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

IV. Hydride Reductions of Bis(phosphine) Cations.
A. Reductions of trans-[(Ph 2PCH 2B(C 8H 14)) 2Re(<strong>CO</strong>) 4][B(C 6F 5) 4] ([1-M 2][B(C 6F 5) 4]).
NMR-scale Reaction of [1-M 2][B(C 6F 5) 4] with 1 equiv [HPt][PF 6].
To a stirring ~0.6 mL C 6D 5Cl solution of 31.3 mg (0.0194 mmol) [1-M 2][B(C 6F 5) 4] was added
12.4 mg (0.0194 mmol) [HPt][PF 6]. Monitoring by NMR spectroscopy showed a slow reaction,
with ~50% conversion after 12 hours, ~70% conversion after 24 hours, and ~90% conversion
after 6 days.
Reaction of [1-M 2][B(C 6F 5) 4] with 1 equiv [HPt][PF 6] in the presence of [Na][BF 4].
A 20 mL scintillation vial was charged with 103.0 mg (0.0637 mmol) [1-M 2][B(C 6F 5) 4], 35.0
(0.319 mmol, 5 equiv) NaBF 4, and 2 mL C 6H 5Cl. With stirring, 49.0 mg (0.0764, 1.2 mmol)
[HPt][PF 6] was added slowly as a solid. The mixture turned yellow and developed precipitates
over a few minutes, and was stirred overnight. The reaction mixture was filtered, and the solvent
removed from the filtrate under vacuum. The solids were extracted with C 6H 6, filtered, and the
solvents removed from the filtrate to afford 59 mg (99%) 2-M 2 as a pale yellow powder in ~95%
purity ([HPt] + was the other observed species, along with small amounts of residual C 6H 5Cl). 1 H
NMR (C 6D 6, 300 MHz): δ 1.49 (br, Ph 2PCH 2B(C 8H 14)), 1.88 (br, Ph 2PCH 2B(C 8H 14)), 7.16
(Ph 2PCH 2B(C 8H 14), 12H), 7.53 (br, Ph 2PCH 2B(C 8H 14), 8H), 13.96 (t, J PH = 6.0 Hz, Re-CHO, 1H).
31 P{ 1 H} NMR (C6D 6, 121 MHz): δ -2 (br, 1P), 6.0 (br, 1P). IR (heptane): ν <strong>CO</strong> 1999 (s), 1950 (s),
1938 (s) cm -1 .
S56