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

E. Reduction of trans-[(Ph 2P(CH 2) 2B(C 8H 14)) 2Mn(<strong>CO</strong>) 4][BF 4] ([1-E 2-Mn][BF 4]).
Reaction of [1-E 2-Mn][BF 4] with 1 equiv NaHBEt 3.
To a rapidly stirring solution of 32 mg (0.034 mmol) [1-E 2-Mn][BF 4] in ~0.6 mL C 6D 5Cl was
added 34 μL (0.034 mmol) NaHBEt 3 (1.0 M in toluene). The solution darkened slightly, and the
mixture was transferred to an NMR tube. Spectroscopic analysis revealed conversion to a
putative boroxycarbene species ( 1 H NMR δ 13.81, 31 P{ 1 H} NMR δ 61.0.). This species was not
further characterized. When the reaction was run in THF-d 8, only a mixture of starting material
and doubly reduced species (see below) was observed, indicating fast disproportionation is
operative.
Reaction of [1-E 2-Mn][BF 4] with 1 equiv [HPt(dmpe) 2] + .
To a stirring solution of 17.6 mg (0.0191 mmol) [1-E 2-Mn][BF 4] was added 12.2 mg [HPt][PF 6]
partwise as a solid. The mixture was stirred for two minutes before being transferred to a J-
Young NMR tube, at which time NMR spectroscopic analysis showed a mixture of the same
boroxycarbene as in the preceding reaction, and cation starting material.
Reaction of [1-E 2-Mn][BF 4] with 2 equiv NaHBEt 3.
To a rapidly stirring solution of 37 mg (0.040 mmol) [1-E 2-Mn][BF 4] in ~0.6 mL THF-d 8 was
added 80 μL (0.080 mmol, 2 equiv) NaHBEt 3 (1.0 M in toluene). The color of the reaction
mixture changed from pale yellow to orange over the course of the addition, and became cloudy.
The mixture was filtered through a sintered glass filter into an NMR tube, and the resulting
spectra revealed one major asymmetric species. Some impurity, with small, broad resonances,
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