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

X-ray Crystallography Procedures.
X-ray quality crystals were grown as indicated in the experimental procedures for each complex.
The crystals were mounted on a glass fiber with Paratone-N oil. Structures were determined
using direct methods with standard Fourier techniques using the Bruker AXS software package.
In some cases, Patterson maps were used in place of the direct methods procedure. Full
crystallographic details are provided in the section below.
II. Reductions of trans-[(PPh 3) 2Re(<strong>CO</strong>) 4] + ([1-Ph 2] + ).
Synthesis of [HPt(dmpe) 2][PF 6] ([HPt][PF 6]).
While the published literature procedure is serviceable, 10 certain alterations improved the yield in
our hands. In particular, the reaction was run more dilute to ensure that all [HPt] + remained in
solution, and the use of EtOH (which appeared to decompose [HPt] + at a reasonably quickly)
was avoided. A 500 mL round bottom flask was charged with 1.96 g (2.49 mmol)
[Pt(dmpe) 2][PF 6] 2, 200 mL acetonitrile, and a stir bar. With the acetonitrile solution stirring,
0.189 g (4.99 mmol, 2 equiv) NaBH 4 (as a 10 wt% mixture in basic alumina) was added as a
solid. The mixture was stirred for ~12 hours, filtered through a fine frit, and the filtrate was dried
under vacuum to afford an off-white powder. The crude material contained only [HPt][PF 6] and
excess NaBH 4. The desired [HPt][PF 6] was extracted with 15 mL C 6H 5Cl, and filtered away
from the insoluble white NaBH 4. The solvent was removed from the filtrate under vacuum, and
the very pale yellow solids were washed with 3 x 5 mL Et 2O to afford 1.414 g (88% yield)
spectroscopically pure [HPt][PF 6]. This procedure provided material with spectroscopic
S4