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

NMR Scale Reaction of [1-Ph 2][BF 4] with [HPt][PF 6] in presence of trialkylborane.
A ~0.6 mL C 6D 5Cl solution of 6.3 mg (0.0300 mmol) t BuCH 2CH 2B(C 8H 14) was added to 9.7 mg
(0.00152 mmol) [HPt][PF 6], and the mixture was added to 13.8 mg (0.0152 mmol) solid [1-
Ph 2][BF 4]. The reaction mixture was transferred to a J-Young NMR tube, and monitored by
multinuclear NMR. After 15 minutes, high conversion to a boroxycarbene species (δ 14.60) was
observed; the reaction was complete within 3 hours. NMR parameters of the ~2:1 mixture of
t BuCH2CH 2B(C 8H 14) : 2-Ph 2 (reversible adduct formation leads to chemical shifts dependent on
the amount of borane present). The product displayed spectral parameters very similar to the
product of reduction of [1-Ph 2][BF 4] with 1 equiv NaHBEt 3 (1.0 M in toluene). 1 H NMR
(C 6D 5Cl, 300 MHz): δ 0.91 (s, t BuCH 2CH 2B(C 8H 14), 18H), 1.15-1.38 (m, t BuCH 2CH 2B(C 8H 14),
16H), 1.59 (br m, t BuCH 2CH 2B(C 8H 14), 4H), 1.65-1.95 (m, t BuCH 2CH 2B(C 8H 14), 24H), 7.07-7.21
(m, PPh 3, 12H), 7.58-7.64 (m, PPh 3, 8H), 14.60 (s, Re-CHO, 1H). 31 P{ 1 H} NMR (C 6D 5Cl, 121
MHz): δ 14.5.
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