2
A. Sinha et al. / Polyhedron xxx (2016) xxx–xxx
114.10–113.45 (m, ipso-C), 22.80 (d, J = 17 Hz, o-CH3), 20.89
2. Experimental
(s, p-CH3); 31P NMR (162 MHz, CDCl3): d ꢀ47.91 (t, J = 37.0 Hz,
1P); 19F NMR (376 MHz, CDCl3): d ꢀ129.46 to ꢀ129.78 (m, 2F),
ꢀ153.03 (t, J = 20.5, 1F), ꢀ161.47 (td, J = 23.9, 8.9, 2F).
2.1. General information
All reactions, unless stated otherwise, were carried out in an
inert atmosphere using standard Schlenk and high vacuum tech-
niques. All common reagents used were obtained from commercial
suppliers without further purification. Ether free Li[B(C6F5)4] [18],
[Ph3C][B(C6F5)4] [19], PBr(C6F5)2 [20] and PBrMes2 [21] were syn-
thesized using previously reported procedures. All solvents used
for reactions were either obtained from a Pure Solv MD-7 solvent
purification system or dried following literature methods [22].
All deuterated solvents used were obtained from commercial
sources and dried using calcium hydride followed by vacuum
distillation. NMR spectra were recorded using Bruker Avance 500
(AV500) and Bruker Avance 400 (DRX400) NMR spectrometers.
Gas Chromatography-Mass Spectrometry (GC–MS) results were
recorded using an Agilent 5975 GCMSD with a HP-5 column (low
resolution quadrupole benchtop mass spectrometer), coupled to
an Agilent 7890A Gas Chromatograph. Known compounds were
identified using the NIST Mass Spectra Library available in the
GC–MS and by their reported 1H NMR data.
2.3.2. Mesityl-bis(pentafluorphenyl)phosphine
A freshly prepared tetrahydrofuran solution (50 mL) of bromo-
mesitylmagnesium (prepared from 13.3 mmol of magnesium and
2.04 mL of bromomesitylene) was added dropwise to an ethereal
solution (50 mL) of PBr(C6F5)2 (2 mL, 13.3 mmol) maintained at
below 0 °C. The resulting cloudy mixture was stirred overnight at
room temperature. The solvent was removed under reduced pres-
sure and the residue stirred vigorously with dry methanol for five
minutes before evaporation. The cycle of methanol addition and sol-
vent removal was performed three times. The resulting solid residue
was dissolved in dry diethyl ether (50 mL) and separated from
MgBr2 by cannula filtration. The solvent was evaporated and the
residue dried under vacuum for 12 h at room temperature. The
crude mixture was purified by recrystallization from dry methanol.
Yield: 3.5 g, 55%. 1H NMR (400 MHz, CDCl3): d 6.93 (d, J = 4.0 Hz,
2H), 2.40 (s, 6H), 2.29 (s, 3H); 13C NMR (100.6 MHz, CDCl3): d
1
1
147.10 (dm, JC–F = 246.8 Hz, CF), 145.05 (d, JC–P = 20.8 Hz, CP),
1
141.96 (d, J = 1.4 Hz), 141.79 (dm, JC–F = 254.6 Hz, CF), 137.67
(dm, 1JC–F = 255.7 Hz, CF), 130.12 (d, J = 6 Hz), 122.76 (d, J = 14 Hz),
109.45–108.61 (m, ipso-C), 22.86 (d, J = 19 Hz, o-CH3), 21.28
(s, p-CH3). 31P NMR (162 MHz, CDCl3): d ꢀ54.71 (q, J = 29 Hz, 1P);
2.2. X-ray crystallography
Single crystal data were measured on a four circles goniometer
Kappa geometry Bruker AXS D8 Venture equipped with a Photon
100 CMOS active pixel sensor detector using a molybdenum
(k = 0.71073 Å) or copper (k = 1.54180 Å) monochromatized X-ray
radiation source.
19F NMR (376 MHz, CDCl3)
ꢀ151.71 (td, J = 20.5, 1.0, 2H), ꢀ160.73 (m, 4H).
d
ꢀ131.28 to ꢀ131.52 (m, 4H),
2.4. Synthesis of phosphonium salts
Frames were integrated with the Bruker SAINT [23] software
package using a narrow-frame algorithm. Data were corrected for
absorption effects using the multi-scan method implanted in the
software (Twinabs) [24]. The structures were solved by the direct
method using the SHELXT program or SIR92 program [25]. Refinement
of the structure was carried out by least squares procedures on
weighted F2 values using the SHELXL-version 2014/6 or using CRYSTALS
[26,27]. All heavy atoms were assigned anisotropic displacement
parameters, hydrogens atoms were located on difference Fourier
maps then introduced as fixed or located geometrically. Compound
2 was found to be twinned, two distinct domains were depicted
using the software Cell_now integrated in package software: APEX
v2014.11.0. [28] The structure although twinned could be solved
and fully refined.
2.4.1. Method I
Ether free Li[B(C6F5)4] (0.69 g, 1.0 mmol) and phosphine
(1.0 mmol) were dissolved in dichloromethane. The solution was
saturated with hydrogen chloride by passing HCl gas through the
solution for five minutes. The reaction vessel was sealed and the
mixture was allowed to stir for 24 h. Resulting mixture was filtered
and the colourless filtrate was concentrated under reduced
pressure. Hexane was added to induce precipitation. The resulting
white solid was washed with hexane and dried in vacuo.
2.4.2. Method II
A flame dried Teflon capped Schlenk tube was charged with
0.92 g of [Ph3C][B(C6F5)4] (1.0 mmol) and 2.0 mL of chloroben-
zene. An excess amount of triisopropylsilane (0.25 mL,
1.22 mmol) was added to the solution which was stirred at room
2.3. Synthesis of phosphines
temperature for 10 min. A chlorobenzene solution of triaryl
phosphine (1.0 mmol) was added to the mixture. After 10 min,
an aliquot was taken to confirm the formation of 1 {31P NMR
(202 MHz): d ꢀ9.95 (s, 1P). 29Si NMR (99 MHz): d 38.61 (d, Si,
J = 22 Hz).}. In the cases of PMes2(C6F5) and PMes(C6F5)2, NMR
data showed the silylium/phosphine mixture to be a Frustrated
Lewis Pair. The reaction tube was immersed into liquid nitrogen
to freeze the solution. The tube was exposed to vacuum and
refilled with hydrogen gas. The reaction vessel was sealed and
the mixture was heated overnight at 60 °C. The resulting pale
brown solution was concentrated under reduced pressure. The
remaining solution was triturated with hexane, yielding a pale
brown precipitate which was isolated and thoroughly washed
with hexane before being dried under vacuum.
2.3.1. Dimesityl(pentafluorophenyl)phosphine
A freshly prepared ethereal solution (50 mL) of bromo(pentaflu-
orophenyl)magnesium (prepared from 58 mmol of magnesium and
7.2 mL of bromopentafluorobenzene) was added dropwise to an
ethereal solution (50 mL) of equimolar amount of bromodime-
sitylphosphine (13.32 g, 58 mmol) maintained in an ice-salt bath.
After complete addition the reaction mixture was allowed to warm
to room temperature and stirred overnight. MgBr2 was separated
by cannula filtration and the reaction was quenched with water
(20 mL). The organic components were extracted with ether
(3 ꢁ 30 mL) and combined extracts were reduced under vacuum.
The crude mixture was purified by column chromatography to
afford the title phosphine as a white solid. Yield: 12.0 g, 50%. 1H
NMR (400 MHz, CDCl3): d 6.84 (d, J = 4.0 Hz, 4H), 2.27 (s, 6H),
2.17 (s, 12H); 13C NMR (100 MHz, CDCl3): 13C NMR (100.6 MHz,
C6D6): d 147.77 (dm, 1JC–F = 249.9 Hz, CF), 143.02 (d, 1JC–P = 18.6 Hz,
2.4.3. Diphenyl(pentafluorophenyl)phosphonium tetrakis
(perfluorophenyl)borate (2)
Off white solid. Yield: 0.72 g (70%). 1H NMR (400 MHz, C6D6): d
7.27 (d, 1H, J = 528 Hz, P–H), 7.41–7.36 (m, 2H, CAr-H), 7.24–8.19
(m, 4H, CAr-H), 7.13–7.07 (dd, 4H, J = 16, 7.6 Hz, CAr-H); 31P NMR
1
1
CP), 141.55 (dm, JC–F = 254.4 Hz, CF), 137.79 (dm, JC–F = 252.5 Hz,
CF), 131.62 (d, J = 7 Hz), 130.65 (d, J = 4 Hz), 130.32 (d, J = 7 Hz),
Sinha, Arup
