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

Reaction of [1-M 1][BAr F
4] with [HPt][BAr F
4]. Reaction of 2-M 1 with pyridine.
A small vial was charged with 38.0 mg (0.0254 mmol) [1-M 1][BAr F
4] and ~0.6 mL C 6D 5Cl. With
stirring, 34.5 mg (0.0254 mmol) [HPt][BAr F
4] was added as a solid, and the mixture was
transferred to a J-Young NMR tube and monitored by NMR spectroscopy. After about 30
minutes, only a small resonance for 2-M 1 was observed. The reaction slowly proceeded over ~24
hours, eventually consuming all [HPt] + and affording spectra matching previous syntheses of 2-
M 1 (using OTf/PF 6 salts).
To the tube containing 2-M 1 was added 4 µL pyridine (0.0503 mmol, 2 equiv), and the
tube was sealed and shaken to mix. NMR spectroscopy revealed consumption of the carbene
with formation of a new bridging alkyl species. Multinuclear NMR spectroscopy was very
similar to analytically characterized 10-E 1 (see below), confirming the analogous structure 10-
M 1-py. For 10-M 1-py: 1 H NMR (C 6D 6, 300 MHz): δ 0.92 (br, 2H, Ph 2PCH 2B(C 8H 14)), 1.17 (br,
4H, Ph 2PCH 2B(C 8H 14)), 1.71 (br m, 6H, Ph 2PCH 2B(C 8H 14)), 1.81 (d, J PH = 13.0 Hz, 2H
Ph 2PCH 2B(C 8H 14)), 1.9-2.2 (br m, 12H, Ph 2PCH 2B(C 8H 14)), 2.32 (d, J PH = 11.5 Hz, 2H,
Ph 2PCH 2B(C 8H 14)), 2.39 (br, 4H, Ph 2PCH 2B(C 8H 14)), 5.05 (d, J PC = 5.7 Hz, 2H, Re-CH 2O-), 6.22
(br, 2H, pyridine), 6.55 (br, 1H, pyridine), 6.9-7.0 (m, 12H, Ph), 7.31 (m, 4H, Ph), 7.48 (m, 4H,
Ph), 7.72 (br, 2H, pyridine). 31 P{ 1 H} NMR (C 6D 6, 121 MHz): δ -4.4 (1P), 2.4 (1P). 13 C{ 1 H}
NMR (C 6D 6, 126 MHz): 15.08 (d, J PC = 11.8 Hz, Ph 2PCH 2B(C 8H 14)), 24.41 (Ph 2PCH 2B(C 8H 14)),
25.57 (Ph 2PCH 2B(C 8H 14)), 26.22 (br, Ph 2PCH 2B(C 8H 14)) 27.18 (d, J PC = 10.6 Hz,
Ph 2PCH 2B(C 8H 14)), 30.45 (Ph 2PCH 2B(C 8H 14)), 32.01 (Ph 2PCH 2B(C 8H 14)), 32.85
(Ph 2PCH 2B(C 8H 14)), 33.16 (Ph 2PCH 2B(C 8H 14)), 54.39 (d, J PC = 6.1 Hz, Re-CH 2O-C(O)-Re),
125.07 (pyridine), 128.34 (d, J PC = 9.3 Hz, m-Ph 2PCH 2B(C 8H 14)), 128.64 (d, J PC = 9.8 Hz, m-
Ph 2PCH 2B(C 8H 14)), 129.85 (d, J PC = 1.9 Hz, p-Ph 2PCH 2B(C 8H 14)), 130.00 (d, J PC = 2.1 Hz, p-
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