When SF5 outplays CF3: effects of pentafluorosulfanyl decorated scorpionates on copper

Polyfluorinated, electron-withdrawing, and sterically demanding supporting ligands are of significant value in chemistry. Here we report the assembly and use of a bis(pyrazolyl)borate, [Ph2B(3-(SF5)Pz)2]− that combines all such features, and involves underutilized pentafluorosulfanyl substituents. The ethylene and carbonyl chemistry of copper(i) supported by [Ph2B(3-(SF5)Pz)2]−, a comparison to the trifluoromethylated counterparts involving [Ph2B(3-(CF3)Pz)2]−, as well as copper catalyzed cyclopropanation of styrene with ethyl diazoacetate and CF3CHN2 are presented. The results from cyclopropanation show that SF5 groups dramatically improved the yields and stereoselectivity compared to the CF3.

Then ethylene (~ 20 g, 0.714 mol, 1.2 equiv) and SF5Cl (95 g, 0.585 mol, 1.0 equiv; obtained according to the previous report 3 ) were condensed to the reactor. Et3B (20 mL, 1.0 M in hexanes) was added at -90 °C, and the mixture was allowed to slowly warm up by passing a weak current of ethylene through the solution. When the temperature reached -50 °C, an additional portion of Et3B (10 mL, 1.0 M in hexanes) was added, and the current of ethylene was stopped. The mixture was allowed to warm to room temperature. The solution was washed with cold water (with ice), dried, and distilled at atmospheric pressure using a rectification column. The product was obtained with impurities of methylene chloride and 1,2-dichloroethane. Yield: 130 g of crude, ~ 50% purity, 58%, colorless oil. 1

Pentafluoro(vinyl)-λ 6 -sulfane (4):
A 500 mL round bottom flask was charged with a solution of 40% KOH (100 mL) and a solution of crude (2-chloroethyl)pentafluoro-λ 6 -sulfane (40 g) in 60 mL of isopropanol. A distillation column was attached to the flask, and the mixture was heated up to boiling (~ 60 °C oil bath temperature). As the product was distilled off, the temperature was increased to 100 °C. The distillate can be used for the next step, despite the possible impurity of methylene.
If water gets into the product during distillation, additional washing with water and drying will be needed. Yield: 25 g of crude, ~ 70% purity, 99%, colorless oil. 1
The filtrate was concentrated under reduced pressure and dissolved in a 1M NaOH solution (150 mL), then the mixture was acidified with 3M HCl. The product was extracted with CHCl3 (3 × 100 mL), concentrated, recrystallized from hexane and dried NMR was used to calculate the yield of 2-diazo-l,l,l-trifluoroethane reactions (CF3 peak)).

Computational studies
All calculations were carried out by using relativistic DFT methods employing the ADF code 11      b Percentage contribution to the total orbital interactions ΔEorb.
c Polulation in a.u. for theylene 1 and 2* orbitals in the resulting complex. in the formation of ethylene-copper complexes. Charge flow from red to blue.