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127.5 (s; m-BC6H5), 127.4 (s; m-NC6H5), 125.3 (s; p-NC6H5), 125.2 and
125.1 (2x s; p-BC6H5 and o-NC6H5), 36.0 (d, JC,P =50.5 Hz; PC(CH3)3),
colorless solid (0.031 g, 73%). X-ray quality crystals were grown by
1
cooling a saturated solution of 4Mes in a THF/n-pentane mixture to
1
26.6 (s; PC(CH3)3), 12.7 ppm (only observed in the HSQC spectrum,
1JC,H coupling with PCH2B; PCH2B); 31P{1H} NMR (162.0 MHz, [D8]THF,
294 K): d=31.8 ppm (s). 11B{1H} NMR (128.4 MHz, [D8]THF, 294 K):
d=À6.8 ppm (s); HR ESI-MS: calcd for C27H35BN3PK (M+K)
482.2293, found 482.2309.
À208C. M.p. (nitrogen, sealed capillary): 2038C (decomp); H NMR
(400.1 MHz, [D8]THF, 297 K): d=7.66 (d, 3JH,H =7.4 Hz, 4H; o-C6H5),
3
3
7.07 (t, JH,H =7.4 Hz, 4H; m-C6H5), 6.96 (t, JH,H =7.2 Hz, 2H; p-C6H5),
2
6.74 (s, 2H; m-MesH), 2.21 (s, 3H; p-MesCH3), 2.00 (d, JH,P =11.9 Hz,
2H; PCH2B), 1.90 (s, 6H; o-MesCH3), 1.20 ppm (d, 3JH,P =14.4 Hz,
18H, PC(CH3)3); 13C{1H} NMR (100.6 MHz, [D8]THF, 297 K): d=152.5
Synthesis of 3tBu: tert-Butyl azide (0.081 g, 0.817 mmol, 1.1 equiv)
was added to a solution of tBu2PCH2BPh2 (1; 0.241 g, 0.743 mmol,
1.0 equiv) in THF (10 mL) at 08C. After addition, the reaction mix-
ture was allowed to warm to room temperature after which it was
stirred overnight. Removal of the solvent and subsequent washing
with n-pentane (38 mL) gave 3tBu as a colorless solid (0.221 g,
70%). X-ray quality crystals were grown at room temperature by
vapor diffusion of n-pentane into a solution of 3tBu in THF. M.p. (ni-
trogen, sealed capillary): 1268C (decomp); 1H NMR (400.1 MHz,
2
(only observed in the HMBC spectrum, JC,H coupling with o-C6H5,
3JC,H coupling with m-C6H5 and PCH2B; ipso-C6H5), 147.5 (s; ipso-
MesC), 134.1 (s; p-MesC), 133.0 (s; o-C6H5), 128.8 (s; m-MesC), 128.6
1
(s; o-MesC), 126.9 (s; m-C6H5), 125.3 (s; p-C6H5), 35.5 (d, JC,P
=
49.0 Hz; PC(CH3)3), 26.9 (s; PC(CH3)3), 20.8 (s; p-MesCH3), 18.7 (s; o-
1
MesCH3), 7.70 ppm (only observed in the HSQC spectrum, JC,H cou-
pling with PCH2B; PCH2B); 31P{1H} NMR (162.0 MHz, [D8]THF, 297 K):
d=91.6 ppm (s); 11B{1H} NMR (128.4 MHz, [D8]THF, 297 K): d=
6.1 ppm (s).
3
3
[D8]THF, 297 K): d=7.49 (d, JH,H =7.3 Hz, 4H; o-C6H5), 7.00 (t, JH,H
=
7.4 Hz, 4H; m-C6H5), 6.84 (t, 3JH,H =7.3 Hz, 2H; p-C6H5), 1.44 (d,
2JH,P =11.0 Hz, 2H; PCH2B), 1.34 (s, 9H; NC(CH3)3), 1.24 ppm (d,
3JH,P =15.3 Hz, 18H; PC(CH3)3); 13C{1H} NMR (100.6 MHz, [D8]THF,
297 K): d=156.5 (only observed in the HMBC spectrum, JC,H cou-
pling with o-C6H5, JC,H coupling with m-C6H5 and PCH2B; ipso-C6H5),
Synthesis of 5: Trimethylsilyl azide (0.088 g, 0.101 mL, 0.763 mmol,
1.1 equiv) was added to a solution of tBu2PCH2BPh2 (1; 0.225 g,
0.694 mmol, 1.0 equiv) in THF (12 mL) at 08C. After addition, the
reaction mixture allowed to warm to room temperature after
which it was stirred for 6 days. Removal of the solvent in vacuo
gave 5 as a colorless solid (0.271 g, 89%). If necessary, the product
was washed with cold n-pentane (08C) to remove impurities. X-ray
quality crystals were grown by cooling a saturated solution of 5 in
2
3
131.5 (s; o-C6H5), 127.0 (s; m-C6H5), 124.1 (s; p-C6H5), 61.7 (s;
1
NC(CH3)3), 37.6 (d, JC,P =25.6 Hz; PC(CH3)3), 28.7 (s; NC(CH3)3), 28.1
(d, 3JH,P =2.7 Hz, 18H; PC(CH3)3), 6.7 ppm (only observed in the
1
HSQC spectrum, JC,H coupling with PCH2B; PCH2B); 31P{1H} NMR
n-pentane to À208C. M.p. (nitrogen, sealed capillary): 948C
(162.0 MHz, [D8]THF, 293 K): d=95.5 ppm (s); 11B{1H} NMR
(128.4 MHz, [D8]THF, 294 K): d=2.9 ppm (s); HR ESI-MS: calcd for
C25H40BN3P (M+H) 424.3047, found 424.3044; calcd for C25H39BN3PK
(M+K) 462.2606, found 462.2611.
(decomp); 1H NMR (400.1 MHz, [D8]THF, 293 K): d=7.36 (d, JH,H
=
=
3
3
3
7.3 Hz, 4H; o-C6H5), 7.02 (t, JH,H =7.4 Hz, 4H; m-C6H5), 6.91 (t, JH,H
2
7.2 Hz, 2H; p-C6H5), 1.52 (d, JH,P =11.7 Hz, 2H; PCH2B), 1.33 ppm (d,
3JH,P =14.3 Hz, 18H; PC(CH3)3), 0.23 (s, 9H; Si(CH3)3); 13C{1H} NMR
(100.6 MHz, [D8]THF, 293 K): d=156.1 (only observed in the HMBC
spectrum, JC,H coupling with o-C6H5, JC,H coupling with m-C6H5 and
PCH2B; ipso-C6H5), 133.9 (s; o-C6H5), 126.5 (s; m-C6H5), 124.5 (s; p-
C6H5), 38.0 (d, 1JC,P =33.1 Hz; PC(CH3)3), 28.2 (d, 2JC,P =2.7 Hz;
Synthesis of 3Mes: Mesitylazide (0.133 g, 0.823 mmol, 1.0 equiv)
was added to a solution of tBu2PCH2BPh2 (1; 0.267 g, 0.823 mmol,
1.0 equiv) in THF (12 mL) at 08C. After addition, the reaction mix-
ture was allowed to warm to room temperature after which it was
stirred for 1 hour. Removal of the solvent and subsequent washing
with n-pentane (33 mL) gave 3Mes as a pale white solid in 80%
yield (0.320 g, 0.659 mmol). X-ray quality crystals were grown at
room temperature from a solution of 3Mes in THF layered with n-
2
3
1
PC(CH3)3), 10.3 (only observed in the HSQC spectrum, JC,H coupling
with PCH2B; PCH2B), 5.1 ppm (s; Si(CH3)3); 31P{1H} NMR (162.0 MHz,
[D8]THF, 293 K): d=84.3 (s); 11B{1H} NMR (128.4 MHz, [D8]THF,
294 K): d=3.2 ppm (s); HR ESI-MS: calcd for C24H40BNPSi (M+H)
412.2755, found 412.2786.
1
pentane. M.p. (nitrogen, sealed capillary): 1758C (decomp); H NMR
(400.1 MHz, [D8]THF, 297 K): d=7.53 (d, 3JH,H =7.3 Hz, 4H; o-C6H5),
7.01 (t, 3JH,H =7.4 Hz, 4H; m-C6H5), 6.88 (s, 2H; m-MesH), 6.86 (t,
Synthesis of 6: A solution of HCl (2m in Et2O, 0.26 mL, 0.52 mmol,
1.0 equiv) was added dropwise to a solution of 5 in THF (8 mL) at
À788C. After addition, the mixture was stirred for 5 minutes at
À788C and was subsequently warmed to room temperature. The
solvent was removed in vacuo to afford a colorless solid that was
washed with n-pentane (34 mL) and subsequently dried in vacuo
to yield 6 as a colorless solid (0.189 g, 81%). M.p. (nitrogen, sealed
3JH,H =7.3 Hz, 2H; p-C6H5), 2.27 (s, 3H; p-MesCH3), 2.25 (s, 6H; o-
3
MesCH3), 1.62 (d, 2JH,P =11.0 Hz, 2H; PCH2B), 1.35 ppm (d, JH,P
=
15.4 Hz, 18H, PC(CH3)3); 13C{1H} NMR (100.6 MHz, [D8]THF, 297 K):
d=156.0 (only observed in the HMBC spectrum, JC,H coupling with
2
3
o-C6H5, JC,H coupling with m-C6H5 and PCH2B; ipso-C6H5), 147.5 (s;
1
ipso-MesC), 135.4 (s; p-MesC), 131.7 (s; o-C6H5), 130.3 (s; o-MesC),
capillary): 938C (decomp); H NMR (400.1 MHz, CD2Cl2, 298 K): d=
129.9 (s; m-MesC), 127.1 (s; m-C6H5), 124.2 (s; p-C6H5), 37.9 (d, 1JC,P
=
7.46 (d, 3JH,H =7.5 Hz, 4H; o-C6H5), 7.16 (t, 3JH,H =7.4 Hz, 4H; m-
24.9 Hz; PC(CH3)3), 28.0 (d, 2JC,P =1.8 Hz; PC(CH3)3), 20.7 (s; p-
MesCH3), 19.8 (s; o-MesCH3), 6.50 ppm (only observed in the HSQC
C6H5), 7.05 (t, JH,H =7.2 Hz, 2H; p-C6H5), 4.68 (d, JH,P =12.7 Hz, 1H;
3
2
2
3
NH), 1.86 (d, JH,P =11.1 Hz, 2H; PCH2B), 1.23 (d, JH,P =14.7 Hz, 18H;
PC(CH3)3), 0.28 ppm (s, 9H; Si(CH3)3); 13C {1H} NMR (100.6 MHz,
CD2Cl2, 300 K): d 133.2 (s; o-C6H5), 127.1 (s; m-C6H5), 125.1 (s; p-
1
spectrum, JC,H coupling with PCH2B; PCH2B); 31P{1H} NMR
(162.0 MHz, [D8]THF, 297 K): d=98.3 ppm (s); 11B{1H} NMR
(128.4 MHz, [D8]THF, 297 K): d=3.8 ppm (s); HR ESI-MS: calcd for
C30H42BN3P (M+H) 486.3204, found 486.3215; calcd for C30H41BN3PK
(M+K) 524.2763, found 524.2757.
1
C6H5), 36.5 (d, JC,P =49.0 Hz; PC(CH3)3), 27.6 (s; PC(CH3)3), 14.8 (only
1
observed in the HSQC spectrum, JC,H coupling with PCH2B; PCH2B),
2.27 ppm (d, JC,P =1.4 Hz; Si(CH3)3), the signal for ipso-C6H5 is unre-
3
solved; 31P{1H} NMR (162.0 MHz, CD2Cl2, 298 K): d=78.1 ppm (s);
11B{1H} NMR (128.4 MHz, CD2Cl2, 299 K): d=2.4 ppm (s); HR LiFDi-
MS: calcd for C24H40BNPSi (MÀCl) 412.2755, found 412.2750.
Synthesis of 7: A solution of anhydrous tetramethylammonium
fluoride (0.0454 g, 0.487 mmol, 1.0 equiv) in MeCN (10 mL) was
added to a solution of 5 (0.200 g, 0.486 mmol, 1.0 equiv) in THF
(15 mL) at 08C. After addition, the reaction mixture was warmed to
room temperature and stirred for 1 hour. Removal of the solvent
Rearrangement of 3Mes to 4Mes: Mesitylazide-FLP adduct 3Mes
(0.043 g, 0.089 mmol) was dissolved in toluene (10 mL), heated to
758C and stirred for 66 hours at this reaction temperature. Subse-
quently, the solvent was removed in vacuo and the product was
dissolved a mixture of n-pentane (8 mL) and THF (1 mL). The solu-
tion was filtered and stored at À208C for 4 days and then 1 day at
À808C, after which crystals had formed. The mother liquor was fil-
tered off and after removal of the solvent 4Mes was obtained as a
Chem. Eur. J. 2019, 25, 13299 –13308
13305 ꢀ 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim