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

III. Synthesis of Complexes with Pendent Boranes.
Synthesis of Crude Ph 2PCH 2B(C 8H 14).
A slurry of 1.42 g (6.87 mmol) Ph 2PCH 2Li in 50 mL pentane was frozen in the cold well of a
glovebox. As the slurry thawed, a thawing 20 mL pentane solution of Cl-9-BBN was added. The
mixture was allowed to warm with stirring, and was stirred for 18 hours. White solids remained
throughout the reaction, which were collected on a frit, and washed with 3 x 5mL THF. The
solids were dried, giving 1.97 g (6.15 mmol, 90%) of white powder assigned as oligomeric
Ph 2PCH 2B(C 8H 14). These solids are insoluble in common organic solvents. The crude
phosphinoborane ligand could be used at this stage, but better results were obtained when the
ligand was treated successively with pyridine and BF 3Et 2O, as follows.
Synthesis of Ph 2PCH 2B(C 8H 14)pyridine.
A 20 mL scintillation vial was charged with 0.756 g (2.36 mmol) Ph 2PCH 2B(C 8H 14), in the form
of crude white insoluble solids as described above. A stirbar and 10 mL toluene was added,
giving a thick white slurry. A 5 mL toluene solution of 0.242 g (3.07 mmol) pyridine was added,
and over a few minutes the slurry steadily became less cloudy, although there were still some
solids that did not dissolve over the course of the reaction. After 6 hours, the cloudy reaction
mixture was filtered, and the filtrate evaporated to dryness in vacuo. The white solids where
washed with 3 x 4 mL pentane, and dried to give 0.700 g (1.75 mmol, 74%) white
microcrystalline Ph 2PCH 2B(C 8H 14)•pyridine. The pyridine adduct was soluble in most organic
solvents (except pentane).
1 H NMR (THF-d8, 500 MHz): δ 1.14-1.25 (m, 3H,
Ph 2PCH 2B(C 8H 14)), 1.38 (d, J PH = 4.7 Hz, 2H, Ph 2PCH 2B(C 8H 14)), 1.38-1.44 (m, 2H,
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