A New Step Towards Solid Base Catalysis: Azidoproazaphosphatranes Immobilized in Nanopores
2.97 (m, 6H, NCH2CH2N), 2.95–2.74 (m, 8H, PNCH2-t-Bu+
N3CH2CH2CH2Si), 2.64–2.43 (m, 6H, NCH2CH2N), 1.33–
found to be 0.46 and 0.55 mmol per gram of residual silica
derived, respectively, from elemental and thermogravimetric
analyses (see Supporting Information, Table S1–Table S3).
1.15 (m, 9H, SiOCH2CH3), 1.08 [s, 27H, NCH2CACTHNUTRGNEUNG(CH3)3 +
N3CH2CH2CH2Si]; 31P NMR (81 MHz, toluene-d8): d=37.22
(s).
2c@SBA-15: 13C CP MAS NMR: d=159.8 (Cpara
of phenyl
ring), 131.5 (Cipso and Cortho of phenyl ring), 114.2 (Cmeta of
phenyl ring), 58 (N3CH2 and SiOCH2), 54.10 (ArOCH3),
Synthesis of Tris(methoxybenzyl)azidophosphatrane (2c):
Product 2c was obtained from 511 mg (0.959 mmol) of 1c
and 284 mg (1.150 mmol, 1.2 equiv.) of 3-azidopropyltrie-
thoxysilane following the same protocol as described for 2a;
yield: 508 mg (68%) 1H NMR (200 MHz, CDCl3): d=7.38
49.25
(PNCH2Ar
and
NCH2CH2N),
22.67
(N3CH2CH2CH2Si), 17.23 (SiCH2CH3), 9.03 (SiCH2); 29Si CP
MAS NMR: d=ꢀ59.82, ꢀ70.17, ꢀ93.3, ꢀ102.8, ꢀ111.3; 31P
CP MAS NMR: d=36.2 (shoulder at d 25); ICP-AES analy-
sis: 1%wt P. The organic content was found to be 0.43 and
0.47 mmol per gram of residual silica derived, respectively,
from elemental and thermogravimetric analyses (see Sup-
porting Information, Table S1–Table S3).
3
3
(d, J=8.60 Hz, 6H, Ar-H), 6.88 (d, J=8.60 Hz, 6H, Ar-H),
3
4.34 (d, JP, H =8.77 Hz, 6H, PNCH2Ar), 3.85–3.63 (m, 8H,
N3CH2 +SiOCH2), 3.80 (s, 9H, ArOCH3), 3.04–2.66 (m,
14H, NCH2CH2 +N3CH2CH2CH2Si), 1.30–1.08 (m, 11H,
SiOCH2CH3 +SiCH2); 13C NMR (50 MHz, toluene-d8): d=
158.97 (CArOMe), 130.93 (CArCH2), 130.14 (CArH), 113.80
(CArH), 64.72 (N3CH2), 57.97 (SiOCH2), 54.27 (ArOCH3),
51.48
(d,
2JP, C =2.6 Hz,
PNCH2Ar),
49.03,
46.59
Characterization Techniques
(NCH2CH2N), 23.47 (N3CH2CH2CH2Si), 18 (SiCH2CH3),
8.89 (SiCH2); 31P NMR (81 MHz, CDCl3): d=36.25 (s); HR-
MS (ESI+): m/z=754.41278, calcd. for (M+HꢀN2)
(C39H60N5O6PSi): 754.4128.
Small-angle X-ray powder diffraction (XRD) data were ac-
quired on a Bruker D5005 diffractometer using Cu Ka mon-
ochromatic radiation (l=1.054184 ꢄ). Nitrogen adsorption-
desorption isotherms at 77 K were measured using a Micro-
meritics ASAP 2020M physisorption analyzer. The samples
were evacuated at 1108C for 24 h before the measurements.
Specific surface areas were calculated following the BET
procedure. Pore size distribution was obtained by using the
BJH pore analysis applied to the desorption branch of the
nitrogen adsorption/desorption isotherm. A Netzsch ther-
moanalyser STA 409PC was used for simultaneous thermal
analysis combining thermogravimetric (TGA) and differen-
tial thermoanalysis (DTA) at a heating rate of 108C minꢀ1
in air from 25–9008C. Solid state NMR MAS and CP-MAS
experiments were performed on a Bruker DSX 400 spec-
trometer at spectral frequencies of 161.99, 79.49 and
100.63 MHz for, respectively, 31P, 29Si and 13C nuclei. Chemi-
cal shifts were referenced to 85% aqueous H3PO4 for
31P NMR and to TMS for 29Si and 13C. A 4 mm triple reso-
nance Bruker MAS probe was used for CP-MAS on 29Si and
13C. The spinning rate for both was 10 kHz and samples
were spun at the magic angle using ZrO2 rotors. The experi-
mental details for the 29Si and 13C CP-MAS NMR experi-
ments were as follows: contact time: 5 ms and 3 ms, respec-
tively, 908 1H transmitter pulse length: 3 ms, number of
scans: 15000 to 50000 and repetition time: 4 s. 31P CP MAS
experiments were performed with a 2.5 mm double reso-
nance Brucker MAS probe at a spinning rate of 20 kHz for
2a@SBA-15 and 2c@SBA-15 and at a spinning rate of
10 kHz for 2b@SBA-15. Contact time was set to 2 ms, repe-
tition time to 10 ms and the number of scans was fixed at
20000 with a 908 1H transmitter pulse of 2.85 ms. Liquid
NMR spectra were recorded on a Bruker AC-200 spectrom-
eter and referenced as following: 1H (200 MHz) and 13C
General Procedure for the Covalent Immobilization
of Azidophosphatranes 2a–c onto SBA-15 silica
The covalent immobilization of azidophosphatranes 2a–c
was performed using a post-grafting procedure. SBA-15 type
silica was first prepared by the acid-catalyzed, non-ionic as-
sembly pathway described elsewhere.[43–45] The structure-di-
recting agent (Pluronic 123) was removed by calcination in
air at 5008C, and the organic-free mesoporous silica was rig-
orously dried under a flow of nitrogen at 2008C prior to the
grafting reaction. 2a–c (~1 mmol) dissolved in dry toluene
were then added dropwise to a suspension of calcined SBA-
15 (1 g) in toluene and stirred at 258C during 3 h to allow
the diffusion of the molecular precursor into the channels of
the pores. The reaction mixture was then heated to 708C for
15 h. After filtration, the unreacted base precursors were re-
moved by thoroughly washing the solid with toluene and
CH2Cl2. Finally, the resulting solids were dried under
vacuum at 508C. The organic-inorganic hybrid materials, de-
noted by 2a–c@SBA-15, have been characterized by several
analytical, physical and spectroscopic techniques including
small-angle X-ray powder diffraction, nitrogen sorption iso-
therms, and solid-state 31P, 29Si and 13C NMR spectra as well
as TGA and elemental analyses.
2a@SBA-15: 13C CP MAS NMR: d=64.9 (N3CH2), 57.9
(SiOCH2), 50.04 (PNCH2 and NCH2), 36.8 (PNCH3), 25.65
(N3CH2CH2CH2Si), 17 (SiOCH2CH3), 8.50 (SiCH2); 29Si CP
MAS NMR: d=ꢀ56.35, ꢀ63.2, ꢀ100.75, ꢀ108.55; 31P CP
MAS NMR: d=36.4; ICP-AES analysis: 2.03%wt P. The or-
ganic content was found to be 0.86 and 0.8 mmol per gram
of residual silica derived, respectively, from elemental and
thermogravimetric analyses (see Supporting Information,
Table S1–Table S3).
1
(50 MHz), chemical shifts measured relative to residual H
or 13C resonances in deuterated solvents and 31P (81 MHz),
external 85% H3PO4 at d=0.00 ppm. Mass spectral analyses
were performed on a Nermag R10–10C for exact mass. Ele-
mental analyses were performed by the Central Analysis
Service of the CNRS at Solaize (SCA). C, N, P elemental
analyses determinations were performed by ICP-AES
(Activa Jobin Yvon) spectroscopy from a solution obtained
by treatment of the solid catalyst with a mixture of HF,
HNO3 and H2SO4 in a Teflon reactor at 1508C.
2b@SBA-15: 13C CP MAS NMR: d=65.8 (CH2CCH3 and
N3CH2), 59.9 (SiOCH2), 48.9 (PNCH2 and NCH2), 34.5
(CH2CCH3), 28.7 (CH2CCH3), 21 (N3CH2CH2CH2Si), 17.17
(SiOCH2CH3), 8.53 (SiCH2); 29Si CP MAS NMR: d=
ꢀ58.65, ꢀ66.64, ꢀ101.06, ꢀ108.28; 31P CP MAS NMR: d=
37.4; ICP-AES analysis: 1.1%wt P. The organic content was
Adv. Synth. Catal. 2011, 353, 2067 – 2077
ꢃ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2075