*2.9. Chromatography*

Concentration was measured with a Trace 1310 gas chromatograph by Thermo Scientific (Dreieich, Germany), equipped with a 1300 flame ionization detector and an Agilent Capillary HP-5 19091 J-433 (0.25 mm × 30 m × 0.25 μm). n-Decane was used as internal standard in all measurements. Temperatures of injector and detector were set to 250 ◦C. Temperature profile started at 90 ◦C, followed by a heating rate of 2 K/min to 100 ◦C, 20 K/min to 130 ◦C, 2 K/min to 138 ◦C and 20 K/min to 160 ◦C.

#### *2.10. X-ray Powder Di*ff*raction (XRPD)*

Solid samples were measured via x-ray powder diffraction (XRPD) to discriminate the solid composition of donor salt and/or product salt. Powder x-ray diffraction data were collected on a Stoe Stadi-P with germanium-monochromatised Cu-Kα-radiation (λ = 1.5418 Å) in horizontal transmission/Debey-Scherrer geometry. The x-rays were detected with a position sensitive detector in the 2Theta range from 5 to 35◦. The 40 kV high voltage and 40 mA current were generated by a Seifert high voltage generator (ID 3003). The equipment was controlled and the raw data were handled with the software STOE WinXPOW (version 2.25, 2009). The position of the 2Theta and ω-circle were adjusted with the (111)-reflex of crystalline silicon (2Theta = 28.44◦). All samples were measured as flat preparation between two layers of poly acetate foil. The sample was spun around its center during the measurement and the ω-circle was also spun with 1/2 2Theta.
