Arsaalkenes R-As=C(NMe2)2 [R = PhC(O), 4-EtC 6H4C(O), 2,4,6-Me3C6H 2C(O), tBuC(O), Me3Si]: Versatile reagents in the chemistry of heterocumulenes

Article abstract of DOI:10.1021/om051084t

Reaction of [Cp(CO)₂M=P=C(SiMe₃)₂] (where M = Mo (3a), W (3b)] with 2 equiv of the arsaalkene PhC(O)As=C(NMe ₂)₂ afforded the metalloarsaalkenes Cp(CO) ₂M-As=C(Ph)-O-P-O-C(Ph)=As-C(SiMe₃)₂ [where M= Mo (6a), W (6b)]. Small amounts of [η³3:η³- (Me₃Si)₂CPAs-AsPC(SiMe₃)₂}-{Mo(CO) ₂Cp}₂] (7) were formed as a minor product. Similarly, 3b and 2 equiv of 4-EtC₆H₄C(O)As=C(NMe₂) ₂ gave rise to the formation of [Cp(CO)₂W-As=C(4-EtC ₆H₄)-O-P-O-C(4-EtC₆H₄)=As- C(SiMe₃)₂] (8). However, treatment of 3a and 3b with an excess of tBuC(O)As=C(NMe₂)₂ yielded cocrystals of the η³-2-phospha-1,3-diarsaallyl complexes [Cp(CO) ₂M{η³-tBuC(O)AsPAsC(O)tBu}] [where M = Mo (13a), W (13b)] and the η³-1,2,3-triarsaallyl complexes [Cp(CO) ₂M{η³-/BuC(O)AsAsAsC-(O)tBu}] [where M = Mo (14a), W (14b)] in varying ratios. Reaction of 3a with Me₃SiAs=C(NMe ₂)₂ afforded the dinuclear 1,2-diphosphapropene complex [η²:η²-(Me₃Si)₂C=P-P(H)-C(H) (SiMe₃)₂}{Mo-(CO)₂Cp}₂] (15). The novel compounds 6a,b, 8, 13a,b, 14a,b. and 15 were characterized by means of spectroscopy (IR and ¹H, ¹³C{¹H}, ³¹P NMR). Moreover the molecular structures of 7, 8, 13a, 14a, 13b, 14b, and 15 were determined by X-ray diffraction analyses.

Full text of DOI:10.1021/om051084t

1786
Organometallics 2006, 25, 1786-1794
Arsaalkenes R-AsdC(NMe2)2 [R ) PhC(O), 4-EtC6H4C(O),
2,4,6-Me3C6H2C(O), tBuC(O), Me3Si]: Versatile Reagents in the
Chemistry of Heterocumulenes
Lothar Weber,* Philipp Bayer, Thomas Braun, Hans-Georg Stammler, and Beate Neumann
Fakulta¨t fu¨r Chemie der UniVersita¨t Bielefeld, UniVersita¨tsstrasse 25, D-33615 Bielefeld, Germany
ReceiVed December 21, 2005
Reaction of [Cp(CO)2MdPdC(SiMe3)2] (where M ) Mo (3a), W (3b)] with 2 equiv of the arsaalkene
PhC(O)AsdC(NMe2)2 afforded the metalloarsaalkenes Cp(CO)2M-AsdC(Ph)-O-P-O-C(Ph)dAs-
C(SiMe3)2 [where M) Mo (6a), W (6b)]. Small amounts of [{η3:η3-(Me3Si)2CPAs-AsPC(SiMe3)2}-
{Mo(CO)2Cp}2] (7) were formed as a minor product. Similarly, 3b and 2 equiv of 4-EtC6H4C(O)Asd
C(NMe2)2 gave rise to the formation of [Cp(CO)2W-AsdC(4-EtC6H4)-O-P-O-C(4-EtC6H4)dAs-
C(SiMe3)2] (8). However, treatment of 3a and 3b with an excess of tBuC(O)AsdC(NMe2)2 yielded
cocrystals of the η3-2-phospha-1,3-diarsaallyl complexes [Cp(CO)2M{η3-tBuC(O)AsPAsC(O)tBu}] [where
M ) Mo (13a), W (13b)] and the η3-1,2,3-triarsaallyl complexes [Cp(CO)2M{η3-tBuC(O)AsAsAsC-
(O)tBu}] [where M ) Mo (14a), W (14b)] in varying ratios. Reaction of 3a with Me3SiAsdC(NMe2)2
afforded the dinuclear 1,2-diphosphapropene complex [{η2:η2-(Me3Si)2CdP-P(H)-C(H)(SiMe3)2}{Mo-
(CO)2Cp}2] (15). The novel compounds 6a,b, 8, 13a,b, 14a,b, and 15 were characterized by means of
spectroscopy (IR and 1H, 13C{1H}, 31P NMR). Moreover the molecular structures of 7, 8, 13a, 14a, 13b,
14b, and 15 were determined by X-ray diffraction analyses.
Scheme 1. Metal-Assisted Cleavage of the AsdC Bond of
Introduction
Arsaalkenesa
During the course of our studies on arsaalkenes1 R-Asd
C(NMe2)2 [R ) Cp*(CO)2Fe, HB(3,5-Me2HC3N2)3(CO)2-
MtC; M ) Mo, W] we observed a facile metal-assisted
cleavage of the AsC multiple bond and the generation of η2-
diarsene complexes 12 or cyclotriarsanes 23 as the result of a
formal dimerization or trimerization of arsanediyls (RAs)
(Scheme 1).
Recently, we described the generation of η3-2-phospha-1-
arsaallyl complexes 4a-d by the formal transfer of arsanediyl
units from arsaalkenes onto the organophosphorus ligand of
phosphavinylidene complexes 3a,b (Scheme 2).4
In contrast to the reactivity of the pivaloylarsaalkene the
employment of the related p-ethylbenzoylarsaalkene 4-EtC6H4C-
(O)-AsdC(NMe2)2 gave rise to the formation of the cyclic
phosphenium complex 5 (Scheme 3).4
Considering these unexpected results, it was obvious to study
the reactivity of organocarbonyl-functionalized arsaalkenes
toward metallo-heterocumulenes 3a and 3b in more detail.
a
[Fe] ) Cp*(CO)2Fe; [M] ) [HB(3,5-Me3HC3N2)3M(CO)2],
M ) Mo, W.
Scheme 2. Formation of 2-Phospha-1-arsaallyl Complexes
4a
Results and Discussions
Treatment of complexes [Cp(CO)2MdPdC(SiMe3)2] (3a, M
) Mo; 3b, M ) W)5 with 2 equiv of freshly prepared arsaalkene
PhC(O)AsdC(NMe2)2 in diethyl ether solution over a temper-
(1) Review: Weber, L. Chem. Ber. 1996, 129, 367.
(2) Weber, L.; Scheffer, M.-H.; Stammler, H.-G., Neumann, B. Inorg.
Chim. Acta 1999, 291, 311.
(3) Weber, L.; Dembeck, G.; Lo¨nnecke, P.; Stammler, H.-G.; Neumann,
B. Organometallics 2001, 20, 2288.
(4) Weber, L.; Bayer, P.; Uthmann, S.; Braun, T.; Stammler, H.-G.;
Neumann, B. Eur. J. Inorg. Chem. 2006, 137.
a
R ) tBuC(O), M ) Mo (a), W (b); R ) Cp*(CO)2Fe, M ) Mo
(c), W (d).
ature range of -30 to 20 °C afforded the yellow microcrystalline
metalloarsaalkenes 6a (80%) and 6b (75%) (Scheme 4).
10.1021/om051084t CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/18/2006

Arsaalkenes R-AsdC(NMe2)2
Scheme 3. Formation of Complex 5
Organometallics, Vol. 25, No. 7, 2006 1787
Scheme 5. Formation of Spiro Compound 8
Scheme 4. Reaction of Phosphavinylidene Complexes 3a,b
with PhC(O)AsdC(NMe2)2
Scheme 6. Formation of 2-Phospha-1-arsaallyl Complex 10
Isolation of the products was effected by column chroma-
tography on Florisil with a 1:1 mixture of pentane/diethyl ether
as eluent. Subsequent crystallization furnished analytically pure
compounds. In the case of the reaction of the molybdenum
complex 3a with PhC(O)AsdC(NMe2)2 a few crystals of a
second product, 7, were isolated from the mother liquor (Scheme
4).
If a 1:1 stoichiometry was used in the reaction of 3a and the
arsaalkene, only compound 6a was formed as a product and
half of the precursor 3a remained unaffected. This is in contrast
to the reaction of 3b with an equimolar amount of arsaalkene
4-EtC6H4C(O)AsdC(NMe2)2, where phosphenium complex 5
was formed as red crystals in 41% yield (Scheme 3).4
Analogously to the synthesis of spiro compound 6b, treatment
of 3b with 2 equiv of 4-EtC6H4C(O)AsdC(NMe2)2 under
comparable conditions led to the formation of spiro compound
8 as yellow crystals in 71% yield. In a control reaction equimolar
amounts of 5 and 4-EtC6H4C(O)AsdC(NMe2)2 were combined.
After 12 h of stirring at 20 °C the 31P NMR spectrum of the
reaction mixture showed only the singlet resonance for com-
pound 8 (Scheme 5).
The outcome of the reaction between phosphavinylidenes 3a,b
and inversely polarized arsaalkenes is sensitively governed by
the nature of the substituent at the arsenic atom. Thus an increase
of the steric demand of this substituent on going from benzoyl
and 4-ethylbenzoyl derivatives to MesC(O)AsdC(NMe2)2 pro-
vides a situation where heterocyclic ligands are no longer formed
by CO incorporation. Instead treatment of 3b with 1 equiv of
the arsaalkene generated the labile phosphenium complex 9,
which in solution rearranged during a few hours to the
2-phospha-1-arsaallyl complex 10. Rearrangement was also
achieved during column chromatography of freshly prepared 9
on Florisil, whereby pure 10 was obtained as orange crystals in
54% yield (Scheme 6). Phosphenium complex 11, analogous
to 5, was not observed in this process.
The 31P{1H} NMR spectra of 6a, 6b, and 8 shows singlets
at δ 258.0, 219.4, and 218.5 ppm, the latter with 183W satellites
(JPW ) 411 and 414 Hz, respectively), indicating the presence
of a coordinative W-P bond. The silyl groups in 6a, 6b, and 8
are chemically and magnetically nonequivalent, giving rise to
two discrete singlets in the 1H NMR spectra at δ 0.36 s, 0.51 s
(6a); 0.36 s, 0.54 s (6b); and 0.40 s, 0.57 s (8) and to two singlets
in the 13C{1H} NMR spectra at δ 3.0 s, 4.3 s (6a); 2.7 s, 4.0 s
(6b); and 3.1 s, 4.4 s (8) ppm. Low-intensity doublets at δ 44.5
(1JPC ) 22.1 Hz) (6a), 43.1 (1JPC ) 13.8 Hz) (6b), and 42.9
(1JPC ) 13.5 Hz) (8) are due to the quarternary carbon atom
adjacent to the P atom. The two chemically and magnetically
nonequivalent carbonyl ligands give rise to doublets at δ 229.5
(2JPC ) 5.8 Hz), 242.5 (2JPC ) 23.0 Hz) (6a); 218.8 (2JPC
)
9.2 Hz), 231.7 (2JPC ) 15.2 Hz) (6b); and 219.4 (2JPC ) 10.8
Hz), 232.4 (2JPC ) 14.8 Hz) (8).
The resonances are shifted to lower fields relative to those
of precursors 3a (δ 230.4 ppm) and 3b (δ 218.9 ppm), indicating
the improved donor capacity of the κ(As,P) arsaalkenyl-
phosphine chelating ligands over the phosphavinylidene system.
2
2
Doublets at δ 204.6 (d, JPC ) 14.9 Hz), 217.9 (d, JPC
)
2
2
8.0 Hz) (6a); 203.4 (d, JPC ) 15.2 Hz), 218.0 (d, JPC ) 9.7
2
2
Hz) (6b); and 204.2 (d, JPC ) 16.2 Hz), 218.5 (d, JPC ) 6.8
Hz) (8) are attributed to the tricoordinate carbon atoms of the
two different AsdC double bonds of the spiro compounds.
These values fall in the typical range for δ(AsdC) of δ 200.6
ppm in MesAsdC(H)NMe2 to δ 241.5 ppm in Me3SiAsd
C(OSiMe3)tBu.1 The IR spectra of 6a, 6b, and 8 in the region
of the CO stretching modes are dominated by two intense bands
at ν˜ 1941, 1885 cm-1 (6a); 1938, 1874 cm-1 (6b); and 1941,
1874 cm-1 (8). The absence of bands for the ν(CO) mode of
an acylarsane (ca. 1650 cm-1) agrees with the incorporation of
this function into the spiro ligand of 6a, 6b, and 8.
(5) (a) Arif, A. M.; Cowley, A. H.; Nunn, C. M.; Quashie, S.; Norman,
N. C.; Orpen, A. G. Organometallics 1989, 8, 1878. (b) Niecke, E.;
Metternich, H.-J.; Nieger, M.; Gudat, D.; Wenderoth, P.; Malisch, W.;
Hahner, C.; Reich, W. Chem. Ber. 1993, 126, 1299.
Identification of intermediate 9 was limited to the observation
of a 31P NMR resonance at δ 264 ppm (1JPW ) 565 Hz).

1788 Organometallics, Vol. 25, No. 7, 2006
Weber et al.
Figure 2. Molecular structure of 7 in the crystal. Selected bond
lengths [Å] and angles [deg]: Mo(1)-C(6) 1.943(5), Mo(1)-C(7)
1.969(6), Mo(1)-C(8) 2.444(5), Mo(1)-P(1) 2.491(1), Mo(1)-
As(1) 2.755(1), P(1)-As(1) 2.260(1), P(1)-C(8) 1.784(5), As(1)-
As(1A) 2.468(1), C(8)-Si(1) 1.908(5), C(8)-Si(2) 1.902(5); C(6)-
Mo(1)-C(7) 80.4(2), C(7)-Mo(1)-C(8) 69.2(2), C(6)-Mo(1)-
As(1) 65.24(17), As(1)-P(1)-C(8) 101.80(17), P(1)-As(1)-
As(1A) 90.51(4), P(1)-C(8)-Si(1) 108.3(2), P(1)-C(8)-Si(2)
121.3(3).
Figure 1. Molecular structure of 8 in the crystal. Selected bond
lengths [Å] and angles [deg]: W(1)-C(1) 1.966(3), W(1)-C(2)
1.962(3), W(1)-C(3-7) 2.323(3)
- 2.352(3), W(1)-P(1)
2.3790(8), W(1)-As(2) 2.6547(3), As(2)-C(24) 1.825(3), O(4)-
C(24) 1.383(3), C(24)-C(25) 1.466(4), P(1)-O(4) 1.649(2), P(1)-
O(3) 1.671(2), P(1)-C(8) 1.804(3), As(1)-C(8) 2.035(3), As(1)-
C(15) 1.820(3), C(15)-O(3) 1.374(4), C(8)-Si(1) 1.945(3), C(8)-
Si(2) 1.919(3), C(15)-C(16) 1.474(4); C(1)-W(1)-C(2) 75.6(1),
C(1)-W(1)-As(2) 70.7(1), P(1)-W(1)-As(2) 74.24(2), P(1)-
W(1)-C(2) 81.0(1), W(1)-As(2)-C(24) 102.8(1), As(2)-C(24)-
O(4) 120.6(2), As(2)-C(24)-C(25) 127.4(2), O(4)-C(24)-C(25)
112.1(3), W(1)-P(1)-O(4) 114.9(1), W(1)-P(1)-O(3) 108.6(1),
O(3)-P(1)-O(4) 99.5(1), P(1)-O(3)-C(15) 114.9(2), P(1)-O(4)-
C(24) 114.4(2), O(3)-P(1)-C(8) 99.2(1), W(1)-P(1)-C(8)
131.8(1), P(1)-C(8)-As(1) 101.9(1), C(8)-As(1)-C(15) 90.9(1),
As(1)-C(15)-O(3) 118.5(2), As(1)-C(15)-C(16) 127.5(2), O(3)-
C(15)-C(16) 113.9(3), W(1)-C(1)-O(1) 175.9(3), W(1)-C(2)-
O(2) 176.0(3).
elongated relative to the W-As σ-bond in complex 12
[2.622(4) Å].6
Repulsion between the lone pair of electrons at As(2) and
the electron-rich W atom may be responsible for the bond
lengthening in 8. The W-P bond length corresponds to values
typical for the coordinative W-P bonds7-9 [e.g., 2.385(2) Å in
Cp(CO)2WCH2P(Ph)N(SiMe3)2].7 This novel chelating ligand
features the double bond As(2)-C(24) [1.820(3) Å] of a
metalloarsaalkene unit and a second double bond As(1)-C(15)
[1.821(3) Å] within the 1,2,4-oxaphosphaarsolene ring. These
values are well comparable to the AsC separation in complex
5 [1.832(2) Å]4 or in the ferrioarsaalkene Cp(CO)2Fe-Asd
C(OSiMe3)tBu [1.821(2) Å].10 The bond lengths C(15)-O(3)
[1.374(4) Å] and C(24)-O(4) [1.383(3) Å] are similar to that
in 5 [1.372(3) Å] or in the ferrioarsaalkene [1.356(3) Å], all of
them being shorter with respect to an sp2 C-O single bond
(ca. 1.41 Å).11 The contacts P(1)-O(3) [1.671(2) Å], P(1)-
O(4) [1.649(2) Å], and P(1)-C(8) [1.804(3) Å] are markedly
shorter than the sum of the covalent radii (1.76 and 1.87 Å)12
but still reflect bond orders of unity. The five-membered ring
is slightly puckered (sum of endocyclic angles 525.3°). The same
is true for the metallaheterocycle (sum of endocyclic angles
526.8°). The plane defined by the atoms P(1), O(3), and C(8)
and the plane defined by the atoms W(1), P(1), and O(4) are
oriented nearly perpendicularly to each other (ψ ) 94.3°).
A few yellow crystals of 7 were isolated from the mother
liquor after removal of 6a and subjected to an X-ray diffraction
analysis (Figure 2, Table 1).
Compound 10 features a 31P NMR absorption at δ -18.2, which
is similar to that in η3-2-phospha-1,3-diarsaallyl complex 4b
(δ -18.7 ppm). The carbon atom of the heteroallylic ligand
was observed as a doublet at δ 29.1 ppm (1JPC ) 103.7 Hz) in
the 13C{1H} NMR spectrum of 10. Singlet resonances at δ 221.9,
223.2 ppm and a doublet at δ 235.9 ppm (2JPC ) 3.8 Hz) are
due to carbonyl ligands and the CO unit of the mesitoyl
substituent. In the region of the carbonyl stretching vibrations
of the IR spectrum of 10 intense bands at ν˜ ) 1937, 1860, and
1654 cm-1 are assigned to these groups.
Yellow crystals of 8 suitable for an X-ray diffraction analysis
were grown from a 2:1 mixture of diethyl ether/pentane at -30
°C. The analysis (Figure 1, Table 1) displays a molecule with
a distorted four-legged piano-stool geometry [C(1)-W(1)-C(2)
75.6(1)°, C(1)-W(1)-As(2) 70.7(1)°, P(1)-W(1)-C(2)
81.0(1)°, P(1)-W(1)-As(2) 74.24(2)°] with two nearly linear
carbonyl ligands [W(1)-C(1)-O(1) 175.9(3)°, W(1)-C(2)-
O(2) 176.6(3)°]. The remaining two legs are represented by a
2-[3′-arsavin-diyl-oxy]-1,2,4-oxaphosphaarsolene, which is chelat-
ing the metal atom through bonds W(1)-As(2) [2.6547(3) Å]
and W(1)-P(1) [2.3790(8) Å]. The W-As bond is slightly
(6) Lang, H.; Huttner, G.; Sigwarth, B.; Weber, U.; Zsolnai, L.; Jibril,
I.; Orama, O. Z. Naturforsch. 1986, B41, 191.
(7) Reisacher, H. U.; Duesler, E. N.; Paine, R. T. J. Organomet. Chem.
1997, 539, 37.
(8) Malisch, W.; Gru¨n, K.; Hirth, U.-A.; Noltemeyer, M. J. Organomet.
Chem. 1996, 513, 31.
(9) Malisch, W.; Gru¨n, K.; Fried, A.; Reich, W.; Schmeusser, M.; Weis,
U.; Abd El Baky, C.; Kru¨ger, C. Z. Naturforsch. 1998, B53, 1506.
(10) Weber, L.; Meine, G.; Boese, R.; Bungardt, D. Z. Anorg. Allg. Chem.
1987, 549, 73.
(11) Schubert, U. In Transition Metal Carbene Complexes; Verlag
Chemie: Weinheim, 1983; p 77.
(12) Holleman-Wiberg. Lehrbuch der Anorganischen Chemie, 91st-
100th ed.; Berlin, 1985; p 133.

Arsaalkenes R-AsdC(NMe2)2
Organometallics, Vol. 25, No. 7, 2006 1789
Table 1. Crystallographic Data and Data Collection Parameters
7
8
13a/14a
13b/14b
15
empirical
formula
C28H46As2Mo2-
O4P2Si4
C32H41As2O4PSi2W
C17H23As2.60MoO4P0.4
C17H23As2.19O4P0.81
W
C28H48Mo2O4P2Si4
C17H23As2.63MoO4P0.37
595.13
+ C4H10O
738.48
M [g mol-1
]
962.67
910.49
814.84
cryst dimens
[mm3]
cryst syst
space group
a [Å]
0.22 × 0.14 × 0.02
0.56 × 0.11 × 0.10
0.30 × 0.16 × 0.10
0.26 × 0.23 × 0.10
0.28 × 0.24 × 0.24
monoclinic
P21/c
16.5420(11)
8.0480(5)
16.5900(9)
90
119.130(3)
90
1929.3(2)
2
triclinic
P1h
monoclinic
P21/c
15.8980(2)
21.8910(3)
12.3770(2)
90
96.3930(8)
90
4280.70(11)
8
triclinic
P1h
triclinic
P1h
10.2900(10)
13.5890(2)
14.1740(2)
96.8760(8)
111.0810(8)
104.9750(9)
1736.08(4)
2
12.0100(1)
14.6750(2)
15.4320(3)
105.7670(7)
91.9150(10)
95.0430(9)
2602.71(7)
4
10.6460(12)
11.9980(12)
15.5100(11)
76.572(8)
84.597(6)
71.855(9)
1830.6(3)
2
b [Å]
c [Å]
R [deg]
â [deg]
γ [deg]
V [Å3]
Z
dcalcd
1.657
1.742
1.847
1.885
1.478
[g cm-3
]
µ [mm-1
F(000)
]
2.590
964
5.368
896
4.671
2329
7.278
1430
0.933
836
θ [deg]
3.51-27.47
3.05-25.00
3.05-25.00
2.96-30.00
2.01-30.00
no. reflns
collected
no. reflns
unique
27 392
50 109
14 891
64 083
92 096
4359
6096
7515
14 709
10 661
R(int)
0.111
3108
0.040
5728
0.117
6539
0.050
12183
0.0324
9155
no, reflns
[(I) > 2σ(I)]
refined
190
387
459
565
553
params
GOF
1.023
1.034
1.023
1.017
1.072
R1 [I > 2σ(I)]
wR2 [all data]
∆F max./min.
0.0478
0.1100
0.999/-0.678
0.0209
0.0510
1.539/-0.778
0.0227
0.0516
0.437/-0.460
0.0308
0.0758
2.299/-1.948
0.0206
0.0428
0.481/-0.453
[e Å-3
]
remarks
2 molecules in the
2 molecules in the
asymmetric unit, which
differ in the occupation
factor of As/P disorder
(60:40; 63:37)
asymmetric unit, which
differ in the occupation
factor of As/P disorder
(89:11; 73:27)
The structure determination of 7 revealed a dinuclear complex
featuring an η3:η3-2,5-diphospha-3,4-diarsa-diallyl ligand with
an inversion center in the middle of single bond As(1)-As-
(1A) [2.468(1) Å]. Both phosphaarsaallyl halves are oriented
in parallel planes, which are separated by 0.8189 Å. Bond
lengths As(1)-P(1) [2.260(1) Å], P(1)-C(8) [1.784(5) Å],
Mo(1)-As(1) [2.755(1) Å], Mo(1)-P(1) [2.491(1) Å], and
Mo(1)-C(8) [2.444(5) Å] are in excellent agreement with the
corresponding data in mononuclear 4c [2.2507(7), 1.791(2),
2.7644(3), 2.4940(6), and 2.420(2) Å].4 The fragment [Cp-
Mo(1)(CO)2] is located above the plane defined by the atoms
As(1)-P(1)-C(8), whereas unit [CpMo(1A)(CO)2] is placed
underneath the plane formed by the atoms As(1A)-P(1A)-
C(8A). The valence angles As(1)-P(1)-C(8) [101.80(17)°] and
P(1)-C(8)-Si(1) [108.3(2)°] are also similar to those in 4c
[99.15(7)°, 108.67(11)°]. The angle at the arsenic atom in 7
[90.51(4)°] is much smaller than in 4c [106.59(2)°], where the
arsenic atom is ligated to iron.
We previously described the reaction between equimolar
amounts of 3b and of the pivaloylarsaalkene tBuC(O)Asd
C(NMe2)2, where the 2-phospha-1-arsaallyl complex [Cp-
(CO)2W{η3-tBuC(O)AsPC(SiMe3)2}] (4b) was isolated in 63%
yield.4 The situation changes significantly when the experiment
was conducted with twice the molar amount of arsaalkene under
otherwise comparable conditions. Here complex 4b was isolated
in only 22% yield from the first orange-red zone of the Florisil-
loaded column. From the second deep-red zone we isolated dark
red crystals, whichsaccording to an X-ray analysisswere
disclosed as an inseparable 81:19 mixture of the η3-2-phospha-
1,3-diarsaallyl complex 13b and η3-1,2,3-triarsaallyl complex
14b. Assuming that an even greater excess of the arsaalkene
would furnish the η3-triarsaallyl complex as the sole product,
phosphavinylidene complex 3b was treated with a 10-fold
amount of the arsaalkene. In this case the heteroallyl complex
[Cp(CO)2W{η3-tBuC(O)AsPC(SiMe3)2}] (4b) was no longer
formed. Purification by column chromatography afforded dark
red crystals of a 35:65 mixture of [Cp(CO)2W{η3-tBuC(O)-
AsPAsC(O)tBu}] (13b) and [Cp(CO)2W{η3-tBuC(O)AsAsAsC-
(O)tBu}] (14b) (Scheme 7).
Analogously, reaction of 3a with a 10-fold excess of
arsaalkene gave a 38:62 mixture of [Cp(CO)2Mo{η3-tBuC(O)-
AsPAsC(O)tBu}] (13a) and [Cp(CO)2Mo{η3-tBuC(O)AsAsAs-
C(O)tBu}] (14a). Medium-intense bands in the IR spectra of
the mixed crystals 13a/14a and 13b/14b at 1660 and 1690 cm-1
are due to the ν(CO) vibration of the pivaloyl functions at the
arsenic atoms. The CO-stretching modes of the terminal
carbonyls in 13a/14a and 13b/14b are observed at 1953 and
1997 cm-1 as broad intense bands. In the 13C{1H} spectra of
13a/14a, doublets at δ 231.2 (2JPC ) 4.6 Hz), 231.4 (2JPC
)
2
5.8 Hz), and 235.9 ppm (d, JPC ) 5.8 Hz) are assigned to the
two different carbonyl ligands and the acyl function at arsenic
of 13a. In the triarsaallyl complex the CO ligands give rise to
singlets at δ ) 226.9 and 233.6 ppm, whereas a singlet at 235.7
ppm is due to the acyl groups. In the 13C{1H} NMR spectrum
of cocrystallizing 13b and 14b a similar situation is observed.
The 31P{1H} NMR spectra of 13a and 13b show singlets at δ
5.8 and 9.4 ppm or δ -54.4 and -61.6 ppm.

1790 Organometallics, Vol. 25, No. 7, 2006
Weber et al.
Scheme 7. Reaction of 3a,b with RAsdC(NMe2)2 (R )
tBuCO)
Figure 4. Molecular structure of 13a/14a in the crystal. Selected
bond lengths [Å] and angles [deg]: Mo(1)-C(6) 2.011(3),
Mo(1)-C(7) 2.004(3), Mo(1)-As(1) 2.6586(4), Mo(1)-As(2)
2.682(7), Mo(1)-As(3) 2.6848(4), As(1)-C(8) 2.030(3), As(3)-
C(13) 2.028(3), C(8)-O(3) 1.206(3), C(13)-O(4) 1.211(3),
As(1)-As(2) 2.382(6), As(2)-As(3) 2.337(8), Mo(1)-P(2)
2.60(3), As(1)-P(2) 2.24(3), As(3)-P(2) 2.35(3). C(6)-Mo(1)-
C(7) 84.4(1), C(6)-Mo(1)-As(3) 86.9(1), C(7)-Mo(1)-As(1)
85.4(1), As(1)-Mo(1)-As(3) 67.94(1), C(8)-As(1)-P(2)
95.3(9), C(13)-As(3)-As(2) 95.8(2), As(1)-P(2)-As(3) 81.1(10),
As(1)-As(2)-As(3) 78.5(2), Mo(1)-C(6)-O(1) 175.5(3), Mo(1)-
C(7)-O(2) 172.2(2).
The most reliable information on the nature of the novel
heteroallyl complexes was provided by the X-ray structural
investigation of the mixed crystals of 13a/14a (M ) Mo) and
13b/14b (M ) W).
The X-ray analysis of the dark red crystals 13b/14b shows
two molecules in the asymmetric unit, which differ in the
occupation factor of the P/As disorder (89:11; 73:27) (Figure
3, Table 1).
The complexes consist of dicarbonyl cyclopentadienyl tung-
sten units, to which a 2-phospha-1,3-diarsaallyl ligand is
coordinated in the η3-mode. There is a disorder about the central
phosphorus atoms P(1) and P(2) by the arsenic atoms As(5B)
and As(6B). As a result, bonding parameters involving these
atoms are of minor accuracy. As the bonding data in both
molecules are not significantly different, only the complex with
atom W(1) will be discussed in more detail. The cyclopenta-
dienyl ring is unsymmetrically coodinated to the metal atom
with W-C distances ranging from 2.279(4) Å [W(1)-C(3)] to
2.372(4) Å [W(1)-C(5)]. The geometry about the metal is that
of a distorted piano-stool [C(6)-W(1)-As(1) ) 82.6(1)°, C(7)-
W(1)-As(2) 86.3(1)°, C(6)-W(1)-C(7) 83.6(2)°] with two
nearly linear carbonyl ligands [W(1)-C(6)-O(1) ) 176.3(3)°,
W(1)-C(7)-O(2) ) 173.9(3)°]. The most interesting parts of
the molecules are the unprecedented 2-phospha-1,3-diarsaallyl
and 1,2,3-triarsaallyl ligands, which are nearly symmetrically
linked to the metal in an η3-fashion through bonds W(1)-As-
(1) [2.6623(4) Å], W(1)-As(2) [2.6662(4) Å], and W(1)-P(1)
[2.59(2) Å] or W(1)-As(5B) [2.65(5) Å]. The W-As π-bonds
are shorter than in complex [Cp(CO)2W{η3-tBuC(O)AsPC-
(SiMe3)2}] (4b) [2.759(1) Å], whereas the W-P contact in 4b
is markedly shorter [2.498(1) Å] than in 13b. Bonding to the
pivaloyl substituents is similar to 4b [As-C(CO) 2.063(2) Å].
Both pivaloyl groups are directed toward the central heteroatom
of the allylic ligand.
A similar result was obtained when 3a was reacted with a
10-fold excess of the arsaalkene. Red crystals were grown from
a diethyl ether/n-pentane mixture at -30 °C. The X-ray analysis
shows two molecules in the asymmetric unit (Figure 4, Table
1), which differ in the occupation factor of As/P disorder
(60:40, 63:37).
Geometric parameters in both molecules do not differ
significantly; thus, only the molecule with Mo(1) will be
discussed in more detail. The situation about the Cp(CO)2Mo
fragment is similar to that in 4c. The unprecedented 2-phospha-
1,3-diarsaallyl and 1,2,3-triarsaallyl ligands are attached to the
metal atom in a η3-fashion.
Figure 3. Molecular structure of 13b/14b in the crystal. Selected
bond lengths [Å] and angles [deg]: W(1)-C(6) 2.002(4), W(1)-
C(7) 1.996(4), W(1)-As(1) 2.6623(4), W(1)-As(2) 2.6662(4),
W(1)-P(1) 2.59(2), W(1)-As(5B) 2.65(5), As(1)-P(1) 2.27(2),
As(2)-P(1) 2.30(2), As(1)-As(5B) 2.34(6), As(2)-As(5B)
2.23(6), As(1)-C(8) 2.044(4), As(2)-C(13) 2.046(4), C(8)-O(3)
1.212(5), C(13)-O(4) 1.207(5). C(6)-W(1)-C(7) 83.6(2), C(6)-
W(1)-As(1) 82.6(1), C(7)-W(1)-As(2) 86.3(1), As(1)-W(1)-
As(2) 70.45(1), C(8)-As(1)-P(1) 93.4(4), C(13)-As(2)-P(1)
92.6(5), As(1)-P(1)-As(2) 84.7(6), C(13)-As(2)-As(5B)
90.8(16), C(8)-As(1)-As(5B) 95.4(13), As(1)-As(5B)-As(2)
84(2).
The bonding parameters within the triarsaallyl complex are
of sufficient accuracy to allow some discussion. The arsenic-

Arsaalkenes R-AsdC(NMe2)2
Scheme 8. Formation of Complex 15
Organometallics, Vol. 25, No. 7, 2006 1791
arsenic bond lengths As(1)-As(2) [2.382(6) Å] and As(2)-
As(3) [2.337(8) Å] are well comparable with the As-As
separation in complexes 12 [2.342(4) Å]6 and are between those
of an As-As single bond [2.468(1) Å in 7] and an unsupported
As-As double bond [2.246(1) Å in Mes*AsdAs{Cr(CO)5}-
CH(SiMe3)2].13 The arsenic metal contacts Mo(1)-As(1)
[2.6586(4) Å], Mo(1)-As(2) [2.682(7) Å], and Mo(1)-As(3)
[2.6848(4) Å] are of similar lengths but considerably shorter
than the respective bond in the 2-phospha-1-arsaallyl complex
4c [2.7644(3) Å]. As in complexes 13b/14b the pivaloyl
substituents are directed toward the center atom As(2). As
already mentioned, to the best of our knowledge there are no
reports on η3-2-phospha-1,3-diarsaallyl and η3-1,2,3-triarsaallyl
complexes in the literature. In a short communication Jutzi et
al. described the formation of lithium derivatives of a triphos-
phaallyl and of a 1,3-diphospha-2-arsaallyl system. Both anions,
which are substituted by supermesityl substituents, were char-
acterized as trans/trans and cis/trans isomers by 31P NMR
spectroscopy.14
Figure 5. Molecular structure of 15 in the crystal. Selected bond
lengths [Å] and angles [deg]: Mo(1)-C(1-5) 2.311(2)-
2.390(2), Mo(1)-C(6) 1.983(2), Mo(1)-C(7) 1.964(2), Mo(1)-
P(1) 2.4699(4), Mo(1)-P(2) 2.5820(4), P(1)-H(1) 1.28(2), P(1)-
P(2) 2.1558(5), P(1)-C(15) 1.833(1), Si(1)-C(15) 1.917(1), Si(2)-
C(15) 1.925(1), P(2)-C(22) 1.788(1), Si(3)-C(22) 1.884(1), Si(4)-
C(22) 1.886(1), Mo(2)-P(2) 2.4283(4), Mo(2)-C(22) 2.458(1),
Mo(2)-C(8-12) 2.312(1)-2.425(2), Mo(2)-C(13) 1.976(1),
Mo(2)-C(14) 1.945(2).
2.1558(5) Å is markedly shorter than a PP single bond (ca. 2.20
Å).12 The contact of atom Mo(1) to atoms P(1) and P(2) differs
by 0.11 Å. A comparable nonsymmetric ligation of two
phosphorus atoms is present in the butterfly complex 16,
featuring two short bonds Mo(1,2)-P(1) [2.466, 2.470 Å] and
two longer bonds Mo(1,2)-P(2) [2.542, 2.546 Å].15
The reaction of arsaalkene Me3SiAsdC(NMe2)2 with mo-
lybdenum complex 3a proceeded with yet a different result.
Combination of the reactants in a 2:1 molar ratio in diethyl ether
in the range -100 to 20 °C afforded the As-free complex 15 as
dark red crystals after chromatographic workup (yield 0.57 g,
64%) (Scheme 8).
The 31P{1H} NMR spectrum of 15 displayed two doublets
at δ -120.3 (1JPP ) 583.0 Hz) and 102.6 ppm (1JPP ) 583.0
Hz), which points to the presence of two directly connected
different P atoms. In the proton-coupled 31P NMR spectrum
the low-field doublet remains unaffected (PB), whereas the
second 31P nucleus (PA) gives rise to a doublet of doublets. A
large JPH coupling of 384.1 Hz agrees with a PH function. The
second JPH coupling of 27.3 Hz is caused by the methyne proton
of the CH(SiMe3)2 substituent. Consistently, a doublet at δ 4.62
(1JPH ) 386.9 Hz) in the 1H NMR spectrum is attributed to the
PH group. A doublet of doublets at δ 2.09 (2JPH ) 25.8 Hz,
3JPH ) 4.4 Hz) is due to the hydrogen atom of the CHSi2 unit.
The appearance of four carbonyl 13C NMR resonances [δ 240.0
The bond length Mo(2)-C(22) [2.4283(4) Å] is similar to
the one in 4a [2.4372(11) Å], and thus the contact of bond P(2)-
C(22) to Mo(2) may be regarded as a π-bond. Investigations
on the ligating properties of 1,2-diphosphapropenes are not new.
R. Appel et al. isolated the dinuclear nickel complexes 17 from
the reaction of diphosphapropenes Ph2PPdC(SiMe3)R (R ) Ph,
Me3Si) with [Ni(CO)4].16
1
2
1
(dd, JPC ) 34.5, JPC ) 5.8 Hz), 242.2 (d, JPC ) 20.7 Hz),
1
2
244.5 (dd, JPC ) 16.0, JPC ) 6.9 Hz); 249.0 (s) ppm] and
four intense ν(CO) bands in the IR spectra point to an
unsymmetric combination of two molecules of 3a, induced by
the electron-abundant arsaalkene. The nature of product 15 was
unambigiously established by an X-ray structure analysis (Figure
5, Table 1). The analysis reveals the presence of a dinuclear
complex in which two [CpMo(CO)2] fragments are linked to
the 1,2-diphosphapropene (Me3Si)2CH-P(H)-PdC(SiMe3)2
from opposite faces via bonds Mo(1)-P(1) [2.4699(4) Å],
Mo(1)-P(2) [2.5820(4) Å], Mo(2)-P(2) [2.4283(4) Å], and
Mo(2)-C(22) [2.458(1) Å]. The separation P(2)-C(22) of
1.788(1) Å is similar to the one in 4c [1.791(2) Å]4 and typical
for an η2-coordinated phosphaalkene. The PP bond length of
In his Ph.D. thesis under the supervision of R. Appel, G.
Bruder carefully investigated the complex formation of diphos-
phapropenes with respect to the substitution pattern at the
tricoordinate phosphorus atom and the substituents at the PdC
backbone. Stable η1-complexes of type 18 were obtained with
tBu2P and tBu(Me3Si)P substituents at the P atom of the PdC
unit.17
(13) Cowley, A. H.; Kilduff, J. E.; Lasch, J. G.; Norman, N. C.; Pakulski,
M.; Ando, F.; Wright, T. C. Organometallics 1984, 3, 1044.
(14) Jutzi, P.; Meyer, U. Phosphorus Sulfur 1988, 40, 275.

1792 Organometallics, Vol. 25, No. 7, 2006
Weber et al.
Scheme 9. Proposed Mechanism for the Formation of 6a,
6b, and 8
Scheme 10. Proposed Mechanism for the Formation of
Compounds 13a,b
For the formation of the 2-phospha-1,3-diarsaallyl complexes
13a,b we propose an initial attack at the P atom of 3a,b to give
C, which first cyclizes and then fragments with liberation of
the putative alkene (Me2N)2CdC(SiMe3)2 and the formation of
metalloarsaphosphene D. The latter is attacked at the metal atom
to yield E. Extrusion of C(NMe2)2 from E and the rearrangement
of F gave one of the final products (Scheme 10). Unfortunately
neither the intermediates nor the alkene was detected by NMR-
monitoring.
Reaction of [Ni(CO)4] with R1R2P-PdC(SiMe3)2 led to the
cleavage of the P-P bond under formation of dinuclear
complexes 19.17 A mode of coordination of a diphosphapropene
as given in molecule 15 where the PdC bond spans two
different metal atoms and the phosphino as well as the
phosphorus atom of the double bond are coordinated to the same
metal center is new.
The mechanism of the formation of 15 is unclear at the
moment.
Conclusions
The reactivity of electron-abundant arsaalkenes RAsd
C(NMe2)2 toward phosphavinylidene complexes [Cp(CO)2Md
PdC(SiMe3)2] (3a,b) is sensitively governed by the substitution
pattern at the arsenic atom and by the stoichiometry of the
reactants employed. Whereas [Cp*(CO)2FeAsdC(NMe2)2] and
3a,b invariantly led to 2-phospha-1-arsaallyl complexes 4c,d,
the results obtained with tBuC(O)AsdC(NMe2)2 appeared to
be different. A 1:1 stoichiometry afforded 2-phospha-1-arsaallyl
complexes 4a,b, whereas a 1:10 stoichiometry gave cocrystals
of novel 1,2,3-triarsaallyl and 2-phospha-1,3-diarsaallyl com-
plexes 14 and 13. The aroyl-substituted arsaalkenes Aryl-C(O)-
AsdC(NMe2)2 (Aryl ) Ph, 4-EtC6H4) and equimolar amounts
of 3a,b underwent reaction to yield 1,2,4-oxaphosphaarsolenium
complexes 5, whereas with a 2 M excess of arsaalkene the spiro
compounds 6a,b and 8 were formed in high yield. Increasing
the steric bulk at the aryl ring as given in MesC(O)Asd
C(NMe2)2 prevented the ring closure, and 2-phospha-1-arsaallyl
complex 10 was obtained. Arsaalkene Me3SiAsdC(NMe2)2
served as a reducing agent toward 3a to give the dinuclear
diphosphapropene complex 15 with a novel mode of coordina-
tion.
Mechanisms
The formation of the spiro compounds 6a, 6b, and 8 involves
compounds such as 5 as intermediates. Their formation from
equimolar amounts of an aroylarsaalkene and 3b has been
discussed4 (Scheme 9).
A second molecule of arsaalkene attacks the MdP double
bond to give A. Extrusion of the carbene C(NME2)2 and P-As
bond formation leads to B, which eventually was converted into
the products by incorporation of the acyclic carbonyl group into
the P-As bond.
The formation of complexes 13a,b/14a,b from 3a,b and an
excess of arsaalkene remains unclear. At the moment we can
only say that the treatment of [Cp(CO)2M{η3-tBuC(O)AsPC-
(SiMe3)2}] (4a,b) with tBuC(O)AsdC(NMe2)2 to give 13a,b
and 14a,b failed, indicating that these species are not intermedi-
ates.
(15) Fenske, D.; Merzweiler, K. Angew. Chem. 1986, 98, 357; Angew.
Chem., Int. Ed. Engl. 1986, 25, 338.
(16) Appel, R.; Casser, C.; Knoch, F. J. Organomet. Chem. 1985, 297,
21.
(17) Bruder, G. Ph.D. Thesis, University of Bonn, 1989.

Arsaalkenes R-AsdC(NMe2)2
Experimental Section
Organometallics, Vol. 25, No. 7, 2006 1793
(d, 3JPC ) 7.0 Hz, i-C-Ph), 140.9 (d, 3JPC ) 12.5 Hz, i-C-Ph), 203.4
(d, 2JPC ) 15.2 Hz, AsdC), 218.0 (d, 2JPC ) 8.3 Hz, AsdC), 218.8
2
2
(d, JPC ) 9.7 Hz, CO), 231.7 (d, JPC ) 15.2 Hz, CO). 31P{1H}
NMR: δ 219.4 (s, 1JWP ) 411 Hz). Anal. Calcd for C28H33As2O4-
PSi2W (854.41): C, 39.56; H, 3.89. Found: C, 39.32; H, 3.78.
General Procedures. All operations were performed under dry,
oxygen-free nitrogen using standard Schlenk techniques. Solvents
were dried by standard techniques and freshly distilled under
nitrogen prior to use. Infrared spectra were recorded with a Bruker
1
FT-IR VECTOR 22 spectrometer. H, 13C, and 31P NMR spectra
[Cp(CO)2WAsdC(4-EtC6H4)-O-P-O-C(4-EtC6H4)dAs-
C(SiMe3)2] (8). The ethereal solution (10 mL) of 4-ethylbenzoyl
were recorded in C6D6 at 22 °C using a Bruker AM Avance DRX
500 (1H, 500.13 MHz; 13C, 125.76 MHz; 31P, 200.46 MHz).
References: SiMe4 (1H, 13C), 85% H3PO4 (31P). Elemental analyses
were performed at the microanalytical laboratory of the University
of Bielefeld. Crystal structures were determinated using a Nonius
Kappa CCD; all data were collected at 100 K. Programs for solution
and refinement were SHELXS-97 and SHELXL-97. Compounds
[Cp(CO)2ModPdC(SiMe3)2] (3a),5 [Cp(CO)2WdPdC(SiMe3)2]
chloride (0.61 g, 3.62 mmol) was added dropwise to the chilled
solution (-30 °C) of Me3SiAsdC(NMe2)2 (0.89 g, 3.62 mmol) in
15 mL of n-pentane. A yellow precipitate of arsaalkene 4-EtC6H4C-
(O)AsdC(NMe2)2 spontaneously separated. The slurry was stirred
for 30 min before the solution of complex 3b (0.89 g, 1.81 mmol)
in 20 mL of diethyl ether was slowly added (-30 °C). It was
warmed to room temperature and stirred for 12 h. Solvent and
volatiles were removed in vacuo, and the dark residue was dissolved
with 10 mL of diethyl ether. Florisil (5 g) was added to this solution,
and the slurry was freed from solvent. The coated Florisil was
loaded on top of a column, filled with Florisil (20 g). A yellow
zone was eluted with a 2:1 mixture of diethyl ether/n-pentane.
Concentration of the elute to the beginning crystallization and
storing at -30 °C afforded 1.17 g (71%) of product 8 as yellow
rods. IR (KBr, cm-1): ν 1941 (vs, CO), 1874 (vs, CO). 1H NMR:
δ 0.40 (s, 9H, SiMe3), 0.57 (s, 9H, SiMe3), 0.85 (t, 3JHH ) 7.6 Hz,
3H, CH3CH2), 0.88 (t, 3JHH ) 7.5 Hz, 3H, CH3CH2), 2.07 (q, 3JHH
(3b),5 and Me3SiAsdC(NMe2)2 were synthesized according to
6
literature procedures. Florisil (Merck), pivaloyl chloride, benzoyl
chloride, 4-ethylbenzoyl chloride, and 2,4,6-trimethylbenzoyl chlo-
ride were purchased commercially.
Preparation of Compounds: [Cp(CO)2Mo-AsdC(Ph)-O-
P-O-C(Ph)dAs-C(SiMe3)2] (6a) and [{η3:η3-(Me3Si)2C-P-
As-As-P-C(SiMe3)2}{Mo(CO)2Cp}2] (7). A solution of benzoyl
chloride (0.50 g, 3.62 mmol) in 15 mL of diethyl ether was
combined with a solution of Me3SiAsdC(NMe2)2 (0.90 g, 3.62
mmol) in 20 mL of n-pentane. The mixture was stirred at -30 °C
for 30 min to give a slurry of arsaalkene PhC(O)AsdC(NMe2)2.
The slurry was transferred into a dropping funnel, which was cooled
to -30 °C, and then added dropwise to the chilled ethereal solution
(-30 °C, 20 mL) of [Cp(CO)2ModPdC(SiMe3)2] (3a) (0.72 g,
1,81 mmol). After stirring for 4 h at -20 °C it was warmed to
ambient temperature. After 12 h of stirring at 20 °C volatile
components were removed in vacuo. The black residue was
dissolved with diethyl ether (20 mL), then Florisil was added (5 g)
and the resulting 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 yellow zone was eluted with a
1:1 mixture of diethyl ether/n-pentane. Concentration to the
beginning of crystallization and storing the solution at -30 °C for
48 h afforded 6a (1.11 g, 80%) as a yellow microcrystalline solid.
3
) 7.5 Hz, 2H, CH3CH2), 2.15 (q, JHH ) 7.5 Hz, 2H, CH3CH2),
4.93 (s, 5H, Cp), 6.65 (d, 3JHH ) 8.2 Hz, 2H, Ph), 6.72 (d, 3JHH
8.2 Hz, 2H, Ph), 7.68 (d, 3JHH ) 8.2 Hz, 2H, Ph), 8.10 (d, 3JHH
)
)
8.2 Hz, 2H, Ph). 13C{1H} NMR: δ 3.1 (s, SiMe3), 4.4 (s, SiMe3),
14.8 (s, CH3CH2), 15.1 (s, CH3CH2), 29.0 (s, CH3CH2), 42.9 [d,
1JPC ) 13.5 Hz, C(SiMe3)2], 89.7 (s, Cp), 124.6 (s, Ph), 125.1 (s,
Ph), 128.6 (s, Ph), 128.8 (s, Ph), 135.8 (d, 3JPC ) 6.7 Hz, i-C-Ph),
3
139.2 (d, JPC ) 13.5 Hz, i-C-Ph), 144.2 (s, Ph), 147.0 (s, Ph),
2
2
204.2 (d, JPC ) 16.2 Hz, AsdC), 218.5 (d, JPC ) 6.8 Hz,
AsdC), 219.4 (d, 2JPC ) 10.8 Hz, CO), 232.4 (d, 2JPC ) 14.8 Hz,
CO). 31P{1H} NMR: δ 218.5 (s, 1JPW ) 414 Hz). Anal. Calcd for
C32H41As2O4PSi2W (910.49): C, 42.22; H, 4.54. Found: C, 42.17;
H, 4.33.
Reaction of [Cp(CO)2WdP-O-C(4-EtC6H4)dAs-C(SiMe3)2]
(5) with 4-EtC6H4-C(O)AsdC(NMe2)2. The arsaalkene was
generated from Me3SiAsdC(NMe2)2 (0.15 g, 0.6 mmol) and 0.10
g (0.6 mmol) of 4-EtC6H4C(O)Cl in 10 mL of diethyl ether at -30
°C. To the slurry of 4-EtC6H4C(O)AsdC(NMe2)2 was added the
ethereal solution (10 mL) of complex 5 (0.42 g, 0.6 mmol). Stirring
was continued for 2 h at -30 °C, before it was warmed to 20 °C.
A 31P NMR spectrum of the reaction mixture after 12 h of stirring
at room temperature displayed only the singlet resonance for 8.
Preparation of [Cp(CO)2W{η3-MesC(O)AsPC(SiMe3)2}] (10).
Arsaalkene MesC(O)AsdC(NMe2)2 was formed as a slurry at -30
°C by slow combination of a solution of MesC(O)Cl (0.33 g, 1.81
mmol) in diethyl ether (15 mL) and a solution of Me3SiAsd
C(NMe2)2 (0.45 g, 1.81 mmol) in n-pentane (20 mL). Stirring at
-30 °C was continued for 30 min, then the slurry was transferred
into a chilled dropping funnel and added dropwise to the chilled
solution (-30 °C) of 3b (0.89 g, 1.81 mmol) in diethyl ether (25
mL). After stirring for 4 h at -30 °C and 12 h at ambient
temperature the 31P{1H} NMR spectrum of the reaction mixture
showed a singlet at δ 264 ppm (1JPW ) 565 Hz) as the only signal.
After removal of solvent and volatiles the black residue was coated
on 5 g of Florisil and chromatographed on Florisil. An orange-red
zone was eluted with a diethyl ether/pentane mixture. Concentration
to the beginning crystallization and storage at -30 °C afforded
0.70 g (54%) of 10 as orange crystals. IR (KBr, cm-1): ν 1654 (s,
AsCO), 1937 (s, WCO), 1860 (s, WCO). 1H NMR: δ 0.16 (s, 9H,
SiMe3), 0.36 (s, 9H, SiMe3), 2.32 (s, 3H, p-CH3), 2.50 (s, 6H,
o-CH3), 5.14 (s, 5H, C5H5), 6.45 (s, 2H, aryl). 13C{1H} NMR: δ
IR (KBr, cm-1): ν 1941 (vs, CO), 1885 (vs, CO). H NMR: δ
1
0.36 (s, 9H, SiMe3), 0.51 (s, 9H, SiMe3), 4.87 (s, 5H, Cp), 6.79-
6.85 (m, 4H, Ph), 6.89-6.92 (m, 2H, Ph), 7.69-7.71 (m, 2H, Ph),
8.06 - 8.08 (m, 2H, Ph). 13C{1H} NMR: δ 3.0 (s, SiMe3), 4.3 (s,
1
SiMe3), 44.5 (d, JPC ) 22.1 Hz, PC), 91.2 (s, Cp), 124.4 (s, Ph),
124.7 (s, Ph), 128.3 (s, Ph), 128.9 (s, Ph), 129.2 (s, Ph), 130.3 (s,
3
3
Ph), 138.0 (d, JPC ) 5.7 Hz, i-C-Ph), 141.7 (d, JPC ) 12.6 Hz,
2
2
i-C-Ph), 204.6 (d, JPC ) 14.9 Hz, AsdC), 217.9 (d, JPC ) 8.0
2
2
Hz, AsdC), 229.5 (d, JPC ) 5.8 Hz, CO), 242.5 (d, JPC ) 23.0
Hz, CO). 31P{1H} NMR: δ 258.0 s. Anal. Calcd for C28H33As2-
MoO4PSi2 (766.49): C, 43.87; H, 4.33. Found: C, 43.69; H, 4.22.
Concentration of the mother liquor and repeated storage at -30
°C gave a few yellow crystals of the dinuclear complex 7. The
characterization of this compound was limited to an X-ray structural
analysis.
[Cp(CO)2WAsdC(Ph)-O-P-O-C(Ph)dAs-C(SiMe3)2] (6b).
Analogously to the preparation of 6a a slurry of in situ-generated
PhC(O)AsdC(NMe2)2 (3.62 mmol) was combined with [Cp-
(CO)2WdPdC(SiMe3)2] (3b) (0.89 g, 1.81 mmol) in a diethyl ether
solution at -30 °C to produce 1.16 g (75%) of yellow solid 6b. IR
1
(KBr, cm-1): ν 1938 (vs, CO), 1874 (vs, CO). H NMR: δ 0.36
(s, 9H, SiMe3), 0.54 (s, 9H, SiMe3), 4.88 (s, 5H, Cp), 6.79-6.84
(m, 4H, Ph), 6.90-6.93 (m, 2H, Ph), 7.66-7.68 (m, 2H, Ph), 8.10-
8.12 (m, 2H, Ph). 13C{1H} NMR: δ 2.7 (s, SiMe3), 4.0 (s, SiMe3),
43.1 (d, 1JPC ) 13.8 Hz, PC), 89.4 (s, Cp), 124.0 (s, Ph), 124.5 (s,
Ph), 128.0 (s, Ph), 128.9 (s, Ph), 129.2 (s, Ph), 130.0 (s, Ph), 137.7

1794 Organometallics, Vol. 25, No. 7, 2006
Weber et al.
4.0 [s, Si(CH3)3], 9.1 [s, Si(CH3)3], 19.3 (s, CH3), 25.4 (s, CH3),
29.1 [d, JPC ) 103.7 Hz, C(SiMe3)2], 90.4 (s, C5H5), 128.0 (s,
Ph), 129.1 (s, Ph), 134.8 (s, Ph), 139.4 (s, Ph), 221.9 (s, WCO),
223.2 (s, WCO), 235.9 (d, 2JPC ) 3.8 Hz, AsCO). 31P{1H} NMR:
δ -18.2 s. Anal. Calcd for C24H34AsO3PSi2W (716.45): C, 40.24;
H, 4.78. Found: C, 40.28; H, 4.63.
tBu), 4.89 (s, 5H, Cp); (14a): δ 1.06 (s, 18H, tBu), 4.70 (s, 5H,
1
3
Cp). 13C{1H} NMR (13a): δ 26.4 [s, C(CH3)3], 33.1 [d, JPC
)
16.1 Hz, C(CH3)3], 87.5 (s, Cp), 87.6 (s, Cp), 231.2 (d, 2JPC ) 4.6
2
2
Hz, CO), 231.4 (d, JPC) 5.8 Hz, CO), 235.9 (d, JPC ) 5.8 Hz,
AsCO); (14a): δ 26.8 [s, C(CH3)3], 50.3 [s, C(CH3)3], 86.2 (s, Cp),
92.2 (s, Cp), 226.9 (s, CO), 233.6 (s, CO), 235.7 (s, AsCO). 31P-
{1H} NMR (13a): δ 5.8 (s), 9.4 (s). Anal. Calcd for C17H23As2.62
-
Reaction of [Cp(CO)2WdPdC(SiMe3)2] (3b) with 2 tBuC-
(O)AsdC(NMe2)2. The arsaalkene was formed as a yellow slurry
by combining the solution of pivaloyl chloride (0.44 g, 3.62 mmol)
in 25 mL of diethyl ether with a pentane solution (30 mL) of Me3-
SiAsdC(NMe2)2 (0.90 g, 3.62 mmol) at -30 °C during 30 min.
The slurry was transferred in a chilled dropping funnel (-30 °C)
and then added dropwise at -30 °C to the ethereal solution (20
mL) of complex 3b (0.89 g, 1.81 mmol). Stirring at -30 °C was
continued for 4 h, then the mixture was stirred at room temperature
for another 12 h. Volatiles were removed in vacuo, and the residue
was chromatographed on a Florisil-loaded column. A first orange-
red zone was eluted with a 5:1 mixture of diethyl ether/n-pentane.
The elute was concentrated to the beginning crystallization and
stored at -30 °C to afford 0.26 g (22%) of [Cp(CO)2W{η3-tBuC-
(O)AsPC(SiMe3)2}] (4b) as orange irregular crystals. Subsequently
a deep-red zone was eluted with a 10:1 mixture of diethyl ether/
pentane, from which 0.51 g (42%) of dark red crystals was isolated.
According to an X-ray structural analysis, the crystals consist of
81% [Cp(CO)2W{η3-tBuC(O)AsPAsC(O)tBu}] (13b) and 19%
[Cp(CO)2W{η3-tBuC(O)AsAsAsC(O)tBu}] (14b). IR (KBr, cm-1):
ν 1660 (s, AsCO), 1690 (m, AsCO), 1953 (br, WCO), 1997 (br,
MoO4P0.38 (595.13): C, 34.40; H, 3.90. Found: C, 34.46; H, 3.89.
Reaction of [Cp(CO)2WdPdC(SiMe3)2] (3b) with 10 tBuC-
(O)AsdC(NMe2)2. As described before, reaction of 3b (0.89 g,
1.8 mmol) and 20 mmol of the arsaalkene afforded 0.11 g (9%) of
dark red crstals, consisting of 35% 13b and 65% 14b.
{η2:η2-(Me3Si)2CdP-P(H)-CH(SiMe3)2}{Mo(CO)2Cp}2] (15).
A solution of Me3SiAsdC(NMe2)2 (0.89 g, 3.62 mL) in n-pentane
(15 mL) was added dropwise at -100 °C to the solution of 3a
(0.89 g, 2.19 mmol) in diethyl ether (20 mL). The mixture was
slowly warmed to room temperature and stirred for 12 h. Solvent
was removed in vacuo (10-5 bar). Unreacted arsaalkene was
recovered by distillation at 10-6 bar and 60 °C (0.61 g, 69%). The
solid residue was chromatographed on a column filled with Florisil
as described before. A dark red zone was eluted with diethyl ether.
Concentration to the beginning crystallization and storing at -30
°C gave compound 15 (0.57 g, 64%) as dark red irregular crystals.
IR (KBr, cm-1): ν 1828 (s, CtO), 1874 (s, CtO), 1923 (s,
1
CtO), 1945 (s, CtO). H NMR: δ 0.10 (s, 9H, SiMe3), 0.15 (s,
9H, SiMe3), 0.37 (s, 9H, SiMe3), 0.49 (s, 9H, SiMe3), 2.09 (dd,
2JPH ) 25.8 Hz, 3JPH ) 4.4 Hz, 1H, CHSi2), 4.62 (d, 1JPH ) 386.9
Hz, PH), 4.88 (s, 5H, Cp), 5.40 (s, 5H, Cp). 13C{1H} NMR: δ
0.63 (s, SiMe3), 0.65 (s, SiMe3), 1.44 [dd, 1JCP ) 26.4, 2JCP ) 1.2
Hz, C(SiMe3)2], 1.99 [dd, 1JCP ) 27.0, 2JCP ) 9.2 Hz, CH(SiMe3)2],
2.55 (s, SiMe3), 6.00 (s, SiMe3), 91.1 (s, Cp), 92.0 (s, Cp), 240.0
(dd, 1JCP ) 34.5, 2JCP ) 5.8 Hz, CtO), 242.2 (d, 1JCP ) 20.7 Hz,
1
WCO). H NMR (13b): δ 1.06 (s, 18H, tBu), 4.66 (s, 5H, Cp);
(14b): δ 1.06 (s, 18H, tBu), 5.05 (s, 5H, Cp). 13C{1H} NMR
3
(13b): δ 26.6 [s, C(CH3)3], 33.3 [d, JPC ) 16.1 Hz, C(CH3)3],
84.0 (s, Cp), 84.1 (s, Cp), 212.0 (d, 2JPC ) 3.4 Hz, CO), 212.1 (d,
2
2JPC ) 4.6 Hz, CO), 234.8 (d, JPC ) 6.9 Hz, AsCO); (14b): δ
26.8 [s, C(CH3)3], 50.2 [s, C(CH3)3], 85.5 (s, Cp), 90.6 (s, Cp),
213.1 (s, CO), 218.9 (s, CO), 235.5 (s. AsCO). 31P{1H} NMR
1
2
CtO), 244.5 (dd, JCP ) 16.0, JCP ) 6.9 Hz, CtO), 249.0 (s,
CO). 31P{1H} NMR: δ -120.3 (d, JPP ) 583.0 Hz), 102.6 (d,
1
(13b): δ -54.4 s, -61.6 s. Anal. Calcd for C30H23As2.19O4P0.81
W
1JPP ) 583.0 Hz, PMo2). 31P NMR: δ -120.3 (ddd, 1JPP ) 583.0,
(664.39): C, 30.73; H, 3.50. Found: C, 30.50; H, 3.82.
1JPH ) 384.1, JPH ) 27.3 Hz, PH), 102.6 (d, JPP ) 583.0 Hz).
Anal. Calcd for C28H48Mo2O4P2Si4 (814.84): C, 41.31; H, 5.94.
Found: C, 41.27; H, 6.00.
2
1
Reaction of [Cp(CO)2ModPdC(SiMe3)2] (3a) with 10 tBuC-
(O)AsdC(NMe2)2. Analogously, the arsaalkene was prepared by
combining pivaloyl chloride (2.4 g, 20 mmol) in 50 mL of diethyl
ether with the solution of Me3SiAsdC(NMe2)2 (5.0 g, 20 mmol)
in 40 mL of n-pentane at -30 °C. A solution of 3a (0.72 g, 1.8
mmol) in 30 mL of diethyl ether was added dropwise to the resulting
slurry. An analogous workup afforded dark red crystals (0.25 g,
23%) of a mixture of 38% [Cp(CO)2Mo{η3-tBuC(O)AsPAsC(O)-
tBu}] (13a) and 62% [Cp(CO)2Mo{η3-tBuC(O)AsAsAsC(O)tBu}]
(14a). IR (KBr, cm-1): ν 1660 (s, AsCO), 1690 (m, AsCO), 1953
Supporting Information Available: Tables of X-ray data,
atomic coordinates, thermal parameters, complete bond lengths and
angles, and thermal ellipsoid plots for compounds 7, 8, 13a/14a,
13b/ 14b, and 15. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
(br, MoCO), 1997 (br, MoCO). H NMR (13a): δ 1.05 (s, 18H,
OM051084T