Hawkeswood et al.
Synthesis of ((µ-R3PN)Bcat)2 (R3 ) Et3 (1), n-Bu3 (2), Ph3 (3),
i-Pr3 (4), n-But-Bu2 (5)), and t-Bu3PNBcat (6). These compounds
were prepared in a similar fashion, and thus, only one preparation
is detailed. A solution of ClBcat (0.270 g, 1.75 mmol) in 20 mL of
toluene was added to a solution of Et3PNSiMe3 (0.360 g, 1.75
mmol) in 2 mL of toluene and was stirred for 1 h at room
temperature. Toluene and SiMe3Cl were removed in vacuo. The
product was washed with pentanes (3 × 2 mL) and dried in vacuo.
ing the structure-reactivity relationship continues to stimulate
research endeavors. In our work to uncover strategies to
improved olefin polymerization catalysts, one recurring
theme has emerged: the resulting reactivity of phosphinimide
complexes is determined by the admixture of the polarity of
the P-N bond and the steric demands of the substituents on
phosphorus.17-19 In an effort to probe the generality of these
observations, we have begun to examine related main group-
phosphinimide chemistry. Initially we probed the role of the
steric demands and showed that while phosphinimines with
small substituents were known to afford species of formula
B(NPR3)3,20 sterically demanding phosphinimines gave the
linear borinium salt [(t-Bu3PN)2B]Cl.21 Similar steric effects
were observed in methyl-abstraction reactions of silyl and
tin phosphinimines.22 Herein we describe steric effects on
the reactions of phosphinimines with catechol and pina-
colboranes.
1
A white solid was isolated. Data for 1: yield 82%; H NMR 7.10
(m, 4H, C6H4 (o-H)), 6.89 (m, 4H, C6H4 (m-H)), 1.22 (dq, 12H,
2
3
3
CH2, JP-H ) 12 Hz, JH-H ) 8 Hz), 0.73 (dt, 18H, Me, JP-H
)
17 Hz, JH-H ) 8 Hz); 31P{1H} NMR 40.7; 13C{1H} NMR 153.4
(s, C6H4 (ipso-C)), 119.0 (s, C6H4 (o-C)), 109.2 (s, C6H4 (m-C)),
16.9, 5.7 (s, Me); 11B{1H} NMR 8.1. Anal. Calcd: H, 7.63; C,
57.41; N, 5.58. Found: H, 7.67; C, 57.59; N, 5.55. Data for 2:
3
1
yield 97%; H NMR (C6D6) 7.02 (m, 4H, C6H4 (o-H)), 6.84 (m,
4H, C6H4 (m-H)), 1.36 (m, 24H, CH2CH2), 1.07 (m, 12H, PCH2),
3
0.76 (t, 18H, Me, JH-H ) 7.2 Hz); 31P{1H} NMR 35.9; 13C{1H}
NMR 153.4 (s, C6H4 (ipso-C)), 118.9 (s, C6H4 (o-C)), 109.2 (s,
C6H4 (m-C)), 25.7 (s, PCH2), 24.8 (s, PCH2CH2), 24.0 (s,
PCH2CH2), 14.0 (s, Me); 11B{1H} NMR 6.0. Anal. Calcd: H, 9.32;
C, 64.49; N, 4.18. Found: H, 9.77; C, 64.25; N, 4.09. Data for 3:
Experimental Section
General Data. All preparations were performed under an
atmosphere of dry O2-free N2 by employing either Schlenk-line
techniques or a Vacuum Atmospheres glovebox. Solvents were
purified employing Grubbs-type column systems manufactured by
Innovative Technologies or were distilled from the appropriate
drying agents under N2. ClBcat, HBpin, n-Bu3P, Et3P, and N3SiMe3
were used as received from Sigma-Aldrich. t-Bu3P and i-Pr3P
were purchased from the Strem Chemical Co. Modified litera-
ture procedures were used to synthesize the phosphinimines.5 1H,
13C{1H}, 31P{1H}, 11B{1H}, and 19F{1H} NMR spectra were
recorded on Bruker Avance spectrometers operating at 300 and 500
MHz, respectively. Deuterated benzene and toluene were purchased
from Cambridge Isotopes Laboratories, vacuum distilled from the
appropriate drying agents, and freeze-pump-thaw-degassed (3×).
C6D6 was used to record the NMR spectra unless otherwise
indicated. Trace amounts of protonated solvents were used as
references, and 1H and 13C{1H} NMR chemical shifts (δ) are
reported relative to SiMe4. 31P{1H}, 11B{1H}, and 19F{1H}
NMR spectra are referenced to 85% H3PO4, BF3(OEt2) and
CFCl3, respectively. Line widths at half-height (∆ν1/2) are re-
ported in hertz. Combustion analyses were performed at the
University of Windsor Chemical Laboratories. Infrared spectra were
collected on a Bruker Vector 22 FT-IR spectrometer using Nujol
mulls. Modified literature procedures were used to synthesize
t-Bu3PNSiMe3, i-Pr3PNSiMe3, n-Bu3PNPh, Et3PNAd, Et3PNH,
n-Bu3PNH, t-Bu3PNH, PhN3, Et3PNH, and n-Bu3PNH.23-29
1
3
yield 69%; H NMR (C6D5CD3 ) 7.70 (dd, 12H, PPh, JP-H )13
Hz, 3JH-H ) 8 Hz), 6.99 (m, 22H, PPh, C6H4), 6.75 (m, 4H, C6H4);
31P{1H} NMR (C6D5CD3) 34.1; 13C{1H} NMR (C6D5CD3, partial)
132.8 (PPh), 131.8 (PPh), 128.8 (PPh), 121.3 (C6H4), 111.5 (C6H4);
11B{1H} NMR (C6D5CD3) 8.4. Anal. Calcd: H, 4.85; C, 72.94; N,
3.54. Found: H, 5.07; C, 72.61; N, 3.58. Data for 4: yield 83%;
1H NMR (C6D5CD3) 6.95 (m, 4H, C6H4 (o-H)), 6.76 (m, 4H, C6H4
2
3
(m-H)), 1.82 (dseptet, 6H, i-Pr, JP-H ) 12 Hz, JH-H ) 7 Hz),
0.96 (dd, 36H, i-Pr, 3JP-H ) 15 Hz, 3JH-H ) 7 Hz); 31P{1H} NMR
(C6D5CD3) 49.2; 13C{1H} NMR (C6D5CD3) 153.0 (C6H4 (o-C)),
121.6 (C6H4 (o-C)), 109.1 (C6H4 (m-C)), 25.2 (d, i-Pr), 17.2 (i-Pr);
11B{1H} NMR (C6D5CD3) 7.8. Anal. Calcd: H, 8.60; C, 61.46; N,
4.78. Found: H, 8.48; C, 61.23; N, 4.65. Data for 5: yield 60%;
1H NMR 7.09 (m, 4H, C6H4 (o-H)), 6.80 (m, 4H, C6H4 (m-H)),
1.67 (m, 4H, PCH2), 1.49 (m, 4H, CH2CH2), 1.26 (m, 4H,
3
CH2Me), 1.03 (d, 36H, t-Bu, JP-H ) 14 Hz), 0.83 (t, 6H, Me,
3JH-H ) 7 Hz); 31P{1H} NMR 38.8; 13C{1H} NMR 151.1 (s, C6H4
(ipso-C)), 121.4 (s, C6H4 (o-C)), 111.5 (s, C6H4 (m-C)), 36.6 (d,
t-Bu, 1JP-C ) 62 Hz), 27.4 (s, t-Bu, 26.5 (d, CH2, 3JP-C ) 13 Hz),
3
3
25.4 (d, CH2CH2, JP-C ) 13 Hz), 22.18 (d, CH2Me, JP-C ) 57
Hz), 14.7 (s, Me); 11B{1H} NMR 24.4. Anal. Calcd: H, 9.32; C,
64.49; N, 4.18. Found: H, 9.29; C, 64.71; N, 4.18. Data for 6:
1
yield 94%; H NMR (C6D5CD3) 7.09 (m, 2H, C6H4 (o-H)), 6.81
3
(m, 2H, C6H4 (m-H)), 1.19 (d, 27H, t-Bu, JP-H ) 13 Hz);
31P{1H} NMR (C6D5CD3) 42.7; 13C{1H} NMR 151.2 (s, C6H4
(ipso-C)), 121.2 (d, C6H4 , J ) 25 Hz), 111.4 (d, C6H4, J ) 28
1
Hz), 40.4 (d, t-Bu, JP-C ) 53 Hz), 29.7 (s, t-Bu); 11B{1H} NMR
(17) Kickham, J. E.; Guerin, F.; Stephan, D. W. J. Am. Chem. Soc. 2002,
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(C6D5CD3) 24.2. Anal. Calcd: H, 9.32; C, 64.49; N, 4.18. Found:
H, 9.44; C, 64.10; N, 4.29.
Synthesis of (µ-Et3PN)Bcat(B(C6F5)3) (7). X (0.034 g, 0.135
mmol) was dissolved in 3 mL of toluene. To this solution was added
solid B(C6F5)3 (0.069 g, 0.135 mmol). The resulting solution was
stirred at ambient temperature for 10 min. The solvent was removed
in vacuo, and the resulting white solid was isolated in 82% yield:
1H NMR 6.78 (m, 2H, C6H4 (o-H)), 6.64 (m, 2H, C6H4 (m-H)),
1.65 (dq, 6H, PCH2, 2JP-H ) 13 Hz, 3JH-H ) 8 Hz), 0.38 (dt, 9H,
Me, 3JP-H ) 19 Hz, 3JH-H ) 8 Hz); 31P{1H} NMR 68.0; 13C{1H}
NMR (C6D5CD3) 147.0 (s, BC6F5), 140.0 (s, C6H4 (ipso-C)), 139.1
(s, BC6F5), 135.3 (s, BC6F5), 122.7 (s, C6H4 (o-C)), 111.7 (s, C6H4
(m-C)), 17.6 (d, PCH2, 1JP-C ) 60 Hz), 5.9 (s, Me); 11B{1H} NMR
28.0 (BO), -6.4; 19F{1H} NMR -162.4, -156.4, -131.8. Anal.
(19) Kickham, J. E.; Guerin, F.; Stewart, J. C.; Urbanska, E.; Ong, C. M.;
Stephan, D. W. Organometallics 2001, 20, 1175-1182.
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1998, 624, 177-178.
(21) Courtenay, S.; Mutus, J. Y.; Schurko, R. W.; Stephan, D. W. Angew.
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(22) Courtenay, S.; Ong, C. M.; Stephan, D. W. Organometallics 2003,
22, 818-825.
(23) Aksnes, G.; Froeyen, P. Acta Chem. Scand. 1969, 23, 2697-703.
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4302 Inorganic Chemistry, Vol. 44, No. 12, 2005