A Systematic Study of the Effects of Complex Structure on Aryl Iodide Oxidative Addition at Bipyridyl‐Ligated Gold(I) Centers

Abstract

Acombined theoretical and experimental approach has been used to study the unusual mechanism of oxidative addition of aryl iodides to [bipyAu(C 2 H 4 )] + complexes.T he modular nature of this system allowed asystematic assessment of the effects of complex structure.C omputational comparisons between cationic gold and the isolobal (neutral) Pd 0 and Pt 0 complexes revealed similar mechanistic features,b ut with oxidative addition being significantly favored for the group 10 metals.F urther differences between Au and Pd were seen in experimental studies:s tudying reaction rates as af unction of electronic and steric properties showed that ligands bearing more electron-poor functionality increase the rate of oxidative addition;i nacomplementary way, electron-rich aryl iodides give faster rates.T his divergence in mechanism compared to Pd suggests that Ar À Xo xidative addition with Au can underpin ab road range of new or complementary transformations.Scheme 1. Oxidative addition at transition metal centers.

A Ruthenium Protic N-Heterocyclic Carbene Complex as a Precatalyst for the Efficient Transfer Hydrogenation of Aryl Ketones

“…1 H NMR (400 MHz, CDCl 3 ): δ = 8.67 (ddd, J = 4.8, 1.7, 0.8 Hz, 1H), 8.40 (dt, J = 8.0, 0.9 Hz, 1H), 8.17 (d, J = 7.8 Hz, 1H), 7.80 (td, J = 7.7, 1.8 Hz, 1H), 7.70 (t, J = 7.7 Hz, 1H), 7.29 (ddd, J = 7.5, 4.8, 1.2 Hz, 1H), 7.17 (d, J = 7.6 Hz, 1H), 2.64 (s, 3H). The spectroscopic data are consistent with the published data …”

“…Compound 1 was synthesized following a modified literature procedure. 58 A sample of 2,2′-bipyridine (6.25 g, 40 mmol) was dissolved in diethyl ether (150 mL) with stirring, and the solution was cooled to 0 °C. Then, methyl lithium in diethyl ether (25 mL, 1.6 M, 40 mmol) was added dropwise via a cannula.…”

“…The spectroscopic data are consistent with the published data. 58 Synthesis of 6-(Bromomethyl)-2,2'-bipyridine (2). The compound was synthesized following a modified literature procedure.…”

“…The ligand synthesis is performed over three steps using commercially available reagents. Direct alkylation of 2,2′bipyridine with methyl lithium followed by oxidative work-up affords 6-methyl-2,2′-bipyridine 1, 58 which is then brominated with N-bromosuccinimide to afford 6-(bromomethyl)-2,2′-bipyridine 2. 59 Treatment of 2 with 4,5-diphenylimidazole furnishes the target bipyridine-tethered imidazole ligand 3.…”

Ligand-enabled oxidation of gold(i) complexes with o-quinones

“…To promote the oxidation of Au( i ) and stabilize the ensuing Au( iii ) species, we then turned to o -carboranyl diphosphines. We wondered if the bending strategy we initially developed to trigger oxidative addition to gold 4 b ,5 a could also work here. Gratifyingly, following halogen abstraction with AgNTf 2 or AgOTf, the tetrachloro o -benzoquinone ( o -chloranil) was found to rapidly and cleanly react with the o -carboranyl diphosphine complex 1 to give 2a (Scheme 1).…”