Cycloarsanes (AsCF3)n (n = 4, 5) - Precursors for the highly reactive diarsene F3CAs=AsCF3

Article abstract of DOI:10.1002/zaac.200500475

Tetrakis(trifluoromethyl) cyclotetraarsane (F₃CAs)₄ (2) was used to repeat the UV initiated [4+2]-cycloaddition reaction of the diarsene F₃CAs=AsCF₃ (1) with cyclohexa-1,3-diene (CHD) and to isolate single crystals of the cycloadduct 4 for a X-ray diffraction analysis. 4 crystallizes in the space group P1 and contains the diarsene group in its E-configuration. 2 was also applied for [2+2]-cycloaddition reactions of 1 with tBuC=P and MeC=C-NⁱPr₂, but in contrast to positive results with (F₃CP)₄ the products were too labile for isolation. However, 2 was successfully used at room temperature as precursor for coordinating 1 as π-donor ligand to the Pd(PPh₃)₂ complex fragment yielding η²- bis(trifluoromethyl)diarsene-bis(triphenylphosphane)-palladium(0) 5, which was characterized by X-ray diffraction of single crystals and by spectroscopic investigations (NMR, IR, MS). Attempts to prove the existence of the diarsene 1, generated by different methods, by spectroscopic studies very probably failed due to its extreme reactivity, not allowing the necessary concentrations for detection. Quantum chemical calculations of the stability of 1 with respect to dimerization, the stability of the [2+2]-cycloadduct with 1-di(isopropyl) aminopropyne and the energy difference between 4 and the 2,3-dimethyl-1,3- butadiene cycloadduct of 1 were performed to understand the considerable differences between 1 and the related diphosphene F₃CP=PCF ₃.

Full text of DOI:10.1002/zaac.200500475

DOI: 10.1002/zaac.200500475
Cycloarsanes (AsCF3)n (n ؍ 4, 5) ؊ Precursors for the Highly Reactive
Diarsene F3CAs؍AsCF3
Joseph Grobea,*, Andreas Karsta, B. Krebsa, M. Lägea and Ernst-Ulrich Würthweinb
a Münster, Institut für Anorganische und Analytische Chemie der Westfälischen Wilhelms-Universität, Germany
b Münster, Organisch-Chemisches Institut der Westfälischen Wilhelms-Universität, Germany
Received December 5th, 2005.
Abstract. Tetrakis(trifluoromethyl) cyclotetraarsane (F3CAs)4 (2)
was used to repeat the UV initiated [4ϩ2]-cycloaddition reaction
of the diarsene F3CAsϭAsCF3 (1) with cyclohexa-1,3-diene (CHD)
and to isolate single crystals of the cycloadduct 4 for a X-ray dif-
the existence of the diarsene 1, generated by different methods, by
spectroscopic studies very probably failed due to its extreme reacti-
vity, not allowing the necessary concentrations for detection.
Quantum chemical calculations of the stability of 1 with respect to
dimerization, the stability of the [2ϩ2]-cycloadduct with 1-di(iso-
propyl)aminopropyne and the energy difference between 4 and the
2,3-dimethyl-1,3-butadiene cycloadduct of 1 were performed to
understand the considerable differences between 1 and the related
diphosphene F3CPϭPCF3.
¯
fraction analysis. 4 crystallizes in the space group P1 and contains
the diarsene group in its E-configuration. 2 was also applied for
[2ϩ2]-cycloaddition reactions of 1 with tBuCϵP and MeCϵC-
NiPr2, but in contrast to positive results with (F3CP)4 the products
were too labile for isolation. However, 2 was successfully used at
room temperature as precursor for coordinating 1 as π-donor li-
gand to the Pd(PPh3)2 complex fragment yielding η2-bis(trifluoro-
methyl)diarsene-bis(triphenylphosphane)-palladium(0) 5, which
was characterized by X-ray diffraction of single crystals and by
spectroscopic investigations (NMR, IR, MS). Attempts to prove
Keywords: Cyclotetraarsane, perfluoromethyl-; Diarsene, perfluoro-
methyl-; Cycloaddition reactions; Ligand properties; Stabilities cal-
culated
Introduction
(1,4-diazabicyclo[5.4.0]unde-7-ene), thus producing the un-
symmetrical diarsene Me*AsϭAs-CH(SiMe3)2. Symmetri-
cal diarsenes (Me3Si)3CAsϭAsC(SiMe3)3 and Mes*Asϭ
AsMes*, respectively, were obtained in the same year by
Couret et al. [5] via dehalogenation of (Me3Si)3CAsCl2 with
tBuLi and in 1989 by Weber et al. [6], using magnesium
for the dehalogenation of Mes*AsCl2. These derivatives in
general are kinetically stabilized by extremely bulky sub-
stituents. As early as 1971 a different method of stabiliz-
ation was employed in the group of West [7] by the prep-
aration of the carbonyl complex (CO)4Fe(η2-C6F5Asϭ
AsC6F5) and by Huttner et al. [8] in the trinuclear complex
(PhAsϭAsPh){Cr(CO)5}3 with one side-on and two ter-
minal complex fragments.
Our experience with the thermodynamic stabilization of
double bonds by the so-called “Perfluoro Effect” [9] in pre-
paring the perfluoroheteroalkenes F3CEϭCF2 (E ϭ P, As)
[10] led to the dehalogenation of F3CAsI2 with SnCl2 in
the presence of dienes yielding [4ϩ2]-cycloadducts of the
diarsene F3CAsϭAsCF3 (1), which suggest the double
bond system as the most probable intermediate. Ϫ In the
present paper the possibility to employ the cyclotetraarsane
(F3CAs)4 (2) [11] as precursor for further investigations of
1 as reactant for suitable partners has been studied. First
attempts concentrated on reactions which had been success-
fully used for the phosphorus analogue F3CPϭPCF3 [12].
In the contribution of ref. [3a] the application of 1 in [4ϩ2]-
cycloadditon reactions was described with the interesting
In recent publications we have reported on the use of per-
fluoro-2-arsapropene F3CAsϭCF2 as tool for [2ϩ2] cyclo-
addition and HEMen (E ϭ N, P, As, n ϭ 2; E ϭ O, S,
Se, n ϭ 1) addition reactions [1, 2]. In comparison to the
analogous phosphorus compound F3CPϭCF2 the reactions
were less selective and the products formed, as a rule, are
more labile. Therefore, in some cases the characterization
of new compounds was exclusively based on spectroscopic
investigations. However, the interesting results encouraged
us to study the reactivity of the even more labile diarsene
F3CAsϭAsCF3 (1) which according to a previous paper
[3a] can be generated in situ from the cycloarsanes
(F3CAs)n (n ϭ 4, 5) or via deiodination of F3CAsI2 with
SnCl2 [3b].
The first representative of diorganodiarsenes has been
prepared by Cowley et al. [4] in 1983 using the intermolecu-
lar HCl elimination from Mes*AsH2 (Mes* ϭ 2,4,6-tri-tert-
butylphenyl; supermesityl) and (Me3Si)2CHAsCl2 by DBU
* Prof. Dr. Dr. h.c. Joseph Grobe
Institut für Anorganische und Analytische Chemie
Westfälische Wilhelms-Universität Münster
Corrensstr. 36
D-48149 Münster
Tel ϩ49(0)251 83 36098; Fax ϩ49(0)251 83 36012
E-mail: grobe@uni-muenster.de
Z. Anorg. Allg. Chem. 2006, 632, 599Ϫ608
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J. Grobe, A. Karst, B. Krebs, M. Läge, E.-U. Würthwein
¯
The triclinic unit cell (space group P1) with a ϭ 7.012(5),
˚
b ϭ 8.686(8) and c ϭ 10.044(6) A and angles of αϭ
82.72(2), β ϭ 81.29(2), γ ϭ 68.19(2)° contains two mole-
cules of 4 which along the y-axis have the same orientation,
whereas along the z-axis pairs of molecules are correlated
by a centre of inversion. Experimental and crystallographic
data are given in Table 4 (Exp. Section).
The exclusive formation of [4ϩ2]-cycloadditon products
from (F3CAs)n (n ϭ 4, 5) and dienes proves the bis(trifluor-
omethyl)diarsene 1 as the most probable intermediate. This
is supported (i) by the easy transfer of 1 from the CHD-
adduct to 2,3-dimethyl-1,3-butadiene and (ii) by the ther-
mal decomposition of the cycloadducts, at least partly oc-
curring as cyclo-reversion to give the corresponding diene
and the cyclodimer of 1.
Figure 1 Molecular structure of the [4ϩ2]-cycloadduct 4 of 1 with
cyclohexa-1,3-diene (CHD)
2. [2؉2]-Cycloaddition reactions of 1
On the basis of the above mentioned results, it was of some
interest to study [2ϩ2]-cycloaddition reactions of 1, es-
pecially with compounds which gave rewarding results in
reactions with both the perfluoroarsaalkene F3CAsϭCF2
[1] and the related diphosphene F3CPϭPCF3 [12]. In view
of the expected difficulties and the lability of 1, the reac-
tions were carried out in sealed NMR-tubes and controlled
by recording the 19F-NMR spectra. Except for the reaction
of the precursor (F3CAs)4 (2) with the corresponding cyclo-
tetraphosphane (F3CP)4, for which no reaction could be ob-
served in the NMR spectrum at temperatures up to 70 °C,
˚
Table 1 Selected bond lengths /A and angles /° of 4
As(1) Ϫ C(1)
As(1) Ϫ C(7)
As(2) Ϫ C(4)
As(2) Ϫ C(8)
As(1) Ϫ As(2)
2.01(2)
2.02(2)
2.02(2)
1.99(2)
2.427(3)
C(1) Ϫ As(1) Ϫ C(7)
C(1) Ϫ As(1) Ϫ As(2)
C(7) Ϫ As(1) Ϫ As(2)
C(4) Ϫ As(2) Ϫ C(8)
C(4) Ϫ As(2) Ϫ As(1)
C(8) Ϫ As(2) Ϫ As(1)
99.8(2)
95.2(2)
95.9(2)
96.6(2)
91.7(2)
96.6(2)
result that only dimethylbutadiene and isoprene react with
(F3CAs)4 (2) in the expected manner already at room tem-
perature, whereas cyclopentadiene, cyclohexadiene and cis-
or trans-piperylene (cis- or trans-penta-1,3-diene) had to be
activated by UV irradiation.
the mixtures of the cycloarsane
2 with tBuCϵP,
MeCϵCNEt2 and HPϭC(F)NEt2, respectively, showed co-
lour changes to yellow on melting and warming at room
temperature. As a rule, complex 19F-NMR spectra were ob-
served indicating the formation of product mixtures which
on turning brown obviously quickly underwent decompo-
sition. Only in case of the alkyne derivative MeCϵCNiPr2,
the 19F-NMR spectrum gives some hints to the expected
[2ϩ2]-cycloaddukt. Two groups of two correlated quartets
were detected at δF Ϫ36.3/Ϫ41.2 (5JFF ϭ 8.6 Hz) and δF
Ϫ41.8/Ϫ44.6 (5JFF ϭ 4.5 Hz), respectively. The chemical
shifts are close to those observed for the trans-F3CPϪPCF3
moiety in the triphosphetene derivatives obtained from the
reaction of (F3CP)4 and phosphaalkynes RCϵP [12] (δF
Ϫ46.2 to Ϫ49.9 for the CF3PϪP unit and δF Ϫ53.2 to
Ϫ55.2 for the CF3P-C fragment).
In conclusion, the attempted [2ϩ2]-cycloaddition reac-
tions with the cyclodimer (F3CAs)4 of 1 do not lead to clear
results, because the products obviously are considerably less
stable than those obtained with the analogous cyclophos-
phane (F3CP)4 [12] or in [4ϩ2]-reactions of (F3CAs)4 with
dienes [3a]. In all described test reactions decomposition
was observed already after short periods at room tempera-
ture.
Results and Discussion
1. Preparation of single crystals of the CHD-adduct
of 1 for structural investigation
For the preparation, the (F3CAs)4 (2)/(F3CAs)5 (3)-mixture,
a slight excess of cyclohexa-1,3-diene and chloroform were
introduced by vacuum condensation into a NMR tube and
sealed under vacuum. After melting, the solution was ir-
radiated with a UV-lamp. 19F-NMR control showed com-
plete reaction of the cycloarsanes after 4 h, but there was no
indication of detectable amounts of the diarsene 1, which
obviously is spontaneously quenched by the diene to form
the cycloadduct 4. The reaction mixture was separated by
fractional vacuum-condensation (traps at Ϫ30 and
Ϫ196 °C) and the product was obtained in the trap at
Ϫ30 °C. Sublimation to a cold finger (Ϫ30 °C) gave colour-
less crystals which were investigated at Ϫ100 °C by X-ray
diffraction. Figure 1 presents the molecular structure of 4.
Selected bond lengths and angles are given in Table 1. The
data support the proposed structural formula based on
NMR-data [3a]. The bicyclic system is the result of the ex-
pected [4ϩ2]-cycloaddition of 1 to CHD with the CF3-
groups in trans-positions. The bond lengths and angles have
values expected for 4. For example, the As-As distance of
3. Stabilization of 1 by coordination
The diarsene 1 contains three coordination centres, two
lone pairs on the As-atoms for σ-bonding and the hetero-
˚
2.427 A is a typical single bond [13].
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Cycloarsanes (AsCF3)n (n ϭ 4, 5)
Scheme 1
olefinic AsϭAs-double bond for side-on η2-coordination.
Due to the electron withdrawing effect of the CF3 groups
the σ-donor capacity of the lone pairs at arsenic will be
strongly reduced, whereas the π-acceptor properties are in-
creased. No wonder, that the first successful coordination
of a diarsene was reported already in 1971 by West et al.
reacting Fe(CO)4(H2CϭCH2) with the cyclotetraarsane
[(F5C6)As]4 yielding Fe(CO)4(η2-RFAsϭAsRF) [7]. Further
Scheme 2
examples
AsPh){(Cr(CO)5}2Cr(CO)5, prepared by Huttner et al. [8],
and the side-on diarsene complex (F5C6Asϭ
are
the
trinuclear
complex
(PhAsϭ
AsC6F5)Pt(PPh3)2 described by West et al. [14]. In all cases
˚
the AsAs bond length is close to 2.40 A indicating a bond
order of 1.0. In 1983 Cowley and co-workers reported on
the preparation of the chromium carbonyl complex
Cr(CO)5{Mes*AsϭAsCH(SiMe3)2} with an AsAs bond
˚
length of 2.25 A which is considerably shorter than in the
side-on coordinated diarsene derivatives [14]. The X-ray dif-
fraction study in this case revealed the σ-donor coordi-
nation of the less shielded As atom. These literature results
encouraged us to investigate the reaction of the cyclotetra-
arsane (F3CAs)4 (2) with tetrakis(triphenylphosphane)pal-
ladium(0).
Scheme 3
In addition, the results of the successful [4ϩ2]-cycloaddi-
ton reactions of (F3CAs)4 with dienes indicate the existence
of an equilibrium according to Scheme 2, equation (2).
On this background, combination of the fragments
Pd(PPh3)2 and F3CAsϭAsCF3 seems feasible and explains
the formation of the observed complex 5.
An alternative possibility could be the reaction of the
folded cyclotetraarsane with two fragments Pd(PPh3)2 gen-
erating bridges across the edges of (F3CAs)4 as shown in
Scheme 3, followed by cleavage of the four-membered ring
to yield two molecules of 5.
Synthesis of (Ph3P)2Pd(F3CAs؍AsCF3) (5)
On melting a mixture of (F3CAs)4 and Pd(PPh3)4 in tolu-
ene, already at 0 °C a colour change to red was observed
indicating a reaction which continued during several hours’
stirring and finally gave a yellow solution (Scheme 1).
After pumping off the solvent, the replaced tri-
phenylphosphane was separated from the product by vac-
uum sublimation, and the residue was dissolved again with
little toluene. Slow evaporation of the solvent in a stream
of argon gas resulted in the precipitation of yellow crystals
of 5, which were investigated by X-ray structural, spectro-
scopic and analytic studies, unambiguously characterizing
the product as η2-bis(trifluoromethyl)diarsene-bis(tri-
phenylphosphane)-palladium(0), which corresponds to the
related diphosphene palladium compound described by
Phillips et al. [16].
The observed colour changes first from colourless to red
and then to yellow suggest a stepwise reaction of the part-
ner molecules. However, spectroscopic control measure-
ments during the product formation gave no conclusive
hints to transition states or definite intermediates. Regard-
ing the relevant literature, the discussion has to respect early
results about the existence of a dissociation equilibrium of
the precursor Pd(PPh3)4 in solution according to Scheme 2,
equation (1) [17Ϫ19].
Characterization of 5
Molecular structure
The structural investigation of 5 gave the molecular struc-
ture presented in Figure 2, in which the hydrogen atoms are
omitted for clarity. The structure proves the side-on coordi-
nation of 1 to the Pd-centre. The AsϪAs bond length of
2.341(1) A is the average of the single bond value in
(F3CAs)4 (2.45 A) [13] and the double bond value in Mes*
AsϭAsCH(SiMe3)2 (2.22 A) [11], as expected for side-on
coordination. In comparison to the above mentioned re-
presentatives, the bond length, due to less bulky substitu-
˚
˚
˚
˚
ents, is reduced by 0.03 Ϫ 0.05 A, probably enhanced by
the ϪI effect of the CF3-groups. All remaining bond lengths
correspond very closely to the sum of the covalent atomic
radii. Selected bond lengths and angles are given in Table 2.
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J. Grobe, A. Karst, B. Krebs, M. Läge, E.-U. Würthwein
Figure 2 Molecular structure of (η2-F3CAsϭAsCF3)(Ph3P)2Pd(0)
(5); hydrogen atoms omitted.
˚
Table 2 Selected bond lengths /A and angles /° of 5
Pd(1)ϪP(1)
Pd(1)ϪP(2)
Pd(1)ϪAs(1)
Pd(1)ϪAs(2)
As(1)ϪAs(2)
As(1)ϪC(37)
As(2)ϪC(38)
P(1)ϪPd(1)ϪP(2)
P(1)ϪPd(1)ϪAs(1)
P(1)ϪPd(1)ϪAs(2)
P(2)ϪPd(1)ϪAs(1)
P(2)ϪPd(1)ϪAs(2)
As(1)ϪPd(1)ϪAs(2)
2.352(1)
2.350(1)
2.475(9)
2.467(9)
2.341(1)
2.006(8)
2.006(7)
109.18(5)
154.74(4)
98.20(4)
96.01(4)
152.29(4)
56.54(2)
Figure 3 NMR-spectra of 5: a) 19F; b) 31P{1H}
C(37)ϪAs(1)ϪAs(2)
C(37)ϪAs(1)ϪPd(1)
As(2)ϪAs(1)ϪPd(1)
C(38)ϪAs(2)ϪAs(1)
C(38)ϪAs(2)ϪPd(1)
As(1)ϪAs(2)ϪPd(1)
92.7(2)
100.3(2)
61.57(2)
93.8(2)
94.5(2)
61.89(3)
Section and compared with selected data of the correspond-
ing diphosphene complex [16]. The 1H-NMR spectrum
shows a typical multiplet resonance for the protons of the
1
phenyl groups at phosphorus at δH 7.2 with H/1H and 31P/
1H couplings. In the 13C{1H}-NMR spectrum the signals
of the nuclei Ca to Cc of the phenyl groups (PϪCaϪCbϪCc
show triplet patterns due to coupling with two 31P atoms
which are strongly coupled through the Pd-centre. The
higher order spectra are therefore the result of PPЈCnCЈn
spin systems (n ϭ a, b or c) generating pseudo-triplet sig-
nals. The assignment was possible with the known coupling
constants of triphenylphosphane [21]. The 13C(CF3) reson-
ance overlaps with those of the phenyl carbon atoms and,
due to the qq pattern, the intensity is distributed to 16 lines.
Therefore the signals could not be separated from those of
the phenyl carbon nuclei.
The angle AsϪPdϪAs of 56.5° is the result of the short
AsϪAs distance. Considering coordination of the diarsene
via the centre of the AsϭAs π-bond leads to a planar tri-
coordinated Pd atom, for which the sum of the angles in
the plane is 360°. The PϪPdϪP angle of 109.18(5)° is the
smallest in the plane because the CF3 groups occupy trans-
positions at the AsϪAs unit and, with angles of 92.7(2)
for C(37)-As(1)-As(2) and 93.8(2)° for C(38)-As(2)-As(1),
respectively, the bonds are almost perpendicular to the
three-membered PdϪAsϪAs ring. They are close to angles
found for other diarsenes [20] and indicative of the nature
of the bonding and lone pair orbitals at fourth row ele-
ments: The bonding orbitals have mainly p-, the lone pair
orbital has mainly s-character. 5 crystallizes in the space
group Pbca with a ϭ 17.314(6), b ϭ 18.501(7) and c ϭ
The 19F NMR spectrum (Fig. 3a) exhibits a pseudo-trip-
let resonance at δF Ϫ30.6 due to the 4JPF coupling of 4.3 Hz
with the 31P atoms of both PPh3-ligands. The same coup-
ling constant is observed in the 31P{1H} signal of the PPh3-
groups at δP 17.4 (Fig. 3b) which appears as a pseudo-sep-
tet.
˚
26.717(8) A.
NMR-spectroscopic data of 5
IR-spectroscopic data of 5
The NMR-spectra have been recorded on a chloroform
The IR-spectrum of 5 was recorded on a solution of the
solution of 5 and the data are collected in the Experimental
crystals in D3-chloroform, and the observed absorption
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Cycloarsanes (AsCF3)n (n ϭ 4, 5)
bands were assigned by comparison with the spectra of
PPh3 and (F3CAs)4. The data are given in the Experimen-
tal Section.
ing result that the cycloadducts are formed already at room
temperature, proving the generation of 1 as highly reactive
intermediate. This assumption is supported by results of
Grützmacher et al. [22], obtained by irradiation of cyclo-
phosphane/diene mixtures, proving the activation of the
cyclophosphane and not that of the dienes.
Mass spectroscopic data of 5
The mass spectrum of 5, recorded at 205 °C with an ionis-
ation potential of 70 eV, shows the molecular ion [Mϩ] at
m/z ϭ 920 with a relative intensity of 4 % for the 108Pd-
isotope with a natural abundance of 26.46 %. The basis
peak of the spectrum is observed at m/z ϭ 262 (100 %) and
corresponds to the fragment ion [PPh3]ϩ. As in case of the
analogous diphosphene complex [16], also peaks of cycloar-
sanes (F3CAs)n are observed with n ϭ 3, 4, 5. The MS data
are given in the Exp. Section. C/H-analytic data consider-
ably differed from the calculated values, due to toluene in-
clusions in the crystals. The high resolution m/z of the mo-
lecular ion [M]ϩ ϭ 919.9182, however, corresponds very
closely to the value, calculated for the peak with 108Pd.
The cyclotetraarsane in vacuo slowly evaporates already
at room temperature. The diluted vapour phase was trans-
ported through a UV irradiated vessel (150 W OSRAM
lamp) for cleavage according to the equilibrium of equation
(2) in Scheme 2, and the starting compound together with
the recombined parts of 1 were collected in the Ϫ30 °C trap,
whereby detectable amounts of 1 could hopefully be con-
densed and detected in the succeeding bulb of the NMR-
tube at Ϫ196 °C. Investigation of both traps, however, led
to the detection of 2 in the Ϫ 30 °C trap and not even a
trace of 1 in the Ϫ196 °C trap.
Oxidative cleavage of 1 from the palladium complex 5
4. Attempts to generate 1 for direct characterization
The principle followed in this case is the oxidative cleavage
of coordinated reactive species from transition metal com-
plexes by C2Cl6, which was successfully applied in phos-
phaalkyne chemistry [23]. In this case, however, the ex-
pected reaction did not occur.
The attempted elimination of 1 from the Pd-complex by
reaction with 1,3-dienes also failed, very probably because
the side-on coordination considerably reduces the olefinic
reactivity of the diarsene.
The results described in the preceding sections have shown
that (F3CAs)4 can act as a useful precursor for 1 in [4ϩ2]-
cycloaddition and complex formation reactions. Therefore,
it was of considerable interest, whether the diarsene also
can be detected conclusively as the free molecule by spectro-
scopic methods. Four different methods for its generation
have been studied:
Thermolytic cleavage of the cyclotetraarsane
(F3CAs)4 (2)
Attempts to detect 1 in the reaction mixture during
the transfer from 4 to DMB
After the successful generation of the labile arsaalkene
F3CAsϭCF2 by an optimized procedure [1], the apparatus
described was also applied to the thermolysis of the cyclo-
tetraarsane. The main problem in this case was expected to
be a fast enough detection of 1 because of its extreme ten-
dency to recombine to the starting cycloarsane. In order to
separate the generated diarsene from small amounts of 2,
passing the hot zone without cleavage or formed by recom-
bination, we tried to condense the cycloarsane in a Ϫ30 °C
trap directly behind the pyrolysis zone. The vacuum of
10Ϫ3 mbar and continuous pumping should guarantee a
passing through of the very volatile 1. 1 and/or its following
products were planned to condensate layer-by-layer with an
inert solvent like chloroform in the Ϫ196 °C trap and to
detect by low temperature NMR measurements.
As reported earlier [3a], the diarsene 1 can be quantitatively
transferred from the CHD-adduct to dimethylbutadiene al-
ready at room temperature. The reaction was followed by
19F-NMR spectroscopy, but neither 1 nor any transition
states or intermediates could be detected. The reason for
the transfer very probably is the bicyclic strain in the CHD-
adduct causing a considerable difference in stability be-
tween 4 and the DMB-cycloadduct of 1 (see Section 5 be-
low). This result opens the chance to use 4 as precursor also
for other transfer reactions.
5. Quantum chemical calculations
These experiments were unsuccessful. At temperatures up
to 400 °C only the cyclotetraarsane 2 was found in the
Ϫ30 °C trap and no product in the bulb of the NMR tube
at Ϫ196 °C. Raising the temperature clearly above 400 °C
led to decomposition products of very low volatility de-
posited already at the end of the pyrolysis tube.
In order to understand the properties of tetrakis(trifluoro-
methyl)cycloatetraarsane 2 as precursor of bistrifluorome-
thyldiarsene 1 and its reactions with the alkynes and dienes
used in the experiments, quantum chemical calculations
using the DFT-method B3LYP/6-311ϩG(d,p) were per-
formed. For comparison, the analogous phosphorus species
have been included in these calculations. The same level of
theory has been proved to be useful in previous studies for
comparable cycloaddition reactions of perfluoro-2-arsapro-
pene [1, 2]. The program package GAUSSIAN 03 [24] was
Photolytic cleavage of 2
Some of the [4ϩ2]-cycloaddition reactions of 2 with dienes
had to be activated by UV irradiation [3a] with the interest-
Z. Anorg. Allg. Chem. 2006, 599Ϫ608
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J. Grobe, A. Karst, B. Krebs, M. Läge, E.-U. Würthwein
phorus analogues the E/Z-difference amounts to 6.7 kcal/
mol. The dimerisation of (E)-1 to give 2 is predicted to be
quite exothermic by Ϫ37.4 kcal/mol, illustrating the high
reactivity of 1 even in the formation of the strained four-
membered ring. This number is only slightly more exother-
mic compared to the dimerisation of the corresponding di-
phosphene (Ϫ36.2 kcal/mol). In accord with the X-ray dif-
fraction study [13] of 2 a D2d structure (trans-trans-trans) is
found to be lowest in energy (Figure 4). The experimental
X-ray structure [13] and the DFT-calculation agree within
2σ with respect to the measured data (Table 3). Other iso-
mers (trans-trans-cis, trans-cis-cis and cis-cis-cis) are 8 to
23 kcal/mol higher in energy. The energy richest isomer (cis-
cis-cis) has all four CF3-groups pointing in the same direc-
tion (C4v).
Table 3. Experimental (X-ray [13]) and calculated (B3LYP/6-
311ϩ(d,p)) geometrical parameters for 2 (D2d) (bond lengths: A,
bond angles:°)
˚
Bond length/angle
exp.
calc.
AsϪAs
AsϪC
CϪF(I)
CϪF(II)
AsϪAsϪAs
AsϪAsϪC
2.454
2.019
1.264
1.312
83.6
2.5102
2.0419
1.3506
1.3493
85.31
94.4
95.31
AsϪCϪF(I)
118.5
109.0
106.7
106.4
115.31
109.53
107.25
107.69
AsϪCϪF(II)
F(I)ϪCϪF(II)
F(II)ϪCϪF(II)
applied for the calculations. All heats of reaction are cor-
rected for 0 K (unscaled).
Stability of the [2؉2]-adduct of 1 with
MeCϵCNiPr2
The formation of the cycloadduct of 1 with MeCϵCNiPr2
is calculated to be exothermic by 30.3 kcal/mol, which is
significantly less exothermic than for the reaction with the
diphosphene (Ϫ41.7 kcal/mol), indicating weaker CϪAs
bonds compared to the CϪP bonds, as expected. The calcu-
lated structure shows a significantly puckered four-mem-
Stability of 1 and its dimer 2
According to the quantum chemical results, diarsene (E)-1
is by 5.9 kcal/mol more stable than the corresponding (Z)-
1, which is well in line with steric and lone pair-repulsion
(Pauli repulsion) arguments. For the corresponding phos-
Figure 4 Calculated DFT-structures for four isomers of 2 with relative energies (kcal/mol) (B3LYP/6-311ϩG(d,p)(Schakal plots)
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Z. Anorg. Allg. Chem. 2006, 599Ϫ608

Cycloarsanes (AsCF3)n (n ϭ 4, 5)
bered heterocycle with the four substituents all in equatorial
positions similar to the dimer 2.
isomeric structures of 2 were also calculated and the all-
trans isomer (D2d), in accord with the molecular structure
derived form X-ray diffraction, was found to be lowest in
energy.
Stability of the [4؉2]-adducts of 1 with 2,3-
dimethylbutadiene and cyclohexa-1,3-diene
Experimental Part
The formation of the hetero-Diels-Alder product from 1
and 2,3-dimethylbutadiene is little less exothermic
(Ϫ26.3 kcal/mol) as compared to the formation of the
[2ϩ2]-ynamine adduct. Here again, the formation of the
corresponding diphosphene adduct is clearly more exother-
mic (Ϫ35.8 kcal/mol). The formation of 4 from 1 and cyclo-
hexa-1,3-diene (CHD) is less exothermic (Ϫ16.4 kcal/mol)
compared to the 2,3-dimethylbutadiene reaction. The for-
mation of the corresponding phosphorus bicyclic product
is predicted to be exothermic by Ϫ25.1 kcal/mol, thus indi-
cating a similar difference between diarsene and diphos-
phene in heat of reaction as for the other cycloaddition re-
actions. From these data the reaction enthalpy for the ex-
change of 2,3-dimethylbutadiene by cyclohexadiene in the
cycloadducts of 1 may be derived. It amounts to 9.8 kcal/
mol in favour of the 2,3-dimethylbutadiene cycloadduct.
For the corresponding diphosphene cycloadduct a prefer-
ence of 10.7 kcal/mol for the 2,3-dimethylbutadiene cyclo-
adduct is calculated.
General: With respect to the general operations and the instruments
for spectroscopic investigations of the volatile and toxic starting
compounds and the products, the reader is advised to follow the
precautions and prescriptions in previous papers [1, 2].
Single crystal structure analysis
The unit cell and diffraction data of compounds 4 and 5 were col-
lected on a SIEMENS P3 diffraction system with Mo-Kα radiation
˚
(λ ϭ 0.71073 A) by using the θ-2θ-scan technique. The collected
reflections were corrected for absorption effects [25]. The structures
were solved by direct methods using the program SHELXL-97 [26].
The final positions of all non-hydrogen atoms were taken from a
series of full-matrix least squares refinement cycles based on F2
with the SHELXL-97 program [27] followed by difference Fourier
syntheses. All non-hydrogen atoms of the molecules 4 and 5 were
refined anisotropically. The hydrogen atoms were placed on calcu-
lated positions and allowed to ride on their corresponding atoms.
The solvent molecule toluene in 5 was refined on disordered posi-
tions with an occupancy factor of 0.5. Crystallographic and exper-
imental details are listed in Table 4. Selected bond lengths and
angles are presented in Tables 1 and 2. Atomic coordinates, thermal
parameters, and all bond lengths and angles have been deposited
with the Cambridge Crystallographic Data Centre (CCDC). Copies
of the data can be obtained free of charge on application to The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (Fax:
int. codeϩ (1223)336-033; e-mail for inquiry: fileserv@ccdc.cam.a-
c.uk; e-mail for deposition: deposit@ccdc.cam.ac.uk) on full quot-
ing the Journal citation and deposition numbers CCDC 290956 (4)
and CCDC 290957 (5).
Conclusion
In spite of the expected difficulties to use the cyclotetra-
arsane (F3CAs)4 (2) as precursor to generate and handle
the labile bis(trifluoromethyl)diarsene 1, it could be applied
for [4ϩ2]-cycloaddition reactions with dienes in thermal or
photochemical processes [3a]. To prove the expected trans-
configuration of 1 in the cycloadducts, single crystals of 4
were used in the present study. In accord with the spectro-
scopic results, the AsϪAs-bond is very close to a single
bond length, and the other bond lengths and angles are in
the range expected for the combination of CHD with
F3CAsϭAsCF3, in case of arsenic as a fourth row element
with angles between 91 and 100° at the As-centres. In reac-
tions with the phosphaalkyne tBuCϵP and the 1-aminosub-
stituted propyne MeCϵCNiPr2 hints to [2ϩ2]-cycloadducts
were obtained, but these were too labile for isolation. The
cyclotetraarsane (F3CAs)4, however, underwent a stepwise
reaction at room temperature with tetrakis(triphenylphos-
phane) palladium(0) yielding the complex (F3CAsϭ
AsCF3)(Ph3P)2Pd(0) (5) with side-on coordination. The
molecular structure of 5 was determined by X-ray diffrac-
tion and corresponds to the structure of the previously pre-
pared analogous palladium complex with side-on coordi-
nated F3CPϭPCF3 [16]. Attempts to detect the diarsene as
intermediate or transition state in thermal or photolytic re-
actions of 1 failed, indicating its very short life-time in the
reactions described. The experimental results are in accord
with quantum chemical calculations of the thermodynamic
stabilities of compounds 1, 2, 4, 5 and the cycloadducts
of 1 and the corresponding diphosphene derivatives. The
The compounds used for the delicate experiments were produced
according to modified literature methods or purchased: F3CAsI2
[28], (F3CAs)n (n ϭ 4, 5) [11], PϵCtBu [29, 30], PϵCNiPr2 [31],
(F3CP)4 [32, 33], Pd(PPh3)4; 1,3-cyclohexadiene, 2,3-dimethylbuta-
diene.
Preparation of single crystals of 4
(F3CAs)4 (2) [0.6 g, 2 mmol of F3CAsϭAsCF3 (1)], 1,3-cyclohexa-
diene (0.4 g, 5 mmol) and chloroform as solvent were transferred
into a NMR-tube (Ϫ196 °C) by vacuum condensation. The tube
was sealed under vacuum and after thawing the mixture was ir-
radiated with a UV lamp (OSRAM 150 W) until 19F-NMR control
measurements indicated complete reaction of the cycloarsane in
about 4 h. The NMR-tube was opened in vacuo and the volatile
components were fractionated via vacuum condensation using
traps at 0, Ϫ30 and Ϫ196 °C. The [4ϩ2]-cycloadduct 4 was ob-
tained in the Ϫ30 °C trap. Repeated condensation to a cold finger
(Ϫ30 °C) gave colourless crystals of sufficient quality for an X-ray
diffraction analysis. Yield: 0.5 g, 1.4 mmol 4 (68 %, rel. to the
F3CAs units in the starting cycloarsane 2).
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J. Grobe, A. Karst, B. Krebs, M. Läge, E.-U. Würthwein
Table 4 Crystal Data and Structure Refinementsfor 4 and 5
4
5
Empirical formula
Temperature
Wavelength
C8 H8 F6 As2
173(2) K
0.71073 A
C38H30F6As2P2Pd x C7H8
293(2) K
0.71073 A
˚
˚
Formula weight
Crystal system
Space group
367.98
1010.93
orthorhombic
Pbca (No. 61)
a ϭ 17.314(6) A
b ϭ 18.501(7) A
triclinic
¯
P 1(No. 2)
˚
˚
˚
˚
˚
Unit cell dimensions
a ϭ 7.012(5) A
b ϭ 8.686(8) A
˚
c ϭ 10.044(6) A
82.72(2)°
c ϭ 26.717(8) A
α
β
γ
81.29(2)°
68.19(2)°
3
3
˚
˚
Volume
559.7(5) A
8558(5) A
Z
2
8
Density (calculated)
Absorption coefficient
F(000)
2.183 Mg/m3
1.569 Mg/m3
6.019 mmϪ1
352
2.099 mmϪ1
3920
Crystal size
Theta range for data collection
Index ranges
0.3 x 0.14 x 0.12 mm
2.39 to 22.05°
0.2 x 0.15 x 0.12 mm
2.39 to 27.05°
0<ϭh<ϭ7, Ϫ9<ϭk<ϭ9, Ϫ10<ϭl<ϭ10
1484
0<ϭh<ϭ22, 0<ϭk<ϭ23, 0<ϭl<ϭ34
8902
Reflections collected
Independent reflections
Refinement method
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I>2σ(I)]
R indices (all data)
Largest diff. peak and hole
1353 [R(int) ϭ 0.0833]
Full-matrix least-squares on F2
1352 / 0 / 115
8901 [R(int) ϭ 0.0229]
Full-matrix least-squares on F2
8896 / 0 / 490
0.875
0.773
R1 ϭ 0.0668, wR2 ϭ 0.1192
R1 ϭ 0.0413, wR2 ϭ 0.0820
R1 ϭ 0.1816, wR2 ϭ 0.1527
R1 ϭ 0.1112, wR2 ϭ 0.0989
Ϫ3
Ϫ3
˚
˚
0.927 and Ϫ0.800 eA
0.474 and Ϫ0.408 eA
MS-data of 5: C38H30F6As2P2Pd; M ϭ 918.844 (natural isotope
distribution). m/z (rel. intensity/%) [fragment]ϩ: 920 (4), [M]ϩ, 901
(36) [M Ϫ F]ϩ, 757 (18) [M Ϫ F Ϫ AsCF3]ϩ, 720 (85) [(AsCF3)5]ϩ,
651 (98) [(AsCF3)5 Ϫ CF3]ϩ, 632 (56), [M Ϫ (AsCF3)2]ϩ, 576 (29)
[(AsCF3)4]ϩ, 507 (55) [(AsCF3)4 Ϫ CF3]ϩ, 432 (43) [(AsCF3)3]ϩ,
370 (4) [PdPPh3]ϩ, 363 (61) [(AsCF3)3 Ϫ CF3]ϩ, 262 (100) [PPh3]ϩ,
185 (9) [PPh2]ϩ, 108 (38) [PPh]ϩ, 69 (4) [CF3]ϩ. Exact [M]ϩ for
108Pd, calc.: 919.91978; exp.: 919.9182.
Preparation of the palladium complex 5
To tetrakis(triphenylphosphane)palladium(0) (1.0 g, 0.87 mmol) in
a 50 mL Schlenk vessel tetrakis(trifluoromethyl)cyclotetraarsane
(0.58 g, 1.0 mmol) and 5 mL toluene were added by vacuum con-
densation (Ϫ196 °C). After warming up to room temperature, the
reaction mixture changed colour from light yellow to dark red, in-
dicating start of a reaction. The mixture was stirred for 24 h ac-
companied by a slow colour change to yellow. All volatile compo-
nents were then removed from the resulting solution in vacuo. The
eliminated triphenylphosphane was separated from the product by
vacuum sublimation. The residue was dissolved in small amounts
of toluene, and the solvent was then partly removed in a slow
stream of dry argon gas yielding light yellow crystals for X-ray
analysis.
Attempted [2؉2]-cycloaddition reactions of 1
In view of the known difficulties to generate 1 from the precursor
(F3CAs)4 (2), all reactions of this type were carried out in sealed
NMR-tubes. The reactants 2 and (i) (F3CP)4, (ii) tBuCϵP, (iii)
MeCϵCNiPr2, (iv) HPϭC(F)NEt2, respectively, as well as benzene
as solvent were introduced into NMR-tubes equipped with bulbs
of about 15 mL volume for effective vacuum condensation at
Ϫ196 °C.
Results: (i) No reaction occurred up to 70 °C. (ii Ϫ iv): All mixtures
showed colour changes on melting and gave yellow solutions at
room temperature. At this stage of reaction 19F-NMR measure-
ments indicated the formation of product mixtures, which then with
turning colour to brown obviously underwent decomposition. Only
in case of MeCϵCNiPr2 19F-data indicated the intermediate for-
mation of the [2ϩ2]-cycloadduct.
Yield: 0.6 g, 0.65 mmol (Ph3P)2Pd(η2-F3CAsϭAsCF3), 75 %, rel.
to the starting Pd(PPh3)4.
NMR-data of 5: 1H-NMR: δH 7.0 Ϫ 7.3, m, 30H of phenyl groups;
13C{1H}-NMR: Phenyl-carbons; δC 128.7, pseudo-t, JPC
ϭ
1
2
5.0 Hz, 6C, PC(Cortho)2(Cmeta)2(Cpara); 134.1, pseudo-t, JPC
ϭ
3
7.0 Hz, 12C, PC(Co)2(Cm)2(Cp); 130.3, pseudo-t, JPC ϭ 1.0 Hz,
12C, PC(Co)2(Cm)2(Cp); 129.4, s, 6C, PC(Co)2(Cm)2(Cp); δC(CF3)
hidden behind the 13C phenyl signals; 19F{1H}-NMR: δF Ϫ30.6,
4
pseudo-t, JPF ϭ 4.3 Hz, 6F; 31P{1H}-NMR: δP 17.4, pseudo-sep-
4
tet, JPF ϭ 4.3 Hz, 2P.
Data of (Ph3P)2Pd(η2-F3CP؍PCF3) [16] for comparison: δF Ϫ37.2,
Experiments for the spectroscopic detection of 1
(i) Thermolytic cleavage of (F3CAs)4 (2)
4
4
pseudo-t, JPF ϭ 4.3 Hz, 6F; δP 22.7, pseudo-septet, JPF
ϭ
4.3 Hz, 2P.
The apparatus and the general procedure used are described in ref.
[1]. The ampoule with 2 is connected to the inlet of the pyrolysis
tube. After evacuating the apparatus thoroughly (10Ϫ3 mbar), the
oven is gradually heated while the gaseous cyclotetraarsane 2 slowly
IR-data of 5: ν/cmϪ1, (rel intensity/%), assignment: 3075 (7), 3063
(10), 2926 (33), νCH; 1439 (40), νPC; 1434 (35), νAsC; 1117 (46), 1103
(74), 1070 (56), νCF; 700 (57), 522 (44), δCF
.
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Cycloarsanes (AsCF3)n (n ϭ 4, 5)
´
flows through the hot zone and first reaches a Ϫ30 °C trap, in
which the unchanged precursor is condensed, whereas the ther-
mally generated 1 is expected to pass this trap for condensation at
Ϫ196 °C in the cooling bulb of the NMR-tube. In several experi-
ments with temperatures up to 400 °C the non-cleaved or from the
diarsene recombined starting compound is obtained in the Ϫ30 °C
trap. Only at temperatures above 400 °C undefined products of
thermal decomposition are observed. No trace of 1 was found in
the NMR-tube.
[5] C. Couret, J. Escudie, Y. Madule, H. Ranaivonjatovo, J.-G.
Wolf, Tetrahedron Lett. 1983, 24, 2769Ϫ2770.
[6] L. Weber, U. Sonnenberg, Chem. Ber. 1989, 122, 1809Ϫ1813.
[7] P. S. Elmes, P. Leverett, B. O. West, J. Chem. Soc., Chem. Com-
mun. 1971, 747Ϫ748.
[8] G. Huttner, H.-G. Schmid, A. Frank, O. Orama, Angew.
Chem. 1976, 88, 255Ϫ256; Angew. Chem. Int. Ed. Engl. 1976,
15, 234Ϫ235.
[9] C. R. Brundle, M. B. Robin, N. A. Kuebler, H. Basch, J. Am.
Chem. Soc. 1972, 94, 1451Ϫ1465.
[10] Examples for hetero-olefinic systems: J. Grobe, D. Le Van,
Angew. Chem. 1984, 96, 716Ϫ717; Angew. Chem. Int. Ed. Engl.
1984, 23, 710Ϫ711; J. Grobe, D. Le Van, J. Nientiedt, B. Krebs,
M. Dartmann, Chem. Ber. 1988, 121, 655Ϫ664; Th. Albers, J.
Grobe, D. Le Van, B. Krebs, M. Läge, Z. Naturforsch. 1995,
50b, 94Ϫ100; A. Haas, B. Koch, N. Welcman, Z. Anorg. Allg.
Chem. 1976, 427, 114Ϫ122; A. Darmadi, A. Haas, B. Koch,
Z. Naturforsch. 1980, 35b, 526Ϫ529; J. Grobe, D. Le Van, J.
Welzel, J. Organomet. Chem. 1990, 386, 321Ϫ332; R. Boese,
A. Haas, M. Spehr, Chem. Ber. 1991, 124, 51Ϫ61; A. Haas,
C. Limberg, M. Spehr, Chem. Ber. 1991, 124, 423Ϫ426; H.
Grützmacher, S. Freitag, R. Herbst-Irmer, G. M. Sheldrick,
Angew. Chem. 1992, 104, 459Ϫ461; Angew. Chem. Int. Ed.
Engl. 1992, 31, 437Ϫ439; B. Pötter, K. Seppelt, A. Simon,
E.-M. Peters, B. Heltich, J. Am. Chem. Soc. 1985, 107,
980Ϫ985; R. Gerhardt, T. Grelbig, J. Buschmann, P. Luger,
K. Seppelt, Angew. Chem. 1988, 100, 1592Ϫ1594; Angew.
Chem. Int. Ed. Engl. 1988, 27, 1534Ϫ1536.
(ii) Photochemical cleavage of 2
The volatility of 2 allows the transfer of a dilute gas phase through
a quartz reaction vessel irradiated with a 150 W OSRAM UV-lamp
to a Ϫ30 °C trap for condensing non-reacted 2 and collecting the
very volatile 1 in the succeeding Ϫ196 °C NMR-trap. This experi-
ment also failed; the starting compound was obtained either un-
changed or via recombination of 1 in the Ϫ30 °C trap.
(iii) Oxidative cleavage of the complex (Ph3P)2Pd(η2-
F3CAs؍AsCF3) (5) with hexachloroethane [23]
A NMR-tube is charged with 5 (0.2 g, 0.22 mmol) and hexachloro-
ethane (1.2 g, 5 mmol), then evacuated at Ϫ196 °C and CD2Cl2
(0.5 mL) added by vacuum condensation. After sealing the probe
is warmed to room temperature and the course of reaction is fol-
lowed by NMR control, while raising the temperature to 90 °C. In
spite of the fairly drastic conditions, the elimination and detection
of 1 was not possible.
[11] A. H. Cowley, A. B. Burg, W. R. Cullen, J. Am. Chem. Soc.
1966, 88, 3178Ϫ3179.
[12] H. Pucknat, J. Grobe, D. Le Van, B. Broschk, M. Hegemann,
B. Krebs, M. Läge, Chem. Eur. J. 1996, 2, 208Ϫ213.
[13] M. Mandel, J. Donohue, Acta Cryst. 1971, 27B, 476Ϫ480;
(iv) Attempted detection of 1 during its transfer from
4 to 2,3-dimethylbutadiene
˚
˚
d(AsϪAs) in (F3CAs)4: 2.45 A; sum of covalent radii: 2.42 A.
[14] P. S. Elmes, M.L. Scudder, B. O. West, J. Organomet. Chem.
1976, 122, 281Ϫ288.
The reaction of 4 (0.25 g, 0.7 mmol) with excess DMB (0.1 g,
1.22 mmol) [3a] was repeated in a NMR experiment with the inten-
tion, to detect 1 as intermediate. The NMR-tube was charged with
the reactants by vacuum condensation and sealed. After thawing,
the components were thoroughly mixed by shaking and the course
of the reaction was controlled in the 19F-NMR spectrum. The
transfer of 1 from the CHD-adduct to DMB occurred without de-
tectable amounts of free 1 in the mixture.
[15] A. H. Cowley, J. G. Lasch, N. C. Norman, M. Pakulski,
Angew. Chem. 1983, 95, 1019; Angew. Chem. Suppl. 1983,
1493Ϫ1502.
[16] I. G. Phillips, R. G. Ball, R. G. Cavell, Inorg. Chem. 1992,
31, 1633Ϫ1641.
[17] L. Malatesta, M. Angoletta, J. Chem. Soc. 1957, 1186Ϫ1188.
[18] R. Ugo, Coord. Chem. 1968, 3, 319Ϫ344
[19] P. Fitton, J. E. McKeon, Chem. Commun. 1968, 4Ϫ6.
[20] L. Weber, Chem. Rev. 1992, 92, 1839Ϫ1906.
Acknowledgements. Financial support by Fonds der Chemischen
Industrie, Deutsche Forschungsgemeinschaft (Graduiertenkolleg
“Hochreaktive Mehrfachbindungssysteme“) and Ministerium für
Wissenschaft und Forschung Nordrhein-Westfalen is gratefully
acknowledged.
[21] E. Breitmaier, G. Bauer, 13C-NMR-Spektroskopie, Georg
Thieme Verlag, Stuttgart, p. 80.
[22] U. Schmidt, I. Boie, C. Osterroht, R. Schröer, H. F.
Grützmacher, Chem. Ber. 1968, 101, 1381Ϫ1397.
[23] P. Binger, G. Glaser, B. Gabor, R. Mynott, Angew. Chem.
1995, 107, 114Ϫ116; Angew. Chem. Int. Ed. Engl. 1995, 34,
81Ϫ83.
[24] Gaussian 03, Revision C.01, M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A.
Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M.
Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M.
Cossi, G. Scalmani, N. Rega,G. A. Petersson, H. Nakatsuji,
M. Hada, M. Ehara, K. Toyota,R. Fukuda, J. Hasegawa, M.
Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene,
X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J.
Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K.
Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
References
[1] Th. Albers, J. Grobe, D. Le Van, A. H. Maulitz, E.-U.
Würthwein, Heteroat. Chem. 2005, 16, 406Ϫ419.
[2] Th. Albers, J. Grobe, A. H. Maulitz, E.-U. Würthwein, Z.
Anorg. Allg. Chem. 2005, 631, 1430Ϫ1438.
[3] a) A. Karst, B. Broschk, J. Grobe, D. Le Van, Z. Naturforsch.
1995, 50b, 189Ϫ195; b) J. Grobe, D. Le Van, J. Schulze, Z.
Naturforsch. 1985, 40b, 1753Ϫ1755.
[4] A. H. Cowley, J. G. Lasch, N. C. Norman, M. Pakulski, J.
Am. Chem. Soc. 1983, 105, 5506Ϫ5507.
Z. Anorg. Allg. Chem. 2006, 599Ϫ608
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
zaac.wiley-vch.de
607

J. Grobe, A. Karst, B. Krebs, M. Läge, E.-U. Würthwein
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J.
Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-
Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M.
W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and
J. A. Pople, Gaussian, Inc., Wallingford CT, 2004. Details of
the quantum chemical calculations (GAUSSIAN 03 archive
entries) may be obtained from E.-U.W. upon request.
[27] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
Refinement, Universität Göttingen (1997).
´
[28] G. R. A. Brandt, H. J. Emeleus, R. N. Haszeldine, J. Chem.
Soc. 1952, 2552Ϫ2555.
[29] G. Becker, G. Gresser, W. Uhl, Z. Naturforsch. 1981, 36b,
16Ϫ19.
[30] G. Becker, H. Schmidt, G. Uhl, W. Uhl, Inorg. Synth. 1990,
27, 249Ϫ25?.
[31] J. Grobe, D. Le Van, B. Lüth, M. Hegemann, Chem. Ber. 1990,
123, 2317Ϫ2320.
[25] Siemens Area Detector Absorption Correction, Siemens.
[26] G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
Determination, Universität Göttingen (1997).
[32] W. Mahler, A. B. Burg, J. Am. Chem. Soc. 1957, 79, 251.
[33] W. Mahler, A. B. Burg, J. Am. Chem. Soc. 1958, 80,
6161Ϫ6167.
608
zaac.wiley-vch.de
 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2006, 599Ϫ608