Addition reactions to the intramolecular mesityl2P-CH 2-CH2-B(C6F5)2 frustrated Lewis pair

Article abstract of DOI:10.1039/c0dt00015a

Hydroboration of dimesitylvinylphosphine with Piers' borane [HB(C ₆F₅)₂] gives the ethylene-bridged intramolecular frustrated P/B Lewis pair 1. It adds pyridine, tert-butyl isocyanide or pivalonitrile to the strongly elect

Full text of DOI:10.1039/c0dt00015a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Addition reactions to the intramolecular mesityl2P–CH2–CH2–B(C6F5)2
frustrated Lewis pair†
Cornelia M. Mo¨mming, Gerald Kehr, Birgit Wibbeling, Roland Fro¨hlich and Gerhard Erker*
Received 22nd February 2010, Accepted 6th May 2010
First published as an Advance Article on the web 8th July 2010
DOI: 10.1039/c0dt00015a
Hydroboration of dimesitylvinylphosphine with Piers’ borane [HB(C6F5)2] gives the ethylene-bridged
intramolecular frustrated P/B Lewis pair 1. It adds pyridine, tert-butyl isocyanide or pivalonitrile to the
strongly electrophilic boron center to yield the respective adducts 5–7. Compound 1 undergoes a
1,1-phosphine/borane addition to the terminal nitrogen center of phenyl azide to yield the
=
five-membered heterocycle 8, featuring a pendant –N N–Ph. This can be regarded as a
boron-stabilized intermediate of a Staudinger reaction. Benzaldehyde and phenyl isocyanate undergo
1,2-P/B additions of 1 to their reactive carbonyl groups to yield the corresponding six-membered
heterocycles 9 and 10, respectively. The P/B Lewis pair reacts with nitrosobenzene by 1,2-addition to
=
the –N O unit under P–N and O–B bond formation to give the six-membered heterocycle 11. The
compounds 5–11 were characterized by X-ray crystal structure analyses.
Introduction
Lewis acids and Lewis bases usually quench each other when
brought together in solution. However, in cases of sufficient steric
bulk this neutralization reaction may become completely or at
least sufficiently hindered that the typical chemical features of both
components prevail in the same solution. Such frustrated Lewis
pairs1,2 may exhibit separately the typical Lewis acid and Lewis
base reactivities of their “antagonistic”3 components.4,5 However,
they may in some cases also work together and e.g. activate or
add to various small molecules in concert and/or cooperatively.
Typical examples include the heterolytic dihydrogen splitting
1,2,6–9
activity of a variety of bulky phosphine/B(C6F5)3
or bulky
Scheme 1 Activation of H2, CO2 and norbornene by the Lewis pair 1.
amine10 or carbene/B(C6F5)3 Lewis pairs.11,12 We have recently
described the ethylene-linked P/B system 1.13 It was characterized
as a weakly interacting frustrated Lewis pair. According to a char-
acterization including an advanced DFT calculation it features
a four-membered heterocyclic global minimum structure. The
activation barrier of reversible P ◊ ◊ ◊ B dissociation was determined
for a series of suitably substituted derivatives as DGπ(280 K) ª 12
kcal mol-1.14 The system reacts with a variety of small molecules
probably from a gauche like open local minimum intermediate.9 It
is currently one of the most active systems of its kind for heterolytic
H2-activation (to give 2) and subsequently for the metal-free
catalytic hydrogenation of enamines and of bulky imines.15,16 It
adds (probably concertedly) to olefins, to conjugated enynes and
alkynes17 and even to carbon dioxide18 (see Scheme 1).
unique system. This study includes reactions with monofunctional
donors that preferentially attach to the electrophilic boron center
and bifunctional reagents that have a choice to also undergo the
cooperative P/B addition.
Results and discussion
Preferred addition reactions to the boron center
The intramolecular P/B Lewis pair 1 was prepared by treatment
of dimesitylvinylphosphine with “Piers’ borane” [HB(C6F5)2].19
At ambient temperature a clean regioselective hydroboration
reaction20 was observed to give 1. We were concerned that the
system 1 might possibly undergo retrohydroboration when treated
with additional reagents. Therefore, this was checked by treatment
of 1 with pyridine, a reagent that would have indicated any
reversibly of the formation of 1 by trapping of the HB(C6F5)2
component by pyridine–[HB(C6F5)2] adduct formation.21 How-
ever, this was not observed. Treatment of 1 with pyridine in
a 1 : 1 molar ratio in pentane at room temperature overnight
resulted in a colourless precipitate of the 1–pyridine adduct (5)
that was eventually isolated as a solid in 65% yield (see Scheme 2).
The compound was characterized by elemental analysis, spectro-
scopically (NMR spectra in d6-benzene, Table 1) and by X-ray
We here wish to report about addition reactions of a variety of
organic substrates to the Lewis pair 1 which serve to further char-
acterize the reactivity and the favoured reaction patterns of this
Organisch-Chemisches Institut, Universita¨t Mu¨nster, Corrensstr. 40,
D-48149, Mu¨nster, Germany. E-mail: erker@uni-muenster.de; Fax: +49
251-83 36503
† Electronic supplementary information (ESI) available: Additional exper-
imental and spectroscopic data. CCDC reference numbers 722646, 722647
and 767246–767250. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c0dt00015a
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Table 1 Selected NMR features (d) of compound 1 and its adducts 5–11
13C
19F
Compound 31P
PCH2 BCH2 11B
o
p
m
1
5
6
7
8
9
+20.6 29.4
18.2
20.0
17.9
19.6
18.2
13.8
+8.8 -128.4 -157.0 -163.6
-0.2 -131.9 -157.4 -163.1
-16.1 24.4
-16.7 26.7
-16.4 25.1
-18
-133.0 -157.5 -163.3
-1.2 -134.7 -157.6 -163.5
-5.4 -132.7 -162.1 -166.3
-0.3 -134.7 -162.5 -166.4
-134.7 -161.4 -165.6
+50
31.2
+19.6 28.9
10
11
+5.1 26.6
14.4
15.4
+0.7 -134.2 -159.2 -164.2
+46.9 28.1
+0.4 -133.1 -161.9 -165.5
Fig. 1 Molecular structure of the pyridine adduct 5.
pyridine moiety were monitored at d 7.99 (o), 6.56 (p), 6.26 (m)
(1H)/d 145.3 (o), 140.6 (p), and 125.3 (m) (13C).
Scheme 2 Formation of the pyridine adduct 5.
Compound 1 formed an adduct (6) with tert-butyl isocyanide
as expected (see Scheme 3). The addition product of the isonitrile
nucleophile to the electrophilic borane subunit of 1 was isolated
as a colourless solid in >70% yield from the reaction mixture. It
diffraction. Single crystals for the X-ray crystal structure analysis
were obtained by slow diffusion of heptane vapor into a solution of
compound 5 in benzene. The structure shows that the pyridine has
added to the boron center (see Fig. 1 and Table 2). Compound 5
consequently contains a tetracoordinated boron and a non-planar
tricoordinated phosphorus atom (sum of C–P–C bonding angles
312.5◦). In the crystal the group of aromatic rings around boron
adopts a propeller-like geometry. The P–CH2–CH2–B unit shows
a slight distortion from an anti-periplanar arrangement.
features a 13C NMR signal of the coordinated isonitrile carbon
-1
≡
˜
center at d 127.8 and a strong IR (C N–) band at n = 2287 cm .
The X-ray crystal structure analysis of compound 6 (see Fig. 2,
Table 2) features a linear [B]–C N– Bu moiety with typical
t
≡
˚
˚
bonding parameters of B1–C3: 1.622(4) A, C3–N4: 1.138(3) A,
The 1H NMR spectrum of compound 5 shows the typical
resonances of the pair of symmetry-equivalent mesityl groups at
phosphorus [d 6.67 (d,4JPH = 2.1 Hz m-CH), d 2.37 (o-CH3), 2.07
(p-CH3); 31P resonance at d -16.1] and the typical 1H NMR signals
of the ethylene linker [d 2.35 (PCH2), d 1.62 (BCH2)]. The 11B
NMR resonance of 5 is found at d -0.2, which is typical of a four-
coordinate boron center with such substituents. This is supported
by the observed small Dm,p difference (5.7 ppm) of the 19F NMR
1
C6F5 resonances.22 The H/13C NMR signals of the coordinated
Scheme 3 Formation of the isonitrile and nitrile adducts 6 and 7.
Table 2 Selected structural data of the adducts 5–11
Compound
5
6
7
8
9
10
11
˚
Bond lengths (A)
P–CH2
CH2–CH2
CH2–B
B–X
P–Y
1.862(2)
1.539(3)
1.627(3)
1.645(3)
—
1.861(3)
1.541(3)
1.630(4)
1.622(4)
—
1.861(3)
1.526(5)
1.619(5)
1.588(5)
—
1.821(2)
1.545(3)
1.648(3)
1.590(2)
1.662(2)
1.833(3)
1.543(3)
1.624(4)
1.497(3)
1.919(2)
1.815(3)
1.539(4)
1.609(4)
1.527(3)
1.855(3)
1.821(4)
1.534(5)
1.623(6)
1.509(5)
1.656(3)
Bond angles (◦)
P–CH2–CH2
CH2–CH2–B
CH2–B–X
109.9(2)
114.6(2)
110.9(2)
—
110.7(2)
112.2(2)
104.9(2)
—
108.7(2)
116.8(3)
102.3(3)
—
108.6(1)
113.2(2)
102.1(2)
96.5(1)
110.7(2)
113.6(2)
108.3(2)
97.3(1)
106.7(2)
110.9(2)
110.2(2)
102.9(1)
115.9(3)
114.0(3)
109.0(3)
100.7(2)
CH2–P–Y
Dihedral angles (◦)
P–CH2–CH2–B
CH2–CH2–B–X
CH2–CH2–P–Y
-162.7(2)
73.7(2)
—
-154.0(2)
-50.7(3)
—
169.8(2)
-66.5(4)
—
-10.0(2)
7.6(2)
7.6(1)
60.3(2)
-58.9(3)
-52.1(2)
-71.9(3)
58.9(3)
47.1(2)
45.8(4)
-17.5(5)
-12.1(3)
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Addition to both the P and B components of the Lewis pair
The P/B Lewis pair 1 reacts with phenyl azide to give the five-
membered heterocyclic product 8 (see Scheme 4), which was
isolated in 77% yield from the respective reaction mixture. The X-
ray crystal structure analysis (single crystals were obtained from
benzene–heptane by the diffusion method) shows that both the
phosphorus and the boron atom have become bonded to the
terminal nitrogen atom of the azide reagent (see Fig. 4). The
˚
resulting P1–N3 bond length amounts to 1.662(2) A, the adjacent
˚
B1–N3 bond length was found at 1.590(2) A (angle P1–N3–B1
◦
˚
118.7(1) ). The N3–N4 bond length is 1.374(2) A;the adjacentN4–
˚
=
N5 bond is much shorter (1.254(2) A), being in the –N N– double
=
bond range. The –N4 N5– unit is trans-configurated (angles N3–
N4–N5: 112.4 (1)◦, N4–N5–C51: 111.8(2)◦).
Fig. 2 A view of the molecular structure of the isonitrile adduct 6.
◦
˚
N4–C5: 1.468(3) A, angles B1–C3–N4: 174.8(3) and C3–N4–C5:
175.3(3)◦.
The reaction of 1 with pivalonitrile could principally have had a
remote chance to lead to 1,2-addition of the P/B pair across the –
≡
C N triple bond. However, we only observed nitrile coordination
to the boron atom as expected. The adduct 7 (see Scheme 3) was
isolated in ca. 60% yield from the reaction mixture (pentane, r.t.,
overnight). The product 7 was characterized spectroscopically [13C
Scheme 4 Reaction of the Lewis pair 1 with phenyl azide.
≡
NMR: d 121.1 ([B]–N C– (for additional data, see Table 1)]. The
-1
t
˜
IR band of the coordinated nitrile [7: n = 2329 cm , cf. free Bu–
-1
≡
˜
C N: n = 2235 cm ] is shifted to higher wavenumbers as it is
typically observed for strong Lewis-acid adducts.23
The X-ray crystal structure analysis of 7 shows an open almost
anti-periplanar [P]–CH2–CH2–[B] framework (see Table 2 and
Fig. 3) with a typical non-planar tricoordinate phosphorus atom
t
≡
and tetracoordinated boron atom. The [B]–N C– Bu unit is linear
◦
˚
[B1–N1:◦ 1.588(5) A, angles B1–N1–C3: 173.7(3) , N1–C3–C4:
˚
178.7(4) ]. The N1–C3 bond is short at 1.136(4) A.
Fig. 4 Molecular structure of compound 8.
The structure of the phenyl azide addition product 8 can be
regarded as an internally boron stabilized intermediate of the
Staudinger reaction.24–26 It actually may be due to the N–B
coordination that the usual course toward the formation of the
=
[P] NPh phosphine-imine product is not completed in this case.
In solution the system 8 shows dynamic 31P NMR spectra. A
broad resonance [d = +50 (n1/2 ~ 1600 Hz)] observed at ambient
temperature decoalesces upon cooling to eventually split into an
1 : 2.3 intensity pair of resonances at d +37.0 and +58.8 (223 K)
Fig. 3 A view of the molecular structure of the nitrile adduct 7.
7558 | Dalton Trans., 2010, 39, 7556–7564
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1
(for details see ESI†). The structure of the two isomers observed
in solution still have to be resolved.26
benzaldehyde –CH(Ph) unit gives rise to H/13C NMR signals
2
1
at d 6.23 (1H, d, JPH = 15.3 Hz) and d 85.5 (d, JPC = 29.6
Hz), respectively. The reaction of 1 with phenyl isocyanate takes
a similar course.27 The P/B Lewis pair undergoes a regioselective
1,2-addition to the reactive carbonyl group of the heterocumulene
reagent to yield 10 (78% isolated, see Scheme 5).
We next reacted the P/B Lewis pair 1 with benzaldehyde.
The reaction in pentane rapidly goes to completion at ambient
temperature. The product 9 (see Scheme 5) precipitated from
the reaction mixture. It was isolated as a white solid in ca.
85% yield. Single crystals of 9 suited for the X-ray crystal
structure analysis were obtained from benzene/heptane by the
diffusion method. The structure (see Fig. 5) shows that the
phosphorus atom of 1 has added to the carbonyl carbon atom
The 19F NMR spectrum of 10 shows a single set of C6F5 reso-
nances (see Table 1) and the H/13C NMR spectra feature single
1
sets of signals of the symmetry-equivalent mesityl substituents at
phosphorus. The C NPh imino 13C NMR signal of 10 is found at
=
of the benzaldehyde reagent (P1–C3: 1.919(2) A, angle P1–C3–
d 149.1 (d, 1JPC = 127 Hz).
˚
O1: 111.3(2)◦) and the former carbonyl oxygen was bonded to t◦he
Single crystals of compound 10 were obtained from
dichloromethane. The X-ray crystal structure analysis of 10 shows
˚
boron atom (B1–O1: 1.497(3) A, angle B1–O1–C3: 117.3 (2) ).
=
The resulting six-membered heterocycle shows a distorted chair-
like conformation17 (dihedral angles P1–C3–O1–B1: -66.8(2)◦,
C1–P1–C3–O1: 55.0(2)◦, C2–B1–O1–C3: 64.4(3)◦). The phenyl
substituent at the ring carbon atom C3 is found in a pseudo-
equatorial position.
that 1,2-P/B addition to the isocyanate C O functionality has re-
sulted in the formation of a six-membered heterocycle (see Fig. 6).
2
˚
It features a C(sp )–O single bond (C3–O1: 1.313(3) A, angle C3–
O1–B1: 128.8(2)◦). The exocyclic imin◦o-functionality (C3–N1:
◦
˚
1.271(3) A, angles P1–C3–N1: 112.7(2) , P1–C3–O1: 121.1(2) ,
O1–C3–N1: 126.3(2)◦) is E-configurated (dihedral angles P1–C3–
N1–C4: 180.0 (2)◦, O1–C3–N1–C4: 0.7(4)◦). The six-membered
ring framework of compound 10 features a distorted half-chair
like conformation.
Scheme 5 Treatment of the Lewis pair 1 with PhCHO, PhNCO and
PhNO.
Fig. 6 A view of the molecular structure of compound 10.
Eventually, we treated the P/B Lewis pair with nitrosoben-
zene. The reaction proceeds as a 1,2-addition between the
=
phosphine/borane Lewis base/Lewis acid pair with the –N O
p-bond of the reagent to give the six-membered heterocyclic
product (11). The new compound was isolated in ca. 50% yield
from the reaction mixture in pentane. Single crystals for the
X-ray crystal structure analysis were obtained by diffusion of
pentane vapor into a solution of 11 in dichloromethane. The
structure determination (see Fig. 7) revealed that P–N and B–
Fig. 5 A Projection of the molecular structure of compound 9.
Due to the presence of the newly formed chiral center (C3) inside
the six-membered heterocycle we observe a total of four separate
1H NMR resonances of the bridging –CH2–CH2– moiety [PCH2:
d 3.30, 3.15; BCH2: d 1.70, 1.09].
As expected, the phosphorus atom bears a pair of diastereotopic
mesityl substituents and the boron atom a pair of diastereotopic
C6F5 substituents (see Table 1 for details). The 31P NMR chemical
shift of 9 is found in the typical phosphonium range (d +19.6)
and the 11B NMR shift is of a borate type (d -0.3). The former
˚
O bond formation had taken place (P1–N4: 1.656(3) A, O3–B1:
◦
◦
˚
1.509(5) A, angles P1–N4–O3: 106.6(2) , N4–O3–B1: 110.9(3) ).
The coordination geometry at the ring-nitrogen atom N4 is slightly
deviating from trigonal planarity (sum of bond angles at N4:
352.7◦).
The 31P NMR spectrum of 11 shows a signal at d 46.9; the
11B NMR feature occurs at d 0.4.
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and on a Varian UnityPlus 600 (1H: 599.9 MHz, 13C: 150.8 MHz,
1
19F: 564.4 MHz, 11B: 192.4 MHz, 31P: 242.7 MHz). H NMR
and 13C NMR: chemical shifts d are given relative to TMS and
referenced to the solvent signal. 19F NMR: chemical shifts d are
given relative to CFCl3 (external reference), 11B NMR: chemical
shifts d are given relative to BF3·Et2O (external reference),
31P NMR: chemical shifts d are given relative to H3PO4 (85%
in H2O) (external reference). NMR assignments were supported
by additional 2D NMR experiments.
X-Ray structure analyses. Data sets were collected with Non-
ius KappaCCD diffractometers, in case of Mo-radiation equipped
with a rotating anode generator. Programs used: data collec-
tion: COLLECT,31 data reduction: Denzo-SMN,32 absorption
correction: Denzo,33 structure solution: SHELXS-97,34 structure
refinement: SHELXL-97,35 graphics: XP (BrukerAXS, 2000).
Thermal ellipsoids are shown on the 50% probability level.
Fig. 7 Molecular structure of the addition product 11 of the Lewis pair
1 to nitrosobenzene.
Conclusions
Compound 5. Dimesitylvinylphosphine (100 mg, 0.34 mmol)
and bis(pentafluorophenyl)borane (117 mg, 0.34 mmol) were
dissolved in pentane (8 mL) and stirred for 15 min. Upon addition
of pyridine (27 mL, 0.34 mmol) the solution became immediately
colourless, and within 2 h a white precipitate was formed. After
stirring the reaction mixture overnight, the precipitate was isolated
via cannula filtration. Then the residue was washed with pentane
(3 ¥ 3 mL) and all volatiles were removed in vacuo to yield
5 (159 mg, 65%) as a white powder. Crystals suitable for the
X-ray crystal structure analysis were obtained by gas diffusion
of heptane into a benzene solution of 5. Found: C, 61.36; H, 4.49;
N, 1.90. Calc. for C37H31BF10NP: C, 61.60; H, 4.33; N, 1.94%.
1H NMR (600 MHz, 298 K, benzene-d6) d 7.99 (2H, m, o-Py),
An increasing amount of addition reactions to frustrated Lewis
pairs is currently appearing from the literature.28 Among them
the addition reactions to unsaturated substrates may gain an
increasing importance, since in some cases this might eventually
lead to the discovery of novel activation pathways for such
substrates. Previously there have been reports of e.g. isocyanate,
carbonyl or azide addition reactions to P/B-Lewis pairs such as
e.g. 12 or 13 (and derivates thereof).4,5,26,27,29 Although the addition
modes were similar to the previously reported systems containing
configurationally fixed phosphine/borane pairs (see Scheme 6),
our new system (1) is special in two ways: it contains a very
strongly Lewis acidic –B(C6F5)2 moiety and it probably reacts from
a conformationally non-restricted reactive open intermediate.
Nevertheless, the addition reactions of 1 to a large variety of
p-substrates seem to be unproblematic and occur readily. This
lets us hope that extensions of this work will eventually result
in synthetically useful variants of such easily performed addition
chemistry of frustrated Lewis pairs.
4
6.67 (4H, d, JPH = 2.1 Hz, m-Mes), 6.56 (1H, m, p-Py), 6.26
(2H, m, m-Py), 2.37 (12H, s, o-CH3Mes), 2.35 (2H, m, PCH2), 2.07
1
(6H, s, p-CH3Mes), 1.62 (2H, m, BCH2). 13C{ H} NMR (151 MHz,
298 K, benzene-d6) d 148.3 (dm, 1JFC = 238 Hz, C6F5), 145.3 (o-
2
Py), 142.2 (d, JPC = 12.8 Hz, o-Mes), 140.6 (p-Py), 139.8 (dm,
1
1JFC = 247 Hz, C6F5), 137.4 (dm, JFC = 248 Hz, C6F5), 137.4
(p-Mes), 134.4 (d, 1JPC = 24.6 Hz, i-Mes), 130.3 (d, 3JPC = 2.6 Hz,
m-Mes), 125.3 (m-Py), 24.4 (d, 1JPC = 15.8 Hz, PCH2), 121.9 (br,
i-C6F5), 23.2 (d, 3JPC = 13.2 Hz, o-CH3Mes), 20.7 (p-CH3Mes), 20.0
1
(br, BCH2). 11B{ H} NMR (64 MHz, 298 K, benzene-d6) d -0.2
1
(n1/2 = 450 Hz). 31P{ H} NMR (81 MHz, 298 K, benzene-d6) d
1
-16.1 (n1/2 = 6 Hz). 19F{ H} NMR (282 MHz, 298 K, benzene-d6)
Scheme 6 Related phosphine/borane linked systems.
d -131.9 (2F, o-C6F5), -157.4 (1F, p-C6F5), -163.1 (2F, m-C6F5).
Crystal data for C37H31BF10NP (5), M = 721.41, monoclinic,
space group P21/n (no. 14), a = 16.1539(6), b = 12.4332(4), c =
Experimental
◦
3
-3
˚
˚
17.1214(7) A, b = 95.333(2) , V = 3423.9(2) A , Dc = 1.400 g cm ,
-1
˚
m = 1.451 mm , Z = 4, l = 1.54178 A, T = 223(2) K, 26661
General considerations
-1
˚
reflections collected ( h, k, l), [(sin q)/l] = 0.60 A , 6016
All manipulations were performed under argon using Schlenk-
type glassware or in a glove-box. Solvents were dried according
to the procedure by Grubbs30 or were distilled from appropriate
drying agents and stored under an argon atmosphere.
independent (Rint = 0.055), and 4855 observed reflections [I ≥
2s(I)], 457 refined parameters, R = 0.047, wR2 = 0.153.
Compound 6. To
a solution of dimesitylvinylphosphine
Melting points were obtained with a DSC Q20 (TA In-
(100 mg, 0.34 mmol) and bis(pentafluorophenyl)borane (117 mg,
0.34 mmol) in pentane (5 mL) tert-butyl isocyanide (42 mL,
0.36 mmol) was added. The solution was immediately decolour-
ized. It was then stirred for 2 days. Removal of all volatiles in vacuo
yielded 6 (178 mg, 74%) as a white solid. Crystals suitable for the
struments). IR spectra were recorded on
a Varian 3100
FT-IR (Excalibur Series). Elemental analyses were performed
on a Elementar Vario El III. NMR spectra were recorded on a
Bruker AC 200 P (11B: 64.0 MHz, 31P NMR: 81.0 MHz), Bruker
ARX 300 (19F: 282.4 MHz); Varian Inova 500 (1H: 499.9 MHz,
13C: 125.7 MHz, 19F: 470.3 MHz, 11B: 160.4 MHz, 31P: 202.3 MHz)
X-ray crystal s◦tructure analysis were obtained from a heptane
-1
˜
solution at -36 C. n(KBr)/cm = 2287 (s, CN). Found: C, 60.96;
7560 | Dalton Trans., 2010, 39, 7556–7564
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H, 4.79; N, 1.87. Calc. for C37H35BF10NP: C, 61.26; H, 4.86; N,
Compound 8. Dimesitylvinylphosphine (100 mg, 0.34 mmol)
and bis(pentafluorophenyl)borane (117 mg, 0.34 mmol) were
dissolved in pentane (8 mL) and stirred for 15 min. After addition
of phenyl azide (40 mg, 0.34 mmol) the reaction mixture became
immediately cloudy. The reaction mixture was stirred for 2 days,
then the precipitate was collected via cannula filtration and washed
with pentane (3 ¥ 3 mL). All volatiles were removed in vacuo to
yield 8 (201 mg, 77%). Crystals suitable for the X-ray crystal
structure analysis were obtained by slow diffusion of heptane
into a benzene solution of 8. Found: C, 59.50; H, 4.10; N, 5.13.
1
1.93%. H NMR (600 MHz, 298 K, benzene-d6) d 6.68 (4H, d,
4JPH = 2.0 Hz, m-Mes), 2.54 (2H, m, PCH2), 2.41 (12H, s, o-
CH3Mes), 2.08 (6H, s, p-CH3Mes), 1.62 (2H, br m, BCH2), 0.75
1
(9H, s, C(CH3)3). 13C{ H} NMR (151 MHz, 298 K, benzene-
d6) d 148.2 (dm, 1JFC = 246 Hz, o-C6F5), 142.0 (d, 2JPC = 13 Hz,
1
1
o-Mes), 140.0 (dm, JFC = 250 Hz, p-C6F5), 137.5 (dm, JFC
=
1
250 Hz, m-C6F5), 137.5 (p-Mes), 134.4 (d, JPC = 24.1 Hz, i-
≡
Mes), 130.4 (m-Mes), 127.8 (C N), 117.4 (i-C6F5), 59.6 (C(CH3)3,
1
3
28.2 (C(CH3)3), 26.7 (d, JPC = 17.0 Hz, PCH2), 23.4 (d, JPC
=
13.0 Hz, o-CH3Mes), 20.8 (p-CH3Mes), 17.9 (br, BCH2). 11B{ H}
Calc. for C38H31BF10N3P: C, 59.94; H, 4.10; N, 5.52%. H NMR
1
1
NMR (192 MHz, 298 K, benzene-d6) d -18 (n1/2 = 230 Hz).
(500 MHz, 298 K, dichloromethane-d2) d 7.28 (2H, m, m-Ph),
7.26 (2H, m, o-Ph), 7.23 (1H, m, p-Ph), 6.95 (4H, d, 4JPH = 4.6 Hz,
m-Mes), 3.28 (2H, m, PCH2), 2.31 (6H, s, p-CH3Mes), 2.15 (12H, s,
31P{ H} NMR (121 MHz, 298 K, benzene-d6) d –16.7 (n1/2 = 7
1
Hz). 19F{ H} NMR (564 MHz, 298 K, benzene-d6) d -133.0 (2F,
1
1
o-C6F5), -157.5 (1F, p-C6F5), -163.3 (2F, m-C6F5).
o-CH3Mes), 1.78 (2H, m, BCH2). 13C{ H} NMR (126 MHz, 298 K,
1
Crystal data for C37H35BF10NP (6), M = 725.44, triclinic, space
dichloromethane-d2) d 149.2 (i-Ph), 148.0 (dm, JFC = 240 Hz,
group P1 (no. 2), a = 10.4592(4), b = 13.2592(5), c = 14.5233(7) A,
C6F5), 143.8 (p-Mes), 142.2 (d, 2JPC = 11.0 Hz, o-Mes), 139.0 (dm,
1JFC = 240 Hz, C6F5), 137.2 (dm, 1JFC = 241 Hz, C6F5), 132.2 (d,
3JPC = 11.8 Hz, m-Mes), 131.4 (br, i-C6F5), 129.3 (m-Ph), 128.6
¯
˚
◦
3
˚
a = 99.281(2), b = 99.394(2), g = 110.205(3) , V = 1812.55(13) A ,
-3
-1
˚
Dc = 1.329 g cm , m = 1.371 mm , Z = 2, l = 1.54178 A, T =
223(2) K, 21458 reflections collected ( h, k, l), [(sin q)/l] =
1
(p-Ph), 124.5 (d, JPC = 87.5 Hz, i-Mes), 121.5 (o-Ph), 31.2 (d,
-1
3
0.60 A , 6332 independent (Rint = 0.047), and 5367 observed
1JPC = 66.2 Hz, PCH2), 22.9 (d, JPC = 5.2 Hz, o-CH3Mes), 21.1
˚
reflections [I ≥ 2s(I)], 460 refined parameters, R = 0.056, wR2 =
(d, JPC = 1.5 Hz, p-CH3Mes), 18.2 (br, BCH2). 11B{ H} NMR
5
1
0.164.
(160 MHz, 298 K, dichloromethane-d2) d -5.4 (n1/2 = 210 Hz).
1
31P{ H} NMR (202 MHz, 298 K, dichloromethane-d2) d +50 (n1/2
~ 1600 Hz). 19F NMR (470 MHz, 298 K, dichloromethane-d2) [all
resonances are broad] d -132.7 (2F, o-C6F5), -162.1 (1F, p-C6F5),
-166.3 (2F, m-C6F5).
Compound 7. Dimesitylvinylphosphine (80 mg, 0.27 mmol)
and bis(pentafluorophenyl)borane (94 mg, 0.27 mmol) were
dissolved in pentane (6 mL) and stirred for 15 min. Upon addition
of pivalonitrile (28 mL, 0.27 mmol) at room temperature the
solution became immediately colourless. After stirring the reaction
mixture for 3 h, a white powder started to precipitate. The reaction
mixture was stirred overnight, then the precipitate was isolated via
cannula filtration and washed with pentane (3 ¥ 2.5 mL). All
volatiles were removed in vacuo to yield a white powder (118 mg,
60%). Crystals suitable for the X-ray crystal structure analysis were
Crystal data for C38H31BF10N3P·2C6H6 (8), M = 917.65, mono-
clinic, space group P21/c (no. 14), a = 15.8351(4), b = 13.8395(4),
◦
3
˚
˚
c = 21.6049(7) A, b = 109.595(1) , V = 4460.5(2) A , Dc =
-3
-1
˚
1.366 g cm , m = 1.250 mm , Z = 4, l = 1.54178 A, T = 223(2)
-1
˚
K, 43759 reflections collected ( h, k, l), [(sin q)/l] = 0.60 A ,
7883 independent (Rint = 0.053), and 6856 observed reflections [I ≥
2s(I)], 592 refined parameters, R = 0.046, wR2 = 0.132.
grown by slow diffusion of heptane into a benzene solution of 7.
Compound 9. Dimesitylvinylphosphine (100 mg, 0.34 mmol)
and bis(pentafluorophenyl)borane (117 mg, 0.34 mmol) were
dissolved in pentane (8 mL) and stirred for 15 min. Upon addition
of benzaldehyde (34 mL, 0.34 mmol) the solution turned to
colourless and after 1 h a white precipitate had formed. The
precipitate was isolated via cannula filtration after 5 h, washed
with pentane (2 ¥ 2 mL) and dried in vacuo to afford 9 (218 mg,
86%). Crystals suitable for X-ray diffraction were grown by slow
diffusion of heptane into a benzene solution of 6. Found: C, 62.29;
-1
˜
n(KBr)/cm = 2329 (s, CN). Found: C, 60.95; H, 4.83; N, 2.05.
1
Calc. for C37H35BF10NP: C, 61.26; H, 4.86; N, 1.93%. H NMR
4
(600 MHz, 298 K, benzene-d6) d 6.69 (4H, d, JPH = 2.1 Hz,
m-Mes), 2.56 (2H, m, PCH2), 2.42 (12H, s, o-CH3Mes), 2.08 (6H, s,
p-CH3Mes), 1.56 (2H, m, BCH2), 0.63 (9H, s, C(CH3)3. 13C{ H}
1
NMR (151 MHz, 298 K, benzene-d6) d 148.1 (dm, 1JFC = 242 Hz,
C6F5), 142.0 (d, 2JPC = 12.8 Hz, o-Mes), 139.8 (dm, 1JFC = 246 Hz,
C6F5), 137.5 (dm, 1JFC = 248 Hz, C6F5), 137.4 (p-Mes), 134.4 (d,
1
1
≡
JPC = 24 Hz, i-Mes), 130.3 (m-Mes), 121.0 (C N), 118.3 (br,
H, 3.86. Calc. for C39H32BF10OP: C, 62.59; H, 4.31%. H NMR
1
i-C6F5), 28.6 (br, C(CH3)3), 25.9 (br, C(CH3)3), 25.1 (d, JPC
=
(500 MHz, 298 K, dichloromethane-d2) d 7.22 (1H, m, p-Ph), 7.11
(2H, m, m-Ph), 7.06 (2H, m, o-Ph), 6.91, 6.85 (each 2H, each br,
16.0 Hz, PCH2), 23.3 (d, JPC = 12.9 Hz, o-CH3Mes), 20.7 (p-
3
CH3Mes), 19.6 (br, BCH2). 11B{ H} NMR (192 MHz, 298 K,
m-Mes), 6.23 (1H, d, JPH = 15.3 Hz, CH), 3.30, 3.15 (each 1H,
1
2
benzene-d6) d -1.2. 31P{ H} NMR (243 MHz, 298 K, benzene-
each m, PCH2), 2.32, 2.24 (each 3H, each s, p-CH3Mes), 2.27, 1.97
(each 6H, each br, o-CH3Mes), 1.70, 1.09 (each 1H, each m, BCH2).
1
d6) d -16.4 (n1/2 = 50 Hz). 19F{ H} NMR (564 MHz, 298 K,
1
1
benzene-d6) d -134.7 (2F, o-C6F5), -157.6 (1F, p-C6F5), -163.5
(2F, m-C6F5).
13C{ H} NMR (126 MHz, 298 K, dichloromethane-d2) d 148.6
1
1
(dm, JFC = 240 Hz, C6F5), 148.2 (dm, JFC = 243 Hz, C6F5),
144.2, 143.4 (p-Mes), 142.7, 142.6 (each br, o-Mes), 139.0 (dm,
Crystal data for C37H35BF10NP (7), M = 725.44, monoclinic,
1
space group P21/n (no. 14), a = 9.5576(1), b = 22.3280(3),
1JFC = 251 Hz, 2 ¥ C6F5), 137.2 (dm, JFC = 248 Hz, 2 ¥ C6F5),
◦
3
c = 16.9958(4) A, b = 104.650(1) , V = 3509.02(10) A , Dc =
137.1 (i-Ph), 132.5, 131.4 (each br d, each 3JPC = 10.2 Hz, m-Mes),
˚
˚
-3
-1
5
4
˚
1.373 g cm , m = 0.159 mm , Z = 4, l = 0.71073 A, T = 223(2)
128.8 (d, JPC = 3.8 Hz, p-Ph), 127.9 (d, JPC = 4.7 Hz, m-Ph),
127.7 (d, 3JPC = 3.2 Hz, o-Ph), 123.1, 124.2 (each br, i-C6F5), 123.4
(d, 1JPC = 55.5 Hz, i-Mes), 121.0 (d, 1JPC = 56.8 Hz, i-Mes), 85.5
(d, 1JPC = 29.6 Hz, CH), 28.9 (d, 1JPC = 42.5 Hz, PCH2), 24.3, 24.0
-1
˚
K, 20451 reflections collected ( h, k, l), [(sin q)/l] = 0.62 A ,
6989 independent (Rint = 0.051), and 5030 observed reflections [I ≥
2s(I)], 491 refined parameters, R = 0.074, wR2 = 0.179.
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 7556–7564 | 7561
©

View Article Online
1
(br, o-CH3Mes), 21.1, 21.0 (br, p-CH3Mes), 13.8 (br, BCH2). 11B{ H}
60.94; H, 4.29; N, 2.03. Calc. for C38H31BF10NOP: C, 60.90; H,
4.17; N, 1.87%. H NMR (600 MHz, 298 K, benzene-d6) d 6.95
1
NMR (192 MHz, 298 K, dichloromethane-d2) d -0.3 (n1/2 = 140
Hz). 31P{ H} NMR (243 MHz, 298 K, dichloromethane-d2) d 19.6
1
(2H, m, o-Ph), 6.67 (2H, m, m-Ph), 6.54 (1H, m, p-Ph), 6.39
4
(n1/2 = 70 Hz). 19F NMR (564 MHz, 298 K, dichloromethane-d2)
(4H, d, JPH = 4.0 Hz, m-Mes), 2.67 (2H, m, PCH2), 2.12 (12
H, br, o-CH3Mes), 2.09 (2H, m, BCH2), 1.82 (6H, s, p-CH3Mes).
d -134.7 (2F, o), -162.5 (1F, p), -166.4 (2F, m) (C6F5A), -134.7
1
13C NMR (126 MHz, 298 K, benzene-d6) d 148.5 (dm, JFC
=
=
=
=
B
(2F, o), -161.4 (1F, p), -165.6 (2F, m) (C6F5 ).
4
2
240 Hz, C6F5), 143.6 (d, JPC = 2.8 Hz, p-Mes), 142.9 (d, JPC
Crystal data for C39H32BF10OP (9), M = 748.43, orthorhombic,
5.4 Hz, i-Ph), 142.2 (d, 2JPC = 10.8 Hz, o-Mes), 139.1 (dm, 1JFC
space group P212121 (no. 19), a = 11.4602(3), b = 13.8298(4),
245 Hz, C6F5), 137.2 (dm, 1JFC = 247 Hz, C6F5), 131.9 (d, 3JPC
c = 21.8599(7) A, V = 3464.63(17) A , Dc = 1.435 g cm-3,
3
˚
˚
5
-1
˚
11.5 Hz, m-Mes), 128.2 (m-Ph), 125.2 (d, JPC = 1.1 Hz, p-Ph),
m = 1.470 mm , Z = 4, l = 1.54178 A, T = 223(2) K, 13725
1
3
-1
˚
124.8 (d, JPC = 76.6 Hz, i-Mes), n.o. (i-C6F5), 121.3 (d, JPC
=
=
reflections collected ( h, k, l), [(sin q)/l] = 0.60 A , 5824
1
3
1.5 Hz, o-Ph), 28.1 (d, JPC = 70.1 Hz, PCH2), 22.6 (d, JPC
independent (Rint = 0.035), and 5536 observed reflections [I ≥
2s(I)], 475 refined parameters, R = 0.039, wR2 = 0.102, Flack
0.00(2).
5
4.0 Hz, o-CH3Mes), 20.6 (d, JPC = 1.4 Hz, p-CH3Mes), 15.4 (br,
BCH2). 11B{ H} NMR (192 MHz, 298 K, benzene-d6) d 0.4 (br).
1
31P{ H} NMR (242 MHz, 298 K, benzene-d6) d 46.9 (n1/2 = 3
1
Compound 10. Dimesitylvinylphosphine (100 mg, 0.34 mmol)
and bis(pentafluorophenylborane) (117 mg, 0.34 mmol) were
dissolved in pentane (6 mL) and stirred for 15 min. Upon addition
of phenyl isocyanate (185 mL, 1.70 mmol) at room temperature a
white solid began to precipitate. After the reaction mixture had
been stirred for 3 h, the solid was isolated via cannula filtration
and washed with pentane (2 ¥ 2 mL). Removal of all volatiles in
vacuo yielded 10 (202 mg, 78%). Crystals suitable for the X-ray
crystal structure analysis were grown by slow evaporation of a
dichloromethane solution at -36 ◦C. Found: C, 61.23; H, 4.22; N,
Hz). 19F{ H} NMR (564 MHz, 298 K, benzene-d6) d -133.1 (2F,
1
o-C6F5), -161.9 (1F, p-C6F5), -165.5 (2F, m-C6F5).
Crystal data for C38H31BF10NOP·CH2Cl2 (11), M = 834.34,
monoclinic, space group P21/n (no. 14), a = 13.0829(6), b =
◦
3
˚
˚
15.0592(7), c = 19.0565(9) A, b = 99.870(2) , V = 3698.9(3) A ,
-3
-1
˚
Dc = 1.498 g cm , m = 2.745 mm , Z = 4, l = 1.54178 A, T =
223(2) K, 27107 reflections collected ( h, k, l), [(sin q)/l] =
-1
˚
0.60 A , 6490 independent (Rint = 0.072), and 4687 observed
reflections [I ≥ 2s(I)], 502 refined parameters, R = 0.069, wR2 =
0.197.
1
1.88. Calc. for C39H31BF10NOP: C, 61.52; H, 4.10; N, 1.84%. H
NMR (600 MHz, 298 K, benzene-d6) d 7.82 (2H, m, o-Ph), 7.20
4
Acknowledgements
(2H, m, m-Ph), 6.91 (1H, m, p-Ph), 6.41 (4H, d, JPH = 4.2 Hz,
m-Mes), 2.69 (2H, m, PCH2), 2.05 (12 H, s, o-CH3Mes), 1.86 (6H, s,
Financial support from the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie is gratefully acknowl-
edged. We thank the BASF for a gift of solvents.
p-CH3Mes), 1.70 (2H, dm, 3JPH = 26.3 Hz, BCH2). 13C{ H} NMR
1
(151 MHz, 298 K, benzene-d6) d 149.1 (d, 1JPC = 127.1 Hz, CN),
148.3 (dm, 1JFC = 239 Hz, C6F5), 145.9 (d, 3JPC = 22.7 Hz, i-Ph),
143.6 (d, 4JPC = 2.9 Hz, p-Mes), 142.9 (d, 2JPC = 9.1 Hz, o-Mes),
139.7 (dm, 1JFC = 252 Hz, C6F5), 137.6 (dm, 1JFC = 252 Hz, C6F5),
132.1 (d, 3JPC = 11.5 Hz, m-Mes), 128.8 (m-Ph), 126.6 (p-Ph), 125.8
References
1 G. C. Welch, L. Cabrera, P. A. Chase, E. Hollink, J. D. Masuda,
P. Wei and D. W. Stephan, Dalton Trans., 2007, 3407; G. C. Welch,
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2 D. W. Stephan and G. Erker, Angew. Chem., 2010, 122, 50; D. W.
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1
(o-Ph), 123.0 (br, i-C6F5), 120.0 (d, JPC = 78.9 Hz, i-Mes), 26.6
(d, 1JPC = 39.9 Hz, PCH2), 23.2 (d, 3JPC = 4.4 Hz, o-CH3Mes), 20.7
1
(p-CH3Mes), 14.4 (br, BCH2). 11B{ H} NMR (192 MHz, 298 K,
1
benzene-d6) d 0.7. 31P{ H} NMR (243 MHz, 298 K, benzene-d6)
1
d 5.1 (n1/2 = 3 Hz). 19F{ H} NMR (564 MHz, 298 K, benzene-d6)
d -134.2 (2F, o-C6F5), -159.2 (1F, p-C6F5), -164.2 (2F, m-C6F5).
3 W. Tochtermann, Angew. Chem., 1966, 78, 355; W. Tochtermann,
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1
2
Crystal data for C39H31BF10NOP·CH2Cl2· C5H12 (10), M =
882.43, monoclinic, space group C2/c (no. 15), a = 29.5440(6),
◦
4 B. A. Arbuzov, G. N. Nikonov, A. S. Balueva, R. M. Kamalov, G. S.
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Nikonov and B. A. Arbuzov, Izv. Akad. Nauk SSR, Ser. Khim., 1990,
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O. A. Erastov, Izv. Akad. Nauk SSR, Ser. Khim., 1989, 2793.
˚
b = 14.3430(4), c = 22.6139(7) A, b = 122.078(1) , V =
3
-3
-1
˚
8119.6(4) A , Dc = 1.444 g cm , m = 2.533 mm , Z = 8, l =
˚
1.54178 A, T = 223(2) K, 57011 reflections collected ( h, k,
-1
˚
l), [(sin q)/l] = 0.60 A , 7244 independent (Rint = 0.054), and
6260 observed reflections [I ≥ 2s(I)], 556 refined parameters, R =
0.062, wR2 = 0.182.
Compound 11. Dimesitylvinylphosphine (100 mg, 0.34 mmol)
and bis(pentafluorophenyl)borane (117 mg, 0.34 mmol) were
dissolved in pentane (6 mL) and stirred for 15 min. After addition
of nitrosobenzene (36 mg, 0.34 mmol) the reaction mixture was
stirred overnight, whereupon a brownish powder precipitated.
The precipitate was collected via cannula filtration and washed
with pentane (2 ¥ 2.5 mL). All volatiles were removed in vacuo
to yield 11 (128 mg, 50%). Crystals suitable for the X-ray crystal
structure analysis were obtained by slow diffusion of pentane
into a dichloromethane solution of 11 at -36 ◦C. Found: C,
7562 | Dalton Trans., 2010, 39, 7556–7564
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
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