Gold(I) Ethylene and Copper(I) Ethylene Complexes Supported by a Polyhalogenated Triazapentadienyl Ligand

Abstract

A rare gold(I) ethylene complex and the closely related copper(I) ethylene adduct have been isolated using [N{(C3F7)C(2,6-Cl2C6H3)N}2]- as the supporting ligand. [N{(C3F7)C(2,6-Cl2C6H3)N}2]Au(C2H4) (1) is an air-stable solid. It features a U-shaped triazapentadienyl ligand backbone and a three-coordinate, trigonal-planar gold center. The copper(I) adduct [N{(C3F7)C(2,6-Cl2C6H3)N}2]Cu(C2H4) (2) also has a similar structure. The 13C NMR signal corresponding to the ethylene carbons of 1 appears at about 64 ppm upfield from the free ethylene, while the ethylene carbons of 2 show a relatively smaller (39 ppm) upfield shift. [N{(C3F7)C(2,6-Cl2C6H3)N}2]M(C2H4) (M=Cu, Au) mediate carbene-transfer reactions from ethyl diazoacetate to saturated and unsaturated hydrocarbons.

Synthesis and Properties of “Sandwich” Diimine-Coinage Metal Ethylene Complexes

“…Only six complexes appear to be characterized by X-ray crystallog raphy. 3,4d–f,12 Specifically, three fluorinated Tp-Au(ethylene) complexes and one complex supported by a fluorinated triazapentadiene have been reported by Dias. 3,4f,12 Two Au(C 2 H 4 ) 3 cationic complexes were structurally characterized by Dias and Krossing.…”

A study of Cu(I)‐ethylene complexation for olefin–paraffin separation

“…Experimental results and theoretical calculations reveal that bonding strength increases in the order of Ag(I) \ Cu(I) \ Au(I). 7,[12][13][14][15] Gold is better than copper in bond strength, but due to the high cost of gold (and silver), copper remains the most economical choice for a reactive absorption system.…”

“…Given a bidentate ligand, the complex forms a trigonal planar structure. 8,10,11,13,[19][20][21][22][23] Given a tridentate ligand, the complex forms a distorted tetrahedral structure. 22,24,25 Figure 4 below illustrates these two structures, where a, b, and c represent ligand attachment sites.…”

“…19 Most Cu(I)-ethylene complexes span these two extremes of 1 H NMR chemical shifts. 8,10,11,13,20,22,24 The amount of the chemical shift has been hypothesized to increase with increasing basicity (pKa) of the auxiliary ligands, as increasingly basic ligands will donate more electron density to the Cu(I) ion. The metal center sheds this electron density through increased p-backbonding, which will increase the chemical shift of the signal observed.…”

“…Addition of excess ethylene broadens this peak, which supports the existence of a labile interaction. 13 Another common method used to investigate Cu(I)-ethylene complexation is X-ray crystallography. X-ray crystallography should show that complexation increases the alkene bond distance, and indeed, this is often the case.…”