Synthesis of 1,3-dichloro- cyclo -1,3-diphosphadiazanes from silylated amino(dichloro)phosphanes

Article abstract of DOI:10.1021/ic4017728

The synthesis of 1,3-dichloro-cyclo-1,3-diphosphadiazanes [ClP(μ-NR)]₂ via elimination of Me₃SiCl from silylated amino(dichloro)phosphanes, R-N(SiMe₃)PCl₂, was studied by different synthetic protocols starting from R-N(H)SiMe₃ (R = Si(SiMe₃)₃ = Hyp, N(SiMe₃)₂, Mes* = 2,4,6-tri-tert-butylphenyl, Ter = 2,4-bis(2,4,6-trimethylphenyl) phenyl, Dipp = 2,6-diisopropylphenyl, Dmp =2,6-dimethylphenyl, Ad = Adamantyl, Trityl = Ph₃C, Tos = tosyl = CH₃C₆H ₄SO₂, n-Oct = n-octyl, and Me₃Si). A new synthetic route using trimethylsilyl-substituted amino(dichloro)phosphanes, R-N(SiMe₃)PCl₂, was developed to form cyclo-diphosph(III)- azanes simply by adding a mixture of R_fOH/base (R_fOH = hexafluoroisopropanole). By this method electron-rich/-poor aryl-, silyl-, and bissilylamino-substituted cyclo-diphosph(III)-azanes are accessible such as the unprecedented (Me₃Si)₂N-substituted species [ClP(μ-NN(SiMe₃)₂)]₂ starting from tris(trimethylsilyl)hydrazine and PCl₃. Additionally, the difficulties with the preparation of cyclo-diphosphadiazanes depending on the starting materials, solvents, and bases due to the competition of different reaction channels are studied.

Full text of DOI:10.1021/ic4017728

Article
pubs.acs.org/IC
Synthesis of 1,3-Dichloro-cyclo-1,3-diphosphadiazanes from Silylated
Amino(dichloro)phosphanes
Axel Schulz,*,†,‡ Alexander Villinger,† and Andrea Westenkirchner†
†Institut fur Chemie, Universitat Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock, Germany
̈
̈
‡Leibniz-Institut fur Katalyse e.V., Universitat Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
̈
̈
S
* Supporting Information
ABSTRACT: The synthesis of 1,3-dichloro-cyclo-1,3-diphospha-
diazanes [ClP(μ-NR)]2 via elimination of Me3SiCl from silylated
amino(dichloro)phosphanes, R−N(SiMe3)PCl2, was studied by
different synthetic protocols starting from R−N(H)SiMe3 (R =
Si(SiMe3)3 = Hyp, N(SiMe3)2, Mes* = 2,4,6-tri-tert-butylphenyl,
Ter = 2,4-bis(2,4,6-trimethylphenyl)phenyl, Dipp = 2,6-diisopro-
pylphenyl, Dmp =2,6-dimethylphenyl, Ad = Adamantyl, Trityl =
Ph3C, Tos = tosyl = CH3C6H4SO2, n-Oct = n-octyl, and Me3Si).
A new synthetic route using trimethylsilyl-substituted amino(dichloro)phosphanes, R−N(SiMe3)PCl2, was developed to form
cyclo-diphosph(III)-azanes simply by adding a mixture of RfOH/base (RfOH = hexafluoroisopropanole). By this method
electron-rich/-poor aryl-, silyl-, and bissilylamino-substituted cyclo-diphosph(III)-azanes are accessible such as the unprecedented
(Me3Si)2N-substituted species [ClP(μ-NN(SiMe3)2)]2 starting from tris(trimethylsilyl)hydrazine and PCl3. Additionally, the
difficulties with the preparation of cyclo-diphosphadiazanes depending on the starting materials, solvents, and bases due to the
competition of different reaction channels are studied.
Scheme 2. Dimerization of Iminophosphanes
INTRODUCTION
■
Four-membered phosphorus−nitrogen heterocycles of the type
[XP(μ-NR)]2 (X = halogen, amino group, organic substituent)
are known as cyclo-1,3-diphospha(III)-2,4-diazanes (short cyclo-
diphosphadiazanes, old name: 1,3-diaza-2,4-diphosphetidines).1
As early as 1894 Michaelis and Schroeter described the first
phosphorus(III)−nitrogen heterocycle which they obtained
from the reaction of aniline hydrochloride with an excess of
PCl3 (Scheme 1).2 Interestingly, the authors assumed to have
materials for (poly)cyclic inorganic and organometallic
compounds.4−6
Scheme 1. First Synthesis of a cyclo-1,3-Diphospha(III)-2,4-
diazane
Depending on the organic group R, the solvent, and the state
of aggregation, 1,3-dichloro-cyclo-diphosphadiazanes, [ClP(μ-
NR)]2, display a monomer−dimer equilibrium between R−N =
P−Cl (iminochlorophosphane) and [ClP(μ-NR)]2, which was
addressed in a series of papers.7,8 For example, Burford et al.
proposed that, dependent upon steric hindrance in derivatives
of [XP(μ-NR)]2, the dimer can be destabilized with respect to
the monomer.8 For instance, for Mes*NPCl (Mes* =
2,4,6-tri-tert-butylphenyl) with bulky Mes* substituent the
iminophosphane monomer is observed in the solid state,9 while
slightly smaller substituents such as 2,6-diisopropylphenyl or m-
terphenyl [Ter = m-terphenyl = 2,6-bis-(2,4,6-trimethyl-
phenyl)] allow dimerization.1,4,8
generated monomeric C6H5NPCl, which they called
“phosphazobenzolchlorid”. However, since their molecular
weight measurements agreed with the double mass, they
speculated on the existence of the dimer (Scheme 2). Today we
know that the dimeric four-membered ring system is the stable
form. Later it was shown that this reaction results in the
formation of the corresponding bis(dichloro)phosphane-
phenylamine, PhN(PCl2)2, rather than the four-membered
ring.3 However, the cyclo-diphosphadiazane is formed upon
thermal elimination of PCl3 from PhN(PCl2)2. cyclo-
Diphosphadiazanes play a major role in preparative phospho-
rus−nitrogen chemistry because such species are good starting
Scheme 3 summarizes different synthetic routes to cyclo-
diphosphadiazanes. The simplest cyclo-diphosph(III)azanes are
the dichloro derivatives, [ClP(μ-NR)]2 (compound 3), which
can be readily synthesized by reaction of a primary amine with
Received: July 10, 2013
Published: September 23, 2013
© 2013 American Chemical Society
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amounts of hydrochlorides which often do not allow follow-up
chemistry. Therefore, we report herein on our search for a
selective synthetic route (Scheme 4), which avoids the
formation of HCl by utilizing trimethylsilyl-substituted amino-
(dichloro)phosphanes, R−N(SiMe3)PCl2. Silylated aminodi-
chlorophosphanes are capable of intrinsically releasing Me3SiCl,
thus forming an iminochlorophosphane (Scheme 2) and finally
cyclo-diphosphazanes upon dimerization. Romanenko et al. and
Klusmann et al. already reported on such Me3SiCl elimination
reactions leading to the desired dimers [ClP(μ-NR)]2 (for R =
t-Bu, Trip = 2,4,6-triisopropylphenyl) or monomeric
Mes*NPCl, respectively.12−14 In this work we show that,
alternatively, the conversion to cyclo-diphosphazanes can be
achieved simply by adding a mixture of RfOH/base (base =
DBU = 1,8-diazabicyclo[5.4.0]undec-7-en). By these two
methods, electron-rich/-poor aryl-, silyl-, and bissilylamino-
substituted cyclo-diphosphazanes are accessible. Here we report
on the scope and advantages of this novel approach to cyclo-
diphosphadiazanes.
Scheme 3. Synthetic Strategies to cyclo-1,3-Diphospha(III)-
2,4-diazanes
RESULTS AND DISCUSSION
■
As illustrated in Scheme 4, the synthesis of cyclo-diphospha-
diazanes [R′P(μ-NR)]2 (often only in situ generated) via
silylated amino(dichloro)phosphanes, R−N(SiMe3)PCl2 (8),
has been studied starting from R−N(H)SiMe3 (7) [ R = Hyp =
Si(SiMe3)3,15 N(SiMe3)2,16,17 Mes*,7d,9 Ter,18−20 Dipp = 2,6-
diisopropylphenyl,21 Dmp = 2,6-dimethylphenyl, Ad =
adamantyl, trityl = Ph3C, Tos = tosyl = CH3C6H4SO2, n-Oct
= n-octyl, and Me3Si22]. The corresponding silylamines R−
N(H)SiMe3 can easily be obtained starting from the amine R−
NH2 in the reaction with n-BuLi and Me3SiCl (see Supporting
Information).23
PCl3.1 Depending on the stoichiometry, the amount and kind
of base, solvent, temperature, etc., the reaction can be carried
out stepwise either via aminobis(dichloro)phosphanes 2 or
amino(dichloro)phosphanes 1.10 These reactions might be
regarded as sequential dehydro-chloride metathesis or in
general as a cyclocondensation process. Conversion of 1 and
2 into cyclo-diphosphazanes (3) can easily be achieved under
mild conditions.11 Bis(organylamino) derivatives (5 or 6) are
obtained by treatment of 3 with primary and secondary amines,
respectively, or in one-pot reactions of PCl3 with an excess of
amine. The heterosubstituted derivatives (4 and 5) are
prepared by reaction of 3 with organolithium compounds or
when PCl3 is treated with an excess of lithium amides.
Problems, which are often encountered, are the formation of
side products such as Cl−P[N(H)R]2 or P[N(H)R]3,10 low
yields due to a poor selectivity, and the formation of large
Synthesis. Synthesis of 3Dipp, 3Dmp, and 3Ad was
achieved when to a stirred solution of R−N(SiMe3)H (R =
Dipp, Dmp, Ad) in Et2O was added n-BuLi dropwise at
ambient temperature, followed by addition of PCl3 at −30 °C
over a period of 20 min. Presumably, in situ formation of R−
N(SiMe3)PCl2 (8) occurred which finally reacted to 3Dipp,
Scheme 4. Synthesis of cyclo-Diphosphazanes Utilizing Silylated Amines
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3Dmp, and 3Ad upon thermal elimination of Me3SiCl at
ambient temperature (Scheme 4). The same protocol leads to a
totally different product for the trityl-substituted species Ph3C−
N(SiMe3)H. In situ generated Ph3C−N(SiMe3)PCl2 releases
methane while a Si−Cphenyl bond is formed leading to the
bicyclic product 14 (Scheme 4). However, trityl-substituted
cyclo-diphosphadiazane, [ClP(μ-NCPh3)]2 (16, Scheme 5), was
ophosphane Ph−N(SiMe3)P(nBu)Cl (18) could be separated
by distillation (Kugelrohr).
The reaction of Tos−N(SiMe3)H and n-Oct−N(SiMe3)H,
respectively, with n-BuLi/PCl3 resulted in a mixture of several
products, which could not be separated by usual methods such
as distillation (Kugelrohr) or fractional crystallization.
Properties and Structure. cyclo-Diphosphadiazanes can
easily be recrystallized from n-hexane or CH2Cl2. Melting
points, 31P NMR data, and yields are summarized in Table 1.
Scheme 5. Synthesis of Ter- and Trityl-Subsituted cyclo-
Diphosphadiazanes
Table 1. Melting Points (°C), 31P NMR Data, and Yields
MP
(°C)
cis/trans
ratio (%)
δ[31P]
cis
δ[31P]
trans
yield
(%)
[R′P(μ-NR)]2
[ClP(μ-
140
87/13
212
174
211
210
308
71
67
83
86
NN(SiMe3)2)]2 (9)
c
[RfOP(μ-NSiMe3)]2
(10)
46/54
265
292
296
[ClP(μ-NDipp)]2
(3Dipp)
216
99/1
93/7
obtained by the conventional two-step procedure when Ph3C−
N(H)PCl2 was treated with NEt3 in diethyl ether at −60 °C.
Obviously, there are two different competing thermal processes
for Ph3C−N(SiMe3)PCl2, which might be caused by steric or
electronic features of the ligand. However, no simple
explanation can be given for the preference of CH4 versus
Me3SiCl elimination. It should be noted that the synthesis and
structure of 3Dipp, obtained from DippNH2 and PCl3 in the
presence of Et3N, was reported by the Burford group (Scheme
1).10
[ClP(μ-NDmp)]2
(3Dmp)
115
a
[ClP(μ-NAd)]2 (3Ad) 263
100/0
100/0
206
198
76
80
a
[ClP(μ-NCPh3)]2
(16)
248
11a
[ClP(μ-NPh)]2
153
100/0
5/95
200
69
b
b
[ClP(μ-NTer)]2
(trans15)
227
264
[Cl2PN(Ph)P(μ-
NPh)]2 (17)
155
0/100
157;
d
56
176
a
b
Decomposition. The cis isomer can be obtained in the reaction of
Stable silylated amino(dichloro)phosphanes, R−N(SiMe3)-
PCl2 (8R), can be isolated for R = N(SiMe3)2, Hyp, and Ter.
8Mes* is only stable over several days at low temperature (−60
°C); storage at ambient temperature triggers the Me3SiCl
elimination resulting in the formation of monomeric imino-
chlorophosphane 13 (Scheme 4). This behavior is in contrast
with that of the arsenic analogue Mes*−N(SiMe3)AsCl2
reported by Burford et al., which does not intrinsically
eliminate Me3SiCl at ambient temperatures.24,25 For 8Hyp,
8Ter, and 8N(SiMe3)2 no spontaneous Me3SiCl elimination
was observed at ambient temperatures. 8Ter is also very robust
against water or strong acids (HCl/HNO3). Decomposition is
only observed upon thermal treatment, which goes along with
the formation of undefined products. Therefore, a strong base
such as DBU and hexafluoroisopropanole (RfOH) was used to
initiate a formal Me3SiCl elimination due to elimination of
DBU·HCl and the ether Me3SiORf. Finally, we added DBU
along with RfOH which now gives for 8N(SiMe3)2 the desired
cyclo-diphosphadiazane 9 (Scheme 4). It is noteworthy that
even methanol can be utilized as weak acid using this protocol.
In contrast, for 8Hyp hypersilylchloride elimination (instead of
Me3SiCl) was observed leading to the formation of
hexafluoroisopropoxy-substituted cyclo-diphosphadiazane 10.
For 8Ter only hexafluoroisopropoxy-substituted species such
as Ter−N(H)P(ORf)Cl (11) and R−N(H)P(ORf)2 (12) were
isolated. Small amounts of of trans-[ClP(μ-NTer)]2 (trans15)
could be isolated and fully characterized, but the diphospha-
diazane is only a minor byproduct using this synthetic method.
Interestingly, a mixture of cis/trans-[ClP(μ-NTer)]2 is formed
in good yields (83%) when Et3N is added to a solution of Ter−
N(H)PCl2 in n-hexane (Scheme 5).26
Ter−N(H)−PCl2 with Et3N in n-hexane,26 while the reaction
according to Scheme 4 yields exclusively small amounts of the trans
c
d
isomer as byproduct. cis = 100%; reaction condition, −50 °C. 157
ppm, endocyclic P; 176 ppm, exocyclic P.
The overall yields for all considered species are good. The
lowest melting points are found for [ClP(μ-NDmp)]2 with 115
°C, [ClP(μ-NN(SiMe3)2)]2 with 140 °C, [ClP(μ-NPh)]2 with
153 °C,11a and [Cl2PN(Ph)P(μ-NPh)]2 with 155 °C, while all
other compounds decompose around 250 °C.
While for [ClP(μ-NN(SiMe3)2)]2 and [RfOP(μ-NSiMe3)]2
mixtures of the cis/trans isomers were isolated, all other studied
cyclo-diphosphadiazanes could be obtained as almost pure cis
isomers ([ClP(μ-NR)]2, R = Dipp, Dmp, Ad, Ph3C, Ph) or
trans isomers ([ClP(μ-NTer)]2 and [Cl2PN(Ph)P(μ-NPh)]2)
as displayed by 31P NMR investigations (Table 1). It is
interesting to note that for both isomers always only one 31P
resonance in solution is observed. The assignment of the 31P
NMR shifts was carried out on the basis of theoretically
obtained values (see Supporting Information, Table S23). The
δ31P values of the cis isomers are shifted upfield compared to
the trans isomers (e.g., [ClP(μ-NN(SiMe3)2)]2; cis 212 vs trans
308 ppm). Also, the chemical shift within the series of different
cis or trans species strongly depends on the substituents. For
instance, a downfield shift is observed for cis-[ClP(μ-NTer]2
with 227 ppm compared to 174 ppm for cis-[RfOP(μ-
NSiMe3)]2. The resonance of the trans chloro species is
observed between 264 and 308 ppm. For comparison, the
starting materials, aminophosphanes and hydrazinophosphanes,
respectively, are detected between 150 and 180 ppm which lies
in the range expected on the basis of numerous data from the
literature for aminophosphanes (cf. 165 ppm for (Me3Si)2N−
N(SiMe3)PCl2, 155 ppm for Dipp-N(H)PCl2, 165 ppm for
Dipp-N(PCl2)2, Dipp = 2,6-diisopropylphenyl).10,17 The
Also, the reaction of Ph−N(SiMe3)H with PCl3 in the
presence of n-BuLi leads to different products. From the
reaction mixture colorless crystals of [Cl2PN(Ph)P(μ-NPh)]2
(17) along with N-phenyl-N-trimethylsilylamino-n-butylchlor-
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Table 2. Crystallographic Details of Compounds 9, 10, 15, and 17
9
10
15
17
chem formula
C12H36Cl2N4P2Si4
481.65
C12H20F12N2O2P2Si2
570.42
C48H50Cl2N2P2
787.74
colorless
orthorhombic
Fdd2
C24H20Cl4N4P4
630.12
fw (g mol−1
)
color
colorless
monoclinic
P2/n
colorless
monoclinic
C2/c
colorless
cryst syst
space group
a (Å)
triclinic
P1
̅
13.0246(5)
15.6553(6)
13.0864(5)
90.00
20.2530(16)
8.7053(7)
13.4567(11)
90.00
21.9363(16)
44.948(3)
8.5007(5)
90.00
9.3256(4)
9.3338(4)
17.1117(7)
105.682(2)
102.272(2)
90.00
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
91.561(2)
90.00
96.091(4)
90.00
90.00
90.00
2667.38(18)
4
2359.1(3)
4
8381.6(10)
8
1398.07(10)
2
ρcalcd (g cm−3
μ (mm−1
)
1.199
1.606
1.249
1.497
)
0.55
0.39
0.27
0.68
λMoKα (Å)
T (K)
0.710 73
173(2)
31 467
0.710 73
173(2)
19 529
0.710 73
173(2)
19 101
5100
0.710 73
173(2)
30 997
6090
measured reflns
indep reflns
reflns with I > 2σ(I)
Rint
6433
4093
4719
2620
4291
3646
0.038
0.035
0.056
0.073
F(000)
1024
1152
3328
640
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
0.0492
0.0378
0.0525
0.1386
1.069
0.0482
0.0962
0.988
0.1344
0.0971
GOF
1.042
1.008
params
232
212
268
325
CCDC no.
957693
957694
957697
957701
Table 3. Crystallographic Details of Compounds 3Dipp, 3Ad, 16, and 14
a
3Dipp
3Ad
16
14
chem formula
C24H34Cl2N2P2
483.37
colorless
monoclinic
P21
C20H30Cl2N2P2
431.30
colorless
monoclinic
P21/c
C38H30Cl2N2P2
647.48
C21H20Cl2NPSi
416.34
fw (g mol−1
)
color
colorless
monoclinic
P21/c
colorless
monoclinic
P21/n
cryst syst
space group
a (Å)
9.7403(3)
17.4140(6)
15.9047(5)
90.00
14.3494(7)
11.8705(6)
12.7844(7)
90.00
21.6043(3)
8.79950(10)
17.6203(3)
90.00
14.9031(4)
16.7323(4)
17.0281(4)
90.00
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
103.603(2)
90.00
110.751(3)
90.00
104.8450(10)
90.00
108.3870(10)
90.00
2622.04(15)
4
2036.36(18)
4
3237.94(8)
4
4029.40(17)
8
ρcalcd (g cm−3
μ (mm−1
)
1.224
1.407
1.328
1.373
)
0.38
0.48
0.33
0.47
λMoKα (Å)
T (K)
0.710 73
173(2)
35 461
13525
0.710 73
173(2)
18 530
4886
0.710 73
200 (2)
37 888
0.710 73
173(2)
52 509
measured reflns
indep reflns
reflns with I > 2σ(I)
Rint
7385
10703
11 191
0.029
2891
5374
7976
0.070
0.106
0.046
F(000)
1024
912
1344
1728
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
0.048
0.0497
0.1093
0.938
0.0449
0.0469
0.1043
1.048
0.1163
0.1198
GOF
1.019
1.037
params
558
235
397
643
CCDC no.
957698
957696
957699
957690
a
A room temperature crystal structure of this compound was reported before by Burford et al. with similar unit cell parameters but the space group
was P21/c (see ref 10).
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Table 4. Selected Bond Lengths (Å) and Angles (deg)
b
P−N
P−E
N−R
N−P−N
P−N−P
N−P−N−P
P···P
[ClP(μ-NN(SiMe3)2)]2 (9)
1.704(2)
1.710(2)
2.092(1)
2.092(1)
1.427(3)
1.427(3)
79.3(1)
79.3(1)
99.0(1)
99.0(1)
13.9(2)
10.8(2)
2.596(1)
2.526(7)
2.572(9)
2.573(1)
[RfOP(μ-NSiMe3)]2 (10)
1.702(1)
1.705(1)
1.684(1)
1.684(1)
1.763(1)
1.763(1)
84.30(6)
84.30(6)
95.70(6)
95.70(6)
0.0
0.0
[ClP(μ-NDipp)]2 (3Dipp)
1.707(2)
1.705(2)
2.0939(9)
2.0983(8)
1.435(3)
1.439(3)
81.4(1)
81.4(1)
97.7(1)
97.9(1)
8.7(1)
8.72(9)
a
[ClP(μ-NDmp)]2 (3Dmp)
1.703(3)
2.111(1)
1.438(4)
1.431(4)
81.6(1)
81.3(1)
97.8(1)
98.2(1)
8.1(1)
8.1(1)
1.700(2)
2.111(1)
1.712(3)
1.704(2)
[ClP(μ-NAd)]2 (3Ad)
1.697(2)
2.129(1)
2.129(1)
1.477(3)
1.476(3)
81.9(1)
81.8(1)
98.2(1)
97.7(1)
5.3(1)
5.3(1)
2.562(9)
2.572(8)
1.698(1)
1.701(2)
1.701(2)
[ClP(μ-NCPh3)]2 (16)
1.694(2)
2.117(8)
2.153(8)
1.504(3)
1.499(2)
81.02(8)
82.14(8)
97.66(9)
97.82(9)
8.79(9)
8.88(9)
1.701(2)
1.716(2)
1.718(2)
a
[ClP(μ-NPh)]2
1.698(1)
1.691(1)
2.075(6)
2.099(9)
1.423(9)
80.1(3)
80.5(4)
99.7(4)
99.7(1)
0
2.590(1)
2.604(1)
trans-[ClP(μ-NTer)]2 (trans15)
1.669(2)
1.728(2)
1.729(2)
1.740(2)
2.099(2)
2.085(2)
1.421(3)
1.421(3)
82.3(1)
80.3(1)
100.1(1)
100.1(1)
−0.1(2)
0.1(2)
[Cl2PN(Ph)P(μ-NPh)]2 (17)
1.710(2)
1.711(2)
1.734(2)
1.680(2)
2.058(1)
2.063(1)
1.409(3)
1.409(3)
79.8(1)
79.8(1)
100.3(1)
100.3(1)
0
2.625(1)
a
b
For [ClP(μ-NDmp)]2 and [ClP(μ-NPh)]2, values taken from refs 8b and 11a, respectively. E = element attached to the P atom.
amino-substituted trans-cyclo-diphosphadiazane [Cl2PN(Ph)P-
(μ-NPh)]2 shows a significant upfield shift (157 and 176 ppm
for the exocyclic P atom) and a remarkably large J(P−P)
coupling constant of 483 Hz.
S6). X-ray quality crystals of all compounds were selected in
Fomblin YR-1800 perfluoroether (Alfa Aesar) at ambient
temperatures.
2
General Structural Trends. In all aminophosphane
derivatives (see Supporting Information, Synthesis of Starting
Material section), as expected, the central nitrogen atom is
almost trigonal planar, and the phosphorus atom trigonal
pyramidal coordinated. The sum of the bond angles at the
amino nitrogen atom is always very close to 360° indicating a
planar environment and hence a formal sp2-hybridization.
Therefore, the lone pair localized at this nitrogen atom is found
in a p-type atomic orbital (AO). Small delocalization of this p-
AO lone pair occurs, which is also known as hyperconjugation,
leading to relatively short P−N bond lengths.30 The P−N bond
lengths of 1.64−1.68 Å are always slightly shorter than expected
for a P−N single bond (cf. Σrcov(NP) = 1.82 Å, Σrcov(NP)
= 1.62 Å).27,28 The sum of the bond angles at the phosphorus
atom are between 297° and 305°, in accord with structural data
of known aminophosphane derivatives.9,28
In the solid state for all considered species only the cis and
for [ClP(μ-NTer)]2, [RfOP(μ-NSiMe3)]2 and [Cl2PN(Ph)P(μ-
NPh)]2 only the trans isomer could be detected as illustrated by
X-ray studies (see below). As pointed out by Stahl,4 most cyclo-
diphosphazanes are thermodynamically more stable as the cis
isomer while the trans isomer is the kinetically favored product.
X-ray Crystallography. The structures of compounds
[ClP(μ-NR)]2 (R = Dipp, Ad, Ph3C, N(SiMe3)2, Ter),
[Cl2PN(Ph)P(μ-NPh)]2, [RfOP(μ-NSiMe3)]2, and the starting
materials Ph3C−NH2, Ph3C−N(H)PCl2, Ph3C−N(H)SiMe3,
Dipp−N(H)SiMe3, Ter−N(SiMe3)PCl2, and Mes*−N-
(SiMe3)PCl2, along with those of the decomposition product
14 (Scheme 4), were determined. Tables 2 and 3 present the X-
ray crystallographic data of the cyclo-diphosphadiazanes and
compound 14. Selected molecular parameters are listed in
Table 4. The molecular structures of all other molecules are
shown in the Supporting Information (Tables S3, S4, S5, and
cyclo-Diphosphadiazanes can exist as cis or trans isomers with
the cis isomer being mostly the thermodynamically more stable
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isomer.4 In general, the cis isomers have slightly puckered P2N2
rings with P−N−P−N dihedral angles between 5° and 14°,1,4
whereas the rings in the trans isomers are planar as depicted in
Figures 1−4. Both trans species [Cl2PN(Ph)P(μ-NPh)]2 and
of known cyclo-diphosphadiazanes.1,4,26 Comparison with the
sum of the covalent radii (vide supra) and computations reveals
highly polarized P−N bonds with bond orders (BO) between 1
and 2.29
The rather bulky groups used prevent all considered species
from significant intermolecular interactions. Therefore, for
instance, in the solid state structures of all considered
compounds neither significant inter- nor intramolecular
hydrogen bonding is observed. Only very weak CH···X and
CH···P interactions are found between the [XP(μ-NR)] dimers
(X = Cl, ORf). Significant hydrogen bonding is known for
smaller substituents.23
[ClP(μ-NN(SiMe3)2)]2 (9). This compound crystallizes from n-
hexane in the monoclinic space group P2/n with four formula
units per unit cell. Both independent molecules in the
asymmetric unit possess almost identical structural parameters.
The structure consists of well separated [(Me3Si)2NNPCl]2
molecules with no significant intermolecular contacts.
Figure 1. ORTEP drawing of the molecular structure [ClP(μ-
NN(SiMe3)2)]2 (9) in the crystal. Thermal ellipsoids with 50%
probability at 173 K. Only one independent molecule is shown.
The molecule adopts a staggered configuration (Figure 1)
with the two planes P1−N1−P1′−N2 and N1−N2−Si1−Si2
perpendicular to each other (∠P1−N1−N2−Si1 = 98.5°). The
phosphorus atom sits in a strongly distorted tetrahedral
environment with bond angles between 79° and 107°. The
experimentally determined P−N bond lengths of 1.704(2) and
1.710(2) Å are slightly shorter than expected for a typical P−N
single bond28,30,31 but comparable with the 1.707(3) Å in the
1,2,3-trisphosphabicyclo[1.1.0] butane species [(Me3Si)2NN-
(SiMe3)P−P−P−C(SiMe3)2].32 To get insight into the
bonding along the PN units, computations at the B3LYP/6-
31G(d) level of theory were carried out (see Supporting
Information). According to NBO analysis,33 the σ bond system
along the P1−N1−N2 unit is highly polarized between P1 and
N2 and almost ideally covalent between the adjacent N1−N2
single bond with a bond distance of 1.427(3) Å (cf. 1.473(4) Å
in PhP(Cl)N(SiMe3)N(SiMe3)2,30 Table 4). The calculated
Figure 2. ORTEP drawing of the molecular structure of [Cl2PN-
(Ph)P(μ-NPh)]2 (17) in the crystal. Thermal ellipsoids with 50%
probability at 173 K.
NBO partial charges are QP1 = +1.22 on phosphorus, QN1
=
−0.94 on the adjacent nitrogen, and QN2 = −1.14 e on the
second nitrogen atom.
[Cl2PN(Ph)P(μ-NPh)]2 (17). This compound was obtained in
the reaction of N-trimethylsilylaniline, Ph−N(SiMe3)H, with
PCl3 after addition of n-BuLi at ambient temperature.
Recrystallization from CH2Cl2 resulted in the deposition of
colorless crystals of 17 at −5 °C. [Cl2PN(Ph)P(μ-NPh)]2
crystallizes in the triclinic space group P1 with two independent
̅
molecules per unit cell. No significant intermolecular contacts
are observed. The asymmetric unit consists of two Ph−N−P−
N(Ph)−PCl2 fragments. All four phenyl rings of one molecule
are arranged parallel to each other. The phosphorus atom sits in
a trigonal pyramidal environment in the planar P2N2 ring with
the two N(Ph)PCl2 groups in trans position (Figure 2). The
phenyl group attached to the endocyclic N atoms is slightly
twisted with respect to the P2N2 plane (25.9°). The P−N bond
lengths within the P2N2 ring are almost identical with 1.710(2)
and 1.711(2) Å, which are slightly shorter compared to the
exocyclic P1−N2 distance of 1.734(2), but longer than the
N2−P2 bond length with 1.680(2) Å. Both the ring nitrogen
and the exocyclic nitrogen atoms are almost planar coordinated.
Therefore, the lone pair localized at these nitrogen atoms is
located in a p-atomic orbital which undergoes hyperconjugation
with acceptor orbitals of adjacent groups, e.g., the PCl2
fragment.
Figure 3. ORTEP drawing of the molecular structure of [RfOP(μ-
NSiMe3)]2 (10) in the crystal. Thermal ellipsoids with 50% probability
at 173 K.
[RfOP(μ-NSiMe3)]2 are centrosymmetric exhibiting a planar
P2N2 four-membered heterocycle. On the contrary, trans-
[ClP(μ-NTer)]2 is also planar but not centrosymmetric. P−N
bond lengths between 1.67 and 1.74 Å (cf. 1.695(10) Å in
[ClP(μ-NPh)]2)11a are observed in accord with structural data
[RfOP(μ-NSiMe3)]2 (10). This compound crystallizes solvent
free in the monoclinic space group C2/c with four formula units
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Figure 4. ORTEP drawings of the molecular structure of [ClP(μ-NR)]2 in the crystal [top left, R = Ad (3Ad); top right, R = Ph3C (16); bottom left,
R = Dipp (3Dipp); bottom right, R = Ter (trans15)]. Thermal ellipsoids with 50% probability at 173 K.
per unit cell. No significant intermolecular contacts are
observed. The asymmetric unit consists of a half molecule,
which lies on a 2-fold crystallographic axis with the whole
bond lengths are found. The P...P distances between 2.57 and
2.62 Å are only slightly longer than the sum of the covalent
radii (2.20 Å) but significantly shorter than the sum of the van
der Waals radii (3.8 Å).31 Thus (like for all other cyclo-
diphosphadiazanes),1 strong van der Waals interactions across
the ring can be assumed. Similar structural features are found in
[XE(μ-NR)]2 (E = P, As, Sb, and Bi; X = halogen,
pseudohalogen)4,6,34 and the biradicaloids [E(μ-NR)]2 (E =
P, As; R = Ter, Hyp).35
cyclo-Silazane 14. This compound crystallizes in the
orthorhombic space group P21/n with eight formula units per
unit cell (see Figure 5). No significant intermolecular contacts
are observed. The asymmetric unit consists of two disordered
independent molecules. The C3SiN heterocycle is almost planar
with dihedral angles between 3.2° and 16.8°, and also the
deviation from planarity for the bicycle is rather small (3.9°).
The angle sum around the N atom is close to 360° (359.9°)
displaying a planar environment around the nitrogen with a
1
molecule generated by the symmetry operation x + /2, −y +
1/2, −z as depicted in Figure 3 leading to a centrosymmetric
dimer.
The CH(CF3)2 group is disordered and split into two parts.
Compound 10 adopts the trans configuration with respect to
the perfluorinated alkoxy group. Thus, the P2N2 ring in 10 is
planar with two very similar PN bond lengths [1.702(1) and
1.705(1) Å]. The N1−P−N1′ angle with 84.30(6)° is
significantly smaller compared to the P1−N1−P1′
[95.70(6)°] angle. The N−P−O angles are found between
97.6° and 103.7°.
[ClP(μ-NR)]2 (R = Ad, Ph3C, Dipp, and Ter). While
compounds [ClP(μ-NR)]2 (R = Ad, Ph3C) and [ClP(μ-
NDipp)]2 crystallize in the monoclinic space groups P21/c and
P21, respectively, with four molecules per unit cell, for [ClP(μ-
NTer)]2 the orthorhombic space group Fdd2 was found with
eight molecules in the unit cell. [ClP(μ-NCPh3)]2 crystallizes
from CH2Cl2 in the monoclinic space group P21 with two
(disordered) solvent molecules per unit cell. In contrast to
[ClP(μ-NTer)]2, which crystallizes as trans isomer, the
molecular structures of all dichloro-substituted compounds
[ClP(μ-NR)] (Figure 4) display cis-substituted dimers with
respect to the position of the chlorine atoms and a slightly
puckered P2N2 core (Table 4) protected by two bulky organic
groups. No significant intermolecular contacts are observed
between [ClP(μ-NR)]2 molecules. It is interesting to note that
cis-[ClP(μ-NTer)]2 crystallizes in the monoclinic space group
C2/c with four formula units per unit cell. The asymmetric unit
consists of a half molecule, which lies on a 2-fold crystallo-
graphic axis.26
Figure 5. ORTEP drawing of the molecular structure of 14 in the
crystal. Thermal ellipsoids with 50% probability at 173 K. Aryl
hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): N1−C1 1.512(2), N1−P1 1.656(2), N1−Si1 1.769(2),
P1−Cl2 2.0695(9), P1−Cl1 2.090(2); C1−N1−P1 114.9(1), C1−
N1−Si1 114.2(1), P1−N1−Si1 130.8(1), N1−P1−Cl2 100.30(7),
N1−P1−Cl1 104.3(8), Cl2−P1−Cl1 97.03(5), N1−Si1−C9 91.3(9),
N1−Si1−C20 113.1(1), N1−C1−C14 104.9(2).
Astonishingly, the metrical parameters of the P2N2 core such
as the P···P and P−N distances or the N−P−N and P−N−P
angles (Table 4) do not change significantly along the [ClP(μ-
NR)]2 (R = Ad, Ph3C, Dipp, and Ter), and are in the same
range found for the cis-[ClP(μ-NN(SiMe3)2)]2 and trans-
[RfOP(μ-NSiMe3)]2 species. Always two slightly different P−N
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NMR. 31P{1H}, 13C{1H}, 29Si-INEPT, 19F{1H}, and 1H NMR
spectra were recorded on Bruker spectrometers AVANCE 300 and
AVANCE 500, respectively. The 1H and 13C chemical shifts were
referenced to solvent signals (C6D6, δ 1H = 7.15, δ 13C = 128.0;
nitrogen lone pair localized in a p-atomic orbital (AO). NBO
analysis indicates strong intramolecular interactions of the p-
AO lone pair with the antibonding σ*(P−Cl) bonds which
strengthens the P−N bond but weakens the P−Cl bonds.
Therefore, the experimentally determined P1−N1 bond length
of N1−P1 with 1.656(2) Å is significantly shorter than
expected for a typical P−N single bond27 indicating a strong
hyperconjugation interaction (cf. 1.704(1) and 1.703(1) Å in p-
C6H4[N(PCl2)2]2).36 Typical single bonds are found for the
Si−N (1.769(2), cf. Σrcov = 1.87 Å)27 and the C−N bonds
(1.512(2) Å, Σrcov = 1.46 Å).27 The phosphorus atom sits in
trigonal pyramidal environment with a Cl−P−Cl angle of
97.03(5)° and a N−P−Cl angle of 104.3(8)°.30 The C1−N1−
Si1 angle with 114.2(1)° is rather large compared to the small
C9−Si−N1 angle (91.3(9)°).
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,
and C6D6 was dried over Na/benzophenone.
IR. Nicolet 380 FT-IR with a Smart Orbit ATR device was used.
Raman. Bruker VERTEX 70 FT-IR with RAM II FT-Raman
module, equipped with a Nd:YAG laser (1064 nm), was used.
CHN Analyses. Analysator Flash EA 1112 from Thermo Quest, or
C/H/N/S-Mikroanalysator TruSpec-932 from Leco, was used.
Melting Points. These are uncorrected (EZ-Melt, Stanford
Research Systems). Heating rate is 20 °C/min (clearing points are
reported).
DSC. DSC 823e from Mettler-Toledo (Heating-rate 5 °C/min) was
used.
CONCLUSION
■
Usually, synthesis of cyclo-diphosphadiazanes is achieved by
treatment of primary amines and ECl3 (E = P and As) with
bases such as Et3N, n-BuLi, DBU, or LDA. Depending on the
used base and reaction conditions different product mixtures
are obtained, which often are difficult to be separated.
Therefore, a convenient synthetic route using trimethylsilyl-
substituted amino(dichloro)phosphanes, R−N(SiMe3)PCl2,
was utilized to form cyclo-diphosph(III)azanes in a one-pot-
reaction. By this method, electron-rich/-poor aryl-, silyl-, and
bissilylamino-substituted cyclo-diphosphazanes are accessible
upon thermal Me3SiCl elimination. The unprecedented
(Me3Si)2N-substituted species [ClP(μ-NN(SiMe3)2)]2 was
isolated simply by adding a mixture of RfOH/base to
tris(trimethylsilyl)hydrazine-(dichloro)phosphane, (Me3Si)2N-
(Me3Si)N−PCl2 (Scheme 4). Additionally, the difficulties with
the preparation of cyclo-diphosphadiazanes depending on the
starting materials, solvents, and bases due to the competition of
different reaction channels are discussed. For example, there are
two competing reaction channels for R−N(SiMe3)PCl2, which
might be caused by steric or electronic features of the ligand.
MS. Finnigan MAT 95-XP from Thermo Electron was used.
X-ray Structure Determination. X-ray quality crystals of all
compounds were selected in 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 =
0.710 73 Å). The structures were solved by direct methods (SHELXS-
97)41 and refined by full-matrix least-squares procedures (SHELXL-
97).42 Semiempirical absorption corrections were applied (SA-
DABS).43 All non-hydrogen atoms were refined anisotropically;
hydrogen atoms (except from H atoms connected to N atoms)
were included in the refinement at calculated positions using a riding
model.
Syntheses. [ClP(μ-NN(SiMe3)2)]2 (9). To a stirred solution of
N,N′,N′-tris(trimethylsilyl)hydrazine(dichloro)phosphane
(Me3Si)2N−N(SiMe3)PCl2 (1.398 g, 4.00 mmol) in THF (10 mL)
was added hexafluoroisopropanole (RfOH) (0.672 g, 4.00 mmol) in
THF (10 mL) dropwise at −60 °C over a period of 10 min. To the
resulting colorless solution was added DBU (0.639 g, 4.20 mmol)
dropwise at −55 °C. The resulting yellowish suspension was warmed
to ambient temperature and stirred for 2 h. The solvent was removed
in vacuo, resulting in a yellowish residue which was extracted with n-
hexane (10 mL) and filtered (and washed several times by repeated
backdistillation of solvent). The resulting yellow solution was
concentrated in vacuo to incipient crystallization and stored for 1 h
at 5 °C, resulting in the deposition of colorless crystals. Removal of
supernatant by syringe and drying in vacuo yielded 0.684 g (2.840
mmol, 71%) of 9 as colorless crystals. Mp: 140 °C. Anal. Calcd %
(Found) for C12H36Cl2N4P2Si4 (481.64): C 29.92 (30.72), H 7.53
(7.35), N 11.63 (11.37). NMR (ratio cis:trans = 87:13) for cis follow.
1H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 0.25 (s, 36H,
N(Si(CH3)3)2). 13C{1H} NMR (25 °C, CD2Cl2, 75.5 MHz):δ = 2.2
(s, Si(CH3)3), 2.6 (t, 4J(13C−31P) = 3.0 Hz, Si(CH3)3). 29Si NMR (25
°C, CD2Cl2, 59.6 MHz): δ = 13.1, 12.5. 31P{1H} NMR (25 °C,
CD2Cl2, 121.5 MHz): δ = 212.4. NMR data for trans follow. 1H NMR
(25 °C, CD2Cl2, 300.13 MHz): δ = 0.30 (s, 36H, N(Si(CH3)3)2).
13C{1H} NMR (25 °C, CD2Cl2, 75.5 MHz): δ = 3.2 (s, Si(CH3)3). 29Si
NMR (25 °C, CD2Cl2, 59.6 MHz): δ = 13.6. 31P{1H} NMR (25 °C,
CD2Cl2, 121.5 MHz): δ = 308.4. IR (ATR, 25 °C, 32 scans, cm−1):
2954 (m), 2898 (m), 1936 (w), 1873 (w), 1575 (m), 1434 (w), 1404
(m), 1373 (w), 1291 (m), 1251 (s), 1195 (m), 1116 (m), 1056 (w),
1009 (w), 927 (m), 887 (m), 835 (w), 818 (m), 771 (m), 754 (m),
684 (w), 671 (s), 623 (s). Raman (800 mW, 839 scans, 25 °C, cm−1):
2959 (5), 2901 (10), 1410 (2), 1266 (1), 1250 (1), 1210 (1), 963 (1),
920 (1), 856 (1), 837 (1), 749 (1), 752 (1), 686 (2), 639 (4), 576 (6),
490 (2), 413 (2), 370 (2), 343 (3), 279 (2), 263 (2), 238 (3), 224 (3),
190 (3), 145 (2), 96 (4). MS (CI+, isobutane): 205 [(Me3Si)2NP]+,
240 [1/2M]+, 445 [M − Cl]+, 481 [M + H]+.
EXPERIMENTAL SECTION
■
General Information. All manipulations were carried out under
oxygen- and moisture-free conditions under argon using standard
Schlenk or drybox techniques.
Dichloromethane, CH2Cl2, was purified according to a literature
procedure,37 dried over P4O10, and freshly distilled prior to use.
Toluene, diethylether, and THF were dried over Na/benzophenone
and freshly distilled prior to use; n-hexane was dried over Na/
benzophenone/tetraglyme and freshly distilled prior to use. 2,6-
Diisopropylphenylamine Dipp−NH2 (Merck), 2,6-dimethylphenyl-
amine Dmp−NH2 (Arcos), p-toluenesulfonylamine p-Tosyl−NH2
(gift of Professor H. Reinke, University of Rostock), adamantylamine
Ad−NH2 (ABCR), and n-BuLi (2.5 M, Acros) were used as received.
PCl3 (99%, Acros), Me3SiCl (Sigma-Aldrich), 1,8-diazabicyclo[5.4.0]-
undec-7-ene DBU (ABCR), 1,1,1,3,3,3-hexafluoroisopropanole RfOH
(Sigma-Aldrich), NEt3 (Merck), n-octyl−NH2 (gift of Professor H.
Reinke, University of Rostock), and aniline (Sigma-Aldrich) were
freshly distilled prior to use. N,N′,N′-Tris(trimethlysilyl)hydrazine-
(dichloro)phosphane (Me3Si)2N−N(SiMe3)PCl2,
17
N-tris-
(trimethylsilyl)silyl-N-trimethylsilylamino(dichloro)phosphane
(Me3Si)3Si−N(SiMe3)PCl2,15 N,N-bis(trimethylsilyl)amino(dichloro)-
phosphan (Me3Si)2NPCl2,22 N-(2,4,6-tri-tert-butylphenyl)-N-trime-
thylsilyl-amine Mes*−N(SiMe3)H,38 N-triphenylmethylamine Ph3C−
NH2,39 and 2,6-bis-(2,4,6-trimethylphenyl)phenyl-N-trimethylsilyl-
amine Ter−N(SiMe3)H40 have been reported previously and were
prepared according to literature procedures.
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Crystals suitable for X-ray crystallographic analysis were obtained by
cooling of a saturated n-hexane solution of 9 to 5 °C.
448 (2), 421 (4), 381 (1), 340 (2), 290 (3), 246 (3), 174 (4), 132 (4),
103 (5), 84 (9). MS (CI+, isobutane): 206 [DippNP]+, 241 [1/2M]+,
447 [M − Cl]+, 483 [M + H]+.
[RfOP(μ-NSiMe3)]2 (10). To a stirred solution of N-tris-
(trimethylsilyl)silyl-N-trimethylsilylamino(dichloro)phosphane
(Me3Si)3Si−N(SiMe3)PCl2 (0.437 g, 1.00 mmol) in THF (10 mL)
was added DBU (0.160 g, 1.05 mmol) dropwise at −70 °C over a
period of 15 min. To the resulting colorless suspension was added
hexafluoroisopropanole RfOH (0.168 g, 1.00 mmol) in THF (5 mL)
dropwise at −65 °C. The yellowish suspension was stirred for 1 h at
low temperature (−65 to −30 °C), warmed to ambient temperature,
and stirred for another 2 h. The solvent was removed in vacuo,
resulting in a yellowish residue which was extracted with n-hexane (10
mL). After filtration (F4), the yellow solution was concentrated in
vacuo to incipient crystallization and stored at −80 °C for 12 h,
resulting in the deposition of colorless crystals. Removal of
supernatant by syringe and drying in vacuo yielded 0.176 g (0.674
mmol, 67%) of 10 as colorless crystals [only stable at low temperature
(−80 °C)]. NMR (ratio cis:trans = 46:54, at temperatures below −50
°C only the cis isomer was observed (173.7 ppm); at ambient
temperature a cis−trans conversion occurs slowly) data for cis follow.
1H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 0.22 (s, 18H, Si(CH3)3),
Crystals suitable for X-ray crystallographic analysis were obtained by
slow cooling of a saturated n-hexane solution of 3Dipp to −40 °C.
[ClP(μ-NDmp)]2 (3Dmp). To a stirred solution of N-(2,6-
dimethylphenyl)-N-trimethylsilylamine, Dmp−N(SiMe3)H (0.387 g,
2.00 mmol), in Et2O (10 mL) was added n-BuLi (2.5M, 0.84 mL, 2.1
mmol) dropwise at ambient temperature over a period of 10 min. The
resulting pale yellow solution was added dropwise to a solution of PCl3
(0.302 g, 2.20 mmol) in Et2O (5 mL) at −30 °C over a period of 20
min. The resulting colorless suspension was warmed to ambient
temperature and stirred for 1 h. The solvent was removed in vacuo,
resulting in a colorless residue which was extracted with n-hexane (10
mL) After filtration (F4) the resulting pale yellow solution was
concentrated in vacuo to incipient crystallization and stored at −40 °C,
resulting in the deposition of colorless crystals. Removal of
supernatant by syringe and drying in vacuo yielded 0.318 g (1.71
mmol, 86%) of 3Dmp as colorless crystals. Mp: 115 °C. Anal. Calcd %
(Found) for C16H18Cl2N2P2: C 51.77 (51.88), H 4.89 (5.83), N 7.55
1
(7.08). NMR (ratio cis:trans = 93:7) data for cis follow. H NMR (25
3
5.19 (m, 2H, J(1H−19F) = 5.2 Hz, CH). 13C{1H} NMR (25 °C,
°C, CD2Cl2, 300.13 MHz): δ = 2.68 (s, 12H, CH3), 7.14 (m, 6H, Ph).
4
13C{1H} NMR (25 °C, CD2Cl2, 75.5 MHz): δ = 19.8 (t, J(13C−31P)
3
CD2Cl2, 75.5 MHz): δ = 0.2 (t, J(13C−31P) = 4.3 Hz, Si(CH3)3),
2
2
67.9−70.8 (m, J(13C−31P) = 2.9 Hz, J(13C−19F) = 34.0 Hz, CH),
121.7 (q, 1J(13C−19F) = 283.0 Hz, CF3). 19F{1H} NMR (25 °C,
CD2Cl2, 282.4 MHz): δ = −73.9 (m, 12F, CF3). 29Si NMR (25 °C,
CD2Cl2, 59.6 MHz): δ = 8.7. 31P{1H} NMR (25 °C, CD2Cl2, 121.5
= 3.2 Hz, CH3), 128.8 (s, Ph), 129.5 (s, Ph), 129.8 (s, Ph). 31P{1H}
NMR (25 °C, CD2Cl2, 121.5 MHz): δ = 210.4 (cis), 295.6 (trans). IR
(ATR, 25 °C, 32 scans, cm−1): 3063 (w), 3020 (w), 2973 (w), 2963
(w), 2946 (w), 2917 (w), 2851 (w), 2729 (w), 2683 (w), 2584 (w),
2567 (w), 1585 (w), 1574 (w), 1532 (w), 1520 (w), 1469 (s), 1442
(m), 1378 (m), 1289 (w), 1261 (s), 1205 (s), 1167 (m), 1097 (m),
1057 (w), 1032 (w), 985 (w), 973 (w), 942 (w), 918 (m), 892 (s), 774
(s), 740 (m), 720 (m), 665 (w), 615 (w), 580 (m), 560 (m), 540 (w),
532 (s). Raman (1000 mW, 250 scans, 25 °C, cm−1): 3175 (1), 3067
(2), 3038 (2), 2974 (1), 2920 (4), 2865 (1), 2731 (1), 2568 (1), 1474
(2). 1445 (1), 1430 (1), 1383 (2), 1329 (1), 1289 (7), 1229 (1), 1206
(1), 1169 (1), 1106 (2), 1029 (1), 990 (1), 976 (1), 921 (1), 826 (1),
776 (1), 751 (1), 708 (1), 664 (1), 616 (5), 564 (2), 543 (2), 514 (1),
502 (1), 491 (1), 462 (2), 400 (1), 371 (3), 348 (1), 330 (1), 317 (1),
280 (1), 224 (3), 215 (3), 195 (2), 132 (2), 89 (10). MS (CI+,
isobutane): 150 [1/2M − Cl]+, 185 [1/2M]+, 335 [M − Cl]+, 371 [M +
H]+.
1
MHz): δ = 173.7. Data for trans follow. H NMR (25 °C, CD2Cl2,
300.13 MHz): δ = 0.14 (s, 18H, Si(CH3)3), 4.79 (m, 2H, J(1H−19F)
3
= 6.0 Hz, 3J(1H−31P) = 8.5 Hz, CH). 13C{1H} NMR (25 °C, CD2Cl2,
75.5 MHz): δ = −0.1 (m, Si(CH3)3). 19F{1H} NMR (25 °C, CD2Cl2,
282.4 MHz): δ = −73.1 (m, 12F, CF3). 29Si NMR (25 °C, CD2Cl2,
59.6 MHz): δ = 7.2. 31P{1H} NMR (25 °C, CD2Cl2, 121.5 MHz): δ =
264.9.
Crystals suitable for X-ray crystallographic analysis were obtained by
slow cooling of a saturated n-hexane solution of 10 to −80 °C.
[ClP(μ-NDipp)]2 (3Dipp). To a stirred solution of N-(2,6-
diisopropylphenyl)-N-trimethylsilylamine, Dipp−N(SiMe3)H (0.499
g, 2.00 mmol), in Et2O (15 mL) was added n-BuLi (2.5M, 0.84 mL,
2.1 mmol) dropwise at ambient temperature over a period of 10 min.
The resulting pale yellow solution was added dropwise to a solution of
PCl3 (0.302 g, 2.20 mmol) in Et2O (5 mL) at −30 °C over a period of
20 min. The resulting yellow suspension was warmed to ambient
temperature and stirred for 1 h. The solvent was removed in vacuo,
resulting in a yellowish residue which was extracted with n-hexane (10
mL) After filtration (F4) the resulting pale yellow solution was
concentrated to incipient crystallization in vacuo and stored at −40 °C,
resulting in the deposition of colorless crystals. Removal of
supernatant by syringe and drying in vacuo yielded 0.401 g (1.66
mmol, 83%) of 3Dipp as colorless crystals. Mp: 216 °C. Anal. Calcd %
(Found) for C24H34Cl2N2P2 (483.39): C 59.63 (58.70), H 7.09 (7.39),
[ClP(μ-NAd)]2 (3Ad). To a stirred solution of N-adamantyl-N-
trimethylsilylamine, Ad−N(SiMe3)H (0.989 g, 4.43 mmol), in Et2O
(10 mL) was added n-BuLi (2.5M, 1.90 mL, 4.65 mmol) dropwise at
ambient temperature over a period of 10 min. The resulting pale
yellow solution was added dropwise to a solution of PCl3 (1.830 g,
13.30 mmol) in Et2O (5 mL) at −30 °C over a period of 20 min. The
resulting pale yellow suspension was warmed to ambient temperature
and stirred for 1 h. The solvent was removed in vacuo, resulting in a
pale yellow residue which was extracted with n-hexane (10 mL) After
filtration (F4) the resulting champagne colored solution was
concentrated in vacuo to incipient crystallization and stored at ambient
temperature, resulting in deposition of colorless crystals. Removal of
supernatant by syringe and drying in vacuo yielded 0.728 g (3.38
mmol, 76%) of 3Ad as colorless crystals. Mp: 263 °C (dec). Anal.
Calcd % (Found) for C20H30Cl2N2P2 (431.32): C 55.69 (54.78), H
7.01 (7.30), N 6.49 (6.41). NMR (ratio cis:trans = 100:0) data for cis
1
N 5.80 (5.70). NMR (ratio cis:trans = 99:1) data for cis follow. H
NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 1.32 (d, 24H, 3J(1H−1H), =
6.8 Hz, CH3), 3.88 (s, 4H, CH), 7.15−7.40 (m, 6H, Ph). 13C{1H}
NMR (25 °C, CD2Cl2, 75.5 MHz): δ = 25.6 (s, CH3), 124.8 (s, m-Ph),
2
129.1 (s, p-Ph), 131.0 (t, J(13C−31P) = 7.15 Hz, Cq), 149.6 (m, Cq).
1
31P{1H} NMR (25 °C, CD2Cl2, 121.5 MHz): δ = 210.5 (cis), 291.5
(trans). IR (ATR, 25 °C, 32 scans, cm−1): 3060 (w), 3015 (w), 2957
(s), 2923 (m), 2864 (m), 1586 (w), 1519 (w), 1463 (m), 1455 (w),
1442 (s), 1383 (s), 1362 (s), 1346 (w), 1319 (m), 1300 (w), 1280
(w), 1248 (s), 1197 (s), 1180 (m), 1163 (w), 1148 (w), 1103 (s),
1055 (m), 1039 (m), 974 (w), 953 (w), 934 (w), 922 (m), 903 (s),
799 (s), 747 (w), 738 (w), 722 (m), 668 (w), 632 (w), 617 (w), 600
(m), 573 (w), 536 (s), 528 (s). Raman (600 mW, 250 scans, 25 °C,
cm−1): 3169 (1), 3088 (2), 3061 (3), 3028 (2), 3017 (2), 2965 (7),
2951 (6), 2932 (9), 2909 (8), 2866 (7), 2757 (2), 2714 (2), 2610 (1),
2519 (1), 1590 (6), 1462 (4), 1443 (4), 1385 (1), 1362 (1), 1339 (3),
1316 (2), 1299 (2), 1281 (10), 1225 (2), 1198 (1), 1181 (2), 1164
(2), 1108 (3), 1048 (2), 982 (2), 955 (2), 924 (1), 888 (3), 840 (1),
793 (1), 733 (1), 678 (1), 633 (4), 602 (1), 573 (1), 539 (2), 496 (2),
follow. H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 1.66 (m, 12H,
CH2), 1.83−2.04 (m, 12H, CH2), 2.12 (m, 6H, CH). 13C{1H} NMR
(25 °C, CD2Cl2, 75.5 MHz): δ = 30.0 (s, CH), 36.1 (s, CH2), 43.9 (t,
3J(13C−31P) = 6.1 Hz, CH2). 31P{1H} NMR (25 °C, CD2Cl2, 121.5
MHz): δ = 206.0. IR (ATR, 25 °C, 32 scans, cm−1): 2904 (s), 2847
(m), 2682 (w), 2634 (w), 2593 (w), 2361 (w), 2343 (w), 2329 (w),
1646 (m), 1594 (w), 1515 (w), 1473 (w), 1447 (m), 1366 (m), 1354
(m), 1346 (w), 1305 (m), 1283 (m), 1262 (w), 1231 (m), 1186 (m),
1156 (w), 1132 (s), 1118 (w), 1101 (w), 1094 (m), 1075 (m), 1043
(m), 1008 (m), 990 (m), 959 (w), 947 (s), 889 (s), 867 (m), 815 (w),
804 (m), 788 (m), 760 (m), 730 (w), 686 (m), 643 (w), 601 (w), 583
(w), 559 (w), 551 (w), 538 (w), 527 (w). Raman (400 mW, 200 scans,
25 °C, cm−1): 2922 (10), 2884 (5), 2855 (4), 2726 (1), 2710 (1),
2685 (1), 2633 (1), 1435 (3), 1368 (1), 1349 (1), 1314 (1), 1275 (2),
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1266 (2), 1233 (1), 1191 (4), 1167 (1), 1100 (2), 1044 (1), 1032 (1),
1000 (1), 984 (2), 971 (3), 944 (1), 884 (1), 867 (1), 820 (1), 766
(5), 722 (1), 687 (3), 645 (1), 610 (1), 585 (2), 492 (1), 464 (1), 452
(1), 423 (1), 396 (3), 375 (1), 340 (1), 315 (2), 298 (1), 288 (1), 263
(2), 205 (2), 194 (3), 176 (2), 151 (2), 103 (2). MS (CI+, isobutane):
395 [M − Cl]+, 430 [M]+.
(m), 1398 (w), 1317 (w), 1281 (w), 1266 (w), 1247 (s), 1207 (m),
1184 (w), 1154 (w), 1141 (m), 1073 (m), 1018 (s), 1000 (w), 981
(m), 967 (m), 929 (m), 921 (m), 909 (w), 883 (m), 846 (s), 805 (m),
787 (s), 766 (m), 745 (s), 720 (w), 708 (m), 696 (s), 685 (w), 645
(w), 637 (w), 628 (m), 618 (w), 580 (w), 535 (w). Raman (400 mW,
250 scans, 25 °C, cm−1): 3187 (1), 3158 (1), 3127 (1), 3063 (6), 3021
(1), 2978 (2), 2959 (2), 2901 (3), 2784 (1), 2583 (1), 1596 (3), 1567
(1), 1495 (1), 1461 (1), 1447 (1), 1408 (1), 1399 (1), 1320 (1), 1293
(1), 1268 (1), 1246 (1), 1189 (2), 1158 (3), 1084 (1), 1073 (1), 1036
(5), 1023 (1), 1002 (6), 969 (1), 930 (1), 909 (1), 886 (1), 876 (1),
845 (1), 793 (1), 768 (1), 743 (1), 710 (1), 699 (1), 689 (1), 647 (2),
631 (1), 620 (1), 535 (1), 504 (1), 475 (4), 458 (2), 446 (1), 435 (1),
419 (3), 392 (2), 365 (2), 325 (1), 303 (1), 282 (1), 249 (3), 215 (1),
195 (1), 167 (1), 155 (1), 124 (5), 93 (10). MS (CI+, isobutane): 380
[M − Cl]+, 416 [M + H]+.
Crystals suitable for X-ray crystallographic analysis were obtained
from the above solution of 3Ad at ambient temperature.
[ClP(μ-NCPh3)]2 (16). To a stirred solution of N-(triphenylmethyl)-
amino(dichloro)phosphane, Ph3C−N(H)PCl2 (0.720 g, 2.00 mmol),
in Et2O (20 mL) was added NEt3 (0.223 g, 2.20 mmol) dropwise at
−60 °C. The resulting colorless suspension was warmed to ambient
temperature and stirred for 1 h. The solvent was removed in vacuo, and
the yellowish residue was extracted with toluene (15 mL). After
filtration (F4) the solvent was removed in vacuo, and CH2Cl2 (2 mL)
was added. The champagne colored solution was concentrated in vacuo
to incipient crystallization and stored at −20 °C, resulting in the
deposition of colorless crystals. Removal of supernatant by syringe and
drying in vacuo yielded 0.517 g (1.60 mmol, 80%) of 16 as colorless
crystals. Mp: 248 °C (dec). Anal. Calcd % (Found) for C38H30Cl2N2P2
(647.51): C 70.49 (69.91), H 4.67 (4.58), N 4.33 (4.30). NMR (ratio
cis:trans = 100:0) data for cis follow. 1H NMR (25 °C, CD2Cl2, 300.13
MHz): δ = 6.60−7.67 (m, 30H, Ph). 13C{1H} NMR (25 °C, CD2Cl2,
Crystals suitable for X-ray crystallographic analysis were obtained by
cooling of a saturated CH2Cl2 solution of 14 to 5 °C.
[PhN(PCl2)-PN(Ph)]2 (17). To a stirred solution of N-trimethylsily-
laniline, Ph−N(SiMe3)H (1.019 g, 6.16 mmol), in Et2O (15 mL) was
added n-BuLi (2.5M, 2.59 mL, 6.49 mmol) dropwise at ambient
temperature. The resulting yellowish solution was added dropwise to a
solution of PCl3 (2.540 g, 18.48 mmol) in Et2O (10 mL) at −80 °C
over a period of 25 min. The colorless suspension was stirred at −75
°C over a period of 30 min, warmed to ambient temperature, and
stirred for 1 h. The solvent was removed in vacuo, and the yellow
residue was extracted with n-hexane (20 mL). After filtration (F4) the
solvent was removed in vacuo, and the yellow oil was distilled
(Kugelrohr, 10−3 mbar, 100 °C). To the yellowish oily residue was
added CH2Cl2 (15 mL), and the yellowish solution was filtered (F4).
The yellowish solution was concentrated to incipient crystallization in
vacuo and stored at 5 °C, resulting in the deposition of colorless
crystals. Removal of supernatant by syringe and drying in vacuo yielded
2.17 g (3.44 mmol, 56%) as colorless crystals which could be identified
by X-ray and NMR as [Cl2PN(Ph)P(μ-NPh)]2 (17). The distillate
(colorless oil) could be identified by NMR as N-phenyl-N-
trimethylsilylamino-n-butylchlorophosphane Ph−N(SiMe3)P(nBu)Cl
(18). Data for 17 follow. Mp: 155 °C (dec). Anal. Calcd %
(Found) for C24H20Cl4N4P4 (630.15): C 45.75 (45.52), H 3.20 (3.26),
N 8.89 (8.89). NMR (ratio cis:trans = 0:100) data for trans follow. 1H
NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 6.61−6.69 (m, 4H, Ph),
6.69−6.77 (m, 4H, Ph), 7.03−7.12 (m, 2H, Ph), 7.17−7.27 (m, 4H,
Ph), 7.31−7.41 (m, 6H, Ph). 13C{1H} NMR (25 °C, CD2Cl2, 75.5
MHz): δ = 114.9 (t, J(13C−31P) = 9.3 Hz, Ph), 122.3 (s, Ph), 129.0 (s,
Ph), 130.4 (s, Ph), 131.5 (s, Ph), 134.5 (s, Cq), 140.2 (t, 2J(13C−31P) =
6.9 Hz, Cq). 31P{1H} NMR (25 °C, CD2Cl2, 121.5 MHz): δ = 157.4
2
75.5 MHz): δ = 76.8 (t, J(13C−31P) = 10.5 Hz, Cq), 128.4 (s, Ph),
128.6 (s, Ph), 130.5 (t, 4J(13C−31P) = 2.7 Hz, o-Ph), 143.1 (t,
3J(13C−31P) = 2.9 Hz, i-Ph). 31P{1H} NMR (25 °C, CD2Cl2, 121.5
MHz): δ = 197.6. IR (ATR, 25 °C, 32 scans, cm−1): 3079 (w), 3056
(w), 3023 (w), 3004 (w), 1595 (w), 1490 (m), 1445 (m), 1321 (w),
1285 (w), 1267 (m), 1212 (m), 1184 (w), 1152 (m), 1085 (w), 1041
(m), 1024 (m), 1001 (m), 981 (s), 920 (m), 905 (w), 855 (w), 847
(w), 833 (s), 795 (w), 765 (w), 751 (m), 737 (s), 698 (s), 639 (m),
626 (w), 619 (w), 582 (w), 529 (w). Raman (460 mW, 150 scans, 25
°C, cm−1): 3194 (1), 3067 (6), 3048 (3), 3028 (1), 3003 (1), 2980
(1), 2778 (1), 2583 (1), 1599 (4), 1588 (2), 1495 (1), 1451 (1), 1293
(1), 1216 (1), 1191 (2), 1164 (2), 1144 (2), 1086 (1), 1034 (4), 1005
(10), 965 (1), 936 (1), 907 (1), 859 (1), 797 (1), 745 (1), 708 (1),
679 (2), 641 (1), 622 (2), 587 (2), 531 (1), 498 (1), 483 (2), 419 (1),
408 (1), 388 (1), 359 (3), 330 (1), 290 (2), 269 (3), 248 (2), 230 (1),
207 (2), 168 (2), 147 (1), 134 (2), 114 (5), 82 (5). MS (EI, m/z,
>10%): 165 (74) [C13H9]+, 166 (14), 182 (13) [H2N(Ph)2]+, 241
(15), 242 (14), 243 (100) [CPh3]+, 244 (70), 646 (1) [M]+.
Crystals suitable for X-ray crystallographic analysis were obtained by
slow cooling of a saturated CH2Cl2 solution of 16 to −20 °C.
Silaazaheterocycle (14). To a stirred solution of N-triphenylmeth-
yl-N-trimethylsilylamine Ph3C−N(SiMe3)H (0.700 g, 2.11 mmol) in
Et2O (10 mL) was added n-BuLi (2.5M, 0.89 mL, 2.22 mmol)
dropwise at ambient temperature. To the resulting yellow suspension a
solution of PCl3 (0.869 g, 6.33 mmol) in Et2O (5 mL) was added at
−40 °C by syringe in one shot. The colorless suspension was warmed
to ambient temperature and stirred for 4 h. The solvent was removed
in vacuo, and the colorless residue was extracted with n-hexane (15
mL). After filtration (F4) the solvent was removed in vacuo, and
CH2Cl2 (5 mL) was added. The pale yellow solution was concentrated
to incipient crystallization in vacuo and stored at 5 °C, resulting in the
deposition of colorless crystals. Removal of supernatant by syringe and
drying in vacuo yielded 0.718 g (1.72 mmol, 82%) of 14 as colorless
crystals. Mp: 137 °C. Anal. Calcd % (Found) for C21H20Cl2NPSi
(416.36): C 60.58 (60.72), H 4.84 (5.26), N 3.36 (3.71). 1H NMR (25
°C, CD2Cl2, 300.13 MHz): δ = 0.70 (s, 6H, CH3), 6.98−7.13 (m, 1H,
Ph), 7.19−7.47 (m. 12H, Ph), 7.50−7.64 (m, 1H, Ph). 13C{1H} NMR
2
2
(d, J(31P−31P) = 483.0 Hz), 176.0 (d, J(31P−31P) = 483.0 Hz). IR
(ATR, 25 °C, 32 scans, cm−1): 3085 (w), 3058 (w), 3031 (w), 3005
(w), 1590 (s), 1557 (w), 1538 (w), 1495 (w), 1484 (s), 1454 (m),
1447 (w), 1403 (w), 1269 (s), 1205 (s), 1176 (m), 1161 (w), 1156
(w), 1101 (m), 1074 (m), 1025 (m), 998 (w), 989 (w), 963 (m), 916
(s), 885 (m), 860 (w), 827 (s), 751 (s), 734 (w), 696 (s), 687 (s), 675
(m), 664 (m), 618 (m). Raman (460 mW, 150 scans, 25 °C, cm−1):
3179 (1), 3067 (5), 3040 (2), 3009 (1), 2965 (1), 2903 (1), 2573 (1),
1644 (1), 1601 (10), 1503 (2), 1455 (1), 1401 (1), 1349 (8), 1299
(1), 1283 (1), 1208 (5), 1177 (2), 1160 (2), 1079 (1), 1036 (3), 1005
(9), 982 (5), 959 (1), 928 (1), 892 (1), 855 (1), 824 (1), 749 (1), 701
(1), 678 (3), 622 (1), 585 (3), 523 (2), 489 (3), 454 (2), 417 (1), 406
(1), 388 (4), 357 (1), 338 (1), 246 (4), 211 (5), 190 (2), 165 (2), 132
(2), 118 (2), 95 (9). MS (CI+, isobutane): 279 [1/2M − Cl]+, 402 [M
− N(Ph)PCl2 − Cl + H]+, 436 [M − N(Ph)PCl2]+, 631 [M − H]+.
Crystals suitable for X-ray crystallographic analysis were obtained by
cooling of a saturated CH2Cl2 solution of 17 to 5 °C.
3
(25 °C, CD2Cl2, 75.5 MHz): δ = 3.0 (d, J(13C−31P) = 2.4 Hz, C1),
4
84.4 (d, 2J(13C−31P) = 30.0 Hz, C2), 126.6 (d, J(13C−31P) = 3.1 Hz,
1
C7/C10), 128.0 (s, C8/C9), 128.4 (s, C6), 128.9 (s, C5), 129.8 (d,
4J(13C−31P) = 4.7 Hz, C4), 130.9 (s, C8/C9), 131.1 (s, C7/C10),
136.0 (d, 3J(13C−31P) = 2.2 Hz, C11), 145.3 (d, 3J(13C−31P) = 5.5 Hz,
C3), 155.3 (d, 3J(13C−31P) = 2.0 Hz, C12). 29Si NMR (25 °C,
CD2Cl2, 59.6 MHz): δ = 21.3. 31P{1H} NMR (25 °C, CD2Cl2, 121.5
MHz): δ = 187.1. IR (ATR, 25 °C, 32 scans, cm−1): 3084 (w), 3056
(w), 3029 (w), 3021 (w), 3002 (w), 2976 (w), 2957 (w), 2926 (w),
2899 (w), 2853 (w), 1590 (w), 1564 (w), 1493 (m), 1459 (w), 1441
Data for 18 follow. H NMR (25 °C, CD2Cl2, 300.13 MHz): δ =
4
5
0.20 (d, J(1H−31P) = 1.5 Hz, Si(CH3)3), 0.82 (t, 3H, J(1H−1H) =
7.3 Hz, CH3), 1.24−1.63 (m, 6H, CH2), 7.03−7.11 (m, 2H, o-Ph),
7.18−7.37 (m, 3H, m/p-Ph). 13C{1H} NMR (25 °C, CD2Cl2, 75.5
MHz): δ = 0.8 (d, J(13C−31P) = 9.2 Hz, Si(CH3)3), 14.1 (s, CH3),
3
24.3 (d, 3J(13C−31P) = 14.1 Hz, CH2), 26.6 (d, 2J(13C−31P) = 22.1 Hz,
CH2), 36.4 (d, 1J(13C−31P) = 32.1 Hz, CH2), 126.5 (s, p/m-Ph), 129.2
(s, p/m-Ph), 129.9 (d, 3J(13C−31P) = 4.0 Hz, o-Ph), 142.5 (d,
11466
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2J(13C−31P) = 8.7 Hz, Cq). 29Si NMR (25 °C, CD2Cl2, 59.6 MHz): δ =
14.7. 31P{1H} NMR (25 °C, CD2Cl2, 121.5 MHz): δ = 142.1.
(14) Romanenko, V. D.; Ruban, A. V.; Reitel, G. V.; Povolotskii, M.
I.; Markovskii, L. N. Zh. Obshch. Khim. 1989, 59, 2129.
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Organomet. Chem. 1966, 5, 199. (c) Westerhausen, M.; Schwarz, W. Z.
Anorg. Allg. Chem. 1993, 619, 1053.
ASSOCIATED CONTENT
■
S
* Supporting Information
Experimental details, a table of crystal data, list of selected bond
lengths and angles, and crystallographic information files in CIF
format. This material is available free of charge via the Internet
at http://pubs.acs.org.
(16) (a) Herler, S.; Villinger, A.; Schmedt auf der Gunne, J.;
̈
Weigand, J. J.; Mayer, P.; Schulz, A. Angew. Chem., Int. Ed. 2005, 44,
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S.; Schiemenz, B.; Kauzlarich, S. M.; Power, P. P. J. Organomet. Chem.
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(20) (a) Twamley, B.; Haubrich, S. T.; Power, P. P. Adv. Organomet.
Chem. 1999, 44, 1. (b) Clyburne, J. A. C.; McMullen, N. Coord. Chem.
Rev. 2000, 210, 73. (c) Wright, R. J.; Steiner, J.; Beaini, S.; Power, P. P.
Inorg. Chim. Acta 2006, 359, 1939. (d) Rivard, E.; Powers, P. P. Inorg.
Chem. 2007, 46, 10047.
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Macdonald, C. L. B.; Phillips, A. D.; Rheingold, A. L.; Stark, L.; Walsh,
D. Can. J. Chem. 2001, 79, 342.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: axel.schulz@uni-rostock.de.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work has been supported by the Deutsche Forschungsge-
meinschaft (SCHU 1170/8-1). We also thank Professor Dr. H.
Reinke and Dr. V. Iaroshenko (University of Rostock) for
generous gifts of chemicals.
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