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

Synthesis of trans-[(Ph 2PCH 2B(C 8H 14)) 2Re(<strong>CO</strong>) 4][B(C 6F 5) 4] ([1-M 2][B(C 6F 5) 4]).
A 20 mL scintillation vial was charged with 0.145 g (0.157 mmol) [Ph 3C][B(C 6F 5) 4] and 5 mL
C 6H 5Cl. To the stirring solution was added 25.1 μL (0.157 mmol) Et 3SiH dropwise. The orange-
brown mixture was stirred for 25 minutes, after which time the mixture was added to a 60 mL
Teflon-stoppered pressure vessel charged with a suspension of 0.156 g (0.157 mmol) mer,trans-
(Ph 2PCH 2B(C 8H 14)) 2Re(<strong>CO</strong>) 3Br in 5 mL C 6H 5Cl. The vessel was sealed, removed from the box,
and the contents frozen in a liquid nitrogen bath. After two freeze-pump-thaw cycles, 1 atm <strong>CO</strong>
gas (treated by passage through a column of activated Mn oxide and sieves) was introduced to
the vessel. The reaction vessel was sealed and stirred overnight. After ~12 hours, the mixture had
a lighter, more yellow color. At this time the vessel was degassed, and the solvents were
concentrated in vacuo to 2 mL. Treatment with 10 mL pentane prompted immediate precipitation
of copious amounts of pale yellow solids. After stirring a few hours, the solids were collected on
a frit, and washed with more pentane. The solids were dried, affording 0.228 g (90%, 0.141
mmol) spectroscopically pure [1-M 2][B(C 6F 5) 4]. X-Ray quality crystals were obtained by
crystallization from 1,2-dichloroethane / pentane mixtures. 1 H NMR (CD 2Cl 2, 500 MHz): δ 0.95
(m, 4H), 1.35-1.43 (m, 8H), 1.48 (br, 4H), 1.63-1.75 (m, 12H), 3.24 (m, 4H), 7.54 (s, 20H).
31 P{ 1 H} NMR (CD2Cl 2, 202 MHz): δ -13.7. 13 C{ 1 H} NMR (CD 2Cl 2, 125 MHz): δ 22.97, 31.51
(br), 34.00, 35.48, 124.5 (v. br, ipso-C 6F 5), 130.07 (t, J PC = 5.3 Hz, m-Ph), 131.62 (t, J PC = 5.6 Hz,
o-Ph), 132.44 (t, J PC = 1.0 Hz, p-Ph), 135.27 (dd, J PC = 25.9, 26.7 Hz, ipso-Ph), 136.88 (dm, J PF =
241.4 Hz), 138.82 (dm, J PF = 245.7 Hz), 148.74 (dm, 239.1 Hz), 186.37 (t, J PC = 7.4 Hz). 11 B
NMR (CD 2Cl 2, 160 MHz): δ 88.6 (br), -16.8 (BAr F
4). IR (C 6D 5Cl): 1998 cm -1 . HRMS (TOF
ES + ): m/z calcd for C 46H 52B 2O 4P 2Re: 939.3102. Found: 939.3076.
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