Hydrophosphination of vinyl-boranes with phosphinoamines

Article abstract of DOI:10.1039/c2dt32677a

Phosphinoamine ligands PhN(H)PR₂ (R = iPr 1, tBu 2) react with R¹CHCR²B(C₆F₅)₂ (R ¹ = Ph, p-FC₆H₄, nPr, Et, R² = H, Ph, Et, C₆F_5<

Full text of DOI:10.1039/c2dt32677a

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Hydrophosphination of vinyl-boranes with
phosphinoamines†
Cite this: Dalton Trans., 2013, 42, 3318
Chunfang Jiang and Douglas W. Stephan*
Received 9th November 2012,
Accepted 11th December 2012
Phosphinoamine ligands PhN(H)PR2 (R = iPr 1, tBu 2) react with R1CHvCR2B(C6F5)2 (R1 = Ph, p-FC6H4,
nPr, Et, R2 = H, Ph, Et, C6F5) to effect uncatalyzed hydrophosphination of the olefinic bond, affording
the C2BNP five-membered cyclization compounds 3–14. All the compounds are fully characterized and
compounds 4, 7, 8 and 9 are studied by X-ray diffraction analysis.
DOI: 10.1039/c2dt32677a
www.rsc.org/dalton
Introduction
The story of “frustrated Lewis pairs (FLPs) began with studies
of the reactions of sterically encumbered phosphines and
boranes with several small molecules.1,2 Most notably, such
FLPs were shown to activate hydrogen,3 but have also been
employed to activate a series of other small molecules.4–7
While a variety of creative perturbations have explored the use
of amines8–17 and carbenes18–20 as Lewis bases, the variations
of Lewis acids have been few and limited to group 13 and 14
reagents. Despite recent advances that providing interesting
functionalized electrophilic boranes, very few studies have uti-
lized either Lewis acids or bases that provide other functional
groups which could be utilized in reactivity. Nonetheless, our
recent studies21,22 of boranes with a pendant olefin fragment
were shown to undergo FLP additions leading to zwitterionic
species with donors including phosphine, pyridines, carbene,
ylide and pyroles (Scheme 1).
Scheme 1 FLP additions to boranes with pendant olefins.
The discovery of 1,1-carboboration of electrophilic borane
with alkynes by the groups of Berke23 and Erker24–30 provides a
readily accessible class of functionalized boranes (Scheme 2).
These compounds have been shown to act as synthons for
tetra-substituted olefins and have also been shown to act as
the Lewis acid partners in FLP mediated catalytic hydrogen-
ations of imines. In this paper, we consider a new approach in
which we generate FLPs that incorporate reactive functional
groups in both the Lewis acid and the Lewis base. To this end,
we have examined the reactions of alkenylboranes with
phosphinoamines. While the phosphinoamines are sterically
encumbered, the incorporation of an NH fragment prompts an
Scheme 2 1,1-Carboborations of alkynes by B(C6F5)3.
Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6,
Canada. E-mail: dstephan@chem.utoronto.ca
†CCDC 910001–910004. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c2dt32677a
unusual uncatalyzed hydrophosphination of the borane-bound
olefinic fragment, leading to cyclization and C2BNP five-
membered rings.
3318 | Dalton Trans., 2013, 42, 3318–3325
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compounds were prepared in a similar fashion and thus
only one preparation is detailed. PhCCH (0.010 g, 0.1 mmol)
was added to a suspension of HB(C6F5)2 (0.034 g, 0.1 mmol) in
Experimental section
General considerations
All manipulations were carried out under an atmosphere of toluene (5 mL) at room temperature. 10 min later, Ph–NH–
dry, O2-free N2 employing standard Schlenk-line and glovebox PiPr2 (0.021 g, 0.1 mmol) was added to the reaction mixture
techniques. Solvents (hexane, THF, toluene) were dried by and allowed the solution to stir overnight at room temperature.
employing a Grubbs-type column system (Innovative Techno- After that, the solvent was removed in vacuum, and hexane
logy), degassed and stored under N2. Deuterated solvents were was used to induce the precipitation. White powder was
dried over Na/benzophenone (C6D6, C7D8) or CaH2 (CD2Cl2) isolated, washed with hexane and dried in vacuum.
and vacuum distilled prior to use. 1H, 19F, 11B, 31P and
3: Yield: 0.048 g (74%). 1H NMR (400 MHz, C6D6): 7.10–7.04
13C spectra were recorded at 25 °C on Varian 400 MHz and (m, 5H), 6.98–6.86 (m, 5H), 4.11 (ddd, J = 20.8, 14.6, 6.9 Hz,
1
Bruker 400 MHz spectrometers. H and 13C spectra are refer- 1H, CH-P), 2.42–2.20 (m, 2H, CH2-B), 1.78 (m, 1H, CH), 1.65
enced to SiMe4 using the residual solvent peak impurity of the (m, 1H, CH), 0.83 (dd, J = 15.6, 7.2 Hz, 6H, CH3), 0.35 (dd, J =
given solvent. 31P, 11B and 19F is referenced to 85% H3PO4, 14.7, 7.2 Hz, 3H, CH3), 0.16 (dd, J = 15.6, 7.2 Hz, 3H, CH3).
BF3·OEt2 and CFCl3, respectively. Chemical shifts are reported 19F NMR (376 Hz, C6D6): −130.7 (dd, J = 25, 8.6 Hz, 2F, o-C6F5),
3
in ppm and coupling constants in Hz as absolute values. Com- −131.1 (dd, J = 25, 8.6 Hz, 2F, o-C6F5), −159.5 (t, JF–F = 21 Hz,
3
bustion analyses were performed in-house employing a Perkin- 1F, p-C6F5), −160.0 (t, JF–F = 21 Hz, 1F, p-C6F5), −164.3 (m, 2F,
Elmer CHN Analyzer. All chemicals were purchased from m-C6F5), −164.6 (m, 2F, m-C6F5). 11B{1H} NMR (128 MHz,
Aldrich and used without further purification.
Synthesis of PhN(H)PiPr2 1. A solution of iPr2PCl (0.76 g, (100 MHz, C6D6): 148.0 (dm, JC–F = 242 Hz, o-C6F5), 142.6
5 mmol) in dry THF (5 mL) was added slowly to a solution of (Ph-C), 139.1 (dm, JC–F = 242 Hz, p-C6F5), 137.3 (dm, JC–F
aniline (0.47 g, 5 mmol) and Et3N (1.02 g, 10 mmol) in THF 245 Hz, m-C6F5), 135.9 (Ph-C), 129.8 (Ph-C), 128.9 (d, JC–P
C6D6): −2.0. 31P{1H} NMR (162 MHz, C6D6): 68.8. 13C{1H} NMR
1
1
1
=
=
(50 mL) at room temperature. The reaction mixture was 2.7 Hz, Ph-C), 128.6 (d, JC–P = 4.6 Hz, Ph-C), 128.4 (d,
allowed to stirred overnight. After that, the solution was JC–P = 1.6 Hz, Ph-C), 126.2 (d, JC–P = 1.9 Hz, Ph-C), 39.7 (d, JC–P
filtrated and the solvent was removed under vacuum. The = 57.4 Hz, CH2), 25.6 (d, JC–P = 45.3 Hz, CH), 23.3 (d, JC–P
=
remaining yellow oil was purified by using silica column 49.4 Hz, CH), 15.6 (d, JC–P = 1.6 Hz, CH3), 15.4 (d, JC–P = 3.4 Hz,
eluted by Et2O–hexane (1 : 1) solution. The product was iso- CH3), 15.1 (CH3), 15.0 (CH3). Anal. Calcd for C32H27BF10NP:
lated as yellow oil. Yield 0.65 g (62%). 1H NMR (400 MHz, C, 58.47; H, 4.14; N, 2.13. Found: C, 57.72; H, 4.37; N, 2.14.
3
C6D6): 7.14 (t, JHH = 8.5 Hz, 2H, Ph-H), 7.01 (dm, J = 8.5 Hz,
4: Yield: 0.045 g (67%). 1H NMR (400 MHz, CD2Cl2): 7.62 (d,
2H, Ph-H), 6.75 (tt, J = 7.3, 1.2 Hz, 1H, Ph-H), 3.31 (d, J = 3JHH = 7.2 Hz, 2H, Ph-H), 7.36 (t, JHH = 7.2 Hz, 2H, Ph-H),
10.7 Hz, 1H, NH), 1.42 (heptd, J = 7.0, 2.2 Hz, 2H, CH), 0.92 7.31–7.27 (m, 1H, Ph-H), 7.13 (m, 3H, Ph-H), 7.06 (m, 2H, Ph-
(m, 12H, CH3). 31P{1H} NMR (162 MHz, C6D6): 47.8. 13C{1H} H), 4.56 (ddd, J = 20.8, 14.8, 6.8 Hz, 1H, CH-P), 2.39–2.25 (m,
NMR (100 MHz, C6D6) 149.1 (d, JC–P = 16.0 Hz, Ph-C), 1H, CH2-B), 2.1 (t, J = 15 Hz, 1H, CH2-B), 1.35 (d, J = 14 Hz, 9H,
129.0 (Ph-C), 118.5 (Ph-C), 115.8 (d, JC–P = 12.0 Hz, Ph-C), CH3), 1.22 (d, J = 14 Hz, 9H, CH3). 19F NMR (376 Hz, CD2Cl2):
3
26.5 (d, JC–P = 12.6 Hz, CH3), 18.6 (d, JC–P = 20.7 Hz, CH), 16.8 −129.9 (dd, J = 24.5, 8.1 Hz, 2F, o-C6F5), −131.5 (dd, J = 25,
3
(d, JC–P = 8.3 Hz, CH3).
8.6 Hz, 2F, o-C6F5), −160.5 (t, JF–F = 21 Hz, 1F, p-C6F5), −162.6
3
Synthesis of PhN(H)PtBu2 2. To a solution of aniline (t, JF–F = 21 Hz, 1F, p-C6F5), −165.2 (m, 2F, m-C6F5), −166.1
(0.47 g, 5 mmol) dissolved in THF (10 mL) was added Butyl- (m, 2F, m-C6F5). 11B{1H} NMR (128 MHz, CD2Cl2): −1.6.
lithium (1.6 M in hexane, 9.6 mL, 6 mmol). The reaction 31P{1H} NMR (162 MHz, CD2Cl2): 72.9. 13C{1H} NMR
mixture was allowed to reflux for 2 h and then cooled to r.t. (100 MHz, CD2Cl2): 148.4 (dm, JC–F = 242 Hz, o-C6F5), 144.1
A solution of tBu2PCl (0.90 g, 5 mmol) in dry THF (5 mL) was (Ph-C), 139.3 (Ph-C), 137.1 (dm, JC–F = 245 Hz, m-C6F5), 131.9
1
1
added to the reaction mixture and refluxed for additional 2 h. (d, JC–P = 4.0 Hz, Ph-C), 130.6 (d, JC–P = 4.8 Hz, Ph-C), 128.9
After that, the solution was filtrated and the solvent was (d, JC–P = 2.3 Hz, Ph-C), 128.2 (d, JC–P = 2.8 Hz, Ph-C), 128.0
removed under vacuum. The pure product was isolated by (d, JC–P = 1.3 Hz, Ph-C), 126.4 (d, JC–P = 2.3 Hz, Ph-C), 43.9 (dt,
using silica column eluted by Et2O–hexane (1 : 1) solution. The JC–P = 50.8, 4.4 Hz, CH2), 42.0 (d, JC–P = 33.8 Hz, CH), 39.7 (d,
product was isolated as orange oil. Yield 0.65 g (55%). 1H NMR JC–P = 38.0 Hz, C(CH3)3), 29.8 (CH3), 29.3 (CH3). Anal. Calcd
3
(400 MHz, C6D6): 7.16 (t, JHH = 8 Hz, 2H, Ph-H), 7.05 (dm, J = for C34H31BF10NP: C, 59.58; H, 4.56; N, 2.04. Found: C, 59.85;
8 Hz, 2H, Ph-H), 6.76 (tt, J = 7.2, 1.2 Hz, 1H, Ph-H), 3.76 (d, J = H, 4.71; N, 2.13.
1
10.8 Hz, 1H, NH), 1.01 (d, J = 11.7 Hz, 18H). 31P{1H} NMR
5: Yield: 0.04 g (60%). H NMR (400 MHz, C6D6): 7.94–6.84
(162 MHz, C6D6): 58.2. 13C{1H} NMR (100 MHz, C6D6): 149.4 (m, 7H, Ph-H), 6.74 (t, J = 8.1 Hz, 2H, Ph-H), 4.00 (m, 1H,
(d, JC–P = 16.0 Hz, Ph-C), 129.1 (Ph-C), 118.5 (Ph-C), 116.1 CH-P), 2.24 (m, 2H, CH2-B), 1.69 (m, 1H, CH), 1.60 (m, 1H,
(d, JC–P = 12.0 Hz, Ph-C), 33.6 (d, JC–P = 20.7 Hz, CH), 27.77 CH), 0.75 (m, 6H, CH3), 0.32 (dd, J = 14.6, 7.2 Hz, 3H, CH3),
(d, JC–P = 15 Hz, CH3).
0.11 (dd, J = 15.5, 7.0 Hz, 3H, CH3). 19F NMR (376 Hz, C6D6):
Synthesis of R2P(NPh)CH(R′)CH2B(C6F5)2, (R′ = Ph, iPr 3, −113.7 (m, 1F, C6H4F), −130.7 (dd, J = 25, 8.5 Hz, 2F, o-C6F5),
3
tBu 4, R′ = pFC6H4, R = iPr 5, tBu 6, R′ = nPr, R = iPr 7, tBu 8, −131.2 (dd, J = 25, 8.5 Hz, 2F, o-C6F5), −159.2 (t, JF–F = 21 Hz,
3
R′ = R″ = Ph, R = iPr 9, R′ = R″ = Et, R = iPr 11, tBu 12). These 1F, p-C6F5), −159.8 (t, JF–F = 21 Hz, 1F, p-C6F5), −164.2 (m, 2F,
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m-C6F5), −166.4 (m, 2F, m-C6F5). 11B{1H} NMR (128 MHz, (376 Hz, CDCl3): −129.5 (dd, J = 25, 8.1 Hz, 2F, o-C6F5), −130.1
3
C6D6): −2.1. 31P{1H} NMR (162 MHz, C6D6): 68.4. 13C{1H} NMR (dd, J = 25, 8.6 Hz, 2F, o-C6F5), −160.2 (t, JF–F = 21 Hz, 1F,
1
3
(100 MHz, C6D6): 162.2 (dm, JC–F = 246 Hz, Ph-C), 147.5 (dm, p-C6F5), −160.7 (t, JF–F = 21 Hz, 1F, p-C6F5), −164.8 (m, 2F,
1JC–F = 250 Hz, o-C6F5), 142.0 (Ph-C), 138.6 (dm, 1JC–F = 250 Hz, m-C6F5), −165.1 (m, 2F, m-C6F5). 11B{1H} NMR (128 MHz,
p-C6F5), 137.2 (dm, JC–F = 242 Hz, m-C6F5), 131.3 (d, JC–P
1
=
CDCl3): −0.9. 31P{1H} NMR (162 MHz, CDCl3): 73.7. 13C{1H}
1
3.0 Hz, Ph-C), 129.8 (m, Ph-C), 129.5 (Ph-C), 128.2 (d, JC–P = 1.6 NMR (100 MHz, CDCl3): 147.8 (dm, JC–F = 248 Hz, o-C6F5),
1
Hz, Ph-C), 126.1 (d, JC–P = 1.6 Hz, Ph-C), 38.3 (d, JC–P = 57.4 Hz, 143.8 (Ph-C), 138.7 (dm, JC–F = 244 Hz, p-C6F5), 136.8 (dm,
CH2), 25.4 (d, JC–P = 45.3 Hz, CH), 23.2 (d, JC–P = 49.5 Hz, CH), 1JC–F = 247 Hz, m-C6F5), 130.8 (Ph-C), 127.5 (d, JC–P = 1.5 Hz,
15.4 (d, JC–P = 1.6 Hz, CH3), 15.1 (d, JC–P = 3.6 Hz, CH3), 15.8 Ph-C), 125.6 (d, JC–P = 2.3 Hz, Ph-C), 40.9 (d, JC–P = 34.6 Hz,
(m, CH3). Anal. Calcd for C32H26BF11NP: C, 56.91; H, 3.88; CH2), 39.7 (d, JC–P = 39.5 Hz, CH2), 37.8 (d, JC–P = 53.5 Hz, CH),
N, 2.07. Found: C, 56.52; H, 3.85; N, 2.13.
6: Yield: 0.04 g (58%). H NMR (400 MHz, C6D6): 7.07–7.02 CH2), 13.8 (d, JC–P 1.4 Hz, CH2). Anal. Calcd for
(m, 4H, Ph-H), 6.90–6.87 (m, 4H, Ph-H), 6.70 (t, JHH = 8.2 Hz, C31H33BF10NP: C, 57.16; H, 5.11; N, 2.16. Found: C, 57.55;
36.2 (C(CH3)3), 29.6 (CH3), 28.7 (CH3), 22.2 (d, JC–P = 14 Hz,
1
=
3
2H, Ph-H), 4.42 (ddd, J = 21.6, 15.2, 6.8 Hz, 1H, CH-P), H, 4.91; N, 2.59.
1
2.64–2.50 (m, 1H, CH2-B), 2.08 (t, J = 15 Hz, 1H, CH2-B), 0.92
9: Yield 0.04 g (55%). H NMR (400 MHz, CD2Cl2): 7.48 (d,
(d, J = 14 Hz, 9H, CH3), 0.75 (d, J = 14 Hz, 9H, CH3). 19F NMR J = 7.4 Hz, 2H, Ph-H), 7.30 (t, J = 7.4 Hz, 2H, Ph-H), 7.24–7.16
(376 Hz, C6D6): −113.6 (m, 1F, C6H4F), −129.3 (dd, J = 24.5, (m, 5H, Ph-H), 6.99 (m, 2H, Ph-H), 6.88 (m, 3H, Ph-H), 6.82 (m,
8.5 Hz, 2F, o-C6F5), −130.8 (dd, J = 25, 8.5 Hz, 2F, o-C6F5), 1H, Ph-H), 4.95 (d, J = 14.6 Hz, 1H, CH-B), 4.74 (dd, J = 20.6,
−158.7 (t, 3JF–F = 21.5 Hz, 1F, p-C6F5), −160.6 (t, 3JF–F = 21.5 Hz, 14.6 Hz, 1H, CH-P), 2.75 (m, 1H, CH), 2.47 (m, 1H, CH), 1.55
1F, p-C6F5), −163.9 (m, 2F, m-C6F5), −164.7 (m, 2F, m-C6F5). (dd, J = 15.6, 7.2 Hz, 3H, CH3), 1.47 (dd, J = 15.6, 7.0 Hz, 3H,
11B{1H} NMR (128 MHz, C6D6): −1.3. 31P{1H} NMR (162 MHz, CH3), 0.99 (dd, J = 15.6, 7.2 Hz, 3H, CH3), 0.64 (dd, J = 15.6,
C6D6): 71.1. 13C{1H} NMR (100 MHz, C6D6): 162.2 (dm, JC–P
=
7.2 Hz, 3H, CH3). 19F NMR (376 Hz, CD2Cl2): −125.1 (br, 2F,
1
3
250 Hz, Ph-C), 147.8 (dm, JC–F = 242 Hz, o-C6F5), 143.6 (Ph-C), o-C6F5), −132.8 (br, 2F, o-C6F5), −160.6 (t, JF–F = 21 Hz, 1F,
1
1
3
138.7 (dm, JC–F = 240 Hz, p-C6F5), 137.6 (dm, JC–F = 242 Hz, p-C6F5), −162.0 (t, JF–F = 21 Hz, 1F, p-C6F5), −165.4 (br, 2F,
m-C6F5), 134.7 (d, JC–P = 3.4 Hz, Ph-C), 131.7 (m, Ph-C), 129.2 m-C6F5), −166.5 (t, JF–F = 21 Hz, 2F, m-C6F5). 11B{1H} NMR
3
(Ph-C), 128.4 (Ph-C), 126.5 (d, JC–P = 1.7 Hz, Ph-C), 125.3 (Ph- (128 MHz, CD2Cl2): −0.6. 31P{1H} NMR (162 MHz, CD2Cl2):
C), 115.5 (dd, J = 21.2, 2.1 Hz, Ph-C), 43.0 (d, JC–P = 51.4 Hz, 66.0. 13C{1H} NMR (100 MHz, CD2Cl2): 148.2 (dm, JC–F
=
1
CH2), 41.2 (d, JC–P = 34.3 Hz, CH), 38.9 (d, JC–P = 38.1 Hz, 242 Hz, o-C6F5), 142.9 (d, JC–P = 2.7 Hz, Ph-C), 141.6 (Ph-C),
1
1
C(CH3)3), 29.2 (CH3), 28.6 (CH3). Anal. Calcd for 138.6 (dm, JC–F = 242 Hz, p-C6F5), 136.6 (dm, JC–F = 245 Hz,
C34H30BF11NP: C, 58.06; H, 4.30; N, 1.99. Found: C, 58.83; m-C6F5), 133.3 (Ph-C), 129.7 (Ph-C), 129.4 (d, JC–P = 5.1 Hz,
H, 4.14; N, 1.97.
Ph-C), 129.0 (d, JC–P = 3.0 Hz, Ph-C), 128.8 (d, JC–P = 2.0 Hz,
1
7: Yield 0.04 g (65%). H NMR (400 MHz, CDCl3): 7.16–7.09 Ph-C), 127.9 (d, JC–P = 3.4 Hz, Ph-C), 127.1 (Ph-C), 126.4 (d, JC–P
=
(m, 3H, Ph-H), 6.87 (d, J = 7.0 Hz, 2H, Ph-H), 2.79 (m, 1H, CH- 2.0 Hz, Ph-C), 124.1 (Ph-C), 44.4 (d, JC–P = 61 Hz, CH), 38.5
P), 2.43 (m, 1H, CH(CH3)2), 2.03 (ddd, J = 32.8, 14.2, 7.8 Hz, (br, CH), 26.2 (d, JC–P = 44.2 Hz, CH), 25.4 (d, JC–P = 51.5 Hz,
1H, CH2-B), 1.74 (m, 2H, CH2), 1.66 (m, 1H, CH2-B), 1.43 (m, CH), 16.7 (m, CH3), 16.5 (d, JC–P = 3.5 Hz, CH3), 15.8 (d, JC–P
=
2H, CH2), 1.38 (dd, J = 15.6, 7.2 Hz, 3H, CH3), 1.28 (dd, J = 1.3 Hz, CH3). Anal. Calcd for C38H31BF10NP: C, 62.23; H, 4.26;
14.7, 7.2 Hz, 3H, CH3), 1.12 (m, 6H, CH3), 0.97 (t, J = 7.0 Hz, N, 1.91. Found: C, 62.31; H, 4.58; N, 1.90.
1
CH3). 19F NMR (376 Hz, CDCl3): −130.9 (dd, J = 25, 8.4 Hz, 2F,
11: Yield 0.025 g (40%). H NMR (400 MHz, C6D6): 6.93 (m,
3H, Ph-H), 6.75 (m, Ph-H), 2.40–2.28 (m, 2H, CH), 2.14 (m, 1H,
o-C6F5), −131.9 (dd, J = 25, 8.6 Hz, 2F, o-C6F5), −160.4 (t, 3JF–F
=
3
21 Hz, 1F, p-C6F5), −160.9 (t, JF–F = 21 Hz, 1F, p-C6F5), −164.6 CH), 1.74 (m, 1H, CH), 1.51 (m, 3H, CH2), 1.25 (m, 3H, CH2),
(m, 2F, m-C6F5), −165.1 (m, 2F, m-C6F5). 11B{1H} NMR 1.07–1.01 (m, 6H, CH3), 0.78 (t, J = 7.6 Hz, 3H, CH3), 0.61 (m,
(128 MHz, CDCl3): −2.0. 31P{1H} NMR (162 MHz, CDCl3): 71.6. 6H, CH3), 0.38 (dd, J = 15.0, 7.2 Hz, 3H, CH3). 19F NMR
13C{1H} NMR (100 MHz, CDCl3): 147.4 (dm, JC–F = 242 Hz, (376 Hz, C6D6): −128.1 (br, 2F, o-C6F5), −129.1 (br, 2F, o-C6F5),
1
o-C6F5), 142.7 (Ph-C), 138.7 (dm, JC–F = 242 Hz, p-C6F5), 136.9 −159.3 (t, 3JF–F = 21 Hz, 1F, p-C6F5), −159.8 (t, 3JF–F = 21 Hz, 1F,
1
1
3
3
(dm, JC–F = 245 Hz, m-C6F5), 129.2 (Ph-C), 128.4 (d, JC–P
=
p-C6F5), −164.3 (t, JF–F = 21 Hz, 1F, m-C6F5), −164.9 (t, JF–F =
1.4 Hz, Ph-C), 125.7 (d, JC–P = 1.6 Hz, Ph-C), 33.5 (d, JC–P
=
21 Hz, 1F, m-C6F5). 11B{1H} NMR (128 MHz, C6D6): −0.6.
26 Hz, CH2), 25.0 (d, JC–P = 48.6 Hz, CH), 24.8 (d, JC–P = 47.5 31P{1H} NMR (162 MHz, C6D6): 69.4. 13C{1H} NMR (100 MHz,
1
Hz, CH), 21.6 (d, JC–P = 16.8 Hz, CH2), 16.7 (CH2), 16.5 (m, C6D6): 148.0 (dm, JC–F = 250 Hz, o-C6F5), 142.2 (Ph-C), 139.0
CH3), 16.3 (d, JC–P = 3.2 Hz, CH3), 13.7 (CH3). Anal. Calcd (dm, JC–F = 248 Hz, p-C6F5), 137.3 (dm, JC–F = 242 Hz,
for C29H29BF10NP: C, 55.88; H, 4.69; N, 2.25. Found: C, 55.74; m-C6F5), 129.6 (Ph-C), 128.9 (d, JC–P = 2.2 Hz, Ph-C), 126.5 (d,
1
1
H, 4.66; N, 2.30.
JC–P = 2.1 Hz, Ph-C), 43.4 (d, JC–P = 55.8 Hz, CH), 27.3 (d, JC–P
=
=
1
8: Yield 0.04 g (63%). H NMR (400 MHz, CDCl3): 7.09 (m, 48.7 Hz, CH), 25.5 (d, JC–P = 22.0 Hz, CH), 25.3 (d, JC–P
2H, Ph-H), 7.02 (m, 2H, Ph-H), 2.81 (m, 1H, CH-P), 2.31 (ddd, 36.3 Hz, CH), 22.0 (d, JC–P = 2.7 Hz, CH2), 17.2 (d, JC–P = 1.5 Hz,
J = 32.7, 13.7, 6.8 Hz, 1H, CH2-B), 2.04 (m, 1H, CH2-B), 1.85 (m, CH3), 16.9 (d, JC–P = 2.8 Hz, CH3), 16.2, 16.0, 15.1, 15.0, 14.1.
2H, CH2), 1.45 (m, 2H, CH2), 1.36 (d, J = 14 Hz, 9H, CH3), 1.34 Anal. Calcd for C30H31BF10NP: C, 56.53; H, 4.90; N, 2.20.
(d, J = 14 Hz, 9H, CH3), 1.00 (t, J = 7.0 Hz, 3H, CH3). 19F NMR Found: C, 56.44; H, 4.88; N, 2.24.
3320 | Dalton Trans., 2013, 42, 3318–3325
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1
12: Yield 0.026 g (40%). H NMR (400 MHz, C6D6): 7.14 (m,
3H, Ph-H), 6.95–6.87 (m, 2H, Ph-H), 2.79 (m, 1H, CH),
1.83–1.69 (m, 4H, CH2), 1.57 (m, 1H, CH), 1.03–0.99 (m, 12H,
CH3), 0.86–0.80 (m, 12H, CH3). 19F NMR (376 Hz, C6D6):
−124.7 (dd, J = 24.5, 7.3 Hz, 2F, o-C6F5), −127.1 (dd, J = 25,
Table 1 Crystallographic data
4
7
8
9
Formula
C
34H31
C29H29
BF10NP
623.31
Triclinic
ˉ
P1
C31H33
BF10NP
651.36
Monoclinic
P21/c
C45H39
BF10NP
825.55
Monoclinic
C2/c
BF10NP
685.38
Monoclinic
P21/c
11.019(1)
17.823(2)
16.359(2)
90
Formula wt
Cryst. sys.
Space group
a (Å)
b (Å)
c (Å)
3
7.5 Hz, 2F, o-C6F5), −159.5 (t, JF–F = 21.5 Hz, 1F, p-C6F5),
3
−159.7 (t, JF–F = 21.5 Hz, 1F, p-C6F5), −164.5 (m, 2F, m-C6F5),
−164.8 (m, 2F, m-C6F5). 11B{1H} NMR (128 MHz, C6D6): 0.8. 31
P
9.898(2)
10.319(1)
15.235(2)
88.992(4)
87.851(5)
63.756(4)
1394.7(4)
2
8.9145(4)
19.253(1)
17.0916(9)
90
99.678(2)
90
2891.8(3)
4
1.496
19.550(2)
11.7262(8)
33.928(3)
90
97.717(3)
90
7708(1)
8
1.423
{1H} NMR (162 MHz, C6D6): 73.1. 13C{1H} NMR (100 MHz,
1
C6D6): 148.4 (dm, JC–F = 245 Hz, o-C6F5), 144.6 (Ph-C), 138.8
(dm, JC–F = 250 Hz, p-C6F5), 137.5 (dm, JC–F = 245 Hz,
m-C6F5), 130.1 (Ph-C), 128.5 (d, JC–P = 1.5 Hz, Ph-C), 126.2 (d,
α (°)
1
1
β (°)
106.482(3)
90
3080.8(5)
4
1.478
0.177
γ (°)
V (Å3)
Z
JC–P = 1.5 Hz, Ph-C), 44.7 (d, JC–P = 49.2 Hz, CH), 41.6 (d, JC–P
=
d (g cm−3
)
1.484
37.3 Hz, CH), 39.3 (d, JC–P = 37.3 Hz, C(CH3)3), 29.8 (CH3), 28.1
(CH3), 25.0 (CH3), 23.7 (d, JC–P = 15.5 Hz, CH2), 17.0, 16.1, 16.0.
Anal. Calcd for C32H35BF10NP: C, 57.76; H, 5.30; N, 2.11.
Found: C, 57.57; H, 5.16; N, 2.13.
µ (mm−1
)
0.187
22 996
6295
0.184
25 061
6624
0.155
26 430
9195
Total data
Unique data
I > 2σ(I2)
Variables
R1
wR2
GOF
27 638
7101
5916
5317
384
5127
404
5336
531
430
Synthesis
of
tBu2P(NPh)C(Ph)HCH(Ph)B(C6F5)2
10.
0.0346
0.0830
1.023
0.0401
0.1176
1.063
0.0380
0.0883
1.017
0.0536
0.1084
0.941
PhCuCPh (0.018 g, 0.1 mmol) was added to a suspension of
HB(C6F5)2 (0.034 g, 0.1 mmol) in toluene (5 mL) at room temp-
erature. 10 min later, Ph–NH–PtBu2 (0.021 g, 0.1 mmol) was
added to the reaction mixture and allowed the solution to stir
at 120 °C for 3 days. After that, the solvent was removed in Ph-H), 6.89–6.84 (m, 4H, Ph-H), 5.30 (d, J = 14.2 Hz, 1H, CH-B),
vacuum, and hexane was used to induce the precipitation. 4.96 (dd, J = 21.2, 14.2 Hz, 1H, CH-P), 2.21 (m, 1H, CH), 1.80
White powder was isolated, washed with hexane and dried in (m, 1H, CH), 0.81 (m, 6H, CH3), 0.48 (m, 6H, CH3). 19F NMR
vacuum.
(376 Hz, C6D6): −125.6 (br, 1F, B-o-C6F5), −128.1 (br, 1F, B-o-
1
10: Yield 0.035 g (47%). H NMR (400 MHz, C6D6): 7.60 (d, C6F5), −133.1 (br, 1F, B-o-C6F5), −135.1 (br, 1F, B-o-C6F5),
J = 6.4 Hz, 2H, Ph-H), 7.11 (m, 3H, Ph-H), 6.94–6.74 (m, 8H, −140.2 (m, 1F, C-o-C6F5), −143.1 (d, J = 21 Hz, 1F, C-o-C6F5),
3
3
Ph-H), 6.62 (t, J = 7.0 Hz, 2H, Ph-H), 5.25 (d, J = 14.6 Hz, 1H, −157.8 (t, JF–F = 22 Hz, 1F, C-p-C6F5), −158.1 (t, JF–F = 21 Hz,
CH-B), 5.06 (dd, J = 20.2, 14.6 Hz, 1H, CH-P), 1.08 (d, J = 1F, B-p-C6F5), −158.8 (t, 3JF–F = 21 Hz, 1F, B-p-C6F5), −162.9 (td,
14.2 Hz, 9H, CH3), 1.02 (d, J = 14.2 Hz, 9H, CH3). 19F NMR (376 J = 21, 6 Hz, 1F, C-m-C6F5), −164.5 (m, 4F, B-m-C6F5), −165.1
Hz, CD2Cl2): −121.6 (br, 1F, o-C6F5), −123.6 (br, 1F, o-C6F5), (td, J = 21, 6 Hz, 1F, C-m-C6F5). 11B{1H} NMR (128 MHz, C6D6):
−0.9. 31P{1H} NMR (162 MHz, C6D6): 64.0. 13C{1H} NMR
3
−129.4 (br, 1F, o-C6F5), −130.7 (br, 1F, o-C6F5), −159.3 (t, JF–F
=
3
1
21 Hz, 1F, p-C6F5), −160.7 (t, JF–F = 21 Hz, 1F, p-C6F5), (100 MHz, C6D6) partial: 148.0 (dm, JC–F = 245 Hz, o-C6F5),
1
−164.7 (br, 2F, m-C6F5), −166.7 (br, 2F, m-C6F5). 11B{1H} NMR 141.4 (Ph-C), 139.0 (dm, JC–F = 245 Hz, p-C6F5), 137.3 (dm,
(128 MHz, CD2Cl2): 0.8. 31P{1H} NMR (162 MHz, CD2Cl2): 68.8. 1JC–F = 242 Hz, m-C6F5), 133.3 (Ph-C), 129.1 (d, JC–P = 2.1 Hz,
13C{1H} NMR (100 MHz, CD2Cl2) partial: 143.6 (Ph-C), 143.3 (d, Ph-C), 128.7 (Ph-C), 128.5 (d, JC–P = 1.2 Hz, Ph-C), 128.4 (d,
JC–P = 14 Hz, Ph-C), 135.4 (Ph-C), 131.3 (Ph-C), 130.1 (Ph-C), JC–P = 3.1 Hz, Ph-C), 126.3 (d, JC–P = 1.6 Hz, Ph-C), 43.7 (d,
126.6 (d, JC–P = 1.8 Hz, Ph-C), 124.3 (Ph-C), 46.9 (d, JC–P
53.3 Hz, CH), 42.2 (d, JC–P = 32 Hz, C(CH3)3), 40.2 (d, JC–P
=
=
JC–P = 62 Hz, CH), 26.8 (d, JC–P = 44.8 Hz, CH), 25.5 (d, JC–P
44.8 Hz, CH), 22.6 (d, JC–P = 35.9 Hz, CH), 16.6 (d, JC–P
=
=
38.4 Hz, C(CH3)3), 34.5 (CH), 30.2 (CH3), 29.5 (t, JC–P = 4.2 Hz, 3.2 Hz, CH3), 16.4 (CH3). Anal. Calcd for C38H26BF15NP:
CH3). Anal. Calcd for C40H35BF10NP: C, 63.09; H, 4.63; N, 1.84. C, 55.43; H, 3.18; N, 1.70. Found: C, 55.30; H, 3.30; N, 1.47.
1
Found: C, 63.97; H, 5.02; N, 1.65.
14: Yield 0.02 g (25%). H NMR (400 MHz, C6D6): 6.92 (m,
Synthesis of R2P(NPh)C(R′)HCH(C6F5)B(C6F5)2 (R′ = Ph, R = 2H, Ph-H), 6.86 (m, 3H, Ph-H), 4.52 (d, J = 14.1 Hz, 1H, CH-B),
iPr 13, R′ = nPr, R = iPr 14). These compounds were prepared 3.55 (m, 1H, CH), 2.24 (m, 1H, CH), 1.77 (m, 1H, CH), 1.46 (m,
in a similar fashion and thus only one preparation is detailed. 2H, CH2), 0.96 (dd, J = 14.8, 7.1 Hz, 3H, CH3), 0.89–0.82 (m,
PhCCH (0.010 g, 0.1 mmol) was added to a toluene solution of 2H, CH2), 0.75–0.62 (m, 9H, CH3), 0.58 (t, J = 7.2 Hz, 3H, CH3).
B(C6F5)3 (0.051 g, 0.1 mmol) at room temperature. 30 min 19F NMR (376 Hz, C6D6): −124.3 (br, 1F, B-o-C6F5), −128.0 (br,
later, Ph–NH–PiPr2 (0.021 g, 0.1 mmol) was added to the reac- 1F, B-o-C6F5), −132.7 (br, 1F, B-o-C6F5), −135.1 (br, 1F, B-o-
tion mixture and allowed the solution to stir overnight at room C6F5), −139.4 (m, 1F, C-o-C6F5), −139.8 (d, J = 21 Hz, 1F, C-o-
3
3
temperature. After that, the solvent was removed in vacuum, C6F5), −158.5 (t, JF–F = 21 Hz, 1F, C-p-C6F5), −158.6 (t, JF–F
=
3
and hexane was used to induce the precipitation. White 21 Hz, 1F, B-p-C6F5), −159.1 (t, JF–F = 21 Hz, 1F, B-p-C6F5),
powder was isolated, washed with hexane and dried in −162.3 (td, J = 23, 6.5 Hz, 1F, C-m-C6F5), −164.7 (m, 4F, B-m-
vacuum.
C6F5), −165.6 (td, J = 23, 6.5 Hz, 1F, C-m-C6F5). 11B{1H} NMR
13: Yield 0.03 g (36%). H NMR (400 MHz, C6D6): 7.20 (m, (128 MHz, C6D6): −0.6. 31P{1H} NMR (162 MHz, C6D6): 69.3.
1
2H, Ph-H), 7.03 (d, J = 7.2 Hz, 2H, Ph-H), 6.95 (t, J = 7.2 Hz, 2H, 13C{1H} NMR (100 MHz, C6D6) partial: 148.2 (dm, 1JC–F = 245 Hz,
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o-C6F5), 141.1 (Ph-C), 138.8 (dm, JC–F = 242 Hz, p-C6F5),
Dalton Transactions
1
1
137.5 (dm, JC–F = 245 Hz, m-C6F5), 129.5 (Ph-C), 128.5 (d, JC–P
1.6 Hz, Ph-C), 126.6 (d, JC–P = 1.8 Hz, Ph-C), 36.8 (d, JC–P
=
=
57.7 Hz, CH), 33.2 (CH2), 28.1 (d, JC–P = 48.8 Hz, CH), 24.8 (d,
JC–P = 44.4 Hz, CH), 22.0 (d, JC–P = 9.1 Hz, CH2), 16.6, 16.4,
16.2, 16.0, 13.9 (CH3). Anal. Calcd for C35H28BF15NP: C, 53.25;
H, 3.58; N, 1.77. Found: C, 53.52; H, 3.41; N, 1.86.
X-ray data collection, reduction, solution and refinement
Single crystals were coated in Paratone-N oil in the glovebox,
mounted on a MiTegen Micromount and placed under an N2
stream. The data were collected on a Bruker Apex II diffracto-
meter. The data were collected at 150( 2) or 293( 2) K for all
crystals. Data reduction was performed using the SAINT soft-
ware package and an absorption correction applied using
SADABS. The structures were solved by direct methods using
XS and refined by full-matrix least-squares on F2 using XL as
implemented in the SHELXTL suite of programs.31 All non-
hydrogen atoms were refined anisotropically. Carbon-bound
hydrogen atoms were placed in calculated positions using an
appropriate riding model and coupled isotropic temperature
factors (see ESI†, Table 1).
Fig. 1 POV-ray depiction of 4. B: green, C: black, F: pink, P: orange, N: blue,
H: light blue.
The 19F NMR spectrum of 3 and 4 revealed two sets of ortho-,
para- and meta-F signals, which suggested the restricted mole-
cules exhibiting two distinct C6F5 environments. The 11B{1H}
NMR signals at −2.0, −1.6 ppm for 3 and 4 respectively, were
consistent with a four-coordinate boron centers. 31P{1H} NMR
data showed significantly downfield shifted signals at 68.8 and
72.9 ppm for 3 and 4, respectively. These data suggested the
formulation of 3 and 4 as the heterocyclic product R2P(NPh)-
CH(Ph)CH2B(C6F5)2, (iPr 3, tBu 4) respectively. X-ray diffraction
analysis of complex 4 further confirmed the formulation as a
heterocycle in which P has added to the beta-carbon of
the vinyl substituent on B (Fig. 1). Concurrently addition of the
N-bound hydrogen to the alpha-carbon results in the net
hydrophosphination of the vinyl-borane. Simultaneous to this
reduction, formally the P is oxidized to phosphinimine,
in which the N atom coordinates to B, affording the five-
membered PNB heterocycle. The N–B and N–P distances in
4 are found to be 1.5998(18) and 1.6527(11) Å, typical of
phosphinimine fragments coordinated to B.
Results and discussion
The phosphinoamines PhN(H)PiPr2 1 and PhN(H)PtBu2 2 are
readily prepared either by the reaction of lithium anilide with
R2PCl at reflux or by the reaction of aniline with R2PCl in the
presence of base. At the same time, the vinyl-borane,
PhCHvCHB(C6F5)2 is readily prepared from the stoichiometric
hydroboration of phenylacetylene using HB(C6F5)2. Sub-
sequent reaction of PhCHvCHB(C6F5)2 with either 1 or 2
resulted in the isolation of new products 3 and 4 in 74 and
1
67% yield respectively (Scheme 3). Resonances in the H NMR
spectrum were appeared at 4.11 and 2.42–2.20 ppm of com-
pound 3, and at 4.56 and 2.39–2.25 ppm of compound 4. In
both cases these were attributed to the CH and CH2 fragments.
In a similar fashion analogous reactions were achieved in
the reactions of 1 and 2 with the vinyl boranes and RCHvCHB-
(C6F5)2 (R = p-FC6H4, nPr). In this fashion the species R2P-
(NPh)CH(R′)CH2B(C6F5)2, (R′ = p-FC6H4, R = iPr 5, tBu 6, R′ =
nPr, R = iPr 7, tBu 8) (Scheme 1) were prepared in yields
ranging from 58–65%. The NMR spectra of 5–8 are similar to 3
and 4. For example, the resonance resulting from the CH
1
moiety of 5 and 6 gave rise to H NMR resonances at 4.00 and
4.42 ppm. The 1H NMR resonance attributable to the CH2 frag-
ment in 5 was observed at 2.24 ppm while in the case of 6 the
CH2 displayed two distinct signals at 2.64–2.50 and 2.08 ppm.
19F NMR spectra of 5–8 also showed two distinct C6F5 environ-
ments exhibiting two sets of ortho-, meta- and para-F peaks,
while the 11B and 31P NMR data are quite similar to those
found described for 3 and 4. The analogous heterocyclic for-
mulations for 7 and 8 were confirmed crystallographically
(Fig. 2 and 3). The N–B bond distances in these two com-
pounds being 1.592(2) and 1.604(2) Å are quite similar. On the
other hand, the N–P distance in compound 8 (1.6549(13) Å) is
Scheme 3 The synthesis of compounds 3–14.
3322 | Dalton Trans., 2013, 42, 3318–3325
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Fig. 4 POV-ray depiction of 9. B: green, C: black, F: pink, P: orange, N: blue,
Fig. 2 POV-ray depiction of 7. B: green, C: black, F: pink, P: orange, N: blue,
H: light blue.
H: light blue.
addition steric congestion arising from the substitution on the
alpha-carbon.
In the final examples of these hydrophosphination of vinyl
boranes R′CHvC(C6F5)B(C6F5)2 (R′ = Ph, nPr) derived from
1,1-carboboration reaction between alkyne and B(C6F5)3 were
employed. In these cases, reaction with 1 afforded compounds
iPr2P(NPh)CH(R′)CH(C6F5)B(C6F5)2 (R′ = Ph 13, nPr 14) in 36%
and 25% yield, respectively. The 11B NMR resonances were
found at −0.6 and −0.9 ppm, and 31P NMR signals appeared at
64.0 and 69.3 ppm for 13 and 14, respectively. 19F NMR spec-
trum of 13 and 14 revealed four peaks attributable to B-bound
ortho-fluorines and two peaks for the B-bound para-F atoms,
and two ortho-F and two para-F atoms attributable to C–C6F5.
These data suggested the restricted rotation of the C6F5
groups. Again it is noteworthy that attempts to make analo-
gous compounds with 2 with the vinyl boranes R′CHvC(C6F5)-
B(C6F5)2 (R′ = Ph, nPr) showed no reaction. Again the increased
steric congestion in these cases is thought to preclude
hydrophosphination.
Fig. 3 POV-ray depiction of 8. B: green, C: black, F: pink, P: orange, N: blue,
H: light blue.
slightly longer than that in 7 (1.6352(14) Å) and is presumed to
be a result of steric congestion.
This reactivity of vinyl boranes could also be extended to
vinyl boranes derived from the internal alkynes and HB(C6F5)2.
In this fashion reactions of 1 and 2 with R′CHvC(R″)B(C6F5)2
(R′ = R″ = Ph, Et), afforded the five-membered heterocyclic ring
compounds 9–12 (Scheme 1) although in these cases the yield
were found to be somewhat lower ranging from 40–55%. The
1H, 19F, 11B and 31P NMR data are quite similar to those found
above and thus the products formulated as the heterocycles
R2P(NPh)C(R′)HCH(R″)B(C6F5)2 (R′ = R″ = Ph, R = iPr 9, tBu 10,
R′ = R″ = Et, R = iPr 11, tBu 12). It is noteworthy that 2 did not
react with PhCHvC(Ph)B(C6F5)2 at room temperature, rather it
required heating to 120 °C for 3 days, to give compound 10
as white solid in 47% yield. In contrast, the less sterically
hindered vinyl-borane CH3CH2CHvC(CH2CH3)B(C6F5)2 react
with both 1 and 2 at room temperature to give compounds 11
and 12 in 40% yield. Compound 9 was also crystallographically
characterized (Fig. 4). In this case, the N−B and N−P distances
were determined to be 1.607(3) and 1.6301(18) Å. The N−B dis-
tance in 9 is slightly longer than that 7 consistent with the
The above reactions demonstrate a reasonably general reac-
tion in which phosphinoamines effect the net hydrophosphi-
nation of vinyl-boranes. Nonetheless, it should be noted that
in contrast to conventional hydrophosphinations which
involve addition of PH bonds, the present reactions utilized
the amino-proton as the hydrogen atom source. The reduction
of the olefinic bond is concurrent with the oxidation of the
phosphinoamine N-atom to boron which orients the phos-
phine for nucleophilic attack of the olefin. This prompts
proton transfer from N to the carbon alpha to boron. This 1,3-
migration completes the cyclization and reduction of the five-
membered heterocycle (Scheme 4). Uncatalyzed hydrophosphi-
nations are generally rare although interestingly Gaumont and
co-workers32 have reported that secondary phosphine-oxides
will undergo reactions with imines, aldehydes, ketones and
electron deficient olefins to hydrophosphination of the unsatu-
rated bond without a catalyst under relatively mild conditions.
It is noteworthy that the present reactivity provides a flexible
route to these heterocycles. An alternative route to such
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Dalton Transactions
3 D. W. Stephan, Org. Biomol. Chem., 2012, 10, 5740–5746.
4 D. W. Stephan and G. Erker, Angew. Chem., Int. Ed., 2010,
49, 46–76.
5 D. W. Stephan, Chem. Commun., 2010, 46, 8526–8533.
6 D. W. Stephan, Dalton Trans., 2009, 3129–3136.
7 D. W. Stephan, Org. Biomol. Chem., 2008, 6, 1535–1539.
8 T. Voss, T. Mahdi, E. Otten, R. Fröhlich, G. Kehr,
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9 S. Schwendemann, R. Fröhlich, G. Kehr and G. Erker,
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Scheme 4 Proposed mechanism of hydrophosphination and cyclization.
10 A. M. Chapman, M. F. Haddow and D. F. Wass, J. Am.
Chem. Soc., 2011, 133, 8826–8829.
11 S. Schwendemann, T. A. Tumay, K. V. Axenov, I. Peuser,
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29, 1067–1069.
12 D. P. Huber, G. Kehr, K. Bergander, R. Fröhlich, G. Erker,
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Scheme 5 Staudinger oxidation of linked phosphino-borane.
13 V. Sumerin, K. Chernichenko, M. Nieger, M. Leskela,
B. Rieger and T. Repo, Adv. Synth. Catal., 2011, 353, 2093–
2110.
14 F. Schulz, V. Sumerin, M. Leskela, T. Repo and B. Rieger,
Dalton Trans., 2010, 39, 1920–1922.
species has recently been communicated by Erker and co-
workers.33 In that case, a Staudinger oxidation of the phos-
phine of linked phosphino-boranes affords the heterocyclic
PNB species with an (NH) fragment linking
(Scheme 5). The NH fragment results from deprotonation of
the mesityl fragment on the original azide reagent.
B and P
15 V. Sumerin, F. Schulz, M. Nieger, M. Atsumi, C. Wang,
M. Leskela, P. Pyykko, T. Repo and B. Rieger, J. Organomet.
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16 V. Sumerin, F. Schulz, M. Nieger, M. Leskela, T. Repo and
B. Rieger, Angew. Chem., Int. Ed., 2008, 47, 6001–6003.
17 V. Sumerin, F. Schulz, M. Atsumi, C. Wang, M. Nieger,
M. Leskela, T. Repo, P. Pyykko and B. Rieger, J. Am. Chem.
Soc., 2008, 130, 14117–14118.
18 D. Palomas, S. Holle, B. Ines, H. Bruns, R. Goddard and
M. Alcarazo, Dalton Trans., 2012, 41, 9073–9082.
19 P. A. Chase, A. L. Gille, T. M. Gilbert and D. W. Stephan,
Dalton Trans., 2009, 7179–7188.
20 D. Holschumacher, T. Bannenberg, C. G. Hrib, P. G. Jones
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Conclusions
The reaction between alkenylborane derivatives R′CHvCR″B-
(C6F5)2 and phosphinoamines PhN(H)PR2 (R = iPr, tBu) results
in the formation of C–C–B–N–P five-membered rings. This
reaction can be described as a [3 + 2] cycloaddition of the PNH
unit to the alkenylborane in which the resulting phosphin-
imine is trapped by internal adduct formation with the borane.
All the compounds have been fully characterized via NMR
and elemental analysis, and some of them were characterized
by X-ray diffraction analysis. Exploring the other reaction
between phosphinoamines PhN(H)PR2 and borane com-
pounds are the subject of an on-going project.
23 C. F. Jiang, O. Blacque and H. Berke, Organometallics, 2010,
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24 R. Liedtke, M. Harhausen, R. Fröhlich, G. Kehr and
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25 G. Kehr and G. Erker, Chem. Commun., 2012, 48, 1839–
1850.
Acknowledgements
Financial support from NSERC of Canada is gratefully
acknowledged. DWS is grateful for the award of a Canada
Research Chair.
26 A. Feldmann, A. Iida, R. Frohlich, S. Yamaguchi, G. Kehr
and G. Erker, Organometallics, 2012, 31, 2445–2451.
27 C. Chen, T. Voss, R. Fröhlich, G. Kehr and G. Erker, Org.
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3324 | Dalton Trans., 2013, 42, 3318–3325
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This journal is © The Royal Society of Chemistry 2013
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