Isoelectronic caesium compounds: The triphosphenide Cs[tBu 3SiPPPSitBu3] and the enolate Cs[OCH=CH2]

Article abstract of DOI:10.1039/b714339g

The caesium triphosphenide Cs[tBu₃SiPPPSitBu₃] was accessible from the reaction of CsF with the sodium triphosphenide Na[tBu ₃SiPPPSitBu₃] in tetrahydrofuran at room temperature. In contrast to the preparation of tetrahydrofuran-solvated silanides M[SitBu ₃] (M = Li, Na, K), our efforts to synthesize the caesium silanide Cs[SitBu₃] as a tetrahydrofuran complex failed. When tBu ₃SiBr was treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate Cs[OCH=CH₂] and the supersilane tBu₃SiH formed rather than the silanide Cs[SitBu ₃]. X-Ray quality crystals of the enolate Cs[OCH=CH₂] (orthorhombic, Pnma) were obtained from tetrahydrofuran at ambient temperature. In contrast to the structures of its homologues M[tBu₃SiPPPSitBu ₃] (M = Na, K), the caesium triphosphenide Cs[tBu ₃SiPPPSitBu₃] features a polymer in the solid state (orthorhombic, Cmcm). The Royal Society of Chemistry.

Full text of DOI:10.1039/b714339g

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Isoelectronic caesium compounds: the triphosphenide Cs[tBu3SiPPPSitBu3]
=
and the enolate Cs[OCH CH2]†‡
Hans-Wolfram Lerner,* Inge Sa¨nger, Frauke Scho¨del, Andreas Lorbach, Michael Bolte and Matthias Wagner
Received 17th September 2007, Accepted 9th November 2007
First published as an Advance Article on the web 29th November 2007
DOI: 10.1039/b714339g
The caesium triphosphenide Cs[tBu3SiPPPSitBu3] was accessible from the reaction of CsF with the
sodium triphosphenide Na[tBu3SiPPPSitBu3] in tetrahydrofuran at room temperature. In contrast to
the preparation of tetrahydrofuran-solvated silanides M[SitBu3] (M = Li, Na, K), our efforts to
synthesize the caesium silanide Cs[SitBu3] as a tetrahydrofuran complex failed. When tBu3SiBr was
treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate
=
Cs[OCH CH2] and the supersilane tBu3SiH formed rather than the silanide Cs[SitBu3]. X-Ray quality
=
crystals of the enolate Cs[OCH CH2] (orthorhombic, Pnma) were obtained from tetrahydrofuran at
ambient temperature. In contrast to the structures of its homologues M[tBu3SiPPPSitBu3] (M = Na,
K), the caesium triphosphenide Cs[tBu3SiPPPSitBu3] features a polymer in the solid state
(orthorhombic, Cmcm).
Introduction
Over the past two decades, phosphides have gained prominence
in wide areas of application. However, up to now only polyphos-
phidic Zintl ions have been found to play an important role in
materials science. These Zintl ions are synthesized generally at
high temperatures by solid-state reactions.1
The first studied phosphanides which consist of discrete
molecules with organic or organosilyl substituents on the P-
centres were alkali metal, alkaline earth metal or transition
metal monophosphanides, M[PHR] and M[PR2].2 Contrary to
the preparation of polyphosphidic Zintl ions, the monophos-
phanides have been synthesized almost under mild conditions.
In contrast to the well-established monophosphanides only a few
monophosphanediide and oligophosphanide derivatives, M2[PR]3
and Mx[PmRm]4 (m > 2), have been fully characterized.
The purpose of this paper is to report about a phosphorus
analogue of the allyl anion (triphosphenide).
Recently we have reported on the reaction of P4 with the
silanides M[SitBu3] (M = Li, Na) and Na[SiPhtBu2] in a 1 : 3
stoichiometry, which cleanly led to the formation of the tetraphos-
phides M3[P4(SitBu3)3] (M = Li, Na) and Na3[P4(SiPhtBu2)3],
respectively, as shown in Scheme 1. However, the tetraphos-
phides M3[P4(SitBu3)3] (M = Li, Na) can be transformed into
the unsaturated triphosphenides M[tBu3SiPPPSitBu3] and the
monophosphanediide M2[PSitBu3].5
Scheme
1
Syntheses
of
supersilylated
phosphanides
and
Li,
phosphenides M2[1], M3[2], M[3], and M4[P8(SitBu3)4] (M
=
Na, K). (I) THF, r.t. (II) + 1 M[SitBu3] (M = Li, Na, K), benzene r.t. (III)
−M2[PSitBu3] (M = Li, Na, K), THF r.t. (IV) hexane r.t.
Otherwise, the reaction of P4 with M[SitBu3] (M = Li, Na,
K) and Na[SiPhtBu2] in a molar ratio of 1 : 2 produces the
=
tetraphosphendiides M2[tBu3SiPP PPSitBu3] (M = Li, Na, K)
=
(M2[1]) and Na2[tBu2PhSiPP PPSiPhtBu2] which dimerize in
weakly polar solvents to the octaphosphides M4[P8(SitBu3)4] (M =
Li, Na, K) and Na4[P8(SitBu2Ph)4].6–8 It is interesting to note
that the potassium silanide K[SitBu3] causes the decomposi-
tion of the tetraphosphendiide K2[1]; K[tBu3SiPPPSitBu3] and
K2[PSitBu3] are formed.8 Contrary to the lithium tetraphosphide
Li3[P4(SitBu3)3] (Li3[2]), the related potassium tetraphosphide
K3[2] is as yet unknown.
Institut fu¨r Anorganische Chemie, J. W. Goethe-Universita¨t, Max-von-
Laue-Str. 7, D-60438, Frankfurt, Germany. E-mail: lerner@chemie.uni-
frankfurt.de; Fax: +49 69 79829260; Tel: +49 69 79829152
=
† CCDC reference numbers 648996 (Cs[OCH CH2]), 648997 (Cs[3]).
For crystallographic data in CIF or other electronic format see DOI:
10.1039/b714339g
‡ The HTML version of this article has been enhanced with colour images.
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The triphosphenide K[tBu3SiPPPSitBu3] (K[3]) may be pro-
duced via an intermediary tetraphosphide K3[2].8
We have now discovered that the thermolysis reaction of Li[3],
Na[3], K[3], and Cs[3] is rather similar to that of the analogous
sodium triazenide Na[tBu3SiNNNSitBu3].9–11 In this context we
have found that the caesium triphosphenide Cs[3] is more stable
than its homologues Li[3],5 Na[3],12 and K[3].8 Therefore, Cs[3]
represents an ideal compound to investigate the properties of the
triphosphaallyl anion. In this paper the structural and chemical
features of two novel caesium allyl compounds, the triphosphenide
Fig. 1 1,1ꢀ-Bicyclotriphosphane 4 and bicyclo[3.1.0]hexaphosphane 5.
=
Cs[3] and the enolate Cs[OCH CH2], respectively, have been
described.
Results and discussion
The successful synthesis of K[3] from P4 with 3 equivalents of
K[SitBu3] in tetrahydrofuran, raised the question whether the
caesium triphosphenide Cs[3] can be prepared by an analogous
synthetic route as that of K[3]. However, our efforts to synthesize
the caesium silanide Cs[SitBu3] as tetrahydrofuran complex failed.
When tBu3SiBr was treated with an excess of caesium metal
in tetrahydrofuran at room temperature, the caesium enolate
=
Scheme 4 Protonation of the triphosphenides Li[3], Na[3], K[3], and
Cs[3]. (I) + 1 CF3CO2H, THF r.t. (II) excess of CF3CO2H, THF r.t.
Cs[OCH CH2] and the supersilane tBu3SiH formed rather than
the silanide Cs[SitBu3]. Single crystals of the caesium enolate
=
Cs[OCH CH2], which is nearly insoluble in organic solvents, were
obtained from the reaction solution (see Scheme 2).
Treatment with a stoichometric amount of electrophile such as
H+ in CF3CO2H leads to the formation of the cyclotriphosphane
derivative 6 exclusively. However, the reaction of Cs[3] with an
excess of acids e.g. CF3CO2H produces the supersilylphosphane
tBu3SiPH2 and phosphorus. Ab initio calculations reveal that
neutral compounds with P3 framework like HP3(SiH3)2 prefer
−
the cyclic form whereas in P3(SiH3)2 the anionic acyclic allylic
conjugation is more stable than the cyclic isomer.12
It is interesting to note that the triphosphenides Li[3], Na[3],
and K[3] are labile compounds. We found that in vacuo Li[3],
Na[3], and K[3] rapidly decompose at ambient temperature.
Obviously the removal of THF ligands led to fragmentation
of the triphosphaallyl anion in the case of Li[3], Na[3], and
K[3], respectively, with the formation of the monophosphanides
M[P(SitBu3)2] (M = Li, Na, K).14 An analogous reaction could be
observed in triazenide thermolysis. We found that the triazenides
M[tBu3SiNNNSiMetBu2] (M = Li, Na) eliminate N2 at room
temperature whereas Na[tBu3SiNNNSitBu3] is more stable and
decomposes at temperatures above 210 ◦C.11
=
Scheme 2 Formation of the caesium enolate Cs[OCH CH2].
As shown in Scheme 3, the reaction of Na[3], which has been
generated by P4 degradation with 3 equivalents of Na[SitBu3], and
CsF conveniently produces Cs[3] in THF at ambient temperature.
In contrast to its homologues the caesium triphosphenide Cs[3]
is stable in vacuo. However, Cs[3] decomposes in benzene slowly
at room temperature. Thereby the 31P NMR spectrum of the
solution of Cs[3] thermolysis reveals several signals. Surpris-
ingly, one of these signals can be assigned to the diphosphene
13
=
=
tBu3SiP PSitBu3. The formation of tBu3SiP PSitBu3 is yet
unclear.14
Generally, the NMR spectra of caesium triphosphenide Cs[3]
resemble those of the related lithium, sodium, and potassium
Scheme 3 Synthesis of the caesium triphosphenide Cs[3].
1
The triphosphenides Li[3], Na[3], K[3], and Cs[3] are sensitive
to oxygen and moisture. Oxidation of the triphosphenides Li[3],
Na[3], K[3], and Cs[3] with TCNE leads to the formation of the
hexaphosphanes 4 and 5 (Fig. 1).12
triphosphenides Li[3], Na[3], and K[3].5,8,12 The 31P{ H}NMR
spectrum of the triphosphenide Cs[3] features two signals with
the splitting pattern of an AX2 spin system in the range for the
unsaturated two-coordinate phosphorus atoms. The 31P NMR
data of triphosphenides Li[3], Na[3], K[3], and Cs[3] are listed
in Table 1.
The triphosphenide Cs[3] reacts spontaneously with acids, as
the homologues Li[3], Na[3], and K[3] do (see Scheme 4).12
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Table 1 31P NMR spectra of triphospenides M[tBu3SiPXPAPXSitBu3]
(M = Li, Na, K, Cs)
Table 2 Bond lengths and bond angles of enolates M[OCH CH2]
=
M
C
C/A
O–C/A
O–C–C/◦
˚
˚
=
Li[3]5
Na[3]12
K[3]8
Cs[3]
15
Li(L)n
1.28(1)–1.40(1)
1.32(1)–1.45(1)
125.1(10)–128.9(9)
d(PA)
d(PX)
1JPP
729.8a
730.0a
732.5a
745.4b
226.6a
212.5a
230.0a
236.2b
Cs
Sr(L)n
Ba(L)n
Sc(L)n
Y(L)n
Ti(L)n
Nb(L)n
1.35(1)
1.42(1)
1.29(1)–1.35(1)
1.30(1)
1.29(1)
1.31(1)
1.26(2)–1.33(4)
1.29(1)
1.41(1)
1.31(1)–1.33(1)
1.34(1)
1.32(1)
1.33(1)
1.35(2)–1.42(3)
127.8(4)
114.3(4)
442.0 Hza
552.7 Hza
550.0 Hza
561.2 Hzb
16
16
126.7(1)–129.1(1)
126.1(4)
a In d8-THF. b In C6D6.
17
18
128.0(6)
128.4(4)
19
20
=
Single crystals of caesium enolate Cs[OCH CH2] suitable for
X-ray crystallography were grown from a tetrahydrofuran solution
of the reaction mixture at ambient temperature. The structure
119.0(20)–126.0(20)
21
Ce(L)n
1.31(1)
1.33(1)
125.5(4)
=
of the caesium enolate Cs[OCH CH2] is shown in Fig. 2 and
=
3. It is interesting to note that Cs[OCH CH2] represents the
first structurally characterized binary metal enolate solely with
hydrogen substituents on the C atoms. Surprisingly, the Cs atoms
=
in Cs[OCH CH2] are coordinated by four enolate anions. Two
of these enolate units coordinate in g -fashion while the other
3
two anions are bound to the Cs cation via the lone pair of their
enolate-O atom. Thereby, the O atoms of the enolate anions
connect two infinite neighbouring chains composed of Cs cations
3
and g -coordinated enolate anions, as shown in Fig. 2 and 3.
The solid-state structure, therefore, features a three-dimensional
network with enolate anions as bridging units, as depicted in
Fig. 3. Obviously, this network results in the poor solubility of
=
Cs[OCH CH2] in organic solvents.
=
Fig.
3
Molecular structure of Cs[OCH CH2] in the solid state.
◦
˚
Selected bond lengths [A] and bond angles [ ]: Cs(1)–O(1)#1 2.974(3),
Cs(1)–O(1)#2 3.160(3), Cs(1)–O(1) 3.189(2), Cs(1)–C(1) 3.407(3),
Cs(1)–C(2) 3.490(3), Cs(1)–C(1)#2 3.541(7), Cs(1)–C(2)#4 3.678(3),
Cs(1)–C(2)#6 3.712(7), O(1)–C(1) 1.288(6), O(1)–Cs(1)#1 2.974(3),
O(1)–Cs(1)#6 3.160(3), C(1)–C(2) 1.350(11), O(1)#1–Cs(1)–O(1)#2
133.00(9), O(1)#1–Cs(1)–O(1) 92.44(7), O(1)#2–Cs(1)–O(1) 108.57(4),
O(1)–Cs(1)–O(1)#3 123.00(11), O(1)#1–Cs(1)–C(1)#3 114.45(9), O(1)–
Cs(1)–C(1)#3 121.31(11), O(1)#2–Cs(1)–C(1) 90.17(12), C(1)#3–Cs(1)–
C(1) 110.66(13), O(1)#2–Cs(1)–C(2)#3 68.09(11), O(1)–Cs(1)–C(2)#3
131.25(10),
126.47(6), C(2)#3–Cs(1)–C(2) 106.82(12), O(1)#1–Cs(1)–C(1)#2
111.81(10), O(1)–Cs(1)–C(1)#2 115.18(6), C(1)–Cs(1)–C(1)#2
C(1)–Cs(1)–C(2)#3
113.40(9),
O(1)#1–Cs(1)–C(2)
102.03(12), C(2)–Cs(1)–C(1)#2 79.64(12), C(1)–O(1)–Cs(1) 88.49(16),
O(1)–C(1)–C(2) 127.8(5), O(1)–C(1)–Cs(1) 69.31(13), C(2)–C(1)–Cs(1)
82.2(2), C(1)–C(2)–Cs(1) 75.29(16). Symmetry transformations used to
generate equivalent atoms: #1 −x,−y + 1,−z + 1; #2 −x+1/2,−y +
1,z−1/2; #3 x,y + 1,z; #4 x−1/2,y,−z + 1/2; #5 x−1/2,y + 1,−z + 1/2
#6 −x + 1/2,−y + 1,z + 1/2; #7 x,y−1,z; #8 x + 1/2,y,−z + 1/2; #9 x +
1/2,y−1,−z + 1/2.
=
Fig. 2 Crystal packing diagram for Cs[OCH CH2].
The metrical parameters of the enolate moiety of
Cs[OCH CH2] are compared with those of other metal enolates in
Table 2. The enolate C–O distance of 1.29(1) A is on the short end
=
˚
CH2)]21 (Ad = adamantyl, TMP = 2,2,6,6-tetrametylpiperidinyl).
=
of the range of values found in e.g. [Li3(THF)3{(NtBu)3S}(OCH
CH2)],15 the doubly enolate-brigded Sr or Ba diphenylmethanide
The C C bond length of 1.35(1) A is within the range of lengths
˚
=
dimers,16 [Sc{(2,6-di-iPr-CH3C6H3)NCMeCHC(Me)N(2,6-di-iPr-
observed in enolates listed in Table 2. The enolate O–C–C bond
angle of 127.8(5)◦ is comparable with known angles.
17
=
CH3C6H3)}{NH(2,6-di-iPrCH3C6H3)}(OCH CH2)], [Y(CH3-
18
19
=
=
C5H4)2(OCH CH2)]2, [TiCp2Ti(OCH CH2)2], [Nb{N(3,5-
The crystal structure of the triphosphenide Cs[3] is shown in
Fig. 4 and 5; selected bond lengths and angles can be found
20
=
=
Me2C5H3)N(Ad)}3(OCH CH2)],
and
[Ce(TMP)2(OCH
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◦
˚
Table 3 Bond lengths [A] and bond angles [ ] of triphosphenides Na[3],
K[3], and Cs[3]
Na[3]12
K[3]8
Cs[3]
P–P
2.096(20) av
3.113(20) av
2.303(20) av
1.948(20) av
104.2(11) av
2.072(2)
2.090(3)
M–P
Si–P
Si–C
P–P–P
3.476(2) av
2.270(1) av
1.952(5) av
101.1(1)
3.766(2) av
2.271(3) av
1.941(9) av
103.7(2)
infinite chain of Cs cations and [tBu3SiPPPSitBu3] anions. By con-
=
trast, a three-dimensional network of Cs cations and [OCH CH2]
=
anions is observed in the structure of Cs[OCH CH2].
The molecular structure of the triphosphenide Cs[3] shows two
short PP bonds and an almost planar W-shaped SiPPPSi skeleton
˚
with a P–P distance of 2.090(3) A. This distance is in the range of
PP double bonds, comparable with those found in the structures of
Na[3] and K[3] (Table 3). As depicted in Fig. 4, the silyl-substituted
triphosphaallylic anions are bridged by Cs cations to form a
polymer in solid state. Therefore each of the triphosphenide anions
˚
in Cs[3] features six P–Cs contacts (P–Cs distance: 3.766(2) A,
average) for every Cs atom. However, these contacts are longer
than the P–Cs bonds in Cs[PHSitBu3] and in other structural
characterized monophosphanides.22 Apart from these P atoms,
the Cs atoms are coordinated by two tetrahydrofuran molecules.
It is interesting to note that both caesium allyl compounds,
Fig. 4 Molecular structure of Cs[3] in the solid state. Hydrogen atoms
◦
˚
omitted for clarity. Selected bond lengths [A] and bond angles [ ]:
Cs(1)–P(1) 3.655(1), Cs(1)–O(31) 3.753(18), Cs(1)–P(2) 3.978(2), P(1)–P(2)
2.090(3), P(1)–Si(1) 2.271(3), P(2)–P(1)#3 2.090(3), Si(1)–C(2) 1.938(7),
Si(1)–C(1) 1.948(9), O(31)–Cs(1)#4 3.753(18), P(1)#1–Cs(1)–P(1)
126.57(5), P(1)–Cs(1)–P(2)#2 148.58(3), P(1)–Cs(1)–P(2) 31.42(3),
P(1)#3–P(2)–P(1) 103.67(16), P(1)–P(2)–Cs(1) 65.73(6). Symmetry trans-
formations used to generate equivalent atoms: #1 x,−y + 1,−z + 1; #2
−x,−y + 1,−z + 1; #3 −x,y,z; #4 −x,−y + 1,z−1/2; #5 x,y,−z + 1/2.
=
Cs[OCH CH2] and Cs[3], have a solid-state structure in which
the Cs cation has the coordination number eight. However, due to
steric repulsion of the supersilyl groups the solid-state structure of
the triphosphenide Cs[3] features an alternated arrangement of the
triphosphaallylic anions, whereas in contrast to that the enolate
=
anions of Cs[OCH CH2] are arranged in a congruent fashion.
Experimental
General procedures
All experiments were carried out under dry argon with strict
exclusion of air and moisture using standard Schlenk techniques or
a glove box. tBu3SiBr,23,24 Na[SitBu3],23,24 and Na[3]5 were prepared
according to literature procedures. The solvents (benzene, toluene,
tetrahydrofuran) were distilled from sodium/benzophenone prior
to use.
The triphosphenide Cs[3] is extremely moisture and oxygen
sensitive. Therefore, the analysis is limited to NMR, UV and
X-ray structure determination. The NMR spectra were recorded
on a Bruker AM 250, a Bruker DPX 250, a Bruker Avance 300
and a Bruker Avance 400 spectrometer. The 29Si NMR spectra
were recorded using the INEPT pulse sequence with empirically
optimised parameters for polarisation transfer from the tBu
substituents. Abbreviations: s = singlet; d = doublet; t = triplet;
q = quartet; mult = multiplet; br = broad; m = meta; o = ortho;
p = para.
Fig. 5 Crystal packing diagram for Cs[3].
in the corresponding caption. X-Ray quality crystals of Cs[3]
(orthorhombic, Cmcm) were grown from tetrahydrofuran. In
contrast to the structures of monomeric Na[3] and dimeric K[3],
the supersilylated triphosphenide Cs[3] features a polymer in the
Reaction of Cs with tBu3SiBr
Cs metal (0.60 g, 4.5 mmol) was added to a solution of tBu3SiBr
=
solid state as Cs[OCH CH2] does. Although the binding mode
(0.20 g, 0.71 mmol) in THF (5 cm3). The reaction mixture was
−
1
of both allyl anions, [tBu3SiPPPSitBu3]− and [OCH CH2] , is
stirred for 2 h at ambient temperature. According to the H, 13C
=
quite similar, however, the solid-state structure of Cs[3] features an
and the 29Si NMR data the supersilane tBu3SiH was formed as a
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1
1
=
soluble main product. X-Ray quality crystals of Cs[OCH CH2]
see Scheme 4)26 −247.5 (1 P, m, JP(1)P(2) −187.1, JP(1)P(3) −142.3,
were grown from the reaction mixture at 2 ◦C. Yield: 0.1 g (80%).
2JP(1)H 17.1, P(1)SitBu3), −260.1 (1 P, m, JP(1)P(3) −187.1, JP(2)P(3)
1
1
2
1
tBu3SiH: dH (250 MHz; C6D6; Me4Si) 1.11 (27 H, s, tBu), 3.54
−223.4, JP(2)H 6.3, P(2)SitBu3)), −260.7 (1 P, m, JP(1)P(2) −187.1,
1JP(2)P(3) −223.4, 1JP(3)H 138.0, P(3)H). (lit.,12 −246.9 (1 P, m, 1JP(1)P(2)
−188.0, 1JP(1)P(3) −141.3, 2JP(1)H 16.6, P(1)SitBu3), −259.5 (1 P, m,
1
(1 H, s, SiH). dC{ H} (75.45 MHz; C6D6; Me4Si) 21.0 (CMe3),
1
30.8 (CMe3). dSi{ H} (79.49 MHz; C6D6; Me4Si) 17.7 (SitBu3).
1
2
1JP(1)P(2) −188.0 JP(2)P(3) −224.2, JP(2)H 6.9, P(2)SitBu3), −260.1
=
Cs[OCH CH2]: Found: C, 14.3; H, 2.2. C2H3CsO requires C,
1
1
1
13.6; H, 1.7.
(1 P, m, JP(1)P(3) −141.3, JP(2)P(3) −224.2, JP(3)H 137.1, P(3)H)).
1
dSi{ H} (79.49 MHz; C6D6; Me4Si) 27.4 (m, SitBu3). tBu3SiPH2:
dH (250 MHz; C6D6; Me4Si) 1.09 (27 H, d, 4JPH 0.49, tBu), 0.94 (1
Reaction of Na[3] with CsF
1
1
H, d, JPH 186, HP). dC{ H} (75.45 MHz; C6D6; Me4Si) 23.1 (d,
CsF (0.16 g, 1.1 mmol) in tetrahydrofuran (10 cm3) was added to
6.3 cm3 of a 0.2 M solution of Na[3] (1.3 mmol) in THF at ambient
temperature and stirred for 2 days. According to the 31P NMR
spectrum the triphosphenide Cs[3] was formed quantitatively. X-
Ray quality crystals of Cs[3] were obtained after the reaction
mixture had been concentrated in vacuo to a volume of 5 cm3
and kept at ambient temperature for 1 month. Yield: 0.55 g (72%).
Selected data for Cs[P3(SitBu3)2]·THF, Cs[3]·THF: dH (250 MHz;
C6D6; Me4Si) 1.49 (54 H, br, tBu), 1.42 (2 H, m, THF-CH2), 3.53 (2
2JPC 5.9, CMe3), 30.7 (d, 3JPC 2.4, CMe3). dP (162.03 MHz; C6D6;
1
1
H3PO4) −264.4 (t, JPH 186). dSi{ H} (79.49 MHz; C6D6, Me4Si)
24.1 (d, 1JSiP 33.2, SitBu3).
=
Crystal structure determinations of Cs[OCH CH2] and Cs[3]
=
Data collections for Cs[3] and Cs[OCH CH2] were performed
on a STOE IPDS-II two-circle diffractometer with graphite-
˚
monochromated Mo-Ka-radiation (k = 0.71073 A). The struc-
1
H, m, THF-OCH2). dC{ H} (75.45 MHz; C6D6; Me4Si) 25.3 (THF-
tures were solved with direct methods27 and refined against F2
by full-matrix least-squares calculations28 (Table 4). Absorption
corrections were performed with the MULABS29 option in
PLATON.30 All non-H atoms have been refined anisotropically,
whereas the H atoms have been treated with a riding model.
1
CH2), 25.5 (br, CMe3), 32.8 (CMe3), 68.9 (THF-OCH2). dP{ H}
1
(162.03 MHz, C6D6; H3PO4) see Table 1. dSi{ H} (79.49 MHz;
C6D6; Me4Si) 18.9 (td, 1JSiP + 3JSiP 64.1, 2JSiP 10.0, SitBu3). UV/vis:
kmax(benzene)/nm 499 (e/dm3 mol−1 cm−1 14) and 551 (11).
=
CCDC reference numbers 648996 (Cs[OCH CH2]), 648997
(Cs[3]).
Reaction of Cs[3] with CF3CO2H
CF3CO2H (0.25 cm3, 3.4 mmol) was added to a solution of
Cs[3] (0.2 mmol) in 1 cm3 THF at ambient temperature and
stirred for 3 h. According to the 31P NMR spectrum the phos-
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b714339g
25
phane tBu3SiPH2 was formed nearly quantitatively. CF3CO2H
Conclusions
(0.02 cm3, 0.2 mmol) was added to a solution of Cs[3] (0.2 mmol) in
1 cm3 THF at ambient temperature and stirred for 3 h. According
to the 31P NMR spectrum the cyclotriphosphane 6 was formed
as the main product (60% P). 6: dH (250 MHz; C6D6; Me4Si)
1.30 (54 H, m, tBu). dP (162.03 MHz; C6D6; H3PO4, P numbering
In contrast to the preparation of tetrahydrofuran-solvated
silanides M[SitBu3] (M = Li, Na, K), our efforts to synthesize
the caesium silanide Cs[SitBu3] as the tetrahydrofuran complex
failed. When tBu3SiBr was treated with an excess of caesium
=
Table 4 Crystal data and experimental details for Cs[OCH CH2] and Cs[3]
=
Cs[OCH CH2]
Cs[3]
Empirical formula
Formula weight
Temperature/K
Crystal size/mm3
Crystal system
Space group
C2H3CsO
175.95
173(2)
C28H62CsOP3Si2
696.78
173(2)
0.28 × 0.25 × 0.11
0.34 × 0.27 × 0.26
Orthorhombic
Orthorhombic
Pnma
7.9917(11)
5.6041(9)
8.5828(13)
384.39(10)
4
3.040
9.404
Cmcm
25.516(2)
12.8382(11)
11.8824(10)
3892.4(6)
4
1.189
1.153
˚
a/A
˚
b/A
˚
c/A
3
˚
V/A
Z
calcd. density/Mg m−3
l/mm−1
Index ranges
−10 ≤ h ≤ 10, −7 ≤ k ≤ 7,
−30 ≤ h ≤ 26, −13 ≤ k ≤ 15,
−11 ≤ l ≤ 10
−14 ≤ l ≤ 14
h-range/◦
4.34 to 27.59
3.55 to 25.37
No. of reflns. collected
No. of indep. reflns.
Rint
4426
491
0.0647
1.183
9944
1899
0.0293
1.074
Goodness-of-fit (F2)
R1, wR2 [I > 2r(I)]
R1, wR2 indices (all data)
R1 = 0.0250, wR2 = 0.0637
R1 = 0.0253, wR2 = 0.0639
1.079 and −1.343
R1 = 0.0941, wR2 = 0.2203
R1 = 0.0974, wR2 = 0.2228
2.054 and −2.869
−3
˚
Largest diff. peak and hole/e A
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metal in tetrahydrofuran at room temperature, the caesium
−260.8. H.-W. Lerner, I. Sa¨nger, F. Scho¨del, M. Bolte, and M. Wagner,
unpublished results.
=
enolate Cs[OCH CH2] and the supersilane tBu3SiH formed as
10 N. Wiberg, P. Karampatses, E. Ku¨hnel, M. Veith and V. Huch, Z. Anorg.
main products, rather than the silanide Cs[SitBu3]. Actually,
the triphosphenide Cs[3] was accessible from the reaction of
CsF with the sodium triphosphenide Na[3] at room temperature
in tetrahydrofuran. In contrast to the structures of homologue
triphosphenides Na[3] and K[3] which possess a monomeric
(Na[3]) or dimeric (K[3]) structure, the triphosphenide Cs[3]
features a polymer in the solid state (orthorhombic, Cmcm). X-
Allg. Chem., 1988, 562, 91.
11 H.-W. Lerner, I. Sa¨nger, F. Scho¨del, Kurt Polborn, M. Bolte
and M. Wagner, Z. Naturforsch., B: Chem. Sci., 2007, 62b,
1285.
12 N. Wiberg, A. Wo¨rner, H.-W. Lerner, K. Karaghiosoff, D. Fenske, G.
Baum, A. Dransfeld and P. von Rague´ Schleyer, Eur. J. Inorg. Chem.,
1998, 833.
13 N. Wiberg, A. Wo¨rner, H.-W. Lerner and K. Karaghiosoff, Z. Natur-
forsch., B: Chem. Sci., 2002, 57b, 1027.
=
Ray quality crystals of the enolate Cs[OCH CH2] (orthorhombic,
14 The monophosphane HP(SitBu3)2 is unstable. After storing a C6D6
solution of HP(SitBu3)2 for one week at ambient temperature the
resonance of HP(SitBu3)2 was no longer observable in the 31P NMR
spectrum. Several signals appeared instead of one in the range typical of
unsaturated two-coordinated phosphorus atom which can be assigned
Pnma) were obtained from tetrahydrofuran at ambient tempera-
ture. It is interesting to note that both caesium allyl compounds,
=
Cs[OCH CH2] and Cs[3], have a solid state structure in which
the Cs cation is coordinated in g -fashion from two allylic anions.
3
=
the diphosphene tBu3SiP PSitBu3: dP(162.03 MHz, C6D6; H3PO4)
817.1 (lit.,13 818.61).
However, due to steric repulsion of the supersilyl groups in Cs[3]
the solid-state structure of the triphosphenide Cs[3] features an
alternate arrangement of the triphosphaallylic anions, whereas
15 B. Walfort, S. K. Pandey and D. Stalke, Chem. Commun., 2001, 1640;
F. Rivals and A. Steiner, Chem. Commun., 2001, 1426; A. Steiner and
D. S. Wright, Chem. Commun., 1997, 283; T. Dube´, S. Gambarotta
and G. P. A. Yap, Angew. Chem., Int. Ed., 1999, 38, 1432; T. Dube´, S.
Gambarotta and G. P. A. Yap, Organometallics, 2000, 19, 817; J. Guan,
T. Dube´, S. Gambarotta and G. P. A. Yap, Organometallics, 2000, 19,
4820; J. Guan, T. Dube´, S. Gambarotta and G. P. A. Yap, Chem.–Eur. J.,
2001, 374; S. De, Angelis, E. Solari, C. Florani, A. Chiesi-Villa and C.
Rizzoli, J. Chem. Soc., Dalton Trans., 1994, 1640.
=
the enolate anions of Cs[OCH CH2] are arranged in a congruent
=
fashion. Moreover, the solid state structure of Cs[OCH CH2]
features a three-dimensional network with enolate anions as bridg-
ing units. Obviously, this network results in the poor solubility of
=
Cs[OCH CH2] in organic solvents.
16 J. S. Alexander and K. Ruhlandt-Senge, Chem.–Eur. J., 2004, 1274.
17 F. Basuli, J. Tomaszewski, J. C. Huffman and D. Mindiola,
Organometallics, 2003, 22, 4705.
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1
9 Thermolysis reaction e.g. of Na[3] produces Na[P(SitBu3)2]: dP{ H}
(162.03 MHz; C6D6; H3PO4) −345.4. Protolysis of Na[P(SitBu3)2] leads
29 R. H. Blessing, Acta Crystallogr., Sect. A., 1995, A51, 33.
30 A. L. Spek, Acta Crystallogr., Sect. A., 1990, A46, C34.
1
to the formation of HP(SitBu3)2: dP{ H} (162.03 MHz; C6D6; H3PO4)
792 | Dalton Trans., 2008, 787–792
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The Royal Society of Chemistry 2008
©