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Synthesis and structure of sterically crowded triarylphosphine bearing 4bromo-2,6-bis(4-tert-butylphenyl)phenyl group
Shigeru Sasaki,*,a Masatoshi Izawa,a and Masaaki Yoshifujia,b
a
Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki AzaAoba, Aoba-ku, Sendai 980-8578, Japan
E-mail: ssasaki@m.tohoku.ac.jp
Supplemental Materials
Experimental
1
H, 13C, and 31P NMR spectra were measured on a Bruker AVANCE 400 spectrometer. 1H and
C NMR chemical shifts are expressed as  from external tetramethylsilane and calibrated to the
13
residual proton of the deuterated solvent ( 7.25 for chloroform-d) or the carbon of the
deuterated solvent ( 77.0 for chloroform-d). 31P NMR chemical shifts are expressed as  rom
external 85% H3PO4. FT-ICR mass spectra were measured on a Bruker APEX III with
electrospray ionization (ESI). Melting points were measured on a Yanagimoto MP-J3 apparatus
without correction. UV-Vis spectra were measured on a Hitachi U-3210 spectrometer. Infrared
spectra were measured on a Horiba FT-300 spectrometer. Microanalyses were performed at
Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku
University. Cyclic voltammetry was performed on a BAS CV-50W controller with a glassy
carbon, Pt wire, and Ag/0.01 mol L–1 AgNO3/0.1 mol L–1 n-Bu4NClO4/CH3CN as a working, a
counter, and a reference electrode, respectively (Ferrocene/Ferrocenium = 0.18 V in
dichloromethane). A substrate (ca. 10–3 mol L–1) was dissolved in dichloromethane with 0.1 mol
L–1 n-Bu4NClO4 as a supporting electrolyte and the solution was degassed by bubbling with
nitrogen gas. Merck silica gel 60 and Sumitomo activated alumina KCG-30 were used for the
column chromatography. All reactions were carried out under an argon atmosphere unless
otherwise specified.
4-Bromo-2,6-bis(4-tert-butylphenyl)iodobenzene (6)
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A solution of 4-tert-butylbromobenzene (6.40 g, 30.0 mmol) in tetrahydrofuran (15 mL) was
added to magnesium (739 mg, 30.4 mmol) in 20 min and the mixture was refluxed for 2 h. To
the solution of the Grignard reagent was added a solution of 1,3,5-tribromo-2-iodobenzene (3.29
g, 7.47 mmol) in tetrahydrofuran (30 mL) in 3 h at room temperature with exclusion of light, and
the mixture was stirred for 12 h, refluxed for 4 h, and cooled to 0 °C. To the mixture was added a
solution of iodine (5.76 g, 22.7 mmol) in tetrahydrofuran (50 mL) in 40 min, and a solution of
sodium hydrogensulfite was added to quench excess iodine. The organic layer was separated,
and the aqueous layer was extracted with ether (40 mL x 3) and combined to the organic layer.
The organic layer was washed with a saturated sodium chloride solution, dried over anhydrous
magnesium sulfate, concentrated under reduced pressure. To the residue was added ethanol and a
precipitation was filtered to give 6 (2.42 g, 4.42 mmol, 59%).
6: colorless solid; mp 185.0–187.0 °C; 1H NMR (400 MHz, CDCl3, 300 K)  7.44 (4H, d, JHH =
8.31 Hz, tBuPh-o), 7.40 (2H, s, arom-m), 7.28 (4H, d, JHH = 8.30 Hz, tBuPh-m), 1.38 (18H, s,
CH3); 13C NMR (101 MHz, CDCl3, 300 K)  150.85 (arom-o or tBuPh-p), 149.64 (arom-o or
tBuPh-p), 141.42 (tBuPh-ipso), 131.26 (arom-m), 128.88 (tBuPh-o), 124.87 (tBuPh-m), 121.77
(arom-p), 102.25 (arom-ipso), 34.66 (C(CH3)3), 31.38 (C(CH3)3); FT-ICR-MS (ESI) Calcd For:
[C26H28BrI]+: 546.0419. Found: 546.0418; Anal. Calcd for C26H28BrI: C, 57.06; H, 5.16; Br,
14.60; I, 23.19. Found: C, 56.68; H, 5.10; Br, 14.49; I, 22.71.
Chlorobis[4-bromo-2,6-bis(4-tert-butylphenyl)phenyl]phosphine (7)
To a solution of iodobenzene 6 (2.18 g, 3.99 mmol) in ether (80 mL) was added n-butyllithium
(2.60 mL, 1.54 mol L–1 in n-hexane, 4.00 mmol) at –78 °C and the mixture was stirred for 30
min. Phosphorus trichloride (0.17 mL, 1.95 mmol) was added and the mixture was wormed to 20
°C, stirred for 5 h, diluted with n-hexane, concentrated under reduced pressure, and purified by
column chromatography (SiO2, n-hexane) and recrystallization from n-hexane to give 7 (1.10 g,
1.22 mmol, 62%).
7: colorless solid; mp 197.0–199.0 °C; 1H NMR (400 MHz, CDCl3, 300 K)  7.38 (8H, d, JHH =
8.13 Hz, tBuPh-o), 7.10 (8H, d, JHH = 8.08 Hz, tBuPh-m), 7.04 (4H, d, JPH = 2.02 Hz), 1.57
(36H, s, CH3); 13C NMR (101 MHz, CDCl3, 300 K)  149.71 (s, tBuPh-p), 149.04 (d, JPC =
17.85 Hz, arom-o), 138.10 (d, JPC = 3.00 Hz, tBuPh-ipso), 135.01 (JPC = 54.46 Hz, arom-ipso),
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132.88 (s, arom-m), 129.00 (s, tBuPh-o), 124.52 (s, tBuPh-m), 123.03 (s, arom-p), 34.56 (s,
C(CH3)3), 31.49 (s, C(CH3)3); 31P NMR (162 MHz, CDCl3, 300 K)  92.0 (s); IR (KBr) 3086 w,
3053 w, 3033 w, 2964 s, 2904 s, 2868 s, 1903 w, 1753 w, 1658 w, 1610 w, 1549 s, 1510 s, 1464
m, 1387 m, 1363 m, 1306 m, 1269 m, 1219 w, 1201 w, 1140 w, 1119 w, 1103 m, 1049 m, 1020
m, 962 w, 945 w, 924 w, 872 m, 831 s, 798 s, 754 m, 712 m, 688 w, 656 w, 636 w, 615 w, 586
m, 565 m, 519 m, 478 m, 463 w, 428 w cm－1; FT-ICR-MS (ESI) Calcd For:
[C36H48PClBr2+Na]+: 727.1441. Found: 727.1438; Anal. Calcd for C52H56PClBr2: C, 68.84; H,
6.22; Cl, 3.91; Br, 17.61. Found: C, 68.74; H, 6.52; Cl, 4.65; Br, 16.92.
[4-Bromo-2,6-bis(4-tert-butylphenyl)phenyl]bis(2,4,6-triisopropylphenyl)phosphine (1)
To a solution of iodobenzene 6 (276 mg, 0.504 mmol) in tetrahydrofuran (10 mL) was added nbutyllithium (0.30 mL, 1.60 mol L–1 in n-hexane, 0.480 mmol) at –78 °C and the mixture was
stirred for 60 min. Copper (I) chloride (50.8 mg, 0.513 mmol) was added from a solid dropping
tube and the mixture was warmed to 20 °C, stirred for 3 h, and cooled to –78 °C. To the mixture
was added a solution of chlorobis(2,4,6-triisopropylphenyl)phosphine (228 mg, 0.481 mmol) in
tetrahydrofuran (10 mL), and the mixture was warmed to room temperature, refluxed for 43 h.
n-Hexane was added to the mixture and insoluble solids were removed by filtration with Celite.
The filtrate was concentrated under reduced pressure, and the residue was purified by column
chromatography (Al2O3, n-hexane) and recrystallization from n-hexane to give 1 (61.3 mg,
0.0714 mmol, 14%).
1: pale yellow prism; mp 258.0–259.0 °C; 1H NMR (400 MHz, CDCl3, 300 K)  7.28 (2H, brs,
tBuPh), 7.13 (2H, brs, tBuPh), 7.12 (2H, d, JPH = 2.51 Hz, arom-m), 6.92 (2H, dd, JPH = 3.13,
JHH = 1.91 Hz, Tip-m), 6.56 (2H, brs, tBuPh), 6.55 (2H, dd, JPH = 3.27, JHH =1.88 Hz, Tip-m),
6.24 (2H, brs, arom), 3.77–3.63 (2H, m, CH-o), 2.81 (2H, sept, JHH = 6.91 Hz, CH-p), 2.77–2.64
(2H, m, CH-o), 1.25 (12H, d, JHH = 6.58 Hz, CHCH3-p), 1.22 (18H, s, C(CH3)3), 1.12 (12H, d,
JHH = 6.57 Hz, CHCH3-o), 1.03 (6H, brd, JHH = 6.60 Hz, CHCH3-o), 0.39 (6H, d, JHH = 6.62 Hz,
CHCH3-o), 0.21 (12H, d, JHH = 6.66 Hz, CHCH3-o); 13C NMR (101 MHz, CDCl3, 300 K) 
153.38 (d, JPC = 19.29 Hz, Tip-o), 152.42 (d, JPC = 18.27 Hz, Tip-o), 151.35 (d, JPC = 23.32 Hz,
arom-o), 149.41 (s, Tip-p or t-BuPh-p), 148.66 (s, Tip-p or t-BuPh-p), 139.21 (d, JPC = 5.14 Hz,
t-BuPh-ipso), 136.45 (d, JPC = 32.94 Hz, Tip-ipso), 134.18 (brs, arom-m), 131.80 (d, JPC = 25.15
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Hz, arom-ipso), 129,44 (brs, t-BuPh-o), 128.26 (brs, t-BuPh-o), 124.51 (brs, t-BuPh-m), 123.15
(brs, t-BuPh-m), 121.80 (d, JPC = 4.90 Hz, Tip-m), 121.38 (d, JPC = 5.21 Hz, Tip-m), 120.73 (s,
arom-p), 34.23 (s, CH-p or C(CH3)3), 34.10 (s, CH-p or C(CH3)3), 33.06 (d, JPC = 18.46 Hz, CHo), 31.26 (s, C(CH3)3), 31.01 (d, JPC = 16.92 Hz, CH-o), 24.99 (s, CH3), 24.25 (s, CH3), 24.16 (s,
CH3), 24.06 (s, CH3), 23.56 (s, CH3), 22.88 (s, CH3); 31P NMR (162 MHz, CDCl3, 300 K)  –
40.7 (s); UV-Vis (CH2Cl2, c = 5.71×10－6 mol L–1) max ()/nm 332 (11300); IR (KBr) 3086 w,
3043 m, 2964 s, 2931 s, 2904 s, 2868 s, 2802 w, 2754 w, 2711 w, 1901 w, 1782 w, 1765 w, 1660
w, 1601 m, 1547 m, 1508 s, 1462 s, 1419 m, 1383 s, 1362 s, 1304 m, 1267 m, 1238 w, 1198 w,
1161 m, 1132 m, 1103 m, 1059 w, 1020 m, 937 m, 876 s, 831 s, 800 s, 756 m, 712 w, 648 m,
604 w, 584 m, 573 m, 557 m, 530 m, 494 w, 455 w cm–1; FT-ICR-MS (ESI) Calcd For:
[C56H74PBr+H]+: 857.4784. Found: 857.4789; Anal. Calcd for C56H74PBr: C, 78.39; H, 8.69; Br,
9.31. Found: C, 78.17; H, 8.76; Br, 9.02.
X-ray crystallography
Single crystal data were collected using a Rigaku RAXIS-IV imaging plate area detector with
graphite monochromated Mo-K radiation ( = 0.71069 Å). A total of 48 4.50°oscillation
images (being exposed for 20.2 min) were collected. The structure was solved by direct methods
(SIR92),1 expanded using Fourier techniques (DIRDIF94),2 and refined by full matrix least
squares on F. The non-hydrogen atoms were refined anisotropically. The hydrogen atoms were
included but not refined. The structure solution, refinement, and graphical representation were
carried out using the teXsan package.3
Crystal data of 1: C56H74PBr, M = 858.08, pale yellow block from n-hexane, crystal dimensions
0.20 x 0.10 x 0.10 mm3, triclinic, space group P–1 (no. 2), a = 13.8537(5), b = 17.0459(6), c =
12.3785(5) Å,  = 110.914(1).  = 104.059(2),  = 98.179 (2) V = 2562.8(2) Å3, Dc = 1.112 g
cm–3,  = 0.869 mm–1, T = 130 K, Z = 2, F(000) = 920.00. Of 19719 reflections measured
(2max = 51.0°), 8919 were unique [I > 0.0(I)] (Rint = 0.053). Variable parameters 524.
Goodness of fit S = 1.41 for observed reflections, and R1 = 0.047 for I > 2.0(I), R = 0.060, Rw =
0.058 for all reflections. The maximum and minimum peaks on the final difference Fourier map
corresponded to 1.00 and –0.49 eÅ–3, respectively. CCDC 983290.
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References
1. Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A.;
Polidori, G. J. Appl. Cryst. 1994, 27, 435.
2. Beuskens, P. T.; Admiraal, G.; Beuskens, G.; Bosman, W. P.; de Gelder, R.; Israel, R.; Smits,
J. M. M. 1994, The DIRDIF-94 program system, Technical Report of the Crystallography
Laboratory, University of Nijmegen, The Netherlands.
3. Molecular Structure Corporation, Rigaku Corporation, 1998. teXsan. Single Crystal Structure
Analysis Software, Version 1.9.
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Selected 1H, 13C and 31P NMR Spectra
Figure S 1: 1H NMR spectrum (400 MHz, 300 K, CDCl3) of 1.
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Figure S 2: 13C NMR spectrum (101 MHz, 300 K, CDCl3) of 1.
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Figure S 3: 31P NMR spectrum (162 MHz, 300 K, CDCl3) of 1.
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Figure S 4: IR spectrum (KBr) of 1.
S 10
Figure S 5: FT-ICR-MS spectrum (ESI, positive) of 1.
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Figure S 6: 1H NMR spectrum (400 MHz, 300 K, CDCl3) of 6.
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Figure S 7: 13C NMR spectrum (101 MHz, 300 K, CDCl3) of 6.
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Figure S 8: Mass spectrum (EI, 70 eV) of 6.
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Figure S 9: 1H NMR spectrum (400 MHz, 300 K, CDCl3) of 7.
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Figure S 10: 13C NMR spectrum (101 MHz, 300 K, CDCl3) of 7.
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Figure S 11: 31P NMR spectrum (162 MHz, 300 K, CDCl3) of 7.
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Figure S 12: IR spectrum (KBr) of 7.
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Figure S 13: FT-ICR-MS spectrum (ESI, positive) of 7.