) compared to the values for free ethylene. X-ray structural data show the presence of pseudo-tetrahedral copper ions and η 2 -bonded ethylene units and relatively unperturbed ethylene C-C distances. The copper adducts [HB(3,5-(CF 3 ) 2 Pz) 3 ]Cu-(C 2 H 4 ) and [HB(3-(CF 3 ),5-(C 6 H 5 )Pz) 3 ]Cu(C 2 H 4 ) are competent aziridination catalysts, readily converting a variety of olefins into the corresponding N-tosyl aziridines with N-tosyl phenyliodinane.

Structural Diversity of Copper(I)–N‐Heterocyclic Carbene Complexes; Ligand Tuning Facilitates Isolation of the First Structurally Characterised Copper(I)–NHC Containing a Copper(I)–Alkene Interaction

“…[21,33] The structure is somewhat unexpected, especially given that elemental analysis gives a ratio of 1:1 NHC:CuBr. Due to the labile nature of copper(I)-NHCs, it is possible that transmetallation occurs during crystallisation giving 1 mole equivalent of the Cu(NHC) 2 Br and 1 mole equivalent of CuBr. The trigonal geometry is surprising, especially considering the steric bulk of the mesityl wingtip groups.…”

“…With this in mind, it is unsurprising then that many of the structurally characterised copper(I)-alkene complexes reported thus far contain chelating N-donor ligands such as tris(pyrazolyl)borate. [2,39] The exact role of the pyridyl in enabling alkene coordination to the metal centre in this case is unclear however; it may be altering the properties of the copper(I) centre directly by coordination to it, or it may be indirectly affecting the copper(I) centre by modifying the donor ability of the NHC (decreasing the energy of the LUMO). Complex 2g crystallised as a monomer, with the coordination environment around the copper(I) centre best described as distorted T-shaped.…”

“…[2] This finding is counterintuitive when considering the different levels of back-bonding in the complexes. Recently, York and co-workers published a DFT study on the impact of ancillary ligand basicity on copper(I)-ethylene binding interactions.…”

“…[1][2][3][4][5] Furthermore, in nature, it is believed that the formation of a copper(I)-ethylene adduct in the ETR 1 plant protein is a key step in the regulation of several aspects of the plant life cycle. [6] As the bonding is relatively weak, many systems take advantage of the reversible binding nature of copper(I)-alkenes.…”

Bright Phosphorescence of a Trinuclear Copper(I) Complex: Luminescence Thermochromism, Solvatochromism, and “Concentration Luminochromism”

“…4,6 Fluorinated ligands also endow other beneficial properties such as improved thermal and oxidative stability, and reduced concentration quenching of luminescence to metal adducts. [6][7][8] Such ligands also enable the isolation of exceedingly rare molecules such as [HB(3,5-(CF 3 ) 2 Pz) 3 ]MCO (where M ) Ag, Au). 9 In this paper, we describe the photophysical properties of the trinuclear copper(I) complex {[3,5-(CF 3 ) 2 Pz]Cu} 3 , henceforth referred to as Cu 3 , which exhibits multicolor bright phosphorescent emissions that are sensitive to temperature, solvent, and concentration.…”