Electronic control in frustrated Lewis pair chemistry: Adduct formation of intramolecular FLP systems with -P(C6F5)2 Lewis base components

Article abstract of DOI:10.1039/c2dt32806b

2-Propenylbis(pentafluorophenyl)phosphane adds Piers' borane [HB(C ₆F₅)₂] with anti-Markovnikov orientation to yield the intramolecular vicinal frustrated P/B Lewis pair 10. The FLP 10 adds pyridine, acetonitrile or alkyl

Full text of DOI:10.1039/c2dt32806b

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Electronic control in frustrated Lewis pair chemistry:
adduct formation of intramolecular FLP systems with
–P(C6F5)2 Lewis base components†
Cite this: Dalton Trans., 2013, 42, 4487
Annika Stute, Gerald Kehr, Constantin G. Daniliuc,‡ Roland Fröhlich‡ and
Gerhard Erker*
2-Propenylbis(pentafluorophenyl)phosphane adds Piers’ borane [HB(C6F5)2] with anti-Markovnikov
orientation to yield the intramolecular vicinal frustrated P/B Lewis pair 10. The FLP 10 adds pyridine,
acetonitrile or alkyl isocyanides to form simple boron Lewis acid adducts 11–14, all of which were charac-
terized by X-ray diffraction. The FLP 10 reacts with trans-cinnamic aldehyde to give a boron carbonyl
adduct 15 that was characterized by an X-ray crystal structure analysis. In contrast, the geminal
FLP (C6F5)2P–CHEt–B(C6F5)2 (3) undergoes 1,2-carbonyl addition reactions with benzaldehyde or trans-
cinnamic aldehyde to yield the respective five-membered heterocyclic products (7, 8, both characterized
by X-ray diffraction). The FLP 10 undergoes 1,2-P/B addition to p-tolylacetylene and to 2-methyl-
butenyne, respectively, to yield the corresponding six-membered heterocyclic products 17 and 18,
respectively (both were characterized by X-ray diffraction).
Received 23rd November 2012,
Accepted 13th December 2012
DOI: 10.1039/c2dt32806b
www.rsc.org/dalton
Introduction
Intramolecular frustrated Lewis pairs (FLPs) have significantly
contributed to the development of FLP chemistry.1,2 Usually,
they contain combinations of the –B(C6F5)2 Lewis acid func-
tionality with phosphane or amine Lewis bases featuring very
bulky substituents, so that both the inter- as well as intramole-
cular neutralizing Lewis acid/Lewis base adduct formation is
precluded or at least substantially hindered (Scheme 1).3 Intra-
molecular vicinal FLPs such as 1 have been shown to activate
dihydrogen under mild conditions4,5 and also to bind a variety
of small molecules (e.g. CO2, alkenes, alkynes, SO2 and even
NO).6–9
Scheme 1
P/B FLPs were not reactive enough to split dihydrogen.
However, they underwent a few other typically frustrated Lewis
pair reactions, which indicated that frustrated Lewis pair for-
mation can become electronically controlled in addition to the
ubiquitous steric control exerted by the presence of sets of
suitable very bulky substituents.10,11
We recently described a regiochemical variant of the
geminal FLP system 3, namely the vicinal isomer 10 (see
below).10 In this account we will describe and compare a
variety of addition reactions to electronically controlled FLPs
3 (geminal) and 10 (vicinal).
In 1 the bulky substituents at boron and phosphorus
hinder the internal LA/LB adduct formation by steric repul-
sion. Compound 1 is a weakly interacting FLP.3,4 It is known
that FLP formation can also be controlled by electronic factors.
Compounds 2 and 3 are intramolecular geminal FLP examples
without any appreciable P–B interaction. They contain
the strongly electron withdrawing –C6F5 substituents at both
boron and phosphorus.10,11 Both these electronically modified
Results and discussion
Reactions of the geminal frustrated Lewis pair
(C6F5)2P–CH(Et)–B(C6F5)2 (3)
Organisch-Chemisches Institut, Corrensstr. 40, 48149 Münster, Germany.
E-mail: erker@uni-muenster.de; Fax: +492518336503
We recently described the synthesis of 3 by HB(C6F5)2 hydro-
boration12 of the alkenylphosphane 4. We also presented first
examples of typical FLP reactions of 3, namely its addition to a
1-alkyne, to ethylene, to an isocyanate and to mesityl azide.10
†Electronic supplementary information (ESI) available: Experimental and
analytical details. CCDC 912772–912781. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c2dt32806b
‡X-ray structure analysis.
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Table 1 Selected NMR data of the FLP compounds 3 and 5–8a
Compound
3
5
6
7c
8
31P
−40.8
−51.3
−0.1
25.2
−8.2
3.40
39.5
9.08b
183.6b
27.9/20.4
1.9/1.9
3.25/3.70
34.2/n.l.
6.36/6.17
85.8/n.l.
23.5
2.6
3.57
34.4
5.88
83.3
11B
70.9
C1H 1H
13C
4.40
34.1
—
4.00
24.7
C4H 1H
13C
—
—
—
a Chemical shifts in ppm, δ-scale. b vC(5)H. c Major/minor isomer. n.l.
not located.
We here studied a few additional addition reactions of 3.
Especially those with aldehydes turned out to be important in
a comparison with the carbonyl addition reactions of the
related electron deficient vicinal FLP system (see below).
The hydroboration product 3 is characterized by a 31P NMR
signal at δ −40.8 and an 11B NMR signal at δ 70.9, which is
typical for the presence of a planar-tricoordinate boron
center.13,14 Consequently, we monitored a single set of –C6F5
19F NMR signals for the –B(C6F5)2 group. In contrast the
–P(C6F5)2 substituent exhibits the 19F NMR resonances of a
pair of diastereotopic C6F5 groups.
The FLP 3 was treated with pyridine in pentane at ambient
temperature to give the adduct 5 which was isolated in 56%
yield as a white solid.15 The NMR signals of the (C6F5)2P unit
of 5 are similar to those of 3, whereas the 11B NMR signal now
indicates the presence of a four-coordinated boron center in
compound 5 (see Table 1). This is supported by the ob-
servation of the 19F NMR signals of pairs of diastereotopic
C6F5 substituents at boron and at phosphorus (see Scheme 2).
Compound 3 cleanly undergoes a 1,2-P/B-addition reaction
to p-tolylacetylene to regioselectively yield the unsaturated five-
membered heterocyclic product 6 (70% isolated). The adduct
shows typical 13C NMR signals of the former acetylene build-
Scheme 2
1
ing block [δC4: 125.5, JPC = 84.1 Hz and δC5: 183.6 (br)].
1
The vC(5)H– H NMR resonance shows a typical rather large
3JPH = 64.3 Hz coupling constant. Again we monitored the
typical set of 19F NMR signals of two diastereotopic pairs of
C6F5-substituents at boron and phosphorus.
Fig. 1 A view of the molecular structure of the trans-7 isomer (thermal ellip-
soids are shown with 30% probability).
We reacted the geminal FLP 3 with benzaldehyde and with
trans-cinnamic aldehyde and isolated the corresponding 1,2-
carbonyl addition products 7 and 8 in 45% and 35% yield,
respectively. The isolated benzaldehyde addition product con-
tained two isomers in a 1 : 0.4 molecular ratio. We assume that
they are the respective trans- and cis-diastereoisomers of 7.
Both were characterized spectroscopically from the mixture
(see Table 1). We obtained single crystals of trans-7 suitable for
characterization by X-ray diffraction (see Fig. 1 and Table 2).
The structure shows a five-membered heterocyclic core11,16
that was formed by 1,2-addition of the FLP 3 to the carbonyl
group of benzaldehyde, forming a new B–O and P–C bond. We
note that the phosphorus–carbon bond in compound trans-7
is very long (see Fig. 1).
Table 2 Selected structural parameters of the compounds trans-7 and trans-8a
Compound
trans-7
trans-8
P1–C1
C1–B1
B1–O1
C4–O1
1.781(3)
1.709(4)
1.486(3)
1.388(3)
1.929(3)
98.0(2)
1.799(2)
1.717(2)
1.490(2)
1.390(2)
1.867(2)
99.7(1)
95.5(1)
115.9(1)
95.3(1)
P1–C4
P1–C1–B1
C1–P1–C4
B1–O1–C4
P1–C4–O1
C1–P1–C4–C5
C1–B1–O1–C4
B1–O1–C4–C5
95.7(1)
113.8(2)
102.7(2)
−118.3(2)
−57.1(3)
151.9(2)
166.1(1)
35.4(2)
−177.2(1)
The isolated material (8) of the FLP addition of 3 to trans-
cinnamic aldehyde contains only a single diastereoisomer.
a Bond lengths in Å, angles in °.
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Fig. 3 Molecular structure of the phosphane 9 (thermal ellipsoids are shown
with 30% probability).
Fig. 2 Molecular structure of the FLP-addition product trans-8 (thermal ellip-
soids are shown with 30% probability).
Table 3 Selected NMR data of FLP 10 and its adducts 11–14a
In situ NMR experiments showed no indication of the
formation of a second isomer (see the ESI†). Compound 8
retained the trans- –CHvCH– double bond. The X-ray crystal
structure analysis of the product (see Fig. 2) shows a trans-
attachment of the –C2H5 and –CHvCHPh substituents at the
five-membered heterocyclic core (trans-8). Again, we note that
the P1–C4 bond is rather long, although not as extreme as
observed in trans-7 (see above).
Compound
10
11
12
13
14
31P
−34.3
66.0
3.63
27.4
2.22
1.67
35.8
−36.3
−1.5
3.10
26.2
2.10
1.00
26.4
−36.3
−6.8
3.26
25.7
1.54
1.54
25.5
−37.3
−19.3
3.10
26.2
1.29
1.29
22.9
−36.9
−19.1
3.25
26.8
1.68
1.60
23.9
11B
PCH: 1H
13C
BCH2: 1H
13C
a Chemical shifts in ppm, δ-scale.
Formation and reactions of the vicinal FLP 10
We noticed that the outcome of the hydroboration of phosphanyl-
substituted alkenes and alkynes with the reactive Piers’ borane
[HB(C6F5)2] reagent was quite sensitive to the substitution
pattern of these substrates.10 It was possible to control the
regiochemistry of the HB(C6F5)2 addition reaction by attaching
alkyl or aryl substituents at specific positions. For this study
we prepared compound 10 as we had recently communicated10
by regioselective HB(C6F5)2 hydroboration of the (2-propenyl)-
bis(pentafluorophenyl)phosphane 9. Compound 9 was pre-
pared by treatment of (C6F5)2PCl17 with 2-propenylmagnesium
bromide. It was isolated in 64% yield after chromatographic
workup. In solution it features 1H NMR signals of the
2-propenyl substituent at δ 5.72 (3JPH = 39.1 Hz) and 5.53
(3JPH = 16.7 Hz) of the CvCH2 unit and a methyl signal at
δ 2.04 (3JPH = 8.4 Hz). The 31P NMR resonance of 9 occurs at
δ −42.8 and the compound shows a single set of 19F NMR
resonances at δ −130.3 (o), −150.9 (p) and −161.4 (m of C6F5).
Compound 9 was also characterized by X-ray diffraction (single
crystals were obtained from pentane) (see Fig. 3). It shows a
trigonal pyramidal coordination geometry at phosphorus (sum
of C–P–C bond angles 309.4°). The C1–C2 bond length of the
2-propenyl substituent was found at 1.320(5) Å.
NMR spectra (see Table 3) indicated that 1,2-addition with
anti-Markovnikov orientation had taken place yielding the
vicinal FLP 10. We monitored the typical 1H and 13C NMR
signals of the central [P]–CH(CH3)–CH2–[B] unit. Due to the
formation of the chiral center (C1, see Scheme 3) the hydrogen
atoms at the adjacent CH2 group are diastereotopic (see
Table 3) as are the C6F5 substituents at phosphorus [e.g.
δ −147.5/−148.5 (p-F of C6F5)]. The observed 11B chemical shift
is typical for a strongly Lewis acidic trigonally planar boron
center. Consequently, we observed only a single set of 19F NMR
resonances of the pair of C6F5 substituents at boron in com-
pound 10 [δ −130.5 (4F, o-), −145.8 (2F, p-), −160.4 (4F, m-F of
C6F5)].
The FLP 10 forms adducts with a variety of nucleophiles
that selectively add to the boron Lewis acid. Treatment with
pyridine (45 min, rt, pentane) gave the respective pyridine
adduct 11 that was isolated in 74% yield. The NMR spectra
showed that the –P(C6F5)2 moiety was not affected. The system
shows the 19F NMR signals of pairs of diastereotopic C6F5 sub-
stituents at both phosphorus and boron. The X-ray crystal
structure analysis of 11 reveals a close to anti-periplanar con-
formational arrangement of the central core of the molecule
[e.g. θ C1–C2–B1–N1 171.1(2)°, B1–N1: 1.638(3) Å] (see Fig. 4
and Table 4)].
For the experiments carried out in this study the FLP 10
was always generated in situ and then used for the respective
trapping experiments. For its spectroscopic characterization
compound 10 was generated directly by treatment of the
alkenylphosphane 9 with the HB(C6F5)2 reagent in C6D6. The
The open vicinal FLP 10 equally facile forms an adduct with
acetonitrile. The product 12 was isolated in 73% yield. It
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Fig. 5 A projection of the molecular structure of the FLP–acetonitrile adduct
12 (thermal ellipsoids are shown with 30% probability).
(CH3–CuN combination), 2253 cm−1 (CuN stretch)]. The here
observed IR effect is similar to that previously observed for the
“parent” (C6F5)3B–NuC–CH3 adduct [IR: ˜ν(CuN)
=
2367 cm−1].18–20
The X-ray crystal structure analysis of the FLP–acetonitrile
adduct shows a linear [B]–NuC–CH3 unit (see Fig. 5 and
Table 4) with pertinent bonding parameters of B1–N1
1.597(3) Å and bond angles B1–N1–C4 173.5(2)° and N1–C4–
C5 179.5(2)°. Coordination of the nitrile to the boron Lewis
acid has resulted in a small shortening of the carbon–nitrogen
triple bond [N1–C4: 1.134(2) Å] relative to the free acetonitrile
reference [acetonitrile α-phase, 208 K, CuN: 1.141(2) Å].19
A similar structural effect had been observed for the aceto-
nitrile ligand in the B(C6F5)3–acetonitrile adduct [d(CuN):
1.124(3) Å, d(B–N): 1.616(3) Å].18 In the FLP–acetonitrile
adduct 12 we find not only a close to anti-periplanar con-
formational arrangement of the [P]C2[B] core of the molecule
in the crystal [dihedral angle P1–C1–C2–B1 −167.4°], but also
a close to gauche arrangement of the attached NuC–CH3 unit
[θ C1–C2–B1–N1 −73.9(2)°].
Scheme 3
The FLP 10 also rapidly adds tert-butyl isocyanide to its
boron Lewis acid functionality. We isolated the respective
adduct 13 as a white solid in 77% yield. The adduct shows
typical NMR features (see Table 3). Compound 13 was charac-
terized by X-ray diffraction (see Fig. 6 and Table 4). It shows
that the tert-butyl isocyanide donor was added to the boron
Lewis acid16 (B1–C4 1.623(4) Å) to give a linear B–L arrange-
ment [B1–C4–N1 176.8(3)°, C4–N1–C5 172.0(3)°, C4–N1
1.137(3) Å]. While the [P]–C1–C2–[B] unit shows an anti-
periplanar conformation (see Table 4). The CuN–tBu donor
group is attached in close to gauche orientation (dihedral angle
C1–C2–B1–C4 51.7(3)°).
Fig. 4 A view of the molecular structure of the FLP–pyridine adduct 11
(thermal ellipsoids are shown with 30% probability).
Table 4 Selected structural data of the FLP adducts 11–14a
Compound
11
12
13
14
P1–C1
C1–C2
C2–B1
ΣC–P1–C
C2–B1–N1 or C4
P1–C1–C2–B1
1.855(2)
1.549(3)
1.636(3)
307.0
109.3(2)
−158.6(2)
1.854(2)
1.545(2)
1.616(3)
308.2
107.7(2)
−167.4(1)
1.853(3)
1.541(4)
1.630(4)
308.5
105.7(2)
−167.0(2)
1.848(2)
1.545(3)
1.631(4)
306.0
108.7(4)
173.0(2)
We also prepared the 10–n-butyl isocyanide adduct 14. It
shows similar NMR data (for details see Tables 3 and 4 and
the ESI†).
a Bond lengths in Å, angles in °.
We reacted the vicinal FLP 10 with trans-cinnamic aldehyde
and with benzaldehyde, respectively. In both cases a reaction
was observed to give 1 : 1 addition products. However, in detail
the outcome of these reactions was markedly different from
shows the NMR features of the [B]-coordinated acetonitrile
ligand at δ 114.9/δ −0.5 (13C) and δ 0.57 (1H), respectively, and
an IR(CuN) band at 2363 cm−1 [free NuC–CH3: ˜ν = 2292 cm−1
4490 | Dalton Trans., 2013, 42, 4487–4499
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Fig. 6 Molecular structure of the tert-butyl isonitrile–FLP adduct 13 (thermal
ellipsoids are shown with 30% probability).
Fig. 7 Molecular structure of the FLP–trans-cinnamic aldehyde adduct 15
respective carbonyl addition reactions with the geminal FLP 3
that we have described above.
(thermal ellipsoids are shown with 30% probability).
From the reaction mixture of 10 with trans-cinnamic alde-
hyde (pentane, rt) a white precipitate was formed. The product
(15) was isolated in 48% yield (see Scheme 4). We obtained
crystals suited for the X-ray crystal structure analysis from
dichloromethane/pentane by the diffusion method (see Fig. 7).
In the crystal, compound 15 is to be described as a simple car-
bonyl adduct to the boron Lewis acid component of the vicinal
frustrated P/B Lewis pair 10. It features a [P]–CHMe–CH2–[B]
framework with a dihedral angle of −160.1(2)°. The aldehyde
oxygen atom is found bonded to boron [B1–O1 1.584(4) Å,
angle C2–B1–O1 107.4(2)°, dihedral angle C1–C2–B1–O1
−61.7(3)°]. The bonding parameters of the coordinated trans-
cinnamic aldehyde are: O1–C4 1.252(3) Å, C4–C5 1.402(4) Å,
B1–O1–C4 123.2(2)°. The remote phosphane Lewis base is
found untouched by the FLP–trans-cinnamic aldehyde adduct
formation (sum of the C–P–C bond angles at P1: 309.1°).
In solution (CD2Cl2, 299 K) the adduct 15 features the
typical 31P NMR signal of an unperturbed (C6F5)2P– substitu-
ent21 (δ −34.8, quin, 3JPF = 28.5 Hz) and an 11B NMR signal at δ
8.3 typical for tetracoordinated boron. The C6F5 groups at the
boron atom are found diastereotopic (19F NMR below ca.
290 K, see ESI†) due to the carbon chirality center (C1) in the
bridge. The 1H/13C NMR features of the coordinated OvCH-
aldehyde functionality in the adduct 15 were located at δ 8.20/δ
193.8. The NMR spectra of 15 are not temperature invariant.
Lowering of the temperature leads to a shifting of e.g. the alde-
hyde OvCH– 1H NMR signal and of the 31P NMR features.
However, we were only able to monitor a beginning of de-
coalescence of the latter at very low temperature (e.g. below
208 K), giving not enough spectral information for a sound
chemical interpretation (the temperature dependent NMR
spectra of compound 15 are depicted in the ESI†).
The reaction of the vicinal FLP 10 with benzaldehyde gave
the 1 : 1 adduct 16, which was isolated in 74% yield (see
Scheme 4). Single crystals were obtained. The X-ray crystal
structure analysis indicated a six-membered heterocyclic 1,2-
addition product (16B) being present in the crystal. However,
the structure solution was insufficient to describe the bonding
parameters in detail (see the ESI†).
In solution compound 16 shows strongly temperature
dependent NMR spectra. This shall be illustrated by the behav-
ior of the 31P NMR spectra. At 299 K we observed a slightly
broadened single 31P NMR resonance of 16 at ca. δ −5.9
(CD2Cl2). This is a chemical shift which is lying somewhere in
the middle between expected values of a simple [B]–OvCHPh
adduct 16A and a 1,2-P/B addition product 16B. This signal
probably indicates a coalesced mean 31P NMR resonance of an
equilibrating system of adduct isomers. This interpretation is
supported by the changes monitored of the 31P NMR spectrum
with decreasing temperature. Upon lowering the temperature
the 31P NMR resonance is rapidly shifted to positive shift
values. The signal gets much broader and finally decoalesces
at ca. 228 K into a major resonance at δ +20.5 and a minor
signal at ca. δ +5.7 (the spectra are depicted in the ESI†). The
former is very typical of a heterocyclic six-membered FLP
adduct to the aldehyde (see above, e.g. Table 1); the minor
intensity signal could indicate the presence of a second isomer
or conformer, although a clear identification seems not
Scheme 4
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Scheme 5
Fig. 8 Molecular structure of compound 18 (thermal ellipsoids are shown with
30% probability).
possible at this time. However, these data indicate that
there might be an equilibrium between the cyclic adduct 16B
(possibly two stereoisomers) and an open isomer 16A which is
markedly temperature dependent.
The FLP 10 also undergoes 1,2-addition to acetylenes. We
reacted 10 with p-tolylacetylene and isolated the 1,2-addition
product 17 in 52% yield (see Scheme 5). Compound 17
features a typical 31P NMR signal at δ 10.2 and an 11B NMR
resonance at δ −14.6. The 1H NMR signal of the endocyclic
vCH–[B] proton occurs at δ 8.92 with a coupling constant of
3JPH = 64.1 Hz.
reactive enough to split dihydrogen, but they undergo a series
of other typical FLP addition reactions, e.g. to alkynes or to
aldehydes. The latter reaction is special in the way that the
geminal FLP (3) cleanly undergoes a 1,2-addition reaction
whereas the vicinal FLP (10) seems to feature a competing situ-
ation between 1,2-addition and simple carbonyl Lewis acid
adduct formation. This indicates that the reduced phosphane
nucleophilicity brings FLP chemistry in such electronically
controlled systems to its limits. Nevertheless, a variety of FLP
reactions seem to still be possible for these electronically
determined FLPs so that they may be regarded as useful
additions to the manifold of intramolecular frustrated Lewis
pair compounds.
Compound 10 reacts similarly with 2-methylbutenyne to
give the 1,2-P/B FLP addition product 18 to the acetylenic
moiety.22 Compound 18 was isolated admixed with a minor
component (whose structure is described in the ESI†) in
1
52% yield [31P NMR δ 8.8, 11B NMR: δ −14.8, H NMR: δ 8.66
(vCH[B])].
Compound 18 was characterized by X-ray diffraction (see
Fig. 8). In the crystal, compound 18 shows a distorted half-
chair heterocyclohexene conformation with characteristic
bond lengths of P1–C1 1.804(2) Å, P1–C4 1.783(2) Å, C1–C2
1.547(3) Å, C4–C5 1.340(3) Å, C2–B1 1.644(4) Å and B1–C5
1.618(4) Å. It contains the unperturbed 2-propenyl substituent
bonded at C4 (C4–C6 1.493(3) Å, C6–C7 1.332(4) Å).
Experimental
General comments
All experiments were carried out under a dry argon atmosphere
using standard Schlenk techniques or in a glovebox. Solvents
(including deuterated solvents used for NMR) were dried and
distilled prior to use. H, 13C, 11B, 19F, 31P NMR spectra were
1
recorded on a Varian 500 MHz INOVA or a Varian 600 MHz
UNITY plus NMR spectrometer at ambient temperature unless
otherwise stated. Chemical shifts are given in ppm relative to
solvents (1H and 13C) or an external standard [δ(BF3·OEt2) = 0
Conclusions
Lewis acids and bases can very effectively be hindered from for 11B NMR, δ (CFCl3) = 0 for 19F NMR and δ(85% H3PO4) = 0
undergoing neutralizing adduct formation by steric as well as for 31P NMR]. Coupling constants are in Hz. Elemental analy-
electronic means. The introduction of the strongly electron- sis data were recorded on Foss-Heraeus CHNO-Rapid. HRMS
withdrawing C6F5-substituents at phosphorus appears to be an was recorded on GTC Waters Micromass (Manchester, UK).
effective tool for lowering the Lewis basicity beyond a critical X-Ray diffraction: Data sets were collected with a Nonius
threshold for FLP formation. At the same time the hydrobora- KappaCCD diffractometer. Programs used: data collection,
tion reaction of Piers’ borane [HB(C6F5)2] with alkenylbis(penta- COLLECT (Nonius B.V., 1998); data reduction Denzo-SMN;23
fluorophenyl)phosphanes responds very critically to the alkyl absorption
correction,
Denzo;24
structure
solution
(and aryl) substitution pattern at the alkenyl group. In the here SHELXS-97;25 structure refinement SHELXL-9726 and graphics,
described cases the hydroboration reaction of the 1-propenyl XP (BrukerAXS, 2000). Thermal ellipsoids are shown with 30%
derivative resulted in the formation of a geminal FLP (3) probability, R-values are given for observed reflections, and
whereas the (2-propenyl)P(C6F5)2 substrate gave the vicinal FLP wR2 values are given for all reflections. Exceptions and special
10 upon hydroboration. Both the FLPs 3 and 10 are not features: For compound trans-8 an unidentified disordered
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solvent molecule was found in the asymmetrical unit and which turned red-orange. After stirring for one hour at rt the
could not be satisfactorily refined. The program SQUEEZE27 solvent was removed in vacuo to give a brown residue. The
was therefore used to remove mathematically the effect of the crude product was suspended in n-pentane again and the
solvent. The half disordered dichloromethane molecule in solvent was removed via filter cannula. The remaining product
compound 11 and the disordered pentane molecule in com- was then dried in vacuo to give a white solid (299 mg,
pound 12, which could not be refined satisfactorily, were 0.34 mmol, 70%). IR (KBr): ˜ν = 3442 (w), 3029 (w), 2970 (w),
removed using the program SQUEEZE. The chemical formula 2934 (w), 2879 (w), 1644 (s), 1523 (s), 1488 (s), 1462 (s),
and the molecular mass do not include the squeezed part of 1106 (s), 984 (s), 816 (m). Elemental analysis: calcd for
the solvent molecules. For compound 13 one half molecule of C36H14BF20P: C 49.80, H 1.63; found: C 49.54, H 1.23. Mp:
pentane was found in the asymmetric unit and is disordered 170 °C (DSC). 1H NMR (500 MHz, 298 K, C6D6): δ = 9.08 (d,
3
across an inversion centre. Several restraints (SADI, SIMU, 3JPH = 64.3 Hz, 1H, vCH), 7.05 (d, JHH = 7.7 Hz, 2H, o-tol),
3
P
SAME and ISOR) were used in order to improve refinement 6.80 (d, JHH = 7.7 Hz, 2H, m-tol), 3.40 (m, 1H, CHB), 1.90 (s,
stability. For compound 14 the n-butyl isocyanide group was 3H, p-CH3tol), 1.79 (dm, JPH = 29.1 Hz, 1H, CH2), 1.66 (m, 1H,
3
found disordered over two positions. Several restraints (SADI, CH2), 0.75 (t, JHH = 7.3 Hz, CH3). 13C{1H} NMR (126 MHz,
3
SIMU, ISOR and SAME) were used in order to improve refine- 298 K, C6D6): δ = 183.6 (br, vCH), 139.2 (p-tol), 130.8 (d, 2JPC
=
3
ment stability. For compound 16b one disordered half mol- 16.6 Hz, i-tol), 129.9 (m-tol), 126.6 (d, JPC = 5.9 Hz, o-tol),
ecule of benzene, which could not be refined satisfactorily, 125.5 (d, JPC = 84.1 Hz, vCtol), 39.5 (br, PCHB), 21.6 (CH2),
1
3
was removed using the program SQUEEZE. B(C6F5)3 (caution: 20.8 (p-CH3tol), 16.2 (d, JPC = 9.0 Hz, CH3); [C6F5 not listed].
the intermediate involved is explosive),12a–c HB(C6F5)2,12d,e 11B{1H} NMR (160 MHz, 298 K, C6D6): δ = −8.2 (ν1/2 ∼ 50 Hz).
(C6F5)2PCl,17 310 and 1010 were prepared according to pro- 19F NMR (470 MHz, 298 K, C6D6): δ = −127.3 (m, 2F, o-PA),
cedures reported in the literature.
−127.6 (m, 2F, o-PB), −131.7 (m, 2F, o-BA), −132.0 (m, 2F, o-BB),
−138.1 (tm, 3JFF = 22.0 Hz, 1F, p-PB), −139.4 (tm, 3JFF = 22.3 Hz,
1F, p-PA), −156.4 (m, 2F, m-PB), −157.0 (m, 2F, m-PA), −157.6
Preparations
Preparation of compound 5. Bis(pentafluorophenyl)-1-pro- (t, JFF = 20.7 Hz, 1F, p-BA), −158.2 (t, JFF = 20.7 Hz, 1F, p-BB),
penylphosphane (4) (200 mg, 0.49 mmol) and bis(pentafluoro- −163.5 (m, 2F, m-BA), −163.7 (m, 2F, m-BB); [Δδ19Fp,m: 5.9 (BA),
phenyl)borane (170 mg, 0.49 mmol) were dissolved in 5.5 (BB), 17.6 (PA), 18.3 (PB)]. 31P{1H} NMR (202 MHz, 298 K,
n-pentane (30 mL) and stirred for two min. Pyridine (38.9 mg, C6D6): δ = 25.2 (ν1/2 ∼ 50 Hz).
3
3
0.49 mmol) was added and a white solid precipitated immedi-
Preparation of compound 7. Bis(pentafluorophenyl)-1-pro-
ately. The solid was isolated via filter cannula, washed with penylphosphane (4) (200 mg, 0.49 mmol) and bis(pentafluoro-
n-pentane (2 × 20 mL) and dried in vacuo to give the product as a phenyl)borane (170.3 mg, 0.49 mmol) were dissolved in
white powder (228 mg, 0.275 mmol, 56%). IR (KBr): ˜ν = 3136 (w), n-pentane (10 mL) and stirred for 5 min at rt. Benzaldehyde
2973 (w), 2943 (w), 2602 (w), 2363 (w), 1642 (s), 1518 (s), (52.3 mg, 0.49 mmol) was added and a white solid precipi-
1460 (s), 1377 (s), 1284 (s), 1165 (w), 1091 (s), 984 (s), 867 (w), tated. The suspension was stirred for 30 min at rt before the
770 (s), 745 (s), 704 (s). Elemental analysis: calcd for solid was isolated on a Schlenk-frit and washed with n-pentane
C32H11BF20NP: C 46.24, H 1.33, N 1.69; found: C 46.66, H 1.21, (10 mL). Drying in vacuo gave the product (190 mg, 0.22 mmol,
1
N 1.47. Mp (DSC): 161 °C. 1H NMR (500 MHz, 298 K, C7D8): δ = 45%). According to 31P{19F} and H NMR spectra two isomers
3
8.61 (br, 2H, o-py), 6.80 (t, JHH = 7.5 Hz, 1H, p-py), 6.49 (m, in a ratio of 1 : 0.4 are present in CD2Cl2 solution at 258 K.
2H, m-py), 4.00 (m, 1H, PCHB), 1.26/0.46 (each m, each 1H, Single crystals suitable for X-ray crystal structure analysis were
CH2), 0.49 (m, 3H, CH3). 13C{1H} NMR (126 MHz, 298 K, obtained by slow diffusion of n-pentane into a solution of com-
C7D8): δ = 146.5 (d, JPC = 16.2 Hz, o-py), 141.9 (p-py), 124.3 pound 7 in dichloromethane at −30 °C. IR (KBr): ˜ν = 2991 (w),
P
2
(m-py), 24.7 (br, CHB), 23.4 (br d, JPC = 3.9 Hz, CH2), 13.6 (d, 2940 (w), 2885 (w), 1644 (s), 1598 (w), 1519 (s), 1483 (s), 1459 (s),
3JPC = 7.9 Hz, CH3); [C6F5 not listed]. 11B{1H} NMR (160 MHz, 1381 (m), 1287 (m), 1224 (w), 1185 (w), 1103 (s), 1027 (w),
298 K, C7D8): δ = −0.1 (ν1/2 ∼ 200 Hz). 19F NMR (470 MHz, 973 (s), 919 (m), 872 (w), 836 (w), 784 (m), 751 (m), 726 (w),
248 K, C7D8): δ = −125.8 (s, 2F, o-PA), −126.9 (s, 1F, o-BA), 710 (m), 626 (w), 588 (w), 540 (w), 521 (w). Elemental analysis:
−128.2 (s, 2F, o-BB), −129.4 (s, 2F, o-PB), −133.1 (s, 1F, o′-BA), calcd for C34H12BF20P: C 47.58, H 1.41; found: C 47.01, H 0.95.
1
−148.0 (s, 1F, p-PA), −149.8 (t, 3JFF = 2.8 Hz, 1F, p-PB), −154.8 (t, Mp: 159 °C (DSC); Dp: 210 °C (DSC). Major isomer: H NMR
3
3JFF = 21.0 Hz, 1F, p-BA), −156.3 (t, JFF = 20.5 Hz, 1F, p-BB), (500 MHz, 258 K, CD2Cl2): δ = 7.30 (br, 3H, o,p-Ph), 7.25 (m,
2
2
−160.4 (m, 2F, m-PB), −160.5 (br, 1F, m′-BA), −161.1 (m, 2F, 2H, m-Ph), 6.36 (d, JPH = 15.3 Hz, 1H, OCH), 3.25 (br d, JPH
=
m-PA), −162.6 (br, 1F, m-BA), −162.9 (m, 2F, m-BB); [Δδ19Fp,m
:
21.8 Hz, 1H, PCHB), 1.96/1.71 (each br, each 1H, CH2), 0.91 (br,
5.7, 7.8 (BA), 6.6 (BB), 13.1 (PA), 10.6 (PB)]. 31P{1H} NMR 3H, CH3). 13C{1H} NMR (126 MHz, 258 K, CD2Cl2): δ = 133.9
(202 MHz, 298 K, C7D8): δ = −51.3 (m, ν1/2 ∼ 120 Hz).
(i-Ph), 130.1 (d, J = 4.5 Hz, p-Ph)t, 128.7 (m-Ph), 126.9 (br,
Preparation of compound 6. Bis(pentafluorophenyl)-1-pro- o-Ph)t, 85.8 (d, JPC = 30.8 Hz, OCH), 34.2 (br, CHB), 19.5 (m,
1
P
t
penylphosphane (4) (200 mg, 0.49 mmol) and bis(pentafluoro- CH2), 16.6 (m, CH3); [C6F5 not listed, tentatively assigned].
phenyl)borane (169.5 mg, 0.49 mmol) were dissolved in 11B{1H} NMR (160 MHz, 258 K, CD2Cl2): δ = 1.9 (ν1/2 ∼ 120 Hz).
n-pentane (10 mL) and stirred for one hour at rt. p-Tolylacety- 19F NMR (470 MHz, 258 K, CD2Cl2): δ = −124.1 (br, 2F, o-PA),
lene (56.9 mg, 0.49 mmol) was added to the reaction mixture −132.3 (m, 2F, o-BA), n.o. (o-PB), −134.5 (m, 2F, o-BB), −138.7
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Dalton Transactions
(m, 1F, p-PA), −140.0 (m, 1F, p-PB), −155.4 (m, 2F, m-PA), 1.609 mm−1, empirical absorption correction (0.689 ≤ T ≤
3
−157.3 (br, 2F, m-PB), −157.9 (t, JFF = 20.5 Hz, 1F, p-BA), 0.739), Z = 2, triclinic, space group P1 (no. 2), λ = 1.54178 Å,
ˉ
−159.6 (t, JFF = 19.9 Hz, 1F, p-BB), −164.0 (m, 2F, m-BA), T = 223(2) K, ω and φ scans, 33 792 reflections collected ( h,
3
−164.7 (m, 2F, m-BB); [Δδ19Fp,m: 6.1 (BA), 5.1 (BB), 16.7 (PA),
k, l), [(sin θ)/λ] = 0.60 Å−1, 7795 independent (Rint = 0.039)
17.3 (PB)]. 31P{19F} NMR (202 MHz, 258 K, CD2Cl2): δ = 27.9 and 6896 observed reflections [I > 2σ(I)], 614 refined para-
(ν1/2 ∼ 85 Hz). (Minor isomer: see the ESI†.)
meters, R = 0.041, wR2 = 0.122, max. (min.) residual electron
X-ray crystal structure analysis of compound trans-7. density 0.20 (−0.20) e Å−3, hydrogen atoms calculated and
Formula C34H12BF20OP, M = 858.22, colourless crystals, 0.27 × refined as riding atoms.
0.05 × 0.02 mm, a = 8.8560(4), b = 12.7840(6), c = 14.4856(12)
Preparation of phosphane 9.10 Chlorobis(pentafluoro-
Å, α = 95.877(4), β = 96.842(6), γ = 92.121(3)°, V = 1617.74(17) phenyl)phosphane (7.20 g, 18.0 mmol) was dissolved in thf
Å3, ρcalc = 1.762 g cm−3, μ = 2.133 mm−1, empirical absorption (150 mL) and cooled down to −78 °C. 2-Propenylmagnesium
correction (0.596 ≤ T ≤ 0.958), Z = 2, triclinic, space group bromide (0.5 M in thf, 36.0 mL, 18.0 mmol) was added drop-
ˉ
P1 (no. 2), λ = 1.54178 Å, T = 223(2) K, ω and φ scans, 24 788 wise to the reaction mixture, which turned brown after
reflections collected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 5522 addition. The reaction mixture was stirred at rt for two hours
independent (Rint = 0.052) and 4263 observed reflections before the solvent was removed in vacuo. The residue was sus-
[I > 2σ(I)], 515 refined parameters, R = 0.044, wR2 = 0.107, max. pended in n-pentane (100 mL) and filtered in a Schlenk-frit
(min.) residual electron density 0.20 (−0.26) e Å−3, hydrogen over Celite. The filter pad was washed with n-pentane (2 ×
atoms calculated and refined as riding atoms.
80 mL). The filtrate was dried in vacuo. Purification by column
Preparation of compound 8. Bis(pentafluorophenyl)-1-pro- chromatography (SiO2 : cyclohexane, Rf
=
0.66) gave the
penylphosphane (4) (200 mg, 0.49 mmol) and bis(pentafluoro- product (4.69 g, 11.5 mmol, 64%). [Comment: the product
phenyl)borane (170 mg, 0.49 mmol) were dissolved in should be kept in the fridge otherwise it slowly decomposes to
n-pentane (15 mL) and stirred at rt for five min before trans- (C6F5)2P–P(C6F5)2.] Crystals suitable for crystal structure analy-
cinnamic aldehyde (64.8 mg, 0.49 mmol) was added. The sis were obtained by slow evaporation of an n-pentane solution
solution turned yellow and was stirred at rt for one hour. The at rt.
reaction mixture was concentrated in vacuo until a white solid
X-ray crystal structure analysis of compound 9. Formula
precipitated, which was isolated via filter cannula and then C15H5F10P, M = 406.16, colourless crystals, 0.20 × 0.13 ×
dried in vacuo to give the product as a white solid (151 mg, 0.05 mm, a = 10.0879(2), b = 14.1955(5), c = 11.6037(3) Å, β =
0.171 mmol, 35%). Single crystals suitable for X-ray crystal 113.101(2)°, V = 1528.44(7) Å3, ρcalc = 1.765 g cm−3, μ =
structure analysis were obtained from a solution of 8 in C6D6. 2.672 mm−1, empirical absorption correction (0.617 ≤ T ≤
IR (KBr): ˜ν = 2964 (w), 2935 (w), 2877 (w), 1644 (m), 1522 (s), 0.878), Z = 4, monoclinic, space group P21/c (no. 14), λ =
1486 (s), 1464 (s), 1389 (w), 1305 (m), 1293 (m), 1105 (s), 981 1.54178 Å, T = 223(2) K, ω and φ scans, 15 206 reflections col-
(s), 752 (m), 694 (w), 639 (w), 526 (w). Elemental analysis: calcd lected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 2642 independent (Rint
for C36H14BF20OP: C 48.90, H 1.60; found: C 48.71, H 1.77. Mp: = 0.042) and 2233 observed reflections [I > 2σ(I)], 236 refined
90 °C (DSC); Dp: 131 °C (DSC). 1H NMR (500 MHz, 298 K, parameters, R = 0.050, wR2 = 0.142, max. (min.) residual elec-
3
3
CD2Cl2): δ = 7.30 (m, 5H, Ph), 6.97 (dd, JHH = 15.2 Hz, JHH
=
tron density 0.68 (−0.22) e Å−3, hydrogen atoms calculated and
7.4 Hz, 1H, vCHCH), 6.33 (d, 3JHH = 15.2 Hz, 1H, vCHPh), 5.88 refined as riding atoms.
(br d, JHH = 7.4 Hz, 1H, OCH), 3.57 (dm, JPH = 16.8 Hz, 1H,
Preparation of compound 11. Bis(pentafluorophenyl)-2-pro-
penylphosphane (9) (150 mg, 0.369 mmol) and bis(pentafluoro-
3
2
PCHB), 1.91/1.65 (each br m, each 1H, CH2), 0.93 (t, JHH
=
3
7.4 Hz, 3H, CH3). 13C{1H} NMR (126 MHz, 298 K, CD2Cl2): δ = phenyl)borane (127.8 mg, 0.369 mmol) were dissolved in
136.1 (d, 2JPC = 13.6 Hz, vCHCH), 135.6 (d, 4JPC = 4.6 Hz, i-Ph), n-pentane (10 mL) and stirred for 10 min at rt to give a white
3
129.2 (p-Ph), 129.1, 127.0 (each Ph), 120.1 (d, JPC = 5.6 Hz, suspension. Pyridine (29.2 mg, 0.369 mmol) was added and a
vCHPh), 83.3 (d, JPC = 38.1 Hz, OCH), 34.4 (br, PCHB), 21.5 white solid precipitated. After stirring for 45 min at rt all vola-
1
(CH2), 16.4 (d, JPC = 6.4 Hz, CH3); [C6F5 not listed]. 11B{1H} tiles were removed in vacuo, the residue was washed with
3
NMR (160 MHz, 298 K, CD2Cl2): δ = 2.6 (ν1/2 ∼ 70 Hz). 19F NMR n-pentane (3 × 2 mL) and dried in vacuo to give the product as
(470 MHz, 298 K, CD2Cl2): δ = −124.5 (br, 2F, o-PA), −125.8 (br, a white solid (226 mg, 0.272 mmol, 74%). Crystals suitable for
2F, o-PB), −133.7 (m, 4F, o-BA,B), −138.8 (m, 1F, p-PA), −139.4 X-ray crystal structure analysis were obtained by slow diffusion
(m, 1F, p-PB), −155.8 (br, 2F, m-PA), −156.7 (br, 2F, m-PB), of n-pentane into a solution of the product 11 in dichloro-
−159.0 (br, 1F, p-BA), −159.8 (br, 1F, p-BB), −164.6 (br, 2F, methane at −30 °C. Exact mass: calcd for C32H11BF20NP + H+:
m-BA), −165.2 (br, 2F, m-BB); [Δδ19Fp,m: 5.6 (BA), 5.4 (BB), 17.0 832.04811 m/z; found: 832.04798 m/z. IR (KBr): ˜ν = 3433 (br),
(PA), 17.3 (PB)]. 31P{1H} NMR (202 MHz, 298 K, CD2Cl2): δ = 2973 (w), 2936 (w), 1642 (s), 1518 (s), 1469 (s), 1380 (s), 1284 (s),
23.5 (ν1/2 ∼ 60 Hz).
1224 (m), 1190 (w), 1088 (s), 976 (s), 841 (m), 809 (m), 693 (s),
X-ray crystal structure analysis of compound trans-8. 626 (m), 577 (w), 506 (w). Elemental analysis: calcd for
Formula C36H14BF20OP·1.5 C6H6, M = 1001.41, colourless C32H11BF20NP: C 46.24, H 1.33, N 1.69; found: C 46.43, H 1.29,
crystals, 0.25 × 0.20 × 0.20 mm, a = 13.5250(20), b = 13.9090 N 1.77. Mp: 200 °C (DSC). 1H NMR (500 MHz, 299 K, C6D6): δ =
(30), c = 14.5825(11) Å, α = 111.609(7), β = 113.015(11), γ = 8.08 (m, 2H, o-py), 6.46 (m, 1H, p-py), 6.18 (m, 2H, m-py), 3.10
3
94.428(12)°, V = 2267.7(6) Å3, ρcalc = 1.467 g cm−3, μ = (m, 1H, PCH), 2.10 (m, 1H, BCH2), 1.29 (dd, JPH = 21.5 Hz,
4494 | Dalton Trans., 2013, 42, 4487–4499
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Paper
3JHH = 6.7 Hz, 3H, CH3), 1.00 (m, 1H, BCH2). 13C{1H} NMR 0.21 mm, a = 10.7188(3), b = 12.7599(6), c = 13.1819(5) Å, α =
(126 MHz, 299 K, C6D6): δ = 144.7 (o-py), 140.9 (p-py), 125.6 78.178(4), β = 78.512(3), γ = 80.597(3)°, V = 1715.13(11) Å3, ρcalc
(m-py), 120.2 (br, i-C6F5B), 108.9 (m, i-C6F5P), 26.4 (br, BCH2), = 1.536 g cm−3, μ = 1.944 mm−1, empirical absorption correc-
2
26.2 (m, PCH), 17.5 (d, JPC = 25.2 Hz, CH3); [C6F5 not listed]. tion (0.533 ≤ T ≤ 0.685), Z = 2, triclinic, space group P1 (no. 2),
ˉ
11B{1H} NMR (64 MHz, 300 K, C6D6): δ = −1.5 (ν1/2 ∼ 430 Hz). λ = 1.54178 Å, T = 223(2) K, ω and φ scans, 24 911 reflections
19F NMR (470 MHz, 299 K, C6D6): δ = −129.6 (m, 2F, o-PA), collected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 5920 independent
−130.25 (m, 2F, o-PB), −130.33 (m, 2F, o-BA), −132.1 (m, 2F, (Rint = 0.043) and 5299 observed reflections [I > 2σ(I)], 471
o-BB), −148.9 (t, JFF = 21.1 Hz, 1F, p-PA), −149.9 (t, JFF
=
refined parameters, R = 0.040, wR2 = 0.111, max. (min.)
3
3
21.1 Hz, 1F, p-PB), −155.9 (t, 3JFF = 21.1 Hz, 1F, p-BA), −156.5 (t, residual electron density 0.19 (−0.24) e Å−3, hydrogen atoms
3JFF = 20.4 Hz, 1F, p-BB), −160.1 (m, 2F, m-PB), −160.5 (m, 2F, calculated and refined as riding atoms.
m-PA), −162.8 (m, 4F, m-BA,B); [Δδ19Fp,m: 6.9 (BA), 6.3 (BB), 11.6
Preparation of compound 13. (Caution: many isonitriles are
(PA), 10.2 (PB)]. 31P{1H} NMR (202 MHz, 299 K, C6D6): δ = −36.3 toxic and must be handled with due care.) Bis(pentafluoro-
(quin, 3JFF = 31.1 Hz).
phenyl)-2-propenylphosphane (9) (100 mg, 0.246 mmol) and
X-ray crystal structure analysis of compound 11. Formula bis(pentafluorophenyl)borane (85.3 mg, 0.246 mmol) were dis-
C32H11BF20NP, M = 831.20, colourless crystals, 0.33 × 0.10 × solved in n-pentane (5 mL) and stirred for two hours at rt to
0.08 mm, a = 9.4074(2), b = 15.6502(6), c = 22.7817(10) Å, β = give a cloudy solution. t-Butylisonitrile (20.5 mg, 0.246 mmol)
96.343(2)°, V = 3333.6(2) Å3, ρcalc = 1.656 g cm−3, μ = was added to give a clear reaction mixture. After stirring at rt
2.032 mm−1, empirical absorption correction (0.553 ≤ T ≤ for 10 min the reaction mixture was cooled to −78 °C and
0.854), Z = 4, monoclinic, space group P21/c (no. 14), λ = stirred for 30 min at that temperature while a white solid
1.54178 Å, T = 223(2) K, ω and φ scans, 19 676 reflections col- crushed out. The solvent was removed by filter cannula and
lected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 5697 independent (Rint the residue was dried in vacuo to give a white solid (158 mg,
= 0.041) and 4614 observed reflections [I > 2σ(I)], 497 refined 0.189 mmol, 77%) (small impurities are visible in the NMR
parameters, R = 0.042, wR2 = 0.113, max. (min.) residual elec- spectra). Crystals suitable for X-ray crystal structure analysis
tron density 0.18 (−0.27) e Å−3, hydrogen atoms calculated and were obtained by slow diffusion of n-pentane into a solution of
refined as riding atoms.
the product 13 in dichloromethane at −30 °C. IR (KBr): ˜ν =
Preparation of compound 12. Bis(pentafluorophenyl)-2-pro- 3433 (br), 2996 (w), 2930 (w), 2874 (w), 2291 (m), 1643 (m),
penylphosphane (9) (100 mg, 0.246 mmol) and bis(pentafluoro- 1517 (s), 1474 (s), 1379 (m), 1240 (s), 1186 (m), 1140 (m), 1092 (s),
phenyl)borane (85.3 mg, 0.246 mmol) were dissolved in 978 (s), 908 (w), 838 (w), 810 (w), 777 (w), 753 (w), 733 (w),
1
n-pentane (5 mL) and after stirring for five min the reaction 662 (w), 637 (w), 536 (w), 514 (w). H NMR (500 MHz, 299 K,
mixture turned cloudy. Acetonitrile (22.8 mg, 0.246 mmol) was CDCl3): δ = 3.10 (m, 1H, PCH), 1.66 (s, 9H, C(CH3)3), 1.29 (m,
3
3
added to the reaction mixture and a white solid precipitated 2H, BCH2), 1.05 (dd, JPH = 21.4 Hz, JHH = 6.7 Hz, 3H, CH3).
instantly. After stirring the suspension for one hour at rt the 13C{1H} NMR (126 MHz, 299 K, CDCl3): δ = 126.9 (br, NC),
solid was isolated via filter cannula. The product (144 mg, 116.9 (i-C6F5B), 108.6 (m, i-C6F5P), 60.6 (C(CH3)3), 28.9
0.180 mmol, 73%) was washed with n-pentane (5 mL) and (C(CH3)3), 26.2 (m, PCH), 22.9 (br, BCH2), 18.2 (d, JPC
=
2
dried in vacuo. Crystals suitable for X-ray crystal structure 25.5 Hz, CH3); [C6F5 not listed]. 11B{1H} NMR (160 MHz,
analysis were obtained by slow diffusion of n-pentane into a 299 K, CDCl3): δ = −19.3 (ν1/2 ∼ 200 Hz). 19F NMR (470 MHz,
solution of the product 12 in dichloromethane. IR (KBr): ˜ν = 299 K, CDCl3): δ = −129.4, −129.6 (each m, each 2F,
2941 (w), 2363 (m), 1647 (m), 1519 (s), 1469 (s), 1381 (m), 1287 (m), o-PA,B), −132.6, −133.2 (each m, each 2F, o-BA,B), −149.3
3
3
1092 (s), 977 (s), 888 (w), 855 (w), 819 (w), 768 (w), 744 (w), (tm, JFF = 20.5 Hz, 1F, p-PA), −149.9 (tm, JFF = 20.6 Hz, 1F,
675 (w), 511 (w), 426 (w). Elemental analysis: calcd for p-PB), −156.9 (t, JFF = 20.4 Hz, 1F, p-BA), −157.1 (t, JFF
=
3
3
C29H9BF20NP: C 43.92, H 1.14, N 1.77; found: C 43.96, H 1.16, 20.4 Hz, 1F, p-BB), −160.2 (m, 4F, m-PA,B), −163.0 (m, 4F,
N 1.60. Mp: 76 °C (DSC). H NMR (600 MHz, 299 K, C6D6): δ = m-BA,B); [Δδ19Fp,m: 6.1 (BA), 5.9 (BB), 10.9 (PA), 10.3 (PB)]. 31P
1
3.26 (br m, 1H, PCH), 1.54 (m, 2H, BCH2), 0.99 (dd, JPH
=
{1H} NMR (202 MHz, 299 K, CDCl3): δ = −37.3 (quin, JPF
=
3
3
20.9 Hz, JHH = 6.8 Hz, 3H, CH3), 0.57 (s, 3H, NCCH3). 13C{1H} 30.0 Hz).
3
NMR (151 MHz, 299 K, C6D6): δ = 114.9 (NC), 25.7 (br, PCH),
X-ray crystal structure analysis of compound 13. Formula
25.5 (br, BCH2), 18.7 (d, JPC = 24.2 Hz, CH3), −0.5 (NCCH3); C32H15BF20NP·1/2 C5H12, M = 871.30, colourless crystals, 0.27 ×
2
[C6F5 not listed]. 11B{1H} NMR (192 MHz, 299 K, C6D6): δ = 0.10 × 0.10 mm, a = 27.4280(7), b = 20.0877(8), c = 15.7738(4)
−6.8 (ν1/2 ∼ 450 Hz). 19F NMR (564 MHz, 299 K, C6D6): δ = Å, β = 124.926(2)°, V = 7125.5(4) Å3, ρcalc = 1.624 g cm−3, μ =
−130.1 (m, 4F, o-PA,B), −134.5 (br, 4F, o-B), −148.9 (t, JFF
=
1.928 mm−1, empirical absorption correction (0.624 ≤ T ≤
3
21.1 Hz, 1F, p-PA), −149.4 (t, 3JFF = 21.3 Hz, 1F, p-PB), −156.2 (t, 0.830), Z = 8, monoclinic, space group C2/c (no. 15), λ =
3JFF = 21.0 Hz, 2F, p-B), −160.2 (m, 2F, m-PB), −160.3 (m, 2F, 1.54178 Å, T = 223(2) K, ω and φ scans, 17 145 reflections col-
m-PA), −163.0 (m, 4F, m-B); [Δδ19Fp,m: 6.8 (B), 11.4 (PA), 10.8 lected ( h, k, l), [(sinθ)/λ] = 0.60 Å−1, 5948 independent (Rint
(PB)]. 31P{1H} NMR (243 MHz, 299 K, C6D6): δ = −36.3 (quin, = 0.038) and 4883 observed reflections [I > 2σ(I)], 547 refined
3JPF = 29.7 Hz).
parameters, R = 0.050, wR2 = 0.135, max. (min.) residual elec-
X-ray crystal structure analysis of compound 12. Formula tron density 0.30 (−0.24) e Å−3, hydrogen atoms calculated and
C29H9BF20NP, M = 793.15, colourless crystals, 0.37 × 0.21 × refined as riding atoms.
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Dalton Transactions
Preparation of compound 14. (Caution: many isonitriles are 1288 (m), 1267 (w), 1223 (w), 1197 (m), 1090 (s), 975 (s),
toxic and must be handled with due care.) Bis(pentafluorophe- 896 (w), 861 (w), 812 (m), 755 (w), 713 (w), 682 (w), 634 (w), 564 (w).
nyl)-2-propenylphosphane (9) (100 mg, 0.246 mmol) and bis- Elemental analysis: calcd for C36H14BF20OP:
C
48.90,
(pentafluorophenyl)borane (85.3 mg, 0.246 mmol) were dis- H 1.60; found: C 48.21, H 1.84. Mp: 165 °C (DSC). 1H NMR
3
solved in n-pentane (10 mL) and stirred for two hours at rt to (600 MHz, 299 K, C6D6) : δ = 8.20 (d, JHH = 8.6 Hz, 1H, CHO),
give a clear solution. n-Butylisonitrile (20.5 mg, 0.246 mmol) 6.96 (m, 1H, p-Ph), 6.82 (m, 2H, m-Ph), 6.76 (m, 2H, o-Ph), 6.72
3
3
3
was added and the reaction mixture was cooled to −78 °C and (d, JHH = 15.5 Hz, 1H, PhCH), 6.56 (dd, JHH = 15.5 Hz, JHH
=
stirred for one hour at that temperature while a white solid pre- 8.6 Hz, 1H, CHOCH), 3.54 (m, 1H, PCH), 1.73/1.60 (each m,
cipitated. The solvent was removed by filter cannula and the each 1H, BCH2), 1.28 (dd, JPH = 21.2 Hz, JHH = 6.7 Hz, 3H,
residue was dried in vacuo to give a white solid (128 mg, CH3). 13C{1H} NMR (126 MHz, 299 K, C6D6): δ = 193.8 (CHO),
0.153 mmol, 62%) (small amounts of impurities of HB 166.7 (br, PhCH), 135.2 (p-Ph), 132.6 (i-Ph), 131.2 (o-Ph), 129.4
(C6F5)2·CNnBu are visible in the NMR spectra (δ11B{1H}: −30.7). (m-Ph), 123.3 (CHOCH), 28.6 (br, BCH2), 25.9 (PCH), 19.5 (d, 2JPC
Single crystals suitable for X-ray crystal structure analysis were = 23.8 Hz, CH3); [C6F5 not listed]. 11B{1H} NMR (192 MHz,
obtained by slow diffusion of an n-pentane solution of 14 at rt. 299 K, C6D6): δ = 8.3 (ν1/2 ∼ 700 Hz). 19F NMR (564 MHz,
1H NMR (500 MHz, 299 K, C6D6/CD2Cl2): δ = 3.25 (m, 1H, 299 K, C6D6): δ = −129.3 (m, 2F, o-PA), −129.8 (m, 2F, o-PB),
3
3
PCH), 2.49 (td, JHH = 6.7 Hz, J = 1.4 Hz, 2H, NCH2), 1.68/1.60 −133.2 (br, 4F, o-B), −148.6 (t, JFF = 20.5 Hz, 1F, p-PA), −149.6
3
3
3
3
3
(each br m, each 1H, BCH2), 1.07 (dd, JPH = 20.7 Hz, JHH
=
(t, JFF = 21.1 Hz, 1F, p-PB), −155.7 (br, 2F, p-B), −160.2 (m, 4F,
6.9 Hz, 3H, CHCH3), 0.97 (m, 2H, CH2CH2CH2), 0.85 (m, 2H, m-PA,B), −162.6 (br, 4F, m-B); [Δδ19Fp,m: 6.9 (B), 11.6 (PA), 10.6
CH3CH2), 0.54 (t, JHH = 7.4 Hz, 3H, CH2CH3). 13C{1H} NMR (PB)]. 19F NMR (564 MHz, 248 K, CD2Cl2): δ = −129.0, −129.3
3
(126 MHz, 299 K, C6D6/CD2Cl2): δ = 128.7 (br, NC), 117.1 (br, i- (each br, each 2F, o-P), −132.7, −135.3 (each m, each 2F, o-B),
C6F5B), 108.8 (br, i-C6F5P), 43.6 (NCH2), 29.2 (CH2CH2CH2), 26.8 −148.7, −149.6 (each br, each 1F, p-P), −157.2 (t, JFF
=
3
(m, PCH), 23.9 (br, BCH2), 19.3 (CH3CH2), 18.6 (d, JPC = 25.1 20.4 Hz, 1H, p-B), −158.9 (t, 3JFF = 20.5 Hz, 1F, p-B), −160.6 (br
Hz, CHCH3), 12.6 (CH2CH3); [C6F5 not listed]. 11B{1H} NMR m, 4F, m-P), −163.7, −164.6 (each m, 2F, m-B). 31P{1H} NMR
(160 MHz, 299 K, C6D6/CD2Cl2): δ = −19.1 (ν1/2 ∼ 250 Hz). 19F (243 MHz, 299 K, C6D6): δ = −34.8 (quin, 3JPF = 28.5 Hz).
2
NMR (470 MHz, 299 K, C6D6/CD2Cl2): δ = −130.1 (m, 4F,
X-ray crystal structure analysis of compound 15. Formula
o-PA,B), −132.6 (m, 2F, o-BA), −133.4 (m, 2F, o-BB), −148.8 (tm, C36H14BF20OP, M = 884.25, colourless crystals, 0.15 × 0.13 ×
3
3JFF = 20.9 Hz, 1F, p-PA), −149.5 (tm, JFF = 20.9 Hz, 1F, p-PB), 0.04 mm, a = 10.7451(3), b = 24.4031(8), c = 14.3508(6) Å, β =
3
−156.2 (tm, JFF = 20.0 Hz, 2F, p-BA,B), −160.3 (m, 4F, m-PA,B), 110.583(2)°, V = 3522.8(2) Å3, ρcalc = 1.667 g cm−3, μ =
−162.7 (m, 4F, m-BA,B); [Δδ19Fp,m: 6.5 (B), 11.5 (PA), 10.8 (PB)]. 1.979 mm−1, empirical absorption correction (0.755 ≤ T ≤
31P{1H} NMR (202 MHz, 299 K, C6D6/CD2Cl2): δ = −36.9 (quin, 0.925), Z = 4, monoclinic, space group P21/c (no. 14), λ =
3JPF = 30.5 Hz).
1.54178 Å, T = 223(2) K, ω and φ scans, 30 969 reflections col-
X-ray crystal structure analysis of compound 14. Formula lected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 6115 independent (Rint
C32H15BF20NP, M = 835.23, colourless crystals, 0.42 × 0.36 × = 0.049) and 4880 observed reflections [I > 2σ(I)], 534 refined
0.12 mm, a = 9.1649(2), b = 11.6030(2), c = 16.2616(4) Å, α = parameters, R = 0.053, wR2 = 0.144, max. (min.) residual elec-
75.183(1), β = 75.375(1), γ = 85.283(2)°, V = 1617.31(6) Å3, ρcalc
=
tron density 0.33 (−0.30) e Å−3, hydrogen atoms calculated and
1.715 g cm−3, μ = 0.228 mm−1, empirical absorption correction refined as riding atoms.
ˉ
(0.910 ≤ T ≤ 0.973), Z = 2, triclinic, space group P1 (no. 2), λ =
Preparation of compound 16. Bis(pentafluorophenyl)-2-pro-
0.71073 Å, T = 223(2) K, ω and φ scans, 15 281 reflections col- penylphosphane (9) (250 mg, 0.62 mmol) and bis(pentafluoro-
lected ( h, k, l), [(sin θ)/λ] = 0.59 Å−1, 5516 independent (Rint phenyl)borane (212.9 mg, 0.62 mmol) were dissolved in
= 0.037) and 4873 observed reflections [I > 2σ(I)], 552 refined n-pentane (10 mL) and stirred for ten min before benzaldehyde
parameters, R = 0.048, wR2 = 0.120, max. (min.) residual elec- (65.3 mg, 0.62 mmol) was added. A white solid precipitated.
tron density 0.33 (−0.30) e Å−3, hydrogen atoms calculated and After stirring overnight the precipitate was isolated via filter
refined as riding atoms.
cannula and the residue was dried in vacuo to give the product
Preparation of compound 15. Bis(pentafluorophenyl)-2-pro- (392 mg, 0.457 mmol, 74%). Crystals suitable for X-ray crystal
penylphosphane (9) (150 mg, 0.375 mmol) and bis(pentafluoro- structure analysis were obtained by slow diffusion of n-pentane
phenyl)borane (130 mg, 0.375 mmol) were dissolved in into a solution of the product 16 in dichloromethane at
n-pentane (5 mL) and after stirring for five min the reaction −30 °C. Exact mass: calcd for C34H12BF20OP + Na+: 881.03085
mixture turned cloudy. trans-Cinnamic aldehyde (50.0 mg, m/z; found: 881.03027 m/z. IR (KBr): ˜ν = 3437 (br), 2981 (w),
0.375 mmol) was added to the reaction mixture which turned 2935 (w), 1644 (s), 1598 (m), 1576 (m), 1524 (s), 1483 (s), 1463 (s),
green-yellow and a white solid precipitated. The solid was iso- 1394 (m), 1307 (m), 1279 (m), 1230 (w), 1178 (w), 1103 (s),
lated via filter cannula, washed with n-pentane (15 mL) and 1010 (m), 984 (s), 921 (m), 849 (w), 792 (m), 766 (w), 728 (w),
dried in vacuo (158 mg, 0.179 mmol, 48%). Crystals suitable 701 (m), 680 (m), 643 (w), 568 (w), 511 (w). Elemental analysis:
for X-ray crystal structure analysis were obtained by slow calcd for C34H12BF20OP: C 47.58, H 1.41; found: C 47.38,
diffusion of n-pentane into a solution of the product 15 in H 1.04. Mp: 149 °C (DSC); Dp: 220 °C (DSC). 1H NMR (600 MHz,
dichloromethane. IR (KBr): ˜ν = 3434 (br), 2966 (w), 2917 (w), 299 K, CD2Cl2): δ = 7.82 (br s, 1H, OCH), 7.68 (m, 2H, o-Ph),
1643 (m), 1611 (s), 1586 (s), 1518 (s), 1461 (s), 1386 (m), 1330 (w), 7.64 (m, 1H, p-Ph), 7.48 (m, 2H, m-Ph), 3.50 (m, 1H, PCH), 1.66
4496 | Dalton Trans., 2013, 42, 4487–4499
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3
(ddd, JPH = 30.5 Hz, JHH = 15.5 Hz, JHH = 7.4 Hz), 1.43 (m) 0.154 mmol, 52%). Crystals of 18 suitable for X-ray crystal
3
3
(each 1H, BCH2), 1.24 (dd, JPH = 22.1 Hz, JHH = 6.8 Hz, 3H, structure analysis were obtained by slow diffusion of n-pentane
CH3). 13C{1H} NMR (151 MHz, 299 K, CD2Cl2): δ = n.o. (OCH), into a solution of the product mixture in dichloromethane at
1
3
135.4 (br, p-Ph), 133.3 (i-Ph), 130.3 (br, o-Ph), 129.9 (m-Ph), −30 °C. H NMR (600 MHz, 299 K, C7D8): δ = 8.66 (d, JPH
120.5 (br, i-C6F5B), 101.1, 100.8 (each br, i-C6F5P), 28.6 (br d, 65.9 Hz, 1H, vCHB), 4.55 (m, 1H, vCH2), 4.35 (m, 1H,
=
1JPC = 13.3 Hz, PCH), 25.3 (br, BCH2), 19.1 (d, JPC = 7.1 Hz, vCH2), 3.26 (m, 1H, PCH), 1.76 (dd, JPH = 42.6 Hz, JHH
=
2
3
3
CH3); [C6F5 not listed]. 11B{1H} NMR (192 MHz, 299 K, 15.5 Hz, 1H, BCH2), 1.53 (s, 3H, vCH3), 1.24 (br m, 1H, BCH2),
CD2Cl2): δ = 4.6 (ν1/2 ∼ 350 Hz). 19F NMR (564 MHz, 299 K, 0.93 (dm, JPH = 22.8 Hz, CHCH3). 13C{1H} NMR (151 MHz,
3
CD2Cl2): δ = −125.7 (m, 2F, o-PA), −126.9 (m, 2F, o-PB), −134.6 299 K, C7D8): δ = 185.0 (br, vCHB), 142.5 (d, JPC = 12.5 Hz,
2
(br, 4F, o-B), −143.9 (br, 1F, p-PA), −144.1 (br, 1F, p-PB), −158.0 CH3Cv), 117.9 (d, JPC = 71.0 Hz, Cv), 114.5 (d, JPC = 5.8 Hz,
1
P
3
(m, 2F, m-PA), −158.7 (m, 2F, m-PB), −159.4 (br, 2F, p-B), vCH2), 31.7 (d, JPC = 41.1 Hz, CH), 23.6 (br, BCH2), 22.8 (d,
−164.9 (br, 4F, m-B); [Δδ19Fp,m: 5.5 (B), 14.1 (PA), 14.3 (PB)]. 31P 3JPC = 4.2 Hz, vCH3), 18.2 (CHCH3); [C6F5 not listed]. 11B{1H}
{1H} NMR (243 MHz, 299 K, CD2Cl2): δ = −5.9 (ν1/2 ∼ 70 Hz) NMR (192 MHz, 299 K, C7D8): δ = −14.8 (ν1/2 ∼ 50 Hz). 19F
1
P
[for NMR data at lower temperature see the ESI†].
NMR (564 MHz, 299 K, C7D8): δ = −125.8 (br, 2F, o-PA), −127.2
Preparation of compound 17. Bis(pentafluorophenyl)-2-pro- (br, 2F, o-PB), −133.2 (m, 2F, o-BA), −133.9 (m, 2F, o-BB), −136.4
penylphosphane (9) (100 mg, 0.246 mmol) and bis(pentafluoro- (m, 1F, p-PA), −138.7 (m, 1F, p-PB), −156.1 (m, 2F, m-PB),
phenyl)borane (85.3 mg, 0.246 mmol) were dissolved in −156.3 (m, 2F, m-PA), −160.0 (t, JFF = 20.2 Hz, 1F, p-BA),
3
n-pentane (5 mL) and after stirring for five min the reaction −160.5 (t, JFF = 20.4 Hz, 1F, p-BB), −164.3 (m, 2F, m-BA),
3
mixture turned cloudy. p-Tolylacetylene (28.6 mg, 0.246 mmol) −164.8 (m, 2F, m-BB); [Δδ19Fp,m: 4.3 (BA), 4.3 (BB), 20.0 (PA),
was added to the solution which turned orange immediately 17.4 (PB)]. 31P{1H} NMR (243 MHz, 299 K, C7D8): δ = 8.8 (ν1/2
∼
and after one hour a white solid precipitated. The white solid 40 Hz).
was isolated via filter cannula, washed with n-pentane (5 mL)
X-ray crystal structure analysis of compound 18. Formula
and dried in vacuo (114 mg, 0.13 mmol, 52%). Exact mass: C32H12BF20P, M = 818.20, colourless crystals, 0.20 × 0.05 ×
calcd for C36H14BF20P + Na+: 891.05052 m/z; found: 891.05089 0.04 mm, a = 12.6350(4), b = 18.8200(7), c = 12.7955(4) Å, β =
m/z. IR (KBr): ˜ν = 2960 (w), 1936 (w), 1644 (m), 1525 (s), 1484 (s), 99.880(3)°, V = 2997.53(17) Å3, ρcalc = 1.813 g cm−3, μ =
1460 (s), 1395 (m), 1306 (m), 1267 (m), 1111 (s), 1083 (s), 2.237 mm−1, empirical absorption correction (0.663 ≤ T ≤
985 (s), 966 (s), 891 (w), 862 (w), 816 (m), 779 (w), 738 (w), 694 (m), 0.915), Z = 4, monoclinic, space group P21/n (no. 14), λ =
674 (w), 636 (w), 593 (w), 571 (w), 526 (w). Elemental 1.54178 Å, T = 223(2) K, ω and φ scans, 25 276 reflections col-
analysis: calcd for C36H14BF20P: C 49.80, H 1.63; found: lected ( h, k, l), [(sin θ)/λ] = 0.60 Å−1, 5175 independent (Rint
1
C 49.40, H 1.48. Mp: 216 °C (DSC). H NMR (500 MHz, 299 K, = 0.043) and 4252 observed reflections [I > 2σ(I)], 497 refined
3
C6D6): δ = 8.92 (d, JPH = 64.1 Hz, 1H, vCH), 6.84 (m, 2H, parameters, R = 0.041, wR2 = 0.105, max. (min.) residual elec-
P
3
o-tol), 6.69 (m, 2H, m-tol), 3.47 (m, 1H, CH), 1.99 (dd, JPH
=
tron density 0.21 (−0.26) e Å−3, the hydrogen atoms at C7 were
3
B
43.9 Hz, JHH = 15.6 Hz, 1H, CH2), 1.84 (s, 3H, p-CH3tol), 1.57 refined freely, others were calculated and refined as riding
(m, 1H, BCH2), 0.93 (dd, JPH = 22.8 Hz, JHH = 6.6 Hz, 3H, atoms.
3
3
CH3). 13C{1H} NMR (126 MHz, 299 K, C6D6): δ = 187.9 (br,
5
2
vCH), 139.2 (d, JPC = 2.1 Hz, p-tol), 134.9 (d, JPC = 13.7 Hz,
i-tol), 129.7 (d, JPC = 1.1 Hz, m-tol), 127.8 (o-tol), 116.9 (d, JPC
= 71.0 Hz, vCtol), 31.7 (d, 1JPC = 39.1 Hz, PCH), 23.8 (br, BCH2),
4
1
Acknowledgements
20.8 (p-CH3tol), 18.1 (br, CH3). 11B{1H} NMR (160 MHz, 299 K, Financial support by the European Research Council is
C6D6): δ = −14.6 (ν1/2 ∼ 50 Hz). 19F NMR (470 MHz, 299 K, gratefully acknowledged.
C6D6): δ = −126.1, −127.1 (each br, each 2F, o-P), −132.8 (m,
2F, o-BA), −133.9 (m, 2F, o-BB), −135.2, −138.3 (each m, each
3
1F, p-P), −155.8, −156.1 (each m, each 2F, m-P), −159.2 (t, JFF
Notes and references
= 20.1 Hz, 1F, p-BA), −159.9 (t, JFF = 20.6 Hz, 1F, p-BB), −163.8
3
(m, 2F, m-BA), −164.4 (m, 2F, m-BB); [Δδ19Fp,m: 4.6 (BA), 4.5
(BB), 17.5–20.9 (P)]. 31P{1H} NMR (202 MHz, 299 K, C6D6): δ =
10.2 (ν1/2 ∼ 35 Hz).
1 D. W. Stephan and G. Erker, Angew. Chem., 2010, 122,
50–81, (Angew. Chem., Int. Ed., 2010, 49, 46–76).
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3 P. Spies, G. Erker, G. Kehr, K. Bergander, R. Fröhlich,
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4 P. Spies, G. Kehr, K. Bergander, B. Wibbeling, R. Fröhlich
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Preparation of compound 18. Bis(pentafluorophenyl)-2-pro-
penylphosphane (9) (120 mg, 0.295 mmol) and bis(pentafluoro-
phenyl)borane (102.2 mg, 0.295 mmol) were dissolved in
n-pentane (5 mL) and stirred for 15 min at rt to give a cloudy
solution. 2-Methylbut-1-en-3-yne (19.5 mg, 0.295 mmol) was
added and the reaction mixture was stirred for 90 min at rt.
The white precipitate was isolated from the yellow solution by
filter cannula. The residue was washed with n-pentane (2 ×
10 mL) and then dried in vacuo to give a white solid (127 mg,
This journal is © The Royal Society of Chemistry 2013
Dalton Trans., 2013, 42, 4487–4499 | 4497

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8 M. Sajid, A. Klose, B. Birkmann, L. Liang, B. Schirmer,
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5 For related N/B-FLPs see e.g. S. Schwendemann,
R. Fröhlich, G. Kehr and G. Erker, Chem. Sci., 2011, 2,
1842–1849; F. Schulz, V. Sumerin, S. Heikkinen,
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P. Pyykkö, W. Petry and B. Rieger, J. Am. Chem. Soc., 2011,
133, 20245–20257; V. Sumerin, F. Schulz, M. Nieger,
M. Atsumi, C. Wang, M. Leskelä, P. Pyykkö, T. Repo and
B. Rieger, J. Organomet. Chem., 2009, 694, 2654–2660;
V. Sumerin, F. Schulz, M. Atsumi, C. Wang, M. Nieger,
M. Leskelä, T. Repo, P. Pyykkö and B. Rieger, J. Am. Chem.
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4498 | Dalton Trans., 2013, 42, 4487–4499
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This journal is © The Royal Society of Chemistry 2013
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