The reactivity of silylated amino(dichloro)phosphanes in the presence of silver salts

Article abstract of DOI:10.1021/ic500054w

New cyclic and acylic phosphorus-nitrogen compounds have been synthesized in reactions of Hyp-N(SiMe₃)PCl₂ (hypersilyl = Hyp = (Me₃Si)₃Si) with silver salts of the perfluorinated anions [CF₃CO₂]^-, [CF₃SO₃] ^-, and [C₆F₅]^-. Depending on the choice of the silver salt, not only AgCl but also Me₃SiCl elimination could be observed, leading to a transient highly reactive 1,3 dipole molecule. This 1,3 dipole molecule was found to be a key species, which can undergo [3 + 2] cyclization, when a dipolarophile such as acetonitrile is present. Also, dimerization or even cyclo-tetramerization are observed. The occurrence of different reaction channels demonstrates that the hypersilyl moiety can act as a highly reactive functional group. All new compounds have been characterized by single-crystal X-ray diffraction studies.

Full text of DOI:10.1021/ic500054w

Article
pubs.acs.org/IC
The Reactivity of Silylated Amino(dichloro)phosphanes in the
Presence of Silver Salts
Axel Schulz,*,†,‡ Alexander Villinger,† and Andrea Westenkirchner†
†Institut fur Chemie Universitat Rostock, 18059 Rostock, Germany, A.-Einstein-Str. 3a
̈
̈
‡Leibniz Institut fur Katalyse, 18059 Rostock, Germany, A.-Einstein-Str. 29a
̈
S
* Supporting Information
ABSTRACT: New cyclic and acylic phosphorus−nitrogen compounds have
been synthesized in reactions of Hyp−N(SiMe3)PCl2 (hypersilyl = Hyp =
(Me3Si)3Si) with silver salts of the perfluorinated anions [CF3CO2]−,
[CF3SO3]−, and [C6F5]−. Depending on the choice of the silver salt, not
only AgCl but also Me3SiCl elimination could be observed, leading to a
transient highly reactive 1,3 dipole molecule. This 1,3 dipole molecule was
found to be a key species, which can undergo [3 + 2] cyclization, when a
dipolarophile such as acetonitrile is present. Also, dimerization or even cyclo-
tetramerization are observed. The occurrence of different reaction channels
demonstrates that the hypersilyl moiety can act as a highly reactive
functional group. All new compounds have been characterized by single-
crystal X-ray diffraction studies.
demand (cone angle: 199°), good solubility in organic solvents,
INTRODUCTION
■
and the property to react as both σ-acceptor and π-donator.
Therefore, we were interested in utilizing the Hyp group to
stabilize reactive PN intermediates and to study the analogous
Hyp−Cl elimination reaction triggered by the action of the
Lewis acid GaCl3.9 However, in contrast to the Me3Si−Cl
elimination, Hyp−Cl eliminations are not as straightforward as
expected. For example, reaction of Hyp−N(SiMe3)PCl2 (1)
with GaCl3 does not lead to Hyp−NP−Cl, but a surprising
heterobicycle could be isolated (Scheme 1), while for the
analogous (Me3Si)2NPCl2, Me3SiCl elimination was observed
upon the addition of GaCl3 at ambient temperatures (→
[Me3Si−NP][GaCl4] + Me3SiCl).10 Interestingly, also in the
case of the Hyp group, only Me3Si−Cl elimination instead of
Hyp−Cl was observed in a rather complex reaction. The
present work has focused on the reactions of 1 with Ag+ ions as
Lewis acid and perfluorinated anions such as AgTFA (TFA =
OCOCF3 = trifluoroacetate), AgOTf (OTf = trifluoro-
sulfonate), AgC6F5, and AgC6F5·CH3CN, providing enormous
opportunities for adjusting the Lewis acidity of the Ag+ ions in
solution and thus allowing the examination of the product
distribution as a function of the utilized anion.
Me3Si−Cl elimination can be observed for compounds
containing Me3Si groups in the presence of chloride even at
low temperatures due to the high bond energy of the silicon
chlorine bond (ΔH298 = 95 kcal·mol−1); however, often high
activation barriers prevent Me3SiCl elimination.1 A Lewis acid,
such as GaCl3, decreases the activation barrier and is
additionally responsible for product stabilization by adduct
formation after the elimination reaction.2,3
For example, (Me3Si)2NPCl2, which is capable of releasing
two equivalents of Me3SiCl, is shown to be a suitable starting
material to prepare highly reactive PN intermediates by
successive elimination of Me3SiCl. Me3SiCl elimination can
either be triggered thermally and/or by addition of a Lewis acid
such as GaCl3, thus leading to the formation of a highly labile
amino(chloro)phosphenium cation in [(Me3Si)2NPCl][GaCl4]
and iminophosphenium salt [Me3Si−NP][GaCl4] upon
warming to ambient temperatures (Scheme 1, top).4
Thermal elimination of Me3SiCl from (Me3Si)2NPCl2 results
in the formation of Me3Si−NP−Cl in the first step, as was
previously shown by photoelectron spectroscopy.5 There is just
one report of Me3Si−NP−Cl being generated in solution
when a phosphoranimine was reductively dechlorinated by a
tertiary phosphine.6 This iminophosphane is likely to be highly
reactive, prone to polymerize to oligophosphazanes, and could
be detected only as transient species by 31P NMR spectroscopy.
In contrast to Me3Si−NP−Cl, Niecke and Flick prepared a
stable iminophosphane (Me3Si)2N−PN(SiMe3) by eliminat-
ing Me3SiF from (Me3Si)2NP(F)N(SiMe3)2 at ambient
temperature.7
RESULTS AND DISCUSSION
■
Syntheses. Treatment of 1 with AgTFA over the course of
3 h at −75 °C in toluene resulted in the formation of a new
compound with a 31P NMR resonance of 147.7 ppm (cf. 1:
177.0 ppm).9 After extraction with n-pentane, the doubly TFA-
substituted product Hyp−N(SiMe3)P(OCOCF3)2 (2, Scheme
The bulky hypersilyl group (hypersilyl = Hyp = (Me3Si)3Si),
Received: January 9, 2014
Published: February 21, 2014
first introduced by Gilman and Smith,8 exhibits high steric
© 2014 American Chemical Society
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Scheme 1. Different Reaction Channels for (Me3Si)2NPCl2 (top) and Hyp(Me3Si)NPCl2 (bottom)
Scheme 2. Products 2−5 Obtained by Treatment of 1 with Perfluorinated Silver Salts
31P NMR signal at 505.7 ppm, which lies in the expected range
for a PP bond (cf. (Me3Si)N(t-Bu)PPN(t-Bu)(SiMe3) at
499.0 ppm, Mes*PPN(SiMe3)2 at 501.5 ppm).12,13 Com-
pound 3 was formed over a period of 1 h at −60 °C. After
extraction with n-hexane and recrystallization from toluene at
−25 °C, pure orange crystals of 3 suitable for single crystal X-
ray studies were isolated (Figure 2). Whereas in the reaction of
1 with AgTFA only AgCl was precipitated, in the reaction with
AgOTf the diaminodiphosphene 3 was formed upon
elimination of AgCl and Me3SiCl. Astonishingly, at the end
of the reaction sequence, one Me3Si group of the Hyp moiety
2) was obtained. Product 2 was crystallized from n-pentane at
−40 °C (Figure 1). The formation of a covalent P−O bond in
reactions of P−Cl containing moieties with AgTFA was already
observed due to a high P−O bond energy of ΔH298 = 97 kcal·
mol−1, e.g. in the reaction of bis(terphenylamino)-
chlorophosphane (TerNH)2PCl with AgTFA (terphenyl =
Ter = 2,6-(2,4,6-trimethylphenyl)phenyl).1,11
A completely different reaction channel was observed when 1
was treated with AgOTf, which afforded in an unusual reaction
the diaminodiphosphene (TfO)(Me3Si)2Si−N(SiMe3)PP−
N(SiMe3)Si(SiMe3)2(OTf) (3, Scheme 2) in rather good yields
(76%). This compound displays a strongly downfield shifted
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resulted in the formation of crystalline Mes*−PP−Mes*.
In general, dehalogenative coupling of halophosphines can be
realized by utilization of reducing agents such as pure metals
(e.g., magnesium), sodium naphthalenide, organolithium
compounds, bis(trimethylsilyl)mercury, divalent germanium
and tin compounds, or electron-rich olefins. Also, the
elimination of hydrogen halides, salts, or trimethylsilyl halides
provides other methods for diphosphene synthesis.15 We
reported the titanocene-mediated coupling of dichlorophos-
phines to give stable diphosphenes in 2008.16
In a next series of experiments, the reactions of 1 with pure
AgC6F5 and the solvate AgC6F5·CH3CN were investigated. Due
to its sparing solubility, AgC6F5 was added at −70 °C as a solid
to a solution of 1 in CH2Cl2. The reaction mixture was stirred
over 3 h and subsequently warmed up to ambient temperature.
Extraction with n-hexane and concentration of the solution to
incipient crystallization resulted in the deposition of colorless
crystals of 4 which could be isolated in a good yield of 72%.
Single crystal X-ray studies revealed the formation of an eight-
membered macrocycle of the type Ag4(PR2)4 in tetrameric
phosphide-bridged, multinuclear silver complex 4. In this
complex, four silver and four phosphorus atoms are bound
alternately; the latter exhibit both C6F5 and N(SiMe3)Si-
(SiMe3)2Cl substituents (Scheme 2, Figure 3). Moreover, one
Me3Si unit of the Hyp moiety was exchanged by a Cl atom. The
31P NMR spectrum shows an upfield shifted signal at −13.2
ppm (cf. [Ag4(PPh2)4(PMe3)4] −94 ppm).17 Complex 4 can be
regarded as the formal tetramer of the corresponding
mononuclear silver(I) phosphanido complexes (Scheme 4,
Figure 1. ORTEP drawing of the molecular structure of 2 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen
atoms omitted for clarity). Selected bond lengths [Å] and angles
[deg]: P−N 1.633(1), P−O1 1.712(1), P−O3 1.721(1), Si1−
N,1.803(1); N−P−O1 101.62(6), N−P−O3 98.36(6), O1−P−O3
91.90(6), P−N−Si1 124.77(8), P−N−Si2 111.77(7), Si1−N−Si2
123.46(7).
species 10, vide infra) [Ag−PR1R2] (R1 = C6F5, R2
=
Figure 2. ORTEP drawing of the molecular structure of 3 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen
atoms and disorder omitted for clarity). Selected bond lengths [Å] and
angles [deg]: P1−N1 1.704(4), P2−N2 1.747(3), P1−P2 2.050(2);
N1−P1−P2−N2 178.9(2), P2−P1−N1−Si1 1.5(3), P1−P2−N2−Si6
89.6(2).
N(SiMe3)Si(SiMe3)2Cl), which, however, could neither be
detected nor isolated. Similar eight-membered rings with an
Ag4P4 heterocycle have been reported before. Fenske et al.17
obtained [Ag4(Ph2)4(PMe3)4] in the reaction of AgCl and
Ph2PSiMe3 in the presence of PMe3. Hey-Hawkins et al.
described the reaction of [AgCl(PCyp3)]4 or [AgCl(PPh3)2]
with [Na{cyclo-(P5(t-Bu)4)}] yielding [Ag4{cyclo-(P4(t-Bu3))P-
(t-Bu)}4].18
To proof the idea of the presence of a highly reactive
mononuclear silver(I) phosphanido complex bearing a Si−N
double bond (species 8, Scheme 4), discussed as a key
intermediate in the section Reaction Mechanism (see below),
was substituted by an OTf unit (Scheme 3), and in addition a
P−P linkage occurred (see also section Reaction Mechanism).
The first diphosphene was reported by Yoshifuji et al., who
introduced the bulky 2,4,6-tri-tert-butylphenyl group (super-
mesityl, Mes*) as a substituent in 1981.14 The reduction of
supermesityldichlorophosphine with elemental magnesium
Scheme 3. Proposed Reaction Mechanism for the Generation of Species 3 (X = OTf)
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Figure 3. Left: ORTEP drawing of the molecular structure of 4 in the crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms
omitted for clarity). Selected bond lengths [Å] and angles [deg]: Ag1−P2 2.4158(7), Ag1−P1 2.4259(7), Ag2−P3 2.4182(6), Ag2−P2 2.4266(6),
Ag3−P4 2.4150(7), Ag3−P3 2.4245(7), Ag4−P1 2.4162(6), Ag4−P4 2.4271(6), P2−Ag1−P1 160.38(2), P3−Ag2−P2 160.96(2), P4−Ag3−P3
160.78(2), P1−Ag4−P4 160.33(2), Ag4−P1−Ag1 105.61(2), Ag3−P4−Ag4 105.39(2), Ag1−P2−Ag2 104.99(2), Ag2−P3−Ag3 105.09(2). Right:
Ball-and-stick representation of the Ag4P4 core and the Ag···X van der Waals interactions (X = Cl, F): Ag1···Cl1 3.1774(7), Ag2···Cl2 3.1764(7),
Ag3···Cl3 3.1844(9), Ag4···Cl4, 3.1902(7); Ag1···F5 3.314(2), Ag1···F6 3.199(2), Ag2···F6 3.365(2), Ag2···F11 3.211(2), Ag3···F11 3.351(2), Ag3···
F20 3.183(2), Ag4···F20 3.300(2), Ag4···F5 3.176(2).
Scheme 4. Proposed Reaction Mechanism for the Generation of Species 4 and 5 (X = C6F5)
we used the solvate AgC6F5·CH3CN instead of AgC6F5, thus
providing a dipolarophile (CH3CN), which should be capable
of trapping reactive 1,3 dipole species 8 in a [3 + 2]
cycloaddition. The solvate AgC6F5·CH3CN was added as a
solid to 1 at −80 °C, which was dissolved in CH2Cl2. The
reaction mixture was slowly warmed up to ambient temperature
over a period of 8 h. The 31P NMR spectrum displayed only
one new resonance at 177.0 ppm. Extraction with n-hexane and
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Scheme 5. Reaction of 1 with CH3CN and GaCl3 (Including Proposed Intermediates) Leading to the Formation of
Heterocyclus 6
removal of solvent resulted indeed in the formation of a new
five-membered N−Si−N−C−P heterocyclic compound 5,
stabilized as the AgC5F5 adduct. To the best of our knowledge,
no such heterocycle has been reported before, and 5 can
formally be regarded as the [3 + 2] cycloaddition product of
species 8 and MeCN. Compound 5 was crystallized from n-
hexane at −30 °C. After 30 min at this temperature, the
decomposition of 5 occurred, detected by additional signals in
31P NMR spectra. Therefore, 5 could only be characterized by
X-ray analysis and low temperature NMR spectroscopy.
The formation of the five-membered heterocycle as the
AgC6F5 adduct (5) prompted us to use GaCl3 as a Lewis acid,
Figure 4. ORTEP drawing of the molecular structure of 5 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen
atoms and disorder of the C6F5 group omitted for clarity). Selected
bond lengths [Å] and angles [deg]: Si1−N1 1.769(3), Si1−N2
1.797(2), P1−N1 1.672(3), P1−C11 1.864(3), Ag1−N2 2.127(2),
N2−C11 1.270(4), N1−P1−C11 95.18(1), N1−Si1−N2 96.27(1),
N2−C11−P1 117.4(2), P1−N1−Si1 115.12(1), C11−N2−Si1
115.58(2), N1−Si1−N2−C11 3.9(2), Si1−N2−C11−P1−0.3(3),
N1−P1−C11−N2−3.6(3), C11−P1−N1−Si1 6.1(2).
which would be another proof for the Lewis acid induced
Me3SiCl elimination yielding a 1,3 dipole species. Furthermore,
5 was only stable at low temperatures, which we attributed to
the fact that at higher temperatures, AgC6F5 underwent further
reactions triggered by the elimination of AgCl. Thus, avoiding
AgC5F6 should lead to a more stable heterocycle if stabilized by
GaCl3. Therefore, 1 was treated with CH3CN and GaCl3 in a
molar ratio of 1:1:1 in CH2Cl2 at −40 °C (Scheme 5). The 31
P
NMR spectrum of the light orange solution displayed
immediately one resonance at 147.4 ppm (cf. 5: 177.0 ppm).
Removal of the solvent led to a red solid, which was
unequivocally shown to be the five-membered heterocycle
stabilized as the GaCl3 adduct (6) by single crystal X-ray
crystallography (Figure 5) after recrystallization from CH2Cl2
at ambient temperature. It should be noted that, besides 6,
small amounts of the dimeric condensation product 7 could be
isolated as side product (Scheme 6). The presence of 7 can be
best explained by HCl elimination between the P−Cl bond of
one molecule and the acidic H−Cmethyl,acetonitrile bond of another
molecule as depicted in Scheme 6. In contrast to 5, the
synthesis of 6 is simple and almost quantitative (yield: 95%).
Species 1, 2, 4, and 6 are air- and moisture-sensitive;
however, they are stable under an argon atmosphere over a long
period as solids, when stored in sealed tubes and kept cool at 5
°C, as well as in common organic solvents (benzene, CH2Cl2,
diethyl ether).
OTf, C6F5, and C6F5·CH3CN) salts provoked a few questions
regarding the reaction mechanisms. While the reaction of 1
with AgTFA is a simple anion exchange reaction (Scheme 2),
all other silver salts display rather unusual reaction pathways. So
far, we are not able to isolate any intermediates as displayed in
Schemes 3−5; however, in the light of similar products, which
could be isolated and fully characterized for X = OTf, C6F5, and
C6F5·CH3CN, we believe that highly reactive 1,3 dipole species
8 seems to be the key intermediate in all of these reactions. The
formation of intermediate 8 is triggered by the action of the
Lewis acid, either Ag+ or GaCl3, which induces Me3SiCl
elimination. Interestingly, the Me3Si group of the Hyp moiety
and not that attached to the N atom is involved in this
elimination, which therefore can be referred to as a 1.3
elimination, thus leading to the reactive phosphanide species 8
bearing a SiN double bond. Presumably, 8 is stabilized in
solution by adduct formation with the Lewis acids AgX or
GaCl3.
Reaction Mechanisms. The different reaction products
obtained in the reaction of 1 with several AgX (X = OCOCF3,
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Figure 5. ORTEP drawings of the molecular structures of 6 (left) and the dimer 7 (right) in the crystal. Thermal ellipsoids with 50% probability at
173 K (hydrogen atoms omitted for clarity). In Si bounded Me3Si moieties of 7, the positions of Me groups are partially occupied by Cl atoms (0.83
Cl atoms per molecule). Selected bond lengths [Å] and angles [deg], 6: P1−N2 1.664(4), P1−C1 1.862(5), Ga1−N1 1.971(4), Si1−N2 1.776(4),
Si1−N1 1.843(4), N1−C1 1.284(6), N2−P1−C1 95.2(2), N2−Si1−N1 94.9(2), C1−N1−Si1 114.8(4), P1−N2−Si1 116.3(2), N1−C1−P1
117.7(4), N2−Si1−N1−C1−4.1(4), C1−P1−N2−Si1−10.1(3), N1−Si1−N2−P1 9.5(3), Si1−N1−C1−P1−1.9(5), N2−P1−C1−N1 7.4(5). 7:
N1−P1 1.683(3), N1−Si1 1.773(3), N2−C1 1.295(4), N2−Si1 1.842(3), N2−Ga1 1.984(3), P1−C1 1.844(3), P1−C2 1.918(3), C1−C2′
1.479(4), P1−N1−Si1 115.8(2), C1−N2−Si1 114.9(2), N1−P1−C1 96.0(1), N1−Si1−N2 95.4(1), N2−C1−P1 117.7(2), Si1−N1−P1−C1
3.2(2), P1−N1−Si1−N2−2.2(2), C1−N2−Si1−N1−0.5(2), Si1−N2−C1−P1 2.7(3), N1−P1−C1−N2−3.7(2).
Scheme 6. Condensation Reaction of 6 Leading to Tricyclus 7
In the case of the AgOTf reaction, an intramolecular transfer
of the OTf group to the Si atom, which is involved in the SiN
double bond, occurs, while AgCl precipitates, forming
phosphene 9. Finally, 9 dimerizes, affording diphosphene 3.
Obviously, in this case, no stable monomeric or tetrameric
silver(I) phosphanido complex is formed.
When AgC6F5 is utilized, the Cl atom is transferred to the Si
atom, while the C6F5 group is shifted from the Ag center to the
P atom, yielding silver phosphanide species 10 (Scheme 4),
which is the formal monomer of 4. Now, the silver(I)
phosphanido complex 4 is formed in a tetramerization step.
Indirect experimental evidence for the transient presence of
species 8 was obtained by the reaction of AgC6F5·CH3CN with
1, since now acetonitrile can act as a dipolarophile in a [3 + 2]
cycloaddition reaction19 forming five-membered heterocycle 5
stabilized as the AgC6F5 adduct (Scheme 4). To generalize the
idea of Lewis acid triggered Me3SiCl elimination, we also used
GaCl3 in the reaction with 1 and CH3CN, which should also
form species 8. Again, heterocycle 5 was observed, but this time
stabilized as the GaCl3 adduct. It should be noted that without
the use of a Lewis acid no [3 + 2] cycloaddition can be
observed. Therefore, this reaction can be referred to as Lewis
acid assisted [3 + 2] cycloaddition.
The concept of a GaCl3 assisted [3 + 2] cycloaddition, in
which the added Lewis acid GaCl3 decreases the activation
barrier to Me3SiCl elimination and stabilizes the [3 + 2]
heterocycle by adduct formation at the end of the reaction
sequence, was shown in a series of other reactions, involving
even other heteroelements such as arsenic.20−22 For instance,
the reaction of the kinetically stabilized iminophosphane
Mes*−NP−Cl (Mes* = 2,4,6-tritert-butylphenyl), a good
dipolarophile, with (Me3Si)2N−N(SiMe3)−PCl2, a “disguised”
1,3-dipole, yielded a triazadiphosphole (RN3P2, R = Mes*).3,23
The first tetrazaphosphole,24 RN4P (R = Mes*), was also
obtained by a GaCl3-assisted [3 + 2] cycloaddition of Mes*−
NP−Cl with Me3Si−N3. The same reaction with the heavier
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Table 1. Crystallographic Details of 2−4
2
3
4
chem. formula
C16H36F6NO4PSi5
591.88
colorless
monoclinic
C2/c
C20H54F6N2O6P2S2Si8
883.43
C60H108Ag4Cl4F20N4P4Si16
2412.10
fw [g mol−1
]
color
orange
colorless
cryst. syst.
space group
a [Å]
monoclinic
P21/n
triclinic
P1
̅
16.9769(5)
9.3993(3)
37.984(1)
90.00
9.7411(4)
17.2317(9)
27.196(1)
90.00
14.7631(2)
14.7767(2)
24.6511(4)
73.796(1)
88.587(1)
89.952(1)
5162.3(1)
2
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
93.495(2)
90.00
91.248(2)
90.00
6049.9(3)
8
4564.0(4)
4
ρcalcd [g cm−3
μ [mm−1
]
1.300
1.286
1.552
]
0.347
0.453
1.17
λMoKα [Å]
T [K]
0.710 73
173(2)
69 902
9209
0.710 73
173(2)
40 065
0.710 73
173(2)
173 195
37 217
22 342
0.051
measured reflns
independent reflns
reflns with I > 2σ(I)
Rint
10 412
7148
7287
0.0410
2480
0.0475
F(000)
1856
2432
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
0.0412
0.0984
1.040
0.0612
0.046
0.1931
0.085
GOF
1.077
1.017
params
310
580
1045
CCDC #
980 648
980 649
980 650
Table 2. Crystallographic Details of 5−7
5
6
7
chem. formula
C17H30AgClF5N2PSi4
C11H30Cl4GaN2PSi4·CH2Cl2
C21.17H55.52Cl6.83Ga2N4P2Si8·4(CH2Cl2)
1374.18
yellow
fw [g mol−1
]
644.08
630.15
yellow
orthorhombic
Pna21
color
colorless
triclinic
cryst syst
space group
a [Å]
triclinic
P1
P1
̅
̅
8.8451(5)
12.1525(6)
13.8638(8)
90.811(3)
104.190(3)
99.590(3)
1422.2(1)
2
28.748(1)
13.1009(4) Å
15.2495(6) Å
90
9.8121(7)
11.6925(8)
15.072(1)
75.135(5)
74.483(4)
69.088(4)
1531.3(2)
2
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
90
90
5743.3(4)
8
ρcalcd [g cm−3
μ [mm−1
]
1.504
1.458
1.490
]
1.07
1.74
1.76
λMoKα [Å]
T [K]
0.710 73
173(2)
44 724
10 064
6531
0.710 73
173(2)
52 470
10 837
7500
0.710 73
173(2)
43 123
8464
measured reflns
independent reflns
reflns with I > 2σ(I)
Rint
5284
0.043
0.096
0.069
F(000)
652
2576
699
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
0.050
0.050
0.056
0.134
0.089
0.134
GOF
1.016
1.011
1.004
params
348
515
216
CCDC #
980 652
980 653
980 651
arsenic analogue led to the first tetrazarsole.21b All studied
(>90%), and clean reactions. These cyclizations can be carried
GaCl3 assisted [3 + 2] cycloadditions are fast, high-yielding
out even at low temperatures or ambient temperatures (−30 to
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Inorganic Chemistry
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25 °C), whereas classical triazole-forming reactions require
elevated temperatures. The concept of GaCl3 assisted [3 + 2]
cycloaddition reactions can now be extended to Lewis acids
such as AgX salts (X = OTf, C6F5).
Cl distances between 3.1764(7) and 3.1902(7) Å are
significantly shorter than the sum of van der Waals radii of
both atoms (ΣrvdW(Ag···Cl) = 3.47 Å)31 but significantly longer
than the sum of the covalent radii (Σrcov(Ag−Cl) = 2.27 Å).28
Two short Ag···F distances ranging between 3.176(2) and
3.365(2) are found per Ag center, which also might be
indicative for weak van der Waals interactions (ΣrvdW(Ag···F) =
3.19 Å).31 Interestingly, AgCl does not precipitate, indicating
that the Ag+ ions are strongly fixed within the formal [2 + 3]
coordination mode. The shortest Ag···Ag distance amounts to
3.8416(3) Å, which is considerably longer than the sum of van
der Waals radii of two silver atoms, 3.42 Å.31
X-Ray Structure Analysis. The solid-state structures of
compounds 2, 3, 4, 5, 6, and 7 are displayed in Figures 1−5,
along with selected bond lengths and angles. Crystallographic
details for all compounds are given in Tables 1 and 2. X-ray
quality crystals of all species considered were selected in a
Fomblin YR-1800 perfluoroether (Alfa Aesar) at ambient
temperatures. The samples were cooled to 173(2) K during
measurement. The data were collected on a Bruker Apex
Kappa-II CCD diffractometer or on a Bruker-Nonius Apex X8
CCD diffractometer using graphite monochromated Mo Kα
radiation (λ = 0.71073). The structures were solved by direct
methods (SHELXS-97)25 and refined by full-matrix least-
squares procedures (SHELXL-97).26 Semiempirical absorption
corrections were applied (SADABS).27 All non-hydrogen atoms
were refined anisotropically; hydrogen atoms were included in
the refinement at calculated positions using a riding model.
Compound 2 (Figure 1) crystallizes in the monoclinic space
group C2/c with eight formula units per cell. The observed
molecular structure exhibits the expected trigonal pyramidal
environment around the P atom and trigonal planar around the
N atom along with a short P−N distance (1.633(1) Å; cf. 1:
1.6451(9) Å;9 dcov(N−P) = 1.82 and dcov(PN) = 1.62 Å),28
indicating partial double bond character for this highly
polarized P−N bond due to hyperconjugation.29,30
Again all four terminal P−N bond lengths (1.720(2)−
1.724(2) Å) are rather short, and the N atoms sit in an almost
trigonal planar environment.
Compound 5 crystallizes in the triclinic space group P1 with
̅
two formula units per cell. The C6F5 and methyl groups of one
Me3Si moiety are disordered. The five-membered nonaromatic
heterocycle is almost planar with torsion angles between 0.3
and 6.1°. Both N atoms adopt a distorted trigonal planar
coordination geometry (Σ(N) = 360°) in contrast to the P
atom (Σ(P) = 201.9°). The P−Cl bond is nearly perpendicular
to the ring system (C11−P1−Cl1 90.95(1)°; N1−P1−Cl1
105.73(1)°), similar to the situation found for P-chlorodiaza-
phospholenes synthesized by Gudat et al.32 Both Si−N
distances (1.797(2) and 1.769(3) Å) and P−C (1.864(3) Å)
are in the range of single bonds (cf. Σrcov: Si−N 1.87, P−C 1.86
Å),28 while the C−N bond length of 1.270(4) Å represents a
typical CN double bond. Again, due to strong hyperconjugative
effects the P−N bond length (1.672(3) Å) is rather short (e.g.,
compared to the P−C bond), displaying some double bond
character. The N−Ag−C unit is almost linear (N−Ag−C
177.48°), connecting the five-membered diazasilaphosphole
with the C6F5 ring, which is slightly tilted to the five-membered
ring (Si1−N2−C13−C18−11.47°, C11−N2−C13−C14−
7.52°). The bond between the Lewis acid AgC6F5 and the N
atom of the heterocycle can be considered as a donor−acceptor
bond with a Ag−N bond length of 2.127(2) Å (cf. Σrcov(Ag−
N) = 1.99 Å, AgNCO: Ag−N 2.115 Å).28,33 Moreover, the Ag−
N distance is considerably shorter compared to that in the
starting material AgC6F5·CH3CN (Ag−N 2.392 Å), displaying a
stronger donor−acceptor interaction in 5.34
Diphosphene 3 (Figure 2) crystallizes in the monoclinic
space group P21/n with four formula units per cell. The
position of the molecule is disordered with the exception of the
Me3Si moieties on the Si atoms Si1, Si3, Si4, Si5, and Si7. The
P1−P2 bond length amounts to 2.050(2) Å, which lies in the
typical range of a typical PP bond (Σrcov(PP) = 2.02 Å),28
such as in (Me3Si)2N(Me3Si)NPPN(SiMe3)N(SiMe3)2
(2.038(1) Å) and (Me2(t-Bu)Si)2N−PP−N(Si(t-Bu)Me2)2
(2.034 Å).12,16 The P1−N1 and P2−N2 bond lengths are
shorter (1.704(4) and 1.747(3) Å, cf. 1.700(2) Å in
(Me3Si)2N(Me3Si)N−PP−N(SiMe3)N(SiMe3)2) than a typ-
ical P−N single bond (Σrcov(P−N) = 1.80 Å, Σrcov(PN) =
1.61 Å) but a little elongated compared to that in 1 with P−N
1.633(1) Å, still indicating partial double bond character. The
trans bent N1−P1−P2−N2 skeleton is almost planar with a
dihedral angle of −178.9(2)°. While Si1 and Si2 lie in this
plane, Si5 and Si6 are orthogonally arranged with respect to this
plane (Si6−N2−P2−P1−89.6(2)°).
Compound 6·CH2Cl2 crystallizes in the orthorhombic space
group Pna21 with eight formula units per cell. Two
independent heterocycles 6 and two CH2Cl2 solvent molecules,
which are both disordered, are found in the asymmetric unit.
The eight-membered heterocycle 4 crystallizes in the triclinic
The dimer 7 crystallizes in the triclinic space group P1 with two
̅
space group P1 with two formula units per cell. The most
formula units per cell. The asymmetric unit consists of a half
molecule, which lies on a two-fold crystallographic axis with the
whole molecule generated by the symmetry operation −x + 1,
−y + 1, −z as depicted in Figure 5 (right). In Si bound Me3Si
moieties of 7, the positions of Me groups are partially occupied
by Cl atoms (0.83 Cl atoms per molecule). This partial Cl/C
occupation is in line with the arguments given in the section
Reaction Mechanism in accord with the proposed transient
presence of species 8 in Scheme 5.
̅
prominent structural feature of 4 is the eight-membered
heterocycle with alternating tricoordinated P and dicoordinated
Ag atoms and shows along the Ag1−Ag3 axis a slightly folded
arrangement (Ag1−Ag2−Ag3−Ag4 15.724(6)°), similar to the
situation found for the complex [Ag4{cyclo-P4t-Bu3)Pt-Bu}4].18
All eight Ag−P bond lengths are almost equally long and are in
the range between 2.415(7) and 2.427(6) Å, indicating a strong
dative bond (Σrcov(Ag−P) = 2.39 Å).28 As expected for
dicoordinated Ag units, the P−Ag−P angles deviate slightly
from linearity and lie between 160.33(2) and 160.96(2)°, while
the Ag−P−Ag angles only amount to 104.99(2)−105.61(2)°.
In addition, as depicted in Figure 3 (right), intramolecular Ag···
X interactions (X = F, Cl) must be considered (three per Ag
center) and might be the reason for the absence of any
coordinating solvent molecule around the Ag centers. The Ag···
Since all metrical parameters of 6 are very similar to those
found for 5, we will focus on the structure and bond discussion
of 7 and the differences between 6 and 7. In 7, two heterocycles
are bridged by two CH2 moieties, and the C2−P1−C1−C2′−
P1′−C1′ six-membered ring exists in the chair conformation.
Both 6 and 7 are typical charge transfer complexes, and the
bond between the GaCl3 and the N atom of the heterocycle can
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Raman. A Bruker VERTEX 70 FT-IR with a RAM II FT-Raman
module, equipped with a Nd:YAG laser (1064 nm), was used.
CHN Analyses. An Analysator Flash EA 1112 from Thermo Quest
or a C/H/N/S-Mikroanalysator TruSpec-932 from Leco was used.
Melting points are uncorrected (EZ-Melt, Stanford Research
Systems). The heating rate was 20 °C/min (clearing points are
reported).
be described as a donor−acceptor bond (see structure
elucidation of 5) with Ga−N bonds of 1.971(4) in 6 and
1.983(3) Å in 7, respectively (Σrcov(Ga−N) = 1.96 Å).28 These
Ga−N distances are in accord with those in the triazadiphos-
holes (Me3Si)2N−N3P2·GaCl3 (1.978(3) Å)22 and Mes*−
N3P2·GaCl3 (1.9830(5) Å, Mes* = 2,4,6-tri-tert-butylphenyl)3
but shorter than those found for the adducts Cl3Ga·
NMe2SiMe2NMe2 (2.003(5) Å) and MeCl2Ga·H2N−NH(t-
Bu) (2.023(7) Å), respectively.35,36 According to NBO analysis
(NBO = natural bond orbital),37 the charge transfer amounts to
0.16 in 6 and 0.19e in 7, in agreement with values found for
triazadiphosphole or tetrazaphosphole GaCl3 adducts.3,22,24
Emanated from NBO calculations all bonds in the heterocycles
of 6 and 7 are highly polarized. The N atoms exhibit a high
DSC. A DSC 823e from Mettler-Toledo (Heating-rate 5 °C/min)
was used.
MS. A Finnigan MAT 95-XP from Thermo Electron was used.
Synthesis of (Me3Si)3SiN(SiMe3)P(OCOCF3)2 (2). To a solution
of (Me3Si)3SiN(SiMe3)PCl2 (1; 0.437 g, 1.00 mmol) in toluene (5
mL) at −70 °C was added a solution of AgTFA (0.453 g, 2.05 mmol)
dropwise under stirring over a period of 15 min. The colorless
suspension was warmed to room temperature and stirred for 1 h. The
solvent was removed in vacuo, resulting in a yellowish residue which
was extracted with n-pentane (10 mL). After filtration, the colorless
solution was concentrated to incipient crystallization in vacuo and
stored at −40 °C, resulting in the deposition of colorless crystals.
Removal of the supernatant by syringe and drying in vacuo yields 0.450
g (0.760 mmol, 76%) of 2 as colorless crystals. Mp: 101 °C. Anal.
calcd % (found) for C16H36F6NO4PSi5 (591.85): C, 32.47 (32.00); H,
6.13 (6.30); N, 2.37 (2.41). 1H NMR (25 °C, CD2Cl2, 300.13 MHz):
δ 0.29 (d, 27 H, 5J(31P−1H = 1.3 Hz, 1J(13C−1H = 121 Hz,
negative partial charge (6: QN1 = −1.00, QN2 = −1.57; 7: QN1
=
−1.60, QN2 = −1.01e). The lower values of the GaCl3
coordinated N atoms can be attributed to the influence of
the electrophilic Lewis acid.
CONCLUSIONS
■
The reactions of Hyp−N(SiMe3)PCl2 with AgTFA, AgOTf,
AgC6F5, and AgC6F5·CH3CN were shown to result in the
formation of diverse products. While the reaction of 1 with
AgTFA is a simple anion exchange, all other silver salts display
rather unusual reaction pathways, which can be explained by
the presence of a highly reactive intermediate (8) exhibiting a
dicoordinated P atom and a Si−N double bond. The formation
of 8 is triggered by the action of the Lewis acid, either Ag+ or
GaCl3, which induces Me3SiCl elimination. Astonishingly, the
Me3Si group of the Hyp group and not that attached to the N
atom is involved in this elimination. Starting from the
intermediate formation of 1,3 dipole molecule 8, (i) the
reaction with AgOTf finally gives a new diphosphene, and (ii)
the reaction with AgC6F5 yields an eight-member heterocycle;
while the reaction with AgC6F5·CH3CN forms in a formal [3 +
2] cycloaddition, the new five-membered heterocycle 5
stabilized as the AgC6F5 adduct (Scheme 4). The same
heterocycle was obtained with GaCl3, thus extending the
concept of Lewis acid assisted [3 + 2] cycloadditions.
2
Si(Si(CH3)3)3), 0.35 (s, 9 H, J(29Si−1H) = 6.6 Hz, N(Si(CH3)3)).
13C{1H} NMR (25 °C, CD2Cl2, 75.47 MHz): δ 2.24 (d, 4J(31P−13C) =
1
1
5.3 Hz, J(29Si−13C) = 46 Hz, Si(Si(CH3)3)3), 3.79 (s, J(29Si−13C) =
57 Hz, N(Si(CH3)3)), 114.7 (dq, 3J(31P−13C) = 4.3 Hz, 1J(19F−13C) =
286.5 Hz, CF3), 155.4 (dq, J(31P−13C) = 6.8 Hz, J(19F−13C) = 43.7
2
2
Hz, OCO). 19F{1H} NMR (25 °C, CD2Cl2, 282.4 MHz): δ −76.0 (s).
29Si NMR (25 °C, CD2Cl2, 59.63 MHz): δ −26.0 (m, J(31P−29Si) =
2
44 Hz, Si(SiMe3)3)), −12.6 (m, Si(SiMe3), 14.8 (m, 2J(31P−29Si) = 1.9
Hz, N(SiMe3)). 31P{1H} NMR (25 °C, CD2Cl2, 121.49 MHz): δ
147.7 (s). IR (ATR, 32 scans): 2950 (m), 2894 (m), 1787 (s), 1774
(s), 1441 (w), 1398 (w), 1360 (m), 1260 (m), 1245 (m), 1219 (s),
1169 (s), 1149 (s), 1108 (s), 981 (s), 824 (s), 791 (m), 774 (m), 748
(m), 727 (s), 682 (s), 656 (m), 622 (s), 566 (m). Raman (200 mW,
1049 scans, 25 °C, cm−1): 2994 (2), 2952 (5), 2896 (10), 1789 (1),
1776 (1), 1418 (1), 1265 (1), 1241 (1), 1108 (1), 1050 (1), 985 (1),
863 (1), 751 (1), 686 (2), 645 (1), 627 (3), 509 (2), 485 (1), 464 (1),
450 (1), 433 (1), 402 (1), 364 (1), 333 (1), 301 (1), 176 (2), 119 (1).
MS (CI+, isobutane): 478 [M −CF3CO2]+, 518 [M −SiMe3]+, 592 [M
−H]+.
Synthesis of (TfO)(SiMe3)2SiN(SiMe3)P=PN(SiMe3)Si-
(SiMe3)2(OTf) (3). To a solution of (Me3Si)3SiN(SiMe3)PCl2 (1;
0.873 g, 2.00 mmol) in toluene (10 mL) at −60 °C was added a
solution of AgOTf (1.028 g, 4.00 mmol) in toluene (10 mL) dropwise
over a period of 25 min. The brown solution was warmed to room
temperature and stirred for 1 h. The solvent was removed in vacuo, and
the resulting brown residue was extracted with n-hexane (10 mL).
After filtration (F4), the solvent was removed in vacuo, and the brown
solid was solved in toluene (2 mL). The brown solution was
concentrated to incipient crystallization in vacuo and stored at −25 °C
for 12 h, resulting in the deposition of orange crystals. Removal of the
supernatant by syringe and drying in vacuo yield 1.340 g (1.520 mmol,
76%) of 3 as orange crystals. Mp: 134 °C. Anal. calcd % (found) for
C20H54F6N2O6P2S2Si8 (883.4): C 27.19 (26.90), H 6.16 (6.25), N 3,17
EXPERIMENTAL DETAILS
General Information. All manipulations were carried out under
oxygen- and moisture-free conditions under argon using standard
Schlenk or drybox techniques.
■
Dichloromethane was purified according to a literature procedure,38
dried over P4O10, and freshly distilled prior to use. Toluene was dried
over Na/benzophenone and freshly distilled prior to use. Acetonitrile
was dried over P4O10 and freshly distilled prior to use. N-hexane and n-
pentane were dried over Na/benzophenone/tetraglyme and freshly
distilled prior to use. Silvertrifluoroacetate,39 silvertriflate,39 N-
[tris(trimethylsilyl)silyl]-N-trimethylsilyl-amino-dichlorophosphane
(Me3Si)3Si−N(SiMe3)PCl2 (1),9 and pentafluorophenylsilver34 have
been reported previously and were prepared according to a literature
procedure. Gallium trichloride (99.999%, Sigma-Aldrich) was used as
received.
1
(3.06). H NMR (25 °C, CD2Cl2, 300.13 MHz): δ 0.32 (s, 36 H,
1
2J(29Si−1H = 6.5 Hz, J(13C−1H = 121 Hz, Si(Si(CH3)3)2, 0.45 (s, 18
H, 2J(29Si−1H) = 6.2 Hz, N(Si(CH3)3)). 13C{1H} NMR (25 °C,
CD2Cl2, 75.47 MHz): δ 0.51 (s, Si(Si(CH3)3)2), 2.61 (t, 3J(31P−13C) =
NMR. 31P{1H}, 13C{1H}, 29Si-INEPT, and 19F{1H} and H NMR
1
spectra were recorded on Bruker AVANCE 300 and AVANCE 500
spectrometers, respectively. The 1H and 13C chemical shifts were
referenced to solvent signals (C6D6: δ 1H = 7.15, δ 13C = 128.0;
1
8.2 Hz, N(Si(CH3)3)), 119.1 (q, J(19F−13C = 317.8 Hz, S(CF3)).
19F{1H} NMR (25 °C, CD2Cl2, 282.4 MHz): δ −76.8 (s). 29Si NMR
(25 °C, CD2Cl2, 59.63 MHz): δ −14.9 (m, Si(SiMe3)2), 13.1 (m,
NSiMe3), 25.0 (m, Si(SiMe3)2). 31P{1H} NMR (25 °C, CD2Cl2,
121.49 MHz): δ 505.7 (s). IR (ATR, 32 scans): 2955 (m), 2897 (m),
1383 (s), 1244 (s), 1199 (s), 1149 (s), 1072 (m), 1031 (m), 950 (m),
918 (m), 878 (m), 828 (s), 792 (s), 749 (m), 689 (m), 624 (s), 599
(w), 565 (m), 537 (m).
1
1
CD2Cl2: δ H = 5.31, δ 13C = 54.0). The H and 13C NMR signals
were assigned by DEPT and two-dimensional correlation spectra
(HSQC and HMBC) using standard pulse sequences (standard Bruker
software). The 19F, 29Si, and 31P chemical shifts are referred to CFCl3,
TMS, and H3PO4 (85%), respectively. CD2Cl2 was dried over P4O10.
IR. A Nicolet 380 FT-IR with a Smart Orbit ATR device was used.
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Synthesis of Ag4P[(C6F5)N(SiMe3)Si(SiMe3)2Cl]4 (4). To a
solution of (Me3Si)3SiN(SiMe3)PCl2 (1) (0.253 g, 0.58 mmol) in
CH2Cl2 (10 mL) at −70 °C was added AgC6F5 (0.193 g, 0.61 mmol).
The brown solution is warmed to ambient temperature over a period
of 3 h. The solvent was removed in vacuo, and the brown solid was
extracted with n-hexane (10 mL). After filtration (F4), the solvent was
removed in vacuo, and the brown solid was solved in toluene (2 mL).
The brown solution was concentrated to incipient crystallization in
vacuo and stored at 5 °C for 12 h, resulting in the deposition of
colorless crystals. Removal of supernatant by syringe and drying in
vacuo yield 0.216 g (0.35 mmol, 72%) of 4 as colorless crystals. Mp: 79
°C (dec.). Anal. calcd % (found) for C60H108Ag4Cl4F20N4P4Si16
(2412.04): C, 29.88 (30.15); H, 4.51 (4.59); N, 2.32 (2.46). 1H
NMR (−70 °C, CD2Cl2, 300.13 MHz): δ 0.16 (s, 18H, Si(CH3)3, 0.27
(s, 9H, Si(CH3)3). 13C{1H} NMR (−70 °C, CD2Cl2, 75.5 MHz): δ 0.1
(s, Si(CH3)3), 3.0 (s, Si(CH3)3), 143.9 (m, i-C), 147.4 (m, CF), 165.3
(m, CF), 185.0 (m, CF). 19F{1H} NMR (−70 °C, CD2Cl2, 282.4
MHz): δ −163.5 (m, 2F, m-CF), −159.2 (t, 1F, 3J(19F−19F) = 20 Hz,
p-CF), −129.7 (br, 2F, o-CF). 29Si NMR (−70 °C, CD2Cl2, 59.6
MHz): δ −217.2 (m, Si(Si(CH3)3)2Cl), −11.9 (m, Si(CH3)3), 6.5 (m,
Si(CH3)3), 9.3 (m, Si(CH3)3). 31P{1H} NMR (−70 °C, CD2Cl2, 121.5
(9), 76 (10). MS (CI+, isobutane): 297 [M − GaCl3 − SiMe3 + 2H]+,
335 [M − GaCl3 − Cl + 2H]+.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental section, structure elucidation, synthesis of
compounds, and NBO calculations of 6 and 7. This material
is available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: (+)+49-(0)381/498-6381, (+)+49-(0)381/498-6381. E-
mail: axel.schulz@uni-rostock.de. Homepage: http://www.
schulz.chemie.uni-rostock.de/.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
1
MHz): δ = −13.2 (t, J(31P−107/109Ag) ≈ 430 Hz.
We are indebted Marcus Kuprat and Dr. Farooq Ibad for
syntheses of AgC6F5·CH3CN and AgC6F5, respectively.
Synthesis of Diazaphosphasilole Pentafluorophenylsilver
Adduct (5). To a solution of (Me3Si)3Si−N(SiMe3)PCl2 (1; 0.253
g, 0.58 mmol) in CH2Cl2 (10 mL) at −70 °C was added AgC6F5·
CH3CN (0.193 g, 0.61 mmol). The dark red suspension is warmed to
ambient temperature over a period of 8 h. The solvent was removed in
vacuo, and the red oil was extracted with n-hexane (5 mL). The yellow
solution was concentrated to incipient crystallization in vacuo, resulting
in the deposition of colorless crystals. Removal of the supernatant by
syringe and drying in vacuo yield 0.265 g (0.41 mmol, 71%) of 5 as
colorless crystals. Mp: 76 °C (dec.). 1H NMR (−70 °C, CD2Cl2,
300.13 MHz): δ 0.16 (s, 3H, CH3), 0.22 (s, 18H, Si(Si(CH3)3)2), 0.37
(s, 9H, Si(CH3)3). 13C{1H} NMR (−70 °C, CD2Cl2, 75.5 MHz): δ =
−1.2 (m, CH3), 1.8 (d, 4J(13C−31P) = 6.1 Hz, Si(Si(CH3)3)2)), 3.8 (s,
Si(CH3)3), 108.6 (m, i-C), 114.3 (m, CF), 140.1 (m, CF), 149.1 (m,
CF), 208.0 (m, Cq). 19F{1H} NMR (−70 °C, CD2Cl2, 282.4 MHz): δ
−162.5 (m, 2F), −159.6 (t, 1F, 3J(19F−19F) = 19 Hz), −107.9 (m, 2F).
REFERENCES
■
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2
29Si NMR (−70 °C, CD2Cl2, 59.6 MHz): δ −26.7 (m, J(29Si−31P) =
50 Hz, Si(Si(CH3)3)2), −13.1 (m, Si(Si(CH3)3)2), −12.5 (m,
Si(Si(CH3)3)2), 16.1 (m, Si(CH3)3). 31P{1H} NMR (−70 °C,
CD2Cl2, 121.5 MHz): δ 177.0.
Synthesis of Diazaphosphasilole Galliumtrichlorid Adduct
(6). To a solution of (Me3Si)3SiN(SiMe3)PCl2 (1; 2.231 g, 5.12
mmol) in CH2Cl2 (10 mL) at ambient temperature wads added
acetonitrile (0.210 g, 5.12 mmol). To the colorless solution was added
a solution of gallium trichloride (0.899 g, 5.12 mmol) at −40 °C over a
period of 15 min. The bright orange solution was warmed to ambient
temperature and stirred for 1 h. The solvent was removed in vacuo,
which resulted in the formation of 6 (4.85 mmol, 95%) as a red solid.
Crystals suitable for X-ray crystallographic analysis were obtained, by
cooling a saturated CH2Cl2 solution to 0 °C. Mp: 103 °C (dec.). Anal.
calcd % (found) for C11H30Cl4GaN2PSi4 (545.22): C, 24.23 (24.21);
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H, 5.55 (5.47); N, 5.14 (5.06). H NMR (25 °C, CD2Cl2, 300.13
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MHz): δ 0.22 (s, 3H, CH3), 0.38 (d, 18H, J(1H−31P) = 1.16 Hz,
Si(Si(CH3)3)2), 0.46 (d, 9H, 4J(1H−31P) = 0.87 Hz, Si(CH3)3).
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Si(Si(CH3)3)2), 1.7 (s, Si(Si(CH3)3)2), 3.6 (d, J(13C−31P) = 6.3 Hz,
1
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Si(Si(CH3)3)2), −9.7 (m, 3J(29Si−31P) = 2.1 Hz, Si(Si(CH3)3)2),
12.7 (m, Si(CH3)3), 61.6 (m, Si(Si(CH3)3)2). 31P{1H} NMR (25 °C,
CD2Cl2, 121.5 MHz): δ 147.4. IR (ATR, 32 scans): 3139 (w), 2954
(m), 2897 (w), 1504 (w), 1485 (m), 1409 (w), 1361 (w), 1249 (s),
1165 (m), 1124 (m), 1049 (w), 1003 (m), 922 (w), 887 (s), 824 (s),
784 (m), 746 (m), 692 (m), 626 (m), 603 (w), 557 (m), 544 (m).
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1166 (2), 1009 (4), 901 (2), 846 (2), 807 (2), 779 (3), 645 (5), 546
(3), 503 (5), 475 (5), 414 (5), 360 (7), 314 (6), 289 (9), 227 (4), 140
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