Main group lewis acid/base-stabilised phosphanylboranes

Article abstract of DOI:10.1002/ejic.200601186

The parent compounds of phosphanylboranes of the type (LA)H ₂P-BH₂(LB) (LA = Lewis acid, LB = Lewis base) stabilised by Lewis acid/Lewis base have been synthesised by using perfluorinated main-group Lewis acids. The Lewis acid-phosph

Full text of DOI:10.1002/ejic.200601186

FULL PAPER
DOI: 10.1002/ejic.200601186
Main Group Lewis Acid/Base-Stabilised Phosphanylboranes
Ariane Adolf,[a] Manfred Zabel,[a] and Manfred Scheer*[a]
Dedicated to Professor Michael Binnewies on the occasion of his 60th birthday
Keywords: Boron / Phosphorus / Hydrides / Lewis acids / Lewis bases
The parent compounds of phosphanylboranes of the type
(LA)H2P–BH2(LB) (LA = Lewis acid, LB = Lewis base) stabi-
lised by Lewis acid/Lewis base have been synthesised by
using perfluorinated main-group Lewis acids. The Lewis
acid–phosphane adducts (C6F5)3BPH3, (C6F5)3BPPhH2 and
(C6F5)3GaPPhH2 (3) were used as starting materials, which
upon lithiation with nBuLi react with the chlorinated Lewis
base borane adduct ClBH2NMe3. The LA/LB stabilised
phosphanylboranes (C6F5)3BPH2BH2NMe3 (1), (C6F5)3-
BPPhHBH2NMe3 (4) and (C6F5)3GaPPhHBH2NMe3 (5), were
obtained via salt elimination reactions. (C6F5)3GaPH2-
BH2NMe3 (2) was not accessible using this method due to the
unavailability of an efficient synthetic route to (C6F5)3GaPH3.
The synthesis of 2 could be achieved quantitatively via reac-
tion of PH2BH2NMe3 with (C6F5)3Ga·Et2O. All products were
comprehensively characterised by spectroscopic methods
and X-ray crystallography. Additionally, the intermediate
products (C6F5)3BPH2Li and (C6F5)3GaPPhH2 (3) were spec-
troscopically characterised.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
Phosphanylboranes (R2P–BRЈ2)n have attracted much at-
tention since the beginning of the 90’s.[1] However, attempts
to isolate the parent compound of this class (H2P–BH2) (A)
(Scheme 1) have been futile, and only theoretical investi-
gations on A have been performed.[2] Oligophosphanylbor-
anes with the general formula (HRP–BH2)n can be synthe-
sised via dehydrocoupling reactions at elevated tempera-
tures[3] or catalysed by either RhI complexes (R = Ph)[4] or
B(C6F5)3 (R = H).[5] Experimentally accessible monomeric
phosphanylboranes are mostly stabilised by sterically de-
manding substituents to avoid intermolecular oligomeris-
ation.[1] Our approach to the parent compounds of phos-
phanylboranes was to stabilise them by the coordination of
Lewis acids and Lewis bases as type B compounds. By this
way the lone pair of the pnicogen is occupied by a Lewis
acid (LA) and the Group 13 element is coordinated by a
Lewis base (LB) (B).[6] Recently we were able to synthesise
the first phosphanylborane C, which is stabilised only by a
Lewis base.[7]
Scheme 1.
ence on the reactivity of the phosphanylboranes [Equation
(1)]. For example, photolysis of compound D leads to a
dimer with elimination of CO and H2.[6] Furthermore, the
reaction of D with iodine leads to oxidation of the tungsten
atom with concomitant loss of CO and not, as expected, to
halogenation of the phosphorus atom.[9]
The Lewis acid stabilised phosphanylboranes that we
synthesised carry transition metal carbonyls as the Lewis
acid.[6] In contrast, less is known about main group Lewis
acid stabilised group 13/15 compounds.[5,7,8] A disadvantage
of transition metal carbonyls as Lewis acids is their influ-
(1)
[a] Institut für Anorganische Chemie der Universität Regensburg,
93040 Regensburg, Germany
In order to circumvent the problem of CO elimination
reactions, we decided to use main group Lewis acids for the
synthesis of LA/LB stabilised phosphanylboranes.
Fax: +49-941-9434439
E-mail: manfred.scheer@chemie.uni-regensburg.de
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Main Group Lewis Acid/Base-Stabilised Phosphanylboranes
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Herein we report on the synthesis and characterisation of
hydrogen substituted LA/LB stabilised phosphanylboranes
with B(C6F5)3 and Ga(C6F5)3 as main group Lewis acids.[10]
Furthermore, the synthesis of the LA/LB stabilised phos-
phanylboranes is described which are substituted with a
phenyl group at the phosphorus atom.
(2)
Thus, for the synthesis of the LA/LB stabilised phos-
phanylborane 1 [Equation (3)] (C6F5)3BPH3 was metallated
in toluene with nBuLi. The 31P NMR spectrum of the in
situ generated [(C6F5)3BPH2Li] in [D8]THF exhibits a mul-
tiplet of triplets at δ = –165.1 ppm (Figure 1). The strongly
upfield shifted resonance of the phosphorus nucleus of
Results and Discussion
Synthesis and Spectroscopic Characterisation of the
Lewis Acid/Base-Stabilised Phosphanylboranes
For the synthesis of the type B compounds containing [(C6F5)3BPH2Li] can be attributed to the formation of a
1
transition metal carbonyls as the LA, the salt elimination negatively charged phosphanido complex. The JP,H value
method was chosen as a general synthetic route since the of 180 Hz of [(C6F5)3BPH2Li] is comparable with the coup-
H2 elimination had failed. The same behaviour was found ling constant in BH3PH2Li (1JP,H = 175).[11] By treating
for the main group LA containing compounds [Equation [(C6F5)3BPH2Li] with ClBH2NMe3, (C6F5)3BPH2BH2-
(2)].
NMe3 (1) is formed [Equation (3)].
Figure 1. 31P{1H} (top) and 31P NMR spectra (bottom) of [(C6F5)3BPH2Li].
Eur. J. Inorg. Chem. 2007, 2136–2143
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A. Adolf, M. Zabel, M. Scheer
FULL PAPER
(3)
Since (C6F5)3GaPH3 could not be synthesised in suf-
ficient amounts, the LiCl-elimination route is unsuitable.[12]
An elegant way to obtain (C6F5)3GaPH2BH2NMe3 (2) in
[13]
quantitative yields is the reaction of (C6F5)3Ga·OEt2
with PH2BH2NMe3 C in toluene according to Equation (4).
Figure 2. Molecular structure of (C6F5)3GaPPhH2 (3) in the crys-
tal.
(4)
Metalation of (C6F5)3GaPPhH2 3 as well as of (C6F5)3-
BPPhH2 with nBuLi leads to [(C6F5)3EPPhHLi] which were
then treated with ClBH2NMe3 to yield colourless crystals
of (C6F5)3BPPhHBH2NMe3 (4) and (C6F5)3GaPPhHBH2-
NMe3 (5), respectively [Equation (6)].
Furthermore, the synthesis of the LA/LB stabilised phos-
phanylboranes bearing a phenyl substituent at the P atom
was of interest. This additional stabilisation could be help-
ful in subsequent investigations concerning the abstraction
of the Lewis base.
[5]
Since (C6F5)3BPPhH2 was already described in the lit-
erature, the unknown Ga analogue (C6F5)3GaPPhH2 (3)
was synthesised in almost quantitative yield by adding
PPhH2 to a solution of (C6F5)3Ga·OEt2 in toluene [Equa-
tion (5)].
(6)
Only in the mass spectrum of 5 is the molecular ion peak
detected. In the case of 1, 4 and 5 the highest peak is that
of the Lewis acid [E(C6F5)3]+. Furthermore, in the mass
spectrum of 2 a peak corresponding to [PH2BH2NMe3]+
(5)
The 1H NMR spectrum of 3 shows a doublet at δ = was found. The IR spectra of the compounds 1, 2, 4 and 5
4.53 ppm (1JP,H = 369 Hz) attributable to the PH2 protons. reveal absorptions in the range of 2410 cm–1 to 2460 cm–1
The phenyl protons are detected as multiplets between 6.65 for the B–H stretching modes and the P–H stretching fre-
and 6.85 ppm. The 31P{1H} NMR spectrum reveals a reso- quencies appear between 2320 cm–1 and 2440 cm–1. The 19
F
nance at δ = –81.4 ppm which is detected as a triplet (1JP,H NMR spectra of the products show the three separated res-
= 369 Hz). onances for ortho-, meta- and para-fluorine atoms. The or-
(C6F5)3GaPPhH2 (3) crystallises as colourless prisms in tho and the meta resonances of 1 are slightly upfield shifted
¯
the triclinic space group P1. The Ga–P bond length compared to the corresponding resonances of free
(2.477(1) Å] is within the normal range for Ga–P single (C6F5)3B.[18] The para-fluorine resonance of 1, in which the
bonds, which may vary from 2.256(3) Å to 2.462(3) Å.[1b,14] boron atom of the Lewis acid is in a tetrahedral environ-
A π-stacking interaction between the phenyl ring at the P ment, is shifted downfield by about 10 ppm relative to that
atom and one of the perfluorinated phenyl rings of of free (C6F5)3B in which the boron atom possesses a trigo-
(C6F5)3Ga is observed (Figure 2) with a distance of nal planar geometry.
1
3.851(1) Å between the ring centres, which is longer than
In the H NMR spectrum of 1 a singlet is detected at δ
the interlayer distance in graphite (3.354 Å). The angle be- = 2.11 ppm for the trimethylamine group, and a doublet at
tween the planes of these two phenyl rings was determined δ = 4.0 ppm (1JP,H = 345 Hz) arising from the PH2 protons.
to be 24.04°. These results are in good agreement with The 31P{1H} NMR spectrum of 1 shows a broadened sing-
known aryl–perfluoroaryl π-interactions, where the dis- let at δ = –109.8 ppm, while the proton-coupled spectrum
tances and angles between the aromatic rings are in the reveals a broad triplet (1JP,H = 345 Hz). Also, the 11B{1H}
range of 3.3 to 3.8 Å and 20°, respectively.[15–17]
NMR spectrum shows a broad resonance at δ = –0.4 ppm
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Main Group Lewis Acid/Base-Stabilised Phosphanylboranes
FULL PAPER
for the BH2 moiety, which splits into a broad triplet with a Table 1. Selected bond lengths [Å] and angles [°] of the phosphanyl-
1
boranes 1, 2, 4 and 5.
boron–hydrogen coupling constant of JB,H = 133 Hz when
the spectrum is measured with proton coupling. In com-
parison with the trigonal planar surrounded boron atom of
free B(C6F5)3, which can be detected in its 11B NMR spec-
trum at δ = 59.6 ppm, the resonance of the boron atom of P–B
the LA in compound 1, which is in a tetrahedral environ-
1
2
4
5
LAB–P
LAGa–P
2.047(3)
–
1.989(4)
1.601(4)
–
2.046(3)
–
1.974(3)
1.604(4)
–
2.393(1)
1.992(2)
1.586(3)
2.424(1)
1.963(2)
1.606(3)
B–N
LA–P–B
P–B–N
Torsion angles
LA–P–B–N
122.98(13) 116.55(8) 111.02(10) 114.17(9)
112.2(2) 113.36(14) 116.05(16) 115.06(16)
ment, is shifted strongly upfield and appears at δ =
–18.3 ppm as a broad singlet.
The chemical shift for the methyl protons of the Lewis
150.781(26) 154.24(14) 170.18(16) 175.61(12)
1
base of 2 is detected at δ = 1.48 ppm in the H NMR spec-
trum and the PH2 protons show a broad doublet at δ =
2.85 ppm (1JP,H = 318 Hz). The 31P NMR spectrum of 2
shows a broad triplet at δ = –161.1 ppm (1JP,H = 321.8 Hz)
and a broad singlet in the case of the 31P{1H} NMR spec-
trum. In the 11B{1H} NMR spectrum the resonance for the
boron nucleus is detected at δ = –10.81 ppm as a broad
singlet, with no discernible fine structure. Acquisition of the
proton-coupled spectrum only leads to broadening of this
signal.
ment due to coordination of the Lewis base NMe3. The
Lewis acid (1, 4: B(C6F5)3; 2, 5: Ga(C6F5)3) and the Lewis
base NMe3 adopt a trans arrangement and the substituents
around the P–B bond are arranged in a slightly staggered
geometry. The compounds 1 and 2 are isostructural and
¯
crystallise in the centrosymmetric space group P1 revealing
The 1H NMR spectrum of 4 shows a singlet at δ =
1.33 ppm which can be assigned to the NMe3 group, a reso-
nance for the P–H proton, which splits into a doublet at δ =
5.44 ppm (1JP,H = 353 Hz), and multiplets for the aromatic
protons between 6.8 and 7.0 ppm. The 31P{1H} NMR spec-
trum shows a resonance at δ = –51.5 ppm, which is detected
in the 31P NMR as a doublet (1JP,H = 352 Hz). The boron
atom of the Lewis acid (C6F5)3B can be detected in the 11B
NMR and 11B{1H} NMR spectra (δ = –14.7 ppm) as can
that of the BH2 group (δ = –10.8 ppm). The latter signal is
only revealed as a broad singlet, displaying no splitting into
a triplet when a proton-coupled spectrum of 4 is recorded.
1
The H NMR spectrum of 5 shows a broadened doublet
at δ = 4.53 ppm arising from the PH unit (1JP,H = 328 Hz).
The NMe3 resonance is detected at δ = 1.34 ppm and the
protons of the phenyl group are split into a multiplet be-
tween 6.8 and 6.9 ppm. The 31P{1H}NMR spectrum of 5
shows a resonance at δ = –77.9 ppm, which is detected as a
triplet (1JP,H = 328 Hz) in the 31P NMR spectrum. The
11B{1H} NMR spectrum shows a broad signal at δ =
–9.7 ppm, which reveals slightly broadening in the proton-
coupled spectrum.
Figure 3. Molecular structures of 1 (E = B) and 2 (E = Ga) in the
crystal.
X-ray Structural Characterisation of the Lewis Acid/Base-
Stabilised Phosphanylboranes
The compounds 1–5 crystallise as colourless prisms from
a mixture of toluene and n-hexane. The structures were con-
firmed by X-ray diffraction studies (Table 2). Selected bond
lengths and angles of the compounds 1, 2, 4 and 5 are listed
in Table 1.
1, 2, 4 and 5 show the same HRP–BH2 structural motif
[1, 2: R = H (Figure 3); 4, 5: R = Ph (Figure 4)] in the solid
state. This moiety is coordinated to the Lewis acid (1, 4:
B(C6F5)3; 2, 5: Ga(C6F5)3) by the lone pair of the phospho-
rus atom, so that the phosphorus is surrounded by four
Figure 4. Molecular structure of 4 (E = B) and 5 (E = Ga), respec-
substituents. The boron atom is in a tetrahedral environ- tively in the crystal.
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A. Adolf, M. Zabel, M. Scheer
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the same staggered geometry around the P–B core as both
enantiomers show which are present in the solid state (Fig-
ure 5, a).
Figure 5. Staggered conformation around the B–P bonds in 1 (left,
E = B) and 2 (right, E = Ga).
Besides the LA and LB, 1 and 2 are only substituted by
hydrogen atoms. The P–B bond distances of 1 [(1.989(4) Å]
and 2 [(1.992(2) Å] agree well with usual P–B single-bond
distances, which range from 1.90 Å to 2.0 Å.[1] A compari-
son with the P–B bond length in [W(CO)5PH2BH2NMe3] D
[(1.955(2) Å] shows that compounds 1 and 2 possess slightly
longer P–B bond distances. The P–B bond distance in the
calculated LA and LB free compound A is with 1.90 Å[2b]
(1.905 Å[2c]) slightly shortened due to a small P–B π-bond
contribution in A, which is absent in the LA/LB stabilised
molecules 1 and 2. Whereas the P–B–N angles of 1
[(112.2(2)°] and 2 [(113.36(14)°] are very similar, the LA–P–
B angles differ significantly [1: 122.98(13)°; 2: 116.55(8)°],
revealing the different valence radii of the boron and gal-
lium atoms in the LA.
Figure 6. Staggered geometries of 4 (top, E = B) and 5 (bottom, E
= Ga). F atoms and Me groups are omitted for clarity.
Compounds 4 and 5, which possess a phenyl substituent
at the phosphorus atom, show similar structures, although
they do not crystallise in the same space group. The values
of their P–B bond distances do not differ much. Their P–
B–N angles are very similar [4: 116.05(16); 5: 115.06(16)°],
as are their LA–P–B angles [4: 111.02(10)°; 5: 114.17(9)°].
The substituents around the P–B core in 4 and 5 adopt a
staggered geometry (Figure 6).
Whereas the Ga containing LA substituted compound 5
shows some π-stacking interaction between one of the per-
fluorinated phenyl rings of the LA and the phenyl substitu-
ent at the phosphorus atom (Figure 7), no π-stacking inter-
action is noticeable in 4. The center-to-center distance of
the phenyl rings in 5 is 4.082 Å, which is longer than the
distance between the fluoroaryl and the aryl groups in 3
Figure 7. π-stacking interaction in 5.
In 2003 Denis et al. reported on the dehydrocoupling be-
(3.851 Å). The angle formed by the two planes of the stag- tween (C6F5)3BPH2R (R = H or Ph) and BH3/SMe2 to
gered phenyl rings is 29°. form (C6F5)3BPH2BH2SMe2 and (C6F5)3BPH(Ph)-
In comparison with the bond distance of the B–P core of BH2SMe2.[5] They described a subsequent polymerization
the phosphanylboranes the boron containing LA–P bond at 20 °C in the case of the phenyl-substituted derivative and
distances in 1 and 4 are slightly elongated [1: 2.076(3) Å; 4: at 110 °C for 3 h in the case of the hydrogen substituted
2.046(3) Å]. The Ga–P bond distance in compound 5 derivative, which led to the formation of the polymers
[2.424(1) Å] shows nearly the same length as that that is [PHRBH2]n (R = H or Ph) and (C6F5)3BSMe2, as con-
found in the starting material 3 [2.477(1) Å], and is in the firmed by NMR studies. In contrast the NMe3-substituted
normal range for a Ga–P single bond, which varies between LA/LB-stabilised phosphanylboranes 1, 2, 4, and 5, which
2.256(3) Å and 2.462(3) Å.[1b,14] The value of the Ga–P we report herein, show a very high thermal stability up to
bond length of compound 2 [2.393(1) Å] also lies within 150 °C, without any signs of decomposition or dehy-
this range.
drocoupling to form polymerisation products.
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Main Group Lewis Acid/Base-Stabilised Phosphanylboranes
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595 (m), 581 (s), 490 (s), 472 (m), 448 (s), 394 (s) cm–1. IR (KBr):
ν = 3026 (s, CH), 2962 (s, CH), 2925 (m, CH), 2853 (w, CH), 2463
˜
Conclusions
The results reported herein have shown that we were able (s, BH), 2433 (s, BH), 2394 (w, PH), 2324 (vw, PH), 1647 (vs, CF),
1601 (w), 1518 (vs), 1464 (vs), 1376 (s), 1281 (s), 1130 (s), 1110 (vs),
1085 (s), 1071 (w, sh), 982 (s), 966 (s), 868 (m), 826 (m), 784 (s),
772 (s), 736 (m), 709 (m), 674 (s), 670 (s, sh), 624 (m), 575 (m), 472
(br. m) cm–1. C21H13B2F15NP (616.9): calcd. C 40.88, H 2.12, N
2.27; found C 41.25, H 2.38, N 2.28.
to use perfluorinated main group Lewis acids to prepare
LA/LB-stabilised phosphanylboranes. The parent com-
pound H2P–BH2 can be stabilised with NMe3 as the Lewis
base and B(C6F5)3 (1) or Ga(C6F5)3 (2) as the main group
Lewis acid. Furthermore the synthesis of the phenyl-substi-
tuted LA/LB stabilised phosphanylboranes 4 and 5 was Synthesis of (C6F5)3GaPH2BH2NMe3 (2): (C6F5)3GaOEt2 (356 mg,
0.552 mmol) is added to a solution of PH2BH2NMe3 (0.058 mg,
0.552 mmol) in toluene (25 mL). After stirring for 18 h, the solu-
tion is concentrated to ca. 4 mL in vacuo. Colourless crystals of 2
are obtained by slow diffusion of n-hexane into this solution at
room temperature. Yield 401 mg (97%). 1H NMR (C6D6, 25 °C,
achieved. In the solid state, the substituents in all products
show a staggered geometry around the central P–B core. In
the Ga containing compounds 3 and 5, π-stacking interac-
tions between one of the perfluorinated phenyl rings of the
LA and the phenyl substituent at the phosphorus atom con-
tribute to their stability. These compounds do not show any
tendency to polymerise in contrast to previously reported
SMe2-substituted compounds.[5] Furthermore we expect
that removal of the Lewis base from the synthesised com-
1
300 MHz): δ = 1.48 (s, 9 H, N(CH3)3), 2.85 (br. d, JP,H = 318 Hz,
2 H, PH2) ppm. 31P NMR (C6D6, 25 °C, 121.5 MHz): δ = –161.13
1
(br. t, JP,H = 321.8 Hz, PH2) ppm. 31P{1H} NMR: δ = –161.14 (s,
PH2) ppm. 11B NMR (C6D6, 25 °C, 128.4 MHz): δ = –10.94 (br. s,
BH2) ppm. 11B{1H} NMR: δ = –10.81 (br. s, BH2) ppm. 19F NMR
3
pounds will yield stable derivatives stabilised only by a (C6D6, 25 °C, 282.4 MHz): δ = –122.7 (d, JF,F = 18.5 Hz, 6 F, o-
F), –154.4 (t, 3JF,F = 19.6 Hz, 3 F, p-F), –161.9 (m, 6 F, m-F) ppm.
Lewis acid. These investigations are in progress.
EI-MS (70 eV): m/z (%) = 570 (21) [[(C6F5)3Ga]+], 403 (43)
[[(C6F5)2Ga]+], 168 (100) [[C6F5H]+], 105 (12) [[PH2BH2NMe3]+].
IR (KBr): ν = 3026 (s, CH), 2961 (s, CH), 2925 (m, CH), 2853 (br.
˜
Experimental Section
m, CH), 2454 (s, BH), 2424 (s, BH), 2374 (br. m, PH), 2318 (m,
PH), 1643 (vs, CF), 1613 (w), 1556 (w, sh), 1511 (vs), 1467 (vs),
1445 (m, sh), 1411 (m), 1363 (s), 1268 (s), 1243 (m), 1160 (s), 1126
(s), 1066 (vs), 1015 (m), 960 (vs), 863 (s), 798 (m), 756 (m), 740
(w), 720 (w), 700 (m), 608 (m), 490 (m) cm–1. C21H13BF15GaNP
(675.8): calcd. C 37.32, H 1.94, N 2.07; found C 37.21, H 2.01, N
2.02.
General Techniques: All manipulations were performed under an
atmosphere of dry nitrogen using standard Glovebox and Schlenk
techniques. Solvents were purified and degassed by standard pro-
cedures. The compounds B(C6F5)3,[13] (C6F5)3GaOEt2,[13]
(C6F5)3BPH3,[19] (C6F5)3BPPhH2,[5] PH2BH2NMe3,[7] ClBH2-
[20]
[21]
NMe3
and PPhH2
were prepared according to the literature
procedures. nBuLi (Fluka, 1.6 molar solution in n-hexane) was
used as received.
Synthesis of (C6F5)3GaPPhH2 (3): PhPH2 (0.852 mL, 0.853 g,
7.75 mmol) is added slowly to a solution of (C6F5)3GaOEt2 (5 g,
7.75 mmol) in toluene (70 mL) at 0 °C. After stirring the solution
for 18 h at room temperature the solvent is removed in vacuo and
the residue is washed with n-hexane (3ϫ20 mL) leaving
(C6F5)3GaPPhH2 as a white powder. Single crystals of 3 can be
obtained by recrystallisation from a mixture of toluene and n-hex-
ane as colourless prisms. Yield 5.06 g (91%). 1H NMR (C6D6,
The NMR spectra were recorded on either a Bruker 300 or Avance
400 spectrometer with δ referenced to external SiMe4 (1H), H3PO4
(31P), BF3–Et2O (11B) and CFCl3 (19F). IR spectra were measured
on a DIGILAB (FTS 800) FT-IR spectrometer. All mass spectra
were recorded on a Finnigan MAT 95 (FD) or a Finnigan MAT
SSQ 710 A (EI, 70 eV) instrument.
1
25 °C, 400 MHz): δ = 4.53 (d, JP,H = 369 Hz, 2 H, PH2), 6.65–
Synthesis of (C6F5)3BPH2BH2NMe3 (1): To a solution of (C6F5)3-
BPH3 (170 mg, 0.31 mmol) in toluene (20 mL), nBuLi (0.19 mL,
0.31 mmol) is added dropwise at 0 °C. After stirring the solution
at room temperature for 3 h, the formation of (C6F5)3BPH2Li is
confirmed by 31P NMR ([D8]THF, 101.256 MHz, δ = –165.14, mt,
1JP,H = 180 Hz, PH2). ClBH2NMe3 (33 mg, 0.31 mmol) is then
added and the mixture is stirred at room temperature for 18 h. The
LiCl precipitate is filtered through a plug of Celite and the resulting
solution is concentrated to 2 mL in vacuo. Colourless crystals of 1
are obtained as prisms by slow diffusion of n-hexane into this solu-
tion of 1 at room temperature. Yield 163 mg (85%). 1H NMR
(C6D6, 25 °C, 250 MHz): δ = 2.11 (s, 9 H, N(CH3)3), 4.0 (dm, 1JP,H
= 345 Hz, 2 H, PH2) ppm. 31P NMR (C6D6, 25 °C, 101.3 MHz): δ
6.85 (m, 5 H, Ph) ppm. 31P NMR (C6D6, 25 °C, 162 MHz): δ =
–81.44 (t, 1JP,H = 369 Hz, PH2) ppm. 31P{1H} NMR: δ = –81.44 (s,
PH2) ppm. 19F NMR (C6D6, 25 °C, 376.5 MHz): δ = –122.89 (d,
3JF,F = 17 Hz, 6 F, o-F), –151.73 (t, 3JF,F = 20 Hz, 3 F, p-F), –160.46
(m, 6 F, m-F) ppm. 13C{1H} NMR (C6D6, 25 °C, 75.5 MHz): δ =
129.19 (d, 3JC,P = 9 Hz, m-C (C6H5)), 130.74 (s, p-C (C6H5)), 133.79
2
1
(d, JC,P = 12 Hz, o-C (C6H5)), 137.42 (br. d, JC,F = 250 Hz, p-C,
Ga(C6F5)3), 142.06 (br. d, 1JC,F = 254 Hz, m-C, Ga(C6F5)3), 148.97
1
(br. d, JC,F = 235 Hz, o-C, Ga(C6F5)3) ppm. EI-MS (70 eV, tolu-
ene): m/z (%) = 570 (15) [Ga(C6F5)3]+, 168 (100) [C6F5H]+. IR
(KBr): ν = 3067 (m, CH), 2968 (w, CH), 2916 (w, CH), 2880 (w,
˜
CH), 2405 (m, PH), 2323 (m, PH), 1639 (s, CF), 1613 (w), 1576
(w), 1555 (w, sh), 1510 (vs), 1468 (vs), 1443 (s, sh), 1365 (s), 1271
(s), 1221 (m), 1127 (m), 1086 (s, sh), 1068 (vs), 1024 (m), 999 (m),
962 (vs), 844 (s), 799 (m), 738 (s), 719 (w), 691 (m), 611 (m), 582
(w), 491 (m), 460 (w), 412 (m) cm–1. C24H7F15GaP (681): calcd. C
42.33, H 1.04; found C 42.17, H 1.12.
1
= –109.66 (br. t, JP,H = 345 Hz, PH2) ppm. 31P{1H} NMR: δ =
–109.81 (br. s, PH2) ppm. 11B NMR (C6D6, 25 °C, 96.3 MHz): δ =
1
–0.42 (br. t, JB,H = 133 Hz, BH2), –18.27 (br. s, B(C6F5)3) ppm.
11B{1H} NMR: δ = –0.4 (br. s, BH2), –18.27 (br. s, B(C6F5)3) ppm.
19F NMR (C6D6, 25 °C, 282.4 MHz): δ = –130.8 (br. s, 6 F, o-F),
3
–157.52 (t, JF,F = 20.8 Hz, 3 F, p-F), –164.03 (m, 6 F, m-F) ppm.
Synthesis of (C6F5)3BPPhHBH2NMe3 (4): To a solution of
EI-MS (70eV, 180 °C): m/z (%) = 512 (100) [(C6F5)3B]+, 168 (52)
(C6F5)3BPPhH2 (298 mg, 0.479 mmol) in toluene (25 mL), nBuLi
(0.3 mL, 0.48 mmol) is added slowly at 0 °C. After stirring the solu-
tion at room temperature for 1 h, ClBH2NMe3 (51 mg,
[C F H]+, 58 (64) [NMe –H]+. Raman (Solid): ν = 3027 (s, CH),
˜
6
5
3
2973 (s, CH), 2956 (s, CH), 2871 (s, CH), 2471 (br. m, BH), 2433
(s, PH), 2394 (vs, PH), 1647 (s, CF), 1377 (m), 975 (br. m), 850 (s), 0.475 mmol) is added and the solution is stirred overnight at room
Eur. J. Inorg. Chem. 2007, 2136–2143
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2141

A. Adolf, M. Zabel, M. Scheer
FULL PAPER
temperature. Filtration of the reaction mixture over a bed of Celite
followed by concentration of the filtrate to ca. 2 mL and layering
with n-hexane yields 4 as colourless prisms. Yield 266 mg (81%).
0.484 mmol) is added. After filtration through Celite, the solution
is concentrated to ca. 2 mL and layered with n-hexane. Crystals of
5 are obtained as colourless prisms which are washed with n-hexane
1H NMR (C6D6, 25 °C, 400 MHz): δ = 1.33 (s, 9 H, N(CH3)3), (3ϫ20 mL). Yield 311 mg (86%). 1H NMR (C6D6, 25 °C,
1
1
5.44 (dm, JP,H = 353 Hz, 1 H, PH), 6.8–7.0 (m, 5 H, C6H5) ppm. 400 MHz): δ = 4.53 (br. d, JP,H = 328 Hz, 1 H, PH), 1.34 (s, 9 H,
1
31P NMR (C6D6, 25 °C, 162 MHz): δ = –51.5 (d, JP,H = 352 Hz, N(CH3)3), 6.8–6.9 (m, 5 H, C6H5) ppm. 31P NMR (C6D6, 25 °C,
PH) ppm. 31P{1H} NMR: δ = –51.5 (s, PH) ppm. 11B NMR (C6D6,
25 °C, 128.4 MHz): δ = –14.66 (br. s, (C6F5)3B), –10.83 (br. s,
162 MHz): δ = –77.9 (br. d, JP,H = 328 Hz, PH) ppm. 31P{1H}
1
NMR: δ = –77.9 (br. s, PH) ppm. 11B NMR (C6D6, 25 °C,
BH2) ppm. 11B{1H} NMR: δ = –14.66 [s, (C6F5)3B], –10.83 (s, 128.4 MHz): δ = –9.69 (br. m, BH2) ppm. 11B{1H} NMR: δ = –9.69
BH2) ppm. 19F NMR (C6D6, 25 °C, 376.5 MHz): δ = –128.15 (s, 6
(br. s, BH2) ppm. 19F NMR (C6D6, 25 °C, 376.5 MHz): δ = –121.9
3
3
3
3
F, o-F), –158.25 (t, JF,F = 20 Hz, 3 F, p-F), –164.45 (t, JF,F
=
(d, JF,F = 17 Hz, 6 F, o-F), –154.4 (t, JF,F = 20 Hz, 3 F, p-F),
19 Hz, 6 F, m-F) ppm. 13C{1H} NMR (C6D6, 25 °C, 100.6 MHz): –161.94 (m, 6 F, m-F) ppm. 13C{1H} NMR (C6D6, 25 °C,
3
3
3
δ = 52 ppm. 96 (d, JC,P = 4.8 Hz, N(CH3)3), 128.73 (d, JC,P
=
100.6 MHz): δ = 52.58 (d, JC,P = 4.9 Hz, N(CH3)3), 129.03 (d,
4
2
9.2 Hz, m-C, C6H5), 130.75 (d, JC,P = 2.7 Hz, p-C, C6H5), 133.52
(d, JC,P = 5.9 Hz, o-C, C6H5), 137.56 (br. d, JC,F = 248 Hz, p-C,
Ga(C6F5)3), 140.03 (br. d, JC,F = 231 Hz, m-C, Ga(C6F5)3), 148.7
3JC,P = 10 Hz, m-C, C6H5), 129.9 (s, p-C, C6H5), 132.36 (d, JC,P
=
2
1
1
8 Hz, o-C, C6H5), 137.37 (br. d, JC,F = 252 Hz, p-C, Ga(C6F5)3),
141.4 (br. d, JC,F = 250 Hz, m-C, Ga(C6F5)3), 149.39 (br. d, JC,F
= 235 Hz, o-C, Ga(C6F5)3) ppm. FI/FD-MS (toluene): m/z = 750
1
1
1
1
(br. d, JC,F = 242 Hz, o-C, Ga(C6F5)3) ppm. FI/FD-MS (toluene):
m/z (%) = 512 (100), [(C6F5)3B]+, 361.5 (26), [M+ – 2 C6F5]). IR (1%, [M+ – H]), 570 (100%, [(C6F5)3Ga]+). IR (KBr):[22] ν = 3065
˜
(KBr):[22] ν = 3079 (br. m, CH), 3028 (s, CH), 3010 (s, CH), 2954 (w, CH), 3014 (br. s, CH), 2958 (br. s, CH), 2926 (w, CH), 2451
˜
(s, CH), 2924 (w, b, CH), 2846 (s, CH), 2462 (s, BH), 2419 (s, BH),
1645 (vs, CF), 1602 (w), 1518 (vs), 1469 (vs), 1409 (m), 1382 (s),
1372 (w, sh), 1317 (w), 1284 (s), 1158 (m), 1129 (s), 1094 (vs), 1025
(m), 980 (vs), 849 (s, br), 789 (s), 773 (m), 759 (s), 744 (m), 705
(m), 677 (s), 605 (m), 575 (m), 502 (m), 468 (m), 430 (m), 419 (w)
cm–1. C27H17B2F15NP (693.00): calcd. C 46.79, H 2.47, N 2.02;
found C 46.96, H 2.52, N 1.98.
(br. s, BH), 2416 (br. s, BH), 2318 (w, PH), 1639 (vs, CF), 1612 (w),
1556 (w), 1510 (vs), 1484 (m, sh), 1464 (vs), 1446 (s, sh), 1412 (m),
1361 (s), 1328 (w), 1267 (s), 1243 (m), 1155 (m), 1126 (s), 1076 (vs),
1066 (vs), 1016 (m), 959 (vs), 887 (w), 857 (m), 818 (w), 794 (m),
745 (m), 720 (w), 701 (w, sh), 695 (m), 660 (w), 609 (m), 582 (w),
490 (m) (cm–1) cm–1. C27H17BF15GaNP (751.9): calcd. C 43.13, H
2.28, N 1.86; found C 42.76, H 2.22, N 1.86.
Synthesis of (C6F5)3GaPPhHBH2NMe3 (5): nBuLi (0.3 mL,
0.48 mmol) is added dropwise to a solution of (C6F5)3GaPPhH2
(327 mg, 0.48 mmol) in toluene (25 mL) at 0 °C. The solution is
stirred for 1 h at room temperature and then ClBH2NMe3 (52 mg,
Crystal Structure Analyses: The crystal structure analyses of 1, 3,
4 and 5 (Table 2) were performed on a STOE IPDS diffractometer
with Mo-Kα radiation (λ = 0.71073 Å). The crystal structure analy-
sis of 2 was performed on an Oxford Diffraction Gemini Ultra
Table 2. Crystallographic data for compounds 1–5.
1
2
3
4
5
Empirical formula
C21F15H13B2PN
616.91
C21F15H13GaPBN
675.82
C24F15H7GaP
680.99
C27H17F15B2PN
693.01
C27H17F15GaPBN
751.92
Formula mass [gmol–1
]
λ [Å]
Crystal system
Collection temp. [K]
Space group
a [Å]
b [Å]
c [Å]
α [°]
0.71073
triclinic
0.71073
triclinic
0.71073
triclinic
0.71073
monoclinic
173(1)
0.71073
monoclinic
173(1)
100(1)
123(1)
123(1)
¯
¯
¯
P1
P1
P1
P21/c
P21/n
9.5020(19)
11.544(2)
11.592(2)
70.93(3)
76.51(3)
77.44(3)
1157(4)
2
9.8314(5)
11.6007(6)
11.98837(16)
70.792(7)
75.442(7)
77.731(4)
1236.6(2)
2
7.6898(7)
10.9916(10)
14.1418(12)
84.309(11)
89.773(11)
77.249(11)
1159.89(19)
2
9.0723(8)
14.5892(9)
21.3383(18)
90
93.773(11)
90
2818.2(4)
4
1.633
14.0153(14)
12.6649(8)
17.2272(15)
90
95.067(11)
90
3045.9(5)
4
1.64
β [°]
γ [°]
V [Å3]
Z
Dcalcd. [gcm–3
]
1.774
0.254
612
1.815
1.303
664
1.95
1.39
664
µ [mm–1
F(000)
]
0.218
1384
1.068
1488
2 θ range
Index ranges
3.78–54.08
–11Յh Յ12
–14ՅkՅ14
–14ՅlՅ14
8413
6.20–58.04
–11ՅhՅ13
–15Յ kՅ15
–16ՅlՅ15
14488
4.56–53.7
–9ՅhՅ9
–13Յ kՅ13
–17ՅlՅ17
12608
3.38–51.64
–11ՅhՅ11
–17ՅkՅ17
–26ՅlՅ26
21292
3.60–51.72
–17ՅhՅ17
–15ՅkՅ15
–21ՅlՅ21
29999
Reflections collected
Independent reflections 4688
5537
1.094
0.0210
376
0.0293
0.0797
0.515/–0.459
4609
1.078
0.0283
378
0.0247
0.0644
0.415/–0.233
5374
0.844
0.0462
439
0.0366
0.0893
0.313/–0.203
5850
0.942
0.043
427
0.0324
0.0838
0.454/–0.293
Goodness-of-fit on F2
Rint
0.942
0.0714
380
0.0485
0.1309
0.255/–0.494
Parameters
[a]
R1 [I Ͼ 2s(I)]
[b]
wR2 (all data)
max./min. ∆ρ [e·Å–3
]
2
2 2
2 2
[a] R1 = ∑||F0|–|Fc||/∑|F0|. [b] wR2 = √∑[w(F0 – Fc ) ]/√∑[w(F0 ) ].
2142
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Eur. J. Inorg. Chem. 2007, 2136–2143

Main Group Lewis Acid/Base-Stabilised Phosphanylboranes
FULL PAPER
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tures were solved by direct methods with the program SHELXS-
97,[23a] and full-matrix least-squares refinement on F2 in SHELXL-
97[23b] was performed with anisotropic displacements for non-H
atoms. Hydrogen atoms at the carbon atoms were located in ideal-
ised positions and refined isotropically according to the riding
model. The hydrogen atoms at the phosphorus and boron atoms
could be localised by residual electron density and freely refined.
CCDC-630846 (for 1), -630849 (for 2), -630847 (for 3), -630850 (for
4), and -630848 (for 5) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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material to synthesise B(C6F5)3PH3, Ga(C6F5)3 is only avail-
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Acknowledgments
This work was comprehensively supported by the Deutsche For-
schungsgemeinschaft and the Fonds der Chemischen Industrie.
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Received: December 13, 2006
Published Online: April 10, 2007
Eur. J. Inorg. Chem. 2007, 2136–2143
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2143