Reactivity of the inversely polarized arsaalkenes R-As=C(NMe 2)2 {R = [(η5-C5Me 5)(CO)2Fe], tBuC(O), 4-Et-C6H4C(O)} towards phosphavinylidene complexes [η5-

Article abstract of DOI:10.1002/ejic.200500674

The reaction of the phosphavinylidene complexes [Cp(CO)₂-M=P= C(SiMe₃)₂] [Cp = C₅H₅, M = Mo (2), W (3)] with the ferrioaarsaalkene [Cp* (CO)₂Fe-As=C(NMe ₂)₂] (1a) (Cp*

Full text of DOI:10.1002/ejic.200500674

FULL PAPER
DOI: 10.1002/ejic.200500674
Reactivity of the Inversely Polarized Arsaalkenes R–As=C(NMe2)2
{R = [(η5-C5Me5)(CO)2Fe], tBuC(O), 4-Et–C6H4C(O)} towards
Phosphavinylidene Complexes [η5-(C5H5)(CO)2M=P=C(SiMe3)2]
(M = Mo, W)
Lothar Weber,*[a] Philipp Bayer,[a] Stefan Uthmann,[a] Thomas Braun,[a]
Hans-Georg Stammler,[a] and Beate Neumann[a]
Keywords: Arsaalkenes / Heteroallyl ligands / Molybdenum / Phosphavinylidene complexes / Tungsten
The reaction of the phosphavinylidene complexes [Cp(CO)2-
M=P=C(SiMe3)2] [Cp = C5H5, M = Mo (2), W (3)] with the
ferrioaarsaalkene [Cp*(CO)2Fe–As=C(NMe2)2] (1a) (Cp* =
C5Me5) afforded the novel η3-2-phospha-1-arsaallyl com-
plexes [η3-{[Fe]–As–P–C(SiMe3)2}M(CO)2Cp] {M = Mo, [Fe] =
[Cp*(CO)2Fe] (4a);W (5a)}. Similarly, treatment of equimolar
amounts of 3 with arsaalkene tBu–C(O)–As=C(NMe2)2 (1b)
gave rise to the formation of [η3-{tBuC(O)–As–P–C(SiMe3)2}-
W(CO)2Cp] (5b) by an arsinidene transfer process. In contrast
to this, the more reactive arsaalkene 4-Et–C6H4C(O)–
As=C(NMe2)2 (1c) and complex 3 underwent reaction to give
the cyclic phosphenium complex [Cp(CO)2W=P–O–Ca(4-Et–
C6H4)=As–Cb(SiMe3)2(P–Cb)] (6). The novel compounds 4a,
5a, 5b, and 6 were characterized by elemental analyses and
by means of spectroscopy (IR, 1H, 13C, 31P NMR). Moreover,
the molecular structures of 4a, 5b, and 6 were elucidated by
X-ray diffraction analyses.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
The search for novel ligand systems remains an impor-
tant target for both academic and industrial reasons. Promi-
nent examples are N-heterocyclic carbenes, which, as ancil-
lary ligands in transition-metal complexes, have signifi-
cantly improved the efficiency of a number of catalyzed pro-
cesses.[1] Other remarkable examples concern phosphaalk-
enes, phospholyl compounds, and phosphinines, which have
recently emerged from the status of laboratory curiosities
to become valuable ligands in complex catalysis.[2] Com-
pared to a plethora of synthetically useful η3-allyl com-
plexes[3,4] only a few coordination compounds with η3-1-
phosphaallyl ligands such as I[5] or η3-1,3-diphosphaallyl
ligands such as II[6] and III[7] have been described. In the
dinuclear complexes of type IV the 1,3-diphosphaallyl unit
is incorporated in a 2,4-phospha-1-metallabutadiene ligand
(Scheme 1).[8]
Complex III exhibits catalytic activity in ethylene poly-
merization.[7] Whereas 1,2-diphosphaallyllithium com-
pounds[9] and η1-complexes of the isomeric 1,2-diphos-
Scheme 1. (Heteroallyl)transition-metal complexes.
phaallyl ligand V have been known for some years,[10]
a
paper concerning η3-complex VI was only recently pub-
lished.[11]
[a] Fakultät für Chemie der Universität Bielefeld,
Universitätsstrasse 25, 33615 Bielefeld, Germany
Fax: +49-521-106-6146
E-mail: lothar.weber@uni-bielefeld.de
Eur. J. Inorg. Chem. 2006, 137–143
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FULL PAPER
In this paper we report on the reactivity of inversely pol- spectrum. This high-field position is typical for 31P{1H} res-
arized arsaalkenes R–As=C(NMe2)2 [1: a: R = Cp*(CO)2- onances of η3-phosphaallyl complexes of tungsten as evi-
Fe, b: tBuC(O), c: 4-Et–C6H4C(O)] with phosphavinylidene dent from [η3-(2,4,6-tBu3C6H2PCHCH2)W(CO)2Cp] (δ =
complexes [Cp(CO)2M=P=C(SiMe3)2] (2: M = Mo; 3: M = –48.9 and –28.0 ppm for both isomers).[15] In the η3-1,2-
W),[12] whereby the first complexes with η3-2-phospha-1- diphosphaallyl complex VI the resonances for the central P
arsaallyl ligands are formed. Part of this work has pre- atom were observed at δ = –6.8 ppm (M = Mo, R = tBu)
viously been published in a short communication.[13]
and δ = –61.6 ppm (M = W, R = tBu).[11] In the 13C{1H}
NMR spectra of 4a, 5a, and 5b the carbon atoms of the 2-
phospha-1-arsaallyl ligands appear as doublets at δ =
49.9 ppm (JP,C = 105.0 Hz), 35.7 (JP,C = 101.2 Hz), and 31.8
(JP,C = 98.5 Hz) ppm. The 13C NMR resonances of the car-
bonyl ligands were observed at δ = 234.0 (s), 236.0 (s) (Mo–
CO); 216.7 (s), 218.65 (d, JP,C = 11.5 Hz) (Fe–CO) for 4a,
at δ = 222.7 (s), 224.6 (s) (W–CO); 217.1 (s), 219.0 (s) (Fe–
CO) for 5a, and at δ = 222.8 (s), 223.9 (s) for 5b. A 13C
NMR doublet at δ = 233.5 (JP,C = 4.1 Hz) ppm in the spec-
trum of 5b was attributed to the acylic carbonyl group.
These resonances are shifted to a lower field relative to
those of precursors 2 (δ = 230.4 ppm)[12b] and 3 (δ =
218.9 ppm)[12b] indicating the improved donor capacity of
the η3-2-phospha-1-arsaallyl ligands over the phosphavinyl-
idene system. Similar observations were made with the η3-
1,2-diphosphaallyl complexes of type VI [e.g., M = Mo, R
= tBu; δ13CO = 234.3 (s), 235.5 (s) ppm]. This is also mir-
rored by the carbonyl stretching frequencies in the IR spec-
tra of 4a, 5a, and 5b, which are observed as intense bands
at ν= 1929, 1850 cm–1 (4a), at ν= 1923, 1843 cm–1 (5a), and
Results and Discussion
Treatment of complexes [Cp(CO)2M=P=C(SiMe3)2] (2:
M = Mo; 3: M = W) with an equimolar amount of ferrioar-
saalkene [Cp*(CO)2Fe–As=C(NMe2)2] (1a)[14] in toluene
solution over a temperature range of –30 °C to ambient
temperature afforded the deep red crystalline η3-2-phospha-
1-arsaallyl complexes 4a (35% yield) and 5a (52% yield).
Purification of the products was effected by column
chromatography on Florisil with a mixture of hexane/di-
ethyl ether (2:1, v/v) (4a) or pentane/diethyl ether (5:1, v/v)
(5a) as eluents. The air- and moisture-sensitive complexes
are well soluble in saturated hydrocarbons, ethereal and
aromatic solvents. Analogously, reaction of compound 1b
with an equimolar amount of 3 gives rise to the formation
of heteroallyl complex 5b as an orange solid in 63% yield
(Scheme 2). Tetrakis(dimethylamino)ethene is formed as a
by-product. After removal of toluene from the reaction
mixture, a few drops of the alkene were distilled off and
˜
˜
at ν= 1941, 1874 cm–1 (5b). The differences between the
˜
ν(CO) absorptions of 5a and 5b are due to the electron-
donating iron substituent in 5a and the electron-with-
drawing pivaloyl group in 5b. The corresponding bands in
1
identified by comparison of the H and 13C NMR spectra
with those of an authentic sample.
the precursors 2 and 3 appear at ν= 1944, 1882 cm–1 (KBr)
˜
and 1952, 1880 cm–1 (n-hexane).[12b] In the IR spectrum of
1,2-diphosphaallyl complexes VI ν(CO) bands were regis-
tered at ν= 1943, 1877 cm–1 (M = Mo; R = tBu) and at ν=
˜
˜
1938, 1851 cm–1 (M = W; R = tBu).[11]
Single crystals of 4a and 5a suitable for an X-ray diffrac-
tion analysis were grown from a 1:9 mixture of diethyl
ether/n-pentane at –30 °C. Compound 5a is isostructural to
4a, and only the latter will be discussed in detail.
The analysis (see Figure 1) displays a molecule with a
distorted piano-stool geometry [As(1)–Mo(1)–C(20) =
63.87(7)°, C(20)–Mo(1)–C(21) = 80.83(11)°, C(21)–Mo(1)–
C(13) = 69.07(9)°], with two nearly linear carbonyl ligands
Scheme 2. Formation of the 2-phospha-1-arsaallyl complexes 4a,
5a, 5b.
[Mo(1)–C(20)–O(3)
= 170.9(2)°, Mo(1)–C(21)–O(4) =
175.7(2)°]. The most interesting part of the molecule is the
A singlet at δ = 4.1 ppm in the 31P{1H} NMR spectrum unprecedented 2-phospha-1-arsaallyl ligand which is un-
of 4a, a doublet in the 13C{1H} NMR spectrum at δ = symmetrically linked to the metal atom in an η3-fashion
49.9 ppm (JP,C = 105 Hz), and singlets in the 1H NMR through bonds Mo(1)–As(1) [2.7644(3) Å], Mo(1)–P(1)
spectrum for two different trimethylsilyl groups (δ = 0.26, [2.4940(6) Å], and Mo(1)–C(13) [2.420(2) Å]. The latter
0.61 ppm), the pentamethylcyclopentadienyl (δ = 1.46 ppm) bond length significantly exceeds the Mo(1)–C distances of
and the cyclopentadienyl ligands (δ = 5.10 ppm) as well as the [CpMo] part of the molecule [2.316(2)–2.371(2) Å]. In
the absence of resonances due to the C(NMe2)2 fragment the (1,2-diphosphaallyl)molybdenum complex VI the corre-
indicate the combination of the phosphavinylidene unit of sponding Mo–C bond length was determined to be
2 and the arsanediyl group of 1a to a novel ligand system 2.437(1) Å.[11] The distances between the Mo atom and the
in complex 4a. Accordingly, the tungsten analogue 5a and terminal carbon atom in 4a as well as in VI clearly exceed
the (pivaloylphosphaarsaallyl)tungsten complex 5b display the corresponding Mo–C bond lengths in 1-phosphaallyl
singlets at δ = –18.7 and –8.9 ppm in the 31P{1H} NMR complex VII [2.357(3) Å].[5c]
138
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Reactivity of the Inversely Polarized Arsaalkenes towards Phosphavinylidene Complexes
FULL PAPER
Si(2) in 4a are directed towards the phosphorus atom en-
closing angles Fe(1)–As(1)–P(1) [106.59(2)°], As(1)–P(1)–
C(13) [99.15(7)°], and P(1)–C(13)–Si(2) [108.67(11)°]. Sub-
stituent Si(1)(CH3)3 at C(13) is located above the plane de-
fined by the atoms As(1), P(1), and C(13) with an angle
P(1)–C(13)–Si(1) of 120.88(12)°.
From the view-point of the Wade–Mingos rules molecule
4a as well as the related compounds 5a and 5b possess four
skeleton atoms and 14 skeleton electrons and thus have to
be regarded as arachno clusters.[22] Orange single crystals
of the (η3-2-phospha-1-arsaallyl)tungsten complex 5b were
grown from diethyl ether/n-pentane (1:5) at –30 °C (see Fig-
ure 2). The analysis shows a molecule, the core of which is
similar to that of 4a with the pivaloyl substituent and the
group Si(1)Me3 directed towards the central atom P(1) of
the η3-heteroallyl ligand. The bonds As(1)–P(1) [2.269(1) Å]
and P(1)–C(8) [1.806(2) Å] within the 2-phospha-1-arsaallyl
ligand of 5b are slightly longer than in 4a. The bond As(1)–
C(15) to the carbonyl carbon atom of the pivaloyl substitu-
ent [2.063(2) Å] is markedly elongated when compared with
the As–C(O) contact in the precursor arsaalkene
[1.938(4) Å].[23] The sum of single bond radii of As and C
is 1.98 Å.[24] The formal As=C double bond of precursor
1b was elongated to 1.924(5) Å[23] [in Cp*(CO)2Fe–
As=C(NMe2)2: As–C = 1.876(8) Å].[14] The bond length
C(15)–O(3) is that of a localized carbonyl group.[24] The
atoms C(15) and Si(1) are located in the plane defined by
the atoms C(8), P(1), and As(1). These atoms are attached
to the tungsten center by bonds W(1)–As(1) [2.759(1) Å],
W(1)–P(1) [2.498(1) Å], and W(1)–C(8) [2.439(2) Å]. They
are all well comparable to those in 5a: W(1)–As(1)
[2.7854(2) Å], W(1)–P(1) [2.4955(5) Å], and W(1)–C(8)
Figure 1. Molecular structure of 4a in the crystal. Selected bond
lengths [Å] and angles [°]: Mo(1)–C(20) 1.953(2), Mo(1)–C(21)
1.959(2), Mo(1)–C(13) 2.420(2), Mo(1)–P(1) 2.4940(6), Mo(1)–
As(1) 2.7644(3), P(1)–As(1) 2.2507(7), P(1)–C(13) 1.791(2), As(1)–
Fe(1) 2.4098(4), C(13)–Si(1) 1.898(2), C(13)–Si(2) 1.895(2), C(20)–
Mo(1)–C(21) 80.83(11), C(21)–Mo(1)–C(13) 69.07(9), C(20)–
Mo(1)–As(1) 63.83(7), As(1)–P(1)–C(13) 99.15(7), P(1)–As(1)–
Fe(1) 106.59(2), P(1)–C(13)–Si(1) 120.88(12), P(1)–C(13)–Si(2)
108.67(11).
The metal–phosphorus distances in both complexes 4a
[2.4940(6) Å] and VI (M = Mo) [2.4960(3) Å] are identical,
and intermediate between the Mo–P bond lengths Mo(1,2)–
P(1) [2.466, 2.470 Å] and Mo(1,2)–P(2) [2.542, 2.546 Å] in
VIII.[16] The Mo(1)–As(1) bond in 4a is lengthened when
compared with the Mo–As contacts in tetrahedrane IX
[2.531(3), 2.645(3) Å].[17]
Due to the π-interaction with a metal atom, the As–P
distance within the 2-phospha-1-arsaallyl ligand in 4a
[2.2507(7) Å] is longer than the unsupported As=P double
bonds in the structurally characterized compounds
{(Me3Si)2CH}As=P(2,4,6-tBu3C6H2) [2.124 Å][18] or [Cp*-
(CO)2FeAs{Cr(CO)5}=P(2,4,6-tBu3C6H2)] [2.155(1) Å].[19]
The bond length P(1)–C(13) in 4a [1.791(2) Å]−as is also
found in VI (M = Mo) [1.7875(12) Å]−is elongated with
respect to a localized and unsupported P=C double bond
(1.65–1.72 Å),[20] but is clearly shorter than a P–C single
bond (av. 1.85 Å).[21] In VII the corresponding bond length
Figure 2. Molecular structure of 5b in the crystal. Selected bond
lengths [Å] and angles [°]: W(1)–C(6) 1.968(2), W(1)–C(7) 1.977(2),
W(1)–C(8) 2.439(2), W(1)–P(1) 2.498(1), W(1)–As(1) 2.759(1),
P(1)–C(8) 1.806(2), P(1)–As(1) 2.269(1), As(1)–C(15) 2.063(2),
C(8)–Si(1) 1.912(2), C(8)–Si(2) 1.922(2), O(3)–C(15) 1.214(2),
C(15)–C(16) 1.541(2), C(6)–W(1)–C(7) 80.30(8), C(6)–W(1)–C(8)
67.13(7), C(7)–W(1)–As(1) 67.62(6), C(8)–P(1)–As(1) 97.66(6),
P(1)–As(1)–C(15) 93.86(5), As(1)–C(15)–O(3) 122.37(13), O(3)–
C(15)–C(16) 122.47(16), As(1)–C(15)–C(16) 115.07(12), P(1)–C(8)–
Si(1) 107.49(9), P(1)–C(8)–Si(2) 122.05(10), Si(1)–C(8)–Si(2)
was determined to be 1.755(3) Å.[5c] The atoms Fe(1) and 114.60(9).
Eur. J. Inorg. Chem. 2006, 137–143
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139

L. Weber, P. Bayer, S. Uthmann, T. Braun, H.-G. Stammler, B. Neumann
FULL PAPER
[2.411(2) Å]. The W–As π-bonds in [η1:η2-PhAs= 200.6 ppm in MesAs=CHNMe2 to δ = 241.5 ppm in Me3Si-
AsPhW(CO)5]2 [2.728(4) and 2.769(4) Å] are similar to the As=C(OSiMe3)tBu.[30] The IR spectrum in the region of the
W–As bond length in 5b. The W–P π-bond length in η3- CO stretching modes is characterized by two intense bands
{2,4,6-tBu3C6H2–P(O)CHCH2}W(CO)2Cp [2.488(1) Å] is at ν = 1938, 1859 cm–1. No bands are found for the ν(CO)
˜
˜
also in good agreement with the respective atom distance mode of an acylarsane (e.g., ν = 1660 cm–1 in 5b). Yellow
˜
in 5b.[25] The W(1)–C(8) bond in 5b [2.439(2) Å], however, single crystals of compound 6 (Figure 3) were obtained
is markedly lengthened in comparison to those in η3-{2,4,6- from a diethyl ether solution at –30 °C. The analysis dis-
tBu3C6H2P(O)CHCH2}W(CO)2Cp [2.344(5), 2.335(4) Å].[25]
plays a molecule with a distorted piano-stool geometry
To the best of our knowledge compounds 4a, 5a, and 5b [P(1)–W(1)–C(1) 95.1(1)°, P(1)–W(1)–C(2) 96.2(1)°, C(1)–
are the first η3-2-phospha-1-arsaallyl complexes. One η1-2- W(1)–C(2) 84.6(1)°] with two nearly linear carbonyl ligands
phospha-1-arsaallyl
complex
(η5-C5Me5)(CO)2FeAs- [W(1)–C(1)–O(1) 177.8(3)°, W(1)–C(2)–O(2) 175.1(2)°].
(SiMe3)–P=C(SiMe3)2 was recently described.[26] 2-Phos-
pha-1-arsapropenes are rare compounds. To the best of our
knowledge there are two accounts in the literature of such
[27]
species. Thermolabile Ph2As–P=C(Ph)SiMe3
decom-
poses within 1 d to Ph4As2 and a diphosphabicyclobutane,
whereas tBu2As–P=C(SiMe3)2 is stable at ambient tempera-
ture.[28]
Reaction of phosphavinylidene complex 3 with the more
reactive arsaalkene 4-Et–C6H4C(O)As=C(NMe2)2 (1c) in
diethyl ether took a completely different course. Here the
cyclic phosphenium complex 6 was isolated as red crystals
in 41% yield. (Scheme 3).
Figure 3. Molecular structure of 6 in the crystal. Selected bond
lengths [Å] and angles [°]: W(1)–C(1) 1.976(3), W(1)–C(2) 1.960(3),
W(1)–P(1) 2.232(1), P(1)–O(3) 1.698(2), O(1)–C(1) 1.159(3), O(2)–
C(2) 1.164(3), O(3)–C(15) 1.372(3), C(15)–C(16) 1.472(3), As(1)–
C(15) 1.832(2), As(1)–C(8) 2.023(2), C(8)–Si(1) 1.932(3), C(8)–Si(2)
1.941(3), C(1)–W(1)–C(2) 84.6(1), C(1)–W(1)–P(1) 95.1(1), C(2)–
W(1)–P(1) 146.0(1), W(1)–P(1)–O(3) 114.2(1), W(1)–P(1)–C(8)
146.0(1), O(3)–P(1)–C(8) 99.8(1), P(1)–C(8)–As(1) 106.7(1), C(8)–
As(1)–C(15) 92.1(1), As(1)–C(15)–O(3) 118.5(2), P(1)–O(3)–C(15)
118.7(1), O(3)–C(15)–C(16) 114.5(2), As(1)–C(15)–C(16) 127.0(2).
Scheme 3. Formation of the phosphenium complex 6.
The 31P{1H} NMR spectrum of 6 displays a singlet at δ
= 313.2 ppm with 183W satellites (JP,W = 728 Hz), which
indicates the presence of a W=P double bond. The data are
comparable with the 31P NMR spectra of complexes Xa, b
(δ = 306.4 ppm; 244.8 ppm, JP,W = 604 Hz)[29] and IV (M =
Mo: δ = 304 ppm; M = W: δ = 246.8 ppm, JP,W = 638 Hz).[8]
The third leg is represented by a 1,2,4-oxaphospharsolen-
ium ligand which is linked to the metal atom through a
W=P double bond of 2.232(1) Å. The bond length lies be-
tween those in [Cp(CO)2W=POa–CMe2–CMe2–Ob(P–Ob)]
[2.181 Å][31] and Cp(CO)2W=P(tBu)2 [2.284(4) Å].[32] This
ring ligand without precedent features an As–C(15) double
bond of 1.832(2) Å, which is well comparable to the As–C
separation in the metalloarsaalkene [Cp(CO)2Fe–As=C(O-
SiMe3)tBu] [1.821(2) Å].[33] The bond length C(15)–O(3)
Both silyl groups are chemically and magnetically equiv- [1.372(3) Å] is similar to the one in the metalloarsaalkene
alent giving rise to a singlet at δ = 0.47 ppm in the 1H NMR [1.356(3) Å], both being shorter with respect to an sp2 C–O
spectrum and a singlet at δ = 1.9 ppm in the 13C{1H} NMR single bond (ca. 1.41 Å).[34] The contacts P(1)–O(3)
spectrum of the compound. A doublet of low intensity at δ [1.698(2) Å] and P(1)–C(8) [1.814(2) Å] are markedly
= 60.1 ppm (JP,C = 50.3 Hz) is due to a quaternary carbon shorter than the sum of the covalent radii (1.76 and 1.87 Å)
atom adjacent to the P atom. The two chemically and mag- but still reflect bond orders of unity. The five-membered
netically equivalent carbonyl ligands give rise to a singlet at ring is slightly puckered (sum of endocyclic angles 535°).
δ = 226.9 ppm with 183W satellites (JW,C = 183 Hz). A sing- The plane defined by the atoms P(1), O(3), and C(8) bisects
let at δ = 222.8 ppm is assigned to the 13C nucleus of an the angle C(1)–W(1)–C(2), enclosing angles of 43° with vec-
As=C double bond. This value falls in the range of δ = tor W(1)–C(1) and 41° with vector W(1)–C(2).
140
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Reactivity of the Inversely Polarized Arsaalkenes towards Phosphavinylidene Complexes
FULL PAPER
Mechanisms
Conclusions
It is conceivable that the formation of complexes 4a, 5a,
and 5b is initiated by the nucleophilic attack of the arsaalk-
ene through its As atom on the phosphorus center of pre-
cursors 2 and 3 to give adduct A. Extrusion of C(NMe2)2
would lead to intermediate B. A σ/π-type rearrangement of
B affords the final products (see Scheme 4).
Transition-metal-induced cleavages of inversely polarized
arsaalkenes to give cyclotriarsanes[35] or an η2-diarsene
complex[36] were observed. Here the smooth generation of
η3-2-phospha-1-arsaallyl complexes 4a, 5a, 5b, and complex
6 featuring the 1,2,4-oxaphospharsolenium ligand under-
lines the ability of arsaalkenes to act as convenient sources
for arsanediyl (arsinidene) units under mild conditions.
Experimental Section
General: All manipulations were performed under dry, oxygen-free
nitrogen using standard Schlenk techniques. Solvents were rigor-
ously dried with an appropriate drying agent and freshly distilled
under N2 before use. The following compounds were prepared ac-
cording to literature procedures: [Cp(CO)2M=P=C(SiMe3)2] [M =
Mo (2), W (3)],[12] [Cp*(CO)2Fe–As=C(NMe2)2] (1a),[14] Me3Si–
1
As=C(NMe2)2.[14] IR: Bruker FT-IR VECTOR 22. H-, 13C-, and
31P NMR (C6D6, room temp.): Bruker AM Avance DRX 500 (1H:
500.13 Hz; 13C: 125.75 MHz; 31P: 202.46 MHz); references: SiMe4
(1H, 13C), 85% H3PO4 (31P). Florisil (Merck), pivaloyl chloride,
and 4-ethylbenzoyl chloride were purchased commercially.
tBuC(O)As=C(NMe2)2 (1b): A solution of pivaloyl chloride (0.18 g,
1.50 mmol) in n-pentane (10 mL) was added dropwise to a chilled
solution (–30 °C) of Me3SiAs=C(NMe2)2 (0.37 g, 1.50 mmol) in n-
pentane (30 mL). A yellow precipitate separated. Stirring was con-
tinued for 30 min, and the solvent was decanted. The precipitate
was washed twice with cold n-pentane (30 mL, –30 °C) and dried
in vacuo to afford 0.27 g (69%) of 1b as a pale yellow solid. IR
Scheme 4. Proposed mechanism for the formation of 4a, 5a, and
5b.
(Nujol): ν= 1584, 1530 cm–1. 1H NMR: δ = 1.40 (s, 9 H, tBu), 2.65
˜
(s, 12 H, NCH3) ppm. 13C{1H} NMR: δ = 27.9 [s, C(CH3)3], 43.5
(s, NCH3), 49.8 [s, C(CH3)3], 210.7 (s, CN2), 240.1(s, CO) ppm.
Because of the pronounced thermolability of the compound it was
not possible to obtain reliable elemental analyses.
The formation of the functionalized phosphenium com-
plex 6 may be initiated by the nucleophilic attack of arsaal-
kene 1c through its electron-abundant arsenic atom at the
phosphorus center of 3 affording zwitterion C, which col-
lapses to phospharsirenium complex D. Incorporation of
the carbonyl group into the As–P bond of the strained ring
leads to the observed product 6 (Scheme 5).
[Cp(CO)2Mo{η3-[Cp*(CO)2Fe]AsPC(SiMe3)2}] (4a): A solution of
1a (0.76 g, 1.81 mmol) in toluene (20 mL) was added dropwise to
a well-stirred chilled solution (–30 °C) of 2 (0.72 g, 1.81 mmol) in
toluene (25 mL). It was slowly warmed to ambient temperature and
stirring was continued for 12 h. The reaction mixture was freed
from solvent and volatile components. The black residue was dis-
solved with diethyl ether (10 mL), then Florisil was added (5 g) and
the slurry was concentrated to dryness. The coated Florisil was
transferred to the top of a column (d = 1.5 cm, l = 6 cm) charged
with Florisil (20 g). A dark red zone was eluted with a 2:1 mixture
of diethyl ether/n-pentane. Removal of solvents from the eluate af-
forded 0.46 g (35%) of dark red crystalline 4a. IR (KBr): ν= 1850,
˜
1
1929, 1977 cm–1 (CϵO). H NMR: δ = 0.26 (s, 9 H, SiMe3), 0.61
(s, 9 H, SiMe3), 1.46 (s, 15 H, C5Me5), 5.10 (s, 5 H, Cp) ppm.
13C{1H} NMR: δ = 4.27 (s, SiCH3), 4.35 (s, SiCH3), 9.4 [s, C5-
(CH3)5], 49.9 (d, JP,C = 105 Hz, PCSi2), 91.2 (s, Cp), 95.6 [s,
C5(CH3)5], 216.7 (s, FeCO), 218.65 (d, JP,C = 11.5 Hz, FeCO), 234.3
(s, MoCO), 236.8 (s, MoCO) ppm. 31P{1H} NMR: δ = 4.1 (s) ppm.
C26H38AsFeMoO4PSi2 (728.44): calcd. C 42.87, H 5.26; found C
43.17, H 5.29.
[Cp(CO)2W{η3-[Cp*(CO)2Fe]AsPC(SiMe3)2}] (5a): Analogously,
the combination of 1a (0.76 g, 1.81 mmol) in toluene (20 mL) with
3 (0.89 g, 1.81 mmol) in toluene (25 mL) at –30 °C and identical
workup [Florisil, diethyl ether/n-pentane (5:1)] afforded 0.77 g
(52%) of dark red crystalline 5a. IR (KBr): ν= 1843, 1923,
˜
1
Scheme 5. Proposed mechanism for the formation of 6.
1975 cm–1 (CϵO). H NMR (C6D6): δ = 0.25 (s, 9 H, SiMe3), 0.66
Eur. J. Inorg. Chem. 2006, 137–143
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
141

L. Weber, P. Bayer, S. Uthmann, T. Braun, H.-G. Stammler, B. Neumann
FULL PAPER
Table 1. Crystal data and data collection parameters.
Compound
4a
5b
6
Empirical formula
Mr [gmol–1]
Crystal dimensions [mm]
Crystal system
Space group
a [Å]
C26H38AsFeMoO4PSi2
728.42
0.25 × 0.25 × 0.24
monoclinic
P21/n
12.9620(1)
18.3280(2)
13.7430(2)
104.2460(8)
3164.49(6)
4
C19H32AsO3PSi2W
654.37
0.28 × 0.22 × 0.22
monoclinic
P21/c
12.9170(18)
10.7550(6)
17.904(3)
93.036(13)
2483.8(6)
4
C23H32AsO3PSi2W
702.41
0.38 × 0.32 × 0.20
monoclinic
C2/c
25.798(4)
16.597(2)
15.674(3)
126.137(8)
5420.0(15)
8
b [Å]
c [Å]
β [°]
V [Å3]
Z
ρcalcd. [gcm–3]
1.529
2.047
1.750
6.150
1.722
5.643
µ [mm–1]
F(000)
θ [°]
No. refl. collected
No. refl. unique
R (int)
1480
2.95–30.00
18141
9224
0.0186
1280
3.30–30.00
87578
7234
0.0501
2752
3.02–27.50
81627
6231
0.0453
No. refl. [I Ͼ 2σ(I)]
Refined parameters
GOF
RF [I Ͼ 2σ(I)]
wRF2 [I Ͼ 2σ(I)]
∆ρmax/min [e·Å–3]
7859
336
1.035
0.0318
0.0757
0.970/–0.829
6307
253
1.061
0.0167
0.0326
0.652/–0.573
5302
287
1.141
0.0173
0.0364
0.979/–0.790
(s, 9 H, SiMe3), 1.47 (s, 15 H, C5Me5), 5.13 (s, 5 H, Cp) ppm. dissolved in diethyl ether (10 mL). Florisil (5 g) was added and the
13C{1H} NMR (C6D6): δ = 4.4 (d, JP,C = 9.2 Hz, SiCH3), 9.5 [s,
C5(CH3)5], 10.1 (s, SiCH3), 35.7 (d, JP,C = 101.2 Hz, PCSi2), 89.6
(s, Cp), 95.6 [s, C5(CH3)5], 217.1 (s, FeCO), 219.0 (s, FeCO), 222.7
(s, WCO), 224.6 (s, WCO) ppm. 31P{1H} NMR (C6D6): δ = –18.7
(s) ppm. C26H38AsFeO4PSi2W (816.35): calcd. C 38.26, H 4.49;
found C 38.68, H 4.90.
slurry was freed from solvent. The coated Florisil was transferred
onto the top of a column (d = 1.5 cm, l = 6 cm) charged with
Florisil (20 g). A red zone was eluted with pentane. Removal of
solvents in vacuo afforded 0.52 g (41%) of deep red crystalline 6.
1
IR (KBr): ν= 1859, 1938 (CϵO) cm–1. H NMR: δ = 0.47 (s, 18
˜
H, SiMe3), 1.01 (t, JH,H = 7.5 Hz, 3 H, CH3CH2), 2.30 (q, JH,H
=
7.5 Hz, 2 H, CH3CH2), 5.15 (s, 5 H, Cp), 6.87 (d, JH,H = 8.2 Hz,
2 H, Ph), 7.77 (d, JH,H = 8.2 Hz, 2 H, Ph) ppm. 13C{1H} NMR: δ
= 1.9 (s, SiMe3), 15.4 (s, CH3CH2), 29.2 (s, CH3CH2), 60.1 [d, JP,C
= 60.3 Hz, C(SiMe3)2], 89.6 (s, Cp), 124.4 (s, Ph), 128.3 (s, Ph),
128.7 (s, Ph), 147.4 (s, Ph), 222.8 (s, As=C), 226.9 (s, JW,C = 183 Hz,
CϵO) ppm. 31P{1H} NMR: δ = 313.2 (JP,W = 728 Hz) ppm.
C23H32AsO3PSi2W (702.42): calcd. C 39.33, H 4.59; found C 39.47,
H 4.69.
[Cp(CO)2W{η3-{tBuC(O)}AsPC(SiMe3)2}] (5b): A chilled solution
(–30 °C) of arsaalkene 1b (1.81 mmol) in diethyl ether (20 mL) was
added dropwise to a well-stirred cold solution (–30 °C) of complex
3 (0.89 g, 1.81 mmol) in diethyl ether (25 mL). Stirring at –30 °C
was continued for 4 h before the reaction mixture was slowly
warmed to room temp. After 12 h of stirring, solvent and volatile
components were removed in vacuo. The black residue was dis-
solved in diethyl ether (10 mL). Florisil (5 g) was added and the
slurry was concentrated to dryness. As described earlier, the crude
material was chromatographed on a Florisil column (d = 1.5 cm, l
= 6 cm) charged with Florisil (20 g). An orange-red zone was eluted
with a diethyl ether/pentane mixture (5:1). Removal of solvents
from the eluate afforded 0.75 g (63%) of orange crystalline 5b. IR
X-ray Crystallography: Crystallographic data were collected with a
Nonius Kappa CCD diffractometer with Mo-Kα (graphite mono-
chromator, λ = 0.71073 Å) at 100 K. Crystallographic programs
used for the structure solution and refinement were SHELXS-
97,[37] SIR-97,[38] and SHELXL-97.[37] The structures were solved
by direct methods and were refined by using full-matrix least
squares on F2 of all unique reflections with anisotropic thermal
parameters for all non-hydrogen atoms. Hydrogen atoms were in-
cluded at calculated positions with U(H) = 1.2 Ueq for CH2 groups,
U(H) = 1.5 Ueq for CH3 groups. Crystal data for the compounds
are listed in Table 1. CCDC-250373 (4a), -279437 (5b), and -279438
(6) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_requ-
est/cif.
(KBr): ν= 1941, 1874 (CϵO), 1660 (C=O) cm–1. 1H NMR: δ =
˜
0.16 (d, JP,H = 1.6 Hz, 9 H, SiMe3), 0.45 (s, 9 H, SiMe3), 1.05 (s, 9
H, tBu), 4.96 (s, 5 H, Cp) ppm. 13C{1H} NMR: δ = 4.0 (d, JP,C
9.7 Hz, SiCH3), 8.5 (s, SiCH3), 26.2 [s, C(CH3)3], 31.8 [d, JP,C
=
=
98.5 Hz, C(SiMe3)2], 50.1 [s, C(CH3)3], 90.1 (s, Cp), 222.8 (s,
WCO), 223.9 (s, WCO), 233.53 (d, JP,C = 4.1 Hz, AsCO) ppm.
31P{1H} NMR: δ = –8.9 (s) ppm. C19H32AsO3PSi2W (654.38):
calcd. C 34.87, H 4.93; found C 34.82, H 4.92.
[Cp(CO)2W=POCa(4-Et–C6H4)=AsCb(SiMe3)2(P–Cb)] (6): A solu-
tion of 4-ethylbenzoyl chloride (0.61 g, 3.62 mmol) in diethyl ether
(10 mL) was added dropwise to a chilled solution (–30 °C) of Me3S-
iAs=C(NMe2)2 (0.89 g, 3.62 mmol). Stirring was continued for
30 min to give 1c. A solution of complex 3 (0.89 g, 1.81 mmol) in
diethyl ether (20 mL) was slowly added with vigorous stirring. It
was slowly warmed to room temp. and stirring was continued for
12 h. It was concentrated to dryness and the black residue was
[1]
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142
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Eur. J. Inorg. Chem. 2006, 137–143

Reactivity of the Inversely Polarized Arsaalkenes towards Phosphavinylidene Complexes
FULL PAPER
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Received: July 28, 2005
Published Online: November 10, 2005
Eur. J. Inorg. Chem. 2006, 137–143
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
143