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

V. Equilibrium Studies of Bis(phosphine) Complexes.
Reaction of 2-E 2 with [Pt][PF 6] 2.
To a stirring solution of 22.2 mg (0.021 mmol) [1-E 2][BF 4] in ~0.6 mL C 6D 5Cl was added 21 μL
(0.021 mmol) NaHBEt 3 (1.0 M in toluene) dropwise by syringe. After stirring for a roughly one
minute, the pale yellow solution was transferred to a J-Young NMR tube that had been charged
with 16.5 mg (0.021 mmol) [Pt(dmpe) 2][PF 6] 2. The white Pt salt did not appear to dissolve.
Monitoring by NMR showed no reaction over 24 hours.
Reaction of 2-M 2 with [1-E 2] + .
Boroxycarbene 2-M 2 was prepared by addition of solid [HPt][PF 6] (12.4 mg, 0.0194 mmol) 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] and 8 mg (0.075
mmol, 3.75 equiv) NaBF 4. The mixture was transferred the a J-Young NMR tube, and monitored
by multinuclear NMR spectroscopy. After 22 hours, all [1-M 2] + had been converted to 2-M 2 in
good yield. Once the reaction had run to completion, the contents of the NMR tube were, under a
N 2 atmosphere, filtered through sintered glass onto 20.4 mg (0.0194 mmol) solid [1-E 2][BF 4].
NMR spectroscopy showed only unreacted 2-M 2 and [1-E 2] + over 4 hours.
Reaction of 2-E 2 with [1-M 2] + .
Boroxycarbene 2-E 2 was prepared by dropwise addition of 21.8 µL (0.0218 mmol) NaHBEt 3 (1.0
M in toluene) to a stirring ~0.6 mL C 6D 5Cl solution of 23.0 mg (0.0218 mmol) [1-E 2][BF 4]. 1 H
and 31 P NMR spectroscopy showed clean conversion to 2-E 2. The tube was returned to the
glovebox, where it was poured onto 36.6 mg (0.0227 mmol, 1.04 equiv) [1-M 2] + . Multinuclear
NMR spectroscopy revealed complete hydride transfer had occurred, with no 2-E 2 remaining,
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