Homogeneous CO Hydrogenation: Ligand Effects on the Lewis Acid ...

Low temperature monitoring of the reaction of [1-E 1][OTf] with [HPt][PF 6].
A J-Young tube was charged with 25.8 mg (0.0318 mmol) cation [1-E 1][OTf]. Roughly 0.1 mL
C 6D 5Cl was added, dissolving the cation. The tube was placed in a cold well chilled with liquid
nitrogen, freezing the solution. A small amount of C 6D 5Cl was layered atop the frozen solution as
a buffer, and the contents again were frozen. Roughly 0.3 mL of a C 6D 5Cl solution of 20.4 mg
(0.0318 mmol) [HPt][PF 6] was added to the tube, which was then sealed and the contents frozen
again. The tube was then removed from the box and the contents kept frozen in a dry ice/ acetone
bath. At the NMR spectrometer, the tube was removed from the bath, and warmed until just
thawing, at which point it was vigorously shaken and inserted into the probe (held at 25 °C).
NMR spectra were acquired over ~30 minutes. Initial, spectra showed a mixture of starting
materials and a carbene. Shortly thereafter the starting materials were consumed and a mixture of
the carbene intermediate and the final alkyl product were observed. Over a few minutes at room
temperature the carbene disappears, giving way to alkyl species 10-E 1 as the only observed
product, as monitored by 31 P{ 1 H} NMR. For 2-E 1: 1 H NMR (C 6D 5Cl, 500 MHz -40 °C): δ 0.66
(br), 0.96 (br), 1.32 (br), 1.5-2.1 (br m), 2.32 (br), 7.00 (br), 7.1-7.3 (br m), 7.52 (br), 13.75 (br,
Re-CHO). 31 P{ 1 H} NMR (C 6D 5Cl, 202 MHz, -40 °C): δ 7.4 (s).
S137