Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2- η1-NAr)(NAr)Cl] (Ar = 2,6-Me2

Article abstract of DOI:10.1016/j.poly.2005.02.027

Reactions of the magnesium imides [Mg(NAr)(THF)]₆ (Ar = 2,6-Me₂C₆H₃, 1a; Ph, 1b) with [NbCp ^ClCl₄] (Cp^Cl = η⁵-C ₅H₄(SiMe₂Cl)) afforded

Full text of DOI:10.1016/j.poly.2005.02.027

Polyhedron 24 (2005) 1274–1279
www.elsevier.com/locate/poly
Aryl-imido niobium complexes with chloro-silyl and
aryl-g-amidosilyl cyclopentadienyl ligands: X-ray structure of
the constrained-geometry compound
[Nb(g5-C5H4SiMe2-g1-NAr)(NAr)Cl] (Ar = 2,6-Me2C6H3)
1
*
Rocıo Arteaga-Muller, Javier Sanchez-Nieves, Pascual Royo , Marta E.G. Mosquera
´
´
¨
´ ´ ´ ´
Departamento de Quımica Inorganica, Universidad de Alcala, Campus Universitario, E-28871 Alcala de Henares, Madrid, Spain
Received 14 January 2005; accepted 25 February 2005
Available online 29 April 2005
Abstract
Reactions of the magnesium imides [Mg(NAr)(THF)]6 (Ar = 2,6-Me2C6H3, 1a; Ph, 1b) with [NbCpClCl4] (CpCl = g5-C5H4
(SiMe2Cl)) afforded the imido complexes [NbCpClCl2(NAr)] (Ar = 2,6-Me2C6H3, 2a; Ph, 2b) in good yield. Compound 2a reacted
with excess LiNH(2,6-Me2C6H3) to give the silyl-g-amido complex [Nb(g5-C5H4SiMe2-g1-NAr)Cl(NAr)] (Ar = 2,6-Me2C6H3, 3a).
Hydrolysis of the Si–Cl bond of compounds 2a and 2b yielded the dinuclear complexes [{NbCl2(NAr)}2{(g5-C5H4SiMe2)2(l-O)}]
(Ar = 2,6-Me2C6H3, 4a; Ph, 4b), respectively. All of the new compounds reported were characterized by NMR spectroscopy and the
molecular structure of 3a was determined by X-ray diffraction methods.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Niobium; Constrained-geometry; Half-sandwich; Imido; Hydrolysis
1. Introduction
ization [12–15] and a rich chemistry has been developed
[16–20] since their discovery, showing both similarities
and differences compared with related dicyclopentadie-
nyl compounds. Half-sandwich group 5 metal imido
compounds [21,22] are isolobal with dicyclopentadienyl
group 4 metal complexes, the chemistry of which has
been widely studied [23]. However, constrained geome-
try group 5 metal compounds are still a field to be ex-
plored. Herrmann and Baratta [24] reported that
reaction of C5H5(SiMe2NHtBu) with [M(NMe2)5]
(M = Nb, Ta) gave the photolitically and thermally
unstable silyl-g-amido complexes [M(g5-C5H4SiMe2-
g1-NtBu)(NMe2)3], which transformed into the imido
compounds [M(C5H4SiMe2NMe2)(NMe2)2(NtBu)]. We
have reported the isolation of stable imido silyl-g-amido
niobium complexes [Nb(g5-C5H4SiMe2-g1-NtBu)X-
(Nt-Bu)] (X = Cl, CH2Ph) through N–H activation of
[Nb(C5H4SiMe2NHtBu)(CH2Ph)X(NtBu)] or by reaction
The presence of different functionalities on cyclopen-
tadienyl ligands allows the reactivity of their metal com-
plexes to be modified, inducing changes in both steric
and electronic effects on the metal centres [1]. When this
functionality on the ring is the [SiMe2Cl] group, the
reactivity of the Si–Cl bond facilitates access to a versa-
tile range of products, including catalysts anchored on
solid supports [2–5] and silylamido bridge formation be-
tween the cyclopentadienyl ligand and the metal centre
(constrained-geometry complexes) [6–11].
Silyl-g-amido monocyclopentadienyl groups 3 and 4
metal complexes are active catalysts for olefin polymer-
*
Corresponding author. Tel.: +34 91 885 4765; fax: +34 91 885 4683.
E-mail address: pascual.royo@uah.es (P. Royo).
X-ray diffraction studies.
1
0277-5387/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.02.027

R. Arteaga-Mu¨ller et al. / Polyhedron 24 (2005) 1274–1279
1275
of [Nb(C5H4SiMe2Cl)Cl2(NtBu)] with LiNHtBu [11]. Fi-
nally, Chen and co-workers [25] observed that the imido
compound [Ta(C5Me4H)Cl2(NtBu)] was obtained on
treating TaCl5 with the aminosilyl-cyclopentadiene
C5Me4H(SiMe2NHtBu). From these results, it is clear
that the thermodynamic stability of the M-imido bond
is much higher than that of the bridging cyclopentadie-
nyl-silyl-g-amido-M system (M = group 5 metal).
Most of these group 5 metal compounds containing
the cyclopentadienyl-silyl-g-amido ligand were isolated
as oily products. It has been suggested that aryl-imido
ligands provide more crystalline solids [26]. Conse-
quently, we decided to extend our research on Si–Cl
functionalized monocyclopentadienyl niobium com-
plexes [11,27,28] to isolate new aryl-imido derivatives
using the organomagnesium compounds [Mg(NAr)-
(THF)]6 (Ar = 2,6-Me2C6H3, 1a; Ph, 1b) as imido trans-
fer reagents. This method was first published by Power
and co-workers [29] to obtain titanium and zirconium
imido compounds. The main advantage of the organo-
magnesium compounds is their lower tendency to pro-
mote reduction of the metal centre than their lithium
analogues. The reactivity of the Si–Cl bond of these imi-
do complexes and the first X-ray structure of a group 5
metal silyl-g-amido complex is reported.
Scheme 1.
which is difficult to eliminate because its solubility is
close to that of compounds 2, although the same com-
pounds can also be obtained using the lithium amide
LiNHAr (Ar = 2,6-Me2C6H3, Ph). Also, this procedure
seems to be a faster way to isolate the imido compounds
and demonstrates the remarkable stability of the
Nb-imido bond, formation of which is preferred to a
bridging silyl-g-amido system between the cyclopenta-
dienyl ring and the niobium centre.
The presence of a silicon–chlorine bond in com-
pounds 2 moved us to try the synthesis of the silyl-g-
amido complexes using the same magnesium imide to
transfer the [NAr] moiety, but unfortunately decomposi-
tion was observed. However, reaction of 2a with excess
LiNHAr (Ar = 2,6-Me2C6H3) in diethylether afforded
the desired compound [Nb(g5-C5H4SiMe2-g1-NAr)Cl-
(NAr)] (3a) in moderate yield, whereas the same reaction
for Ar = Ph was unsuccessful. We have observed that
using more than two equivalents of the lithium amide
compound is required although we have never detected
the substitution of the remaining chlorine atom by an-
other amido group, probably due to the steric hindrance
of the [2,6-Me2C6H3] substituent. However, the related
diamido compound [NbCp(NAr)(NHAr)2] (Ar = 2,6-
Me2C6H3) was obtained through an analagous proce-
dure [26]. This is the same method reported previously
for introducing a bridging amido group between the me-
tal atom and the silylcyclopentadienyl ligand in similar
niobium complexes [11].
The dinuclear Si–O–Si bridged compounds [{NbCl2-
(NAr)}2{(g5-C5H4SiMe2)2(l-O)}] (Ar = 2,6-Me2C6H3,
4a; Ph, 4b) were obtained in low yields upon addition
of a stoichiometric amount of H2O to toluene solutions
of compounds 2a and 2b, respectively. The selective
hydrolysis of the Si–Cl bond with formation of a Si–
O–Si bridge was the expected behaviour for this type
of niobium compound [11,27]. In contrast, it was ob-
served [6,30–33] that the hydrolysis reactions of related
monocyclopentadienyl group 4 metal complexes with
2. Results and discussion
The magnesium imide compound [Mg(NAr)(THF)]6
(Ar = 2,6-Me2C6H3, 1a) was synthesized following the
method reported [29] for the analogous phenyl deriva-
tive [Mg(NPh)(THF)]6 (1b). Hence, reaction of [MgBu2]
with 1 equivalent of the corresponding aniline ArNH2
(Ar = 2,6-Me2C6H3) in THF at ꢀ78 ꢁC gave [Mg(NAr)-
(THF)]6 (1a) as a scarcely soluble white solid in high
yield (Eq. (1)). Compound 1a was identified by 1H
NMR, but its instability prevented suitable elemental
analysis being obtained, and the hexameric structure
was proposed by analogy with the phenyl derivative
1b, for which X-ray structure had been determined [29].
THF
!
MgBu2 þ H2NAr
½MgðNArÞðTHFÞꢁ
ð1Þ
6
ꢀ2BuH
Ar¼2;6-Me2C6H3
1a
These magnesium imide compounds [Mg(NAr)-
(THF)]6 (Ar = 2,6-Me2C6H3, 1a; Ph, 1b) can be used
to transfer the imido ligand when reacted with the
monocyclopentadienyl niobium complex [NbCpClCl4]
(CpCl = C5H4(SiMe2Cl)) (Scheme 1). Reaction of the
niobium complex with 1 equivalent of the magnesium
imides gave the new imido compounds [NbCpClCl2-
(NAr)] (Ar = 2,6-Me2C6H3, 2a; Ph, 2b) as red oils after
3 h in diethylether at room temperature. Compared with
the analogous reaction with the alkaline amide com-
pound LiNHAr, this procedure prevents the formation
of the corresponding amine NH2Ar as a by-product,

1276
R. Arteaga-Mu¨ller et al. / Polyhedron 24 (2005) 1274–1279
Table 1
the chloro-silylcyclopentadienyl ligand afforded Si–O–M
bridges. Attempts to produce further hydrolysis of Nb–
Cl bonds failed and led to decomposition products with
elimination of the corresponding amine.
˚
Selected bond distances (A) and bond angles (ꢁ) of compound 3a
˚
Bond lengths (A)
N(1)–Nb
N(2)–Nb
N(1)–Si
Nb–Cg
Cl–Nb
2.016(2)
1.786(2)
1.754(2)
2.1474
The molecular structure of compound 3a was deter-
mined by X-ray diffraction studies on a single crystal.
Fig. 1 shows a view of the molecular structure of com-
plex 3a and Table 1 summarizes selected bond distances
and angles. The coordination around the niobium centre
is typical of half-sandwich imido complexes and could
be described as a pseudo-tetrahedral structure with the
centroid of the cyclopentadienyl ring, the chloro ligand,
the imido nitrogen and the nitrogen of the bridging silyl-
g-amido system occupying the four coordination sites.
The most remarkable feature of this structure is the
distorted geometry due to the presence of this silyl-g-
amido group bridging the cyclopentadienyl ring and
the niobium atom. The Cg–Nb–N(1) (amido-silyl) bond
angle (Cg = centroid of the Cp ring) of 100.76ꢁ for com-
pound 3a is the closest angle reported for amido ligands,
which showed values in the range 106.60ꢁ and 116.67ꢁ
2.3796(9)
Bond angles (ꢁ)
Cg–Nb–Cl
112.85
100.76
130.20
Cg–Nb–N(1)
Cg–Nb–N(2)
N(2)–Nb–N(1)
N(2)–Nb–Cl
N(1)–Nb–Cl
N(1)–Si–C(1)
Si–N(1)–Nb
102.3(1)
101.05(8)
107.83(7)
91.9(1)
108.9(1)
126.6(2)
124.7(8)
172.8(2)
C(13)–N(1)–Si
C(13)–N(1)–Nb
C(21)–N(2)–Nb
Cg is the centroid of the cyclopentadienyl ring.
for unbridged ligands [11,21,26,34,35], and in addition
is smaller than those reported for constrained silyl-g-
amido group 4 metal complexes (105–108ꢁ) [7,36].
Moreover, the Cg–Nb–N(2) (imido ligand) bond angle
of 130.20ꢁ is the most open observed for half-sandwich
imido complexes [11,21,26,34,35], for which the ex-
pected value is in the range 119.24–124.15ꢁ, whereas
the Cg–Nb–Cl bond angle of 112.85ꢁ and the angles
formed by the three N(1), N(2) and Cl substituents
about the niobium atom are in the usual range found
for this type of half-sandwich imido compound.
As a consequence of the constrained bridging situa-
tion, the silicon atom presents a distorted tetrahedral
environment (C(1)–Si–N(1) = 91.9(1)ꢁ) and the N(1) a
distorted
planar
environment
(Si–N(1)–Nb =
108.2(1)ꢁ). Furthermore, the N(1)–Nb and N(1)–Si bond
distances of 2.016(2) and 1.754(2) A are, respectively,
˚
slightly longer than the related Nb–N(amide) and
Si–N(amide) bonds found in monoamide complexes of
the type [NbCpRCl(NHR)(NR)] [26,37] and in the
non-bridged aminosilyl compound [NbCpRCl2(NtBu)]
R
t
˚
(Cp = C5H4(SiMe2NH Bu), Si–N = 1.719(9) A) [11].
This is an indication of the lower N–Nb and N–Si
p-bonding contribution. These data together with the
co-planarity of the Nb, N(1), C(13) and Si atoms are
consistent with the behaviour known for group 4 metal
constrained geometry cyclopentadienylsilyl-g-amido
complexes [7,18].
Regarding the cyclopentadienyl ring, the C–C bond
˚
distances are in the range 1.401–1.432 A, indicating a
preference for g5-coordination in contrast to other
half-sandwich group 5 metal imido and group 4 metal
constrained geometry complexes, for which significant
contribution of a g3-allyl-g2-olefin structure is proposed
[7,21]. On the other hand, the Nb–C bond lengths,
Fig. 1. Molecular structure of compound 3a. (a) ORTEP ellipsoids are
drawn at the 50% probability level and hydrogen atoms are omitted for
clarity. (b) View perpendicular to the cyclopentadienyl ring plane.
˚
2.382–2.519 A, show two bonds clearly longer,

R. Arteaga-Mu¨ller et al. / Polyhedron 24 (2005) 1274–1279
1277
Nb–C(4) and Nb–C(5), corresponding to the C–C bond
3.2. [Nb{g5-C5H4(SiMe2Cl)}Cl2(NAr)] (Ar = 2,
6-Me2C6H3, 2a)
opposite to the imido ligand, as typically found for imi-
do complexes [21,35]. Also, the Nb–C(1) bond support-
ing the bridge is not the shortest one as found in group 4
metal constrained geometry complexes [7,38]. This could
be related with the location of the C(1) atom with re-
spect to the imido ligand.
Another notable feature found in the structure of
complex 3a is that the imido-aryl group is almost per-
pendicular to the Cp ring, whereas in the other 2,6-
disubstituted aryl-imido half-sandwich complexes the
aromatic ring is almost coplanar with the cyclopen-
tadienyl ligand, regardless of the nature of the other
ligands present [21,26,35,37,39]. Moreover, the silyl
group does not occupy the trans position with respect
to the imido ligand as in the silylcyclopentadienyl imido
compounds [NbCpRCl2(NR)] (CpR = C5H4(SiMe2NHt-
Bu) [11], C5H4(SiMe3) [34]). Finally, the Nb–N(2) bond
Diethylether (50 mL) was added to a solid mixture of
[Nb{g5-C5H4(SiMe2Cl)}Cl4] (1.00 g, 2.54 mmol) and
[Mg(NAr)(THF)]6 (1a) (0.54 g, 0.42 mmol) at room tem-
perature and the reaction mixture was stirred for 3 h.
Over this time the mixture became dark red and the sol-
vent was removed to half volume under reduced pres-
sure. Hexane (20 mL) was added and the solution was
filtered. The volatiles were completely removed to give
a dark red oil which was characterized as 2a (1.11 g,
1
90%). Data for 2a: H NMR: 6.78 (d, J = 7.1 Hz, 2H,
Me2C6H3), 6.67 (t, J = 7.1 Hz, 1H, Me2C6H3), 6.25
(m, 2H, C5H4), 5.81 (m, 2H, C5H4), 2.34 (s, 6H,
Me2C6H3), 0.53 (s, 6H, SiMe2). 13C NMR: 154.1 (Ci,
Me2C6H3), 135.1 (Me2C6H3), 129.8 (Me2C6H3), 126.1
(Me2C6H3), 123.1 (C5H4), 122.0 (Ci, C5H4), 113.3
(C5H4), 19.3 (Me2C6H3), 2.3 (SiMe2). Anal. Calc. for
C15H19Cl3NNbSi: C, 40.88; H, 4.35; N, 3.18. Found:
C, 41.09; H, 4.45; N, 3.12%.
˚
distance of 1.786(2) A and the almost linear Nb–N(2)–
C(21) bond angle of 172.8 (2)ꢁ of the imido ligand cor-
respond to a typical triple bond of a 4-electron-donor
ligand [23].
3.3. [Nb{g5-C5H4(SiMe2Cl)}Cl2(NAr)] (Ar = C6H5,
2b)
3. Experimental
Compound 2b was prepared from [Nb{g5-C5H4(Si-
Me2Cl)}Cl4] (1.00 g, 2.54 mmol) and [Mg(NAr)(THF)]6
(1b) (0.47 g, 0.42 mmol) following the method given for
2a and was obtained as a red oil (0.94 g, 90% yield).
All manipulations were performed under argon
atmosphere, using standard Schlenk techniques or a
glovebox. Solvents used were previously dried and
freshly distilled under argon: diethylether and tetrahy-
drofuran from sodium benzophenone, ketyl and hexane
from sodium–potassium amalgam. Deuterated solvents
from Scharlau were degassed and stored over molecular
sieves. NMR spectra were recorded on a Varian Unity
FT-300 and chemical shifts are given in ppm (d). C, H
and N microanalyses were performed on a Perkin–
Elmer 240B microanalyzer. Unless otherwise stated, re-
agents were obtained from commercial sources and
used as received. ArNH2 (Ar = 2,6-Me2C6H3, Ph)
(Aldrich) were distilled before use and stored under
argon. LiNHAr was prepared in tetrahydrofuran in
almost quantitative yield from ArNH2 and nBuLi
(Aldrich, 1.6 M in hexane) and the resulting product
was washed with hexane (2 · 10 mL). [Mg(NPh)(THF)]6
(1b) [29] and [Nb[g5-C5H4(SiClMe2)]Cl4] [27] were pre-
pared according to the literature procedures.
1
Data for 2a: H NMR: 7.02–6.80 (m, 5H, C6H5), 6.28
(m, 2H, C5H4), 5.86 (m, 2H, C5H4), 0.49 (s, 6H, SiMe2).
13C NMR: 156.0 (Ci, C6H5), 129.6 (C6H5), 128.7
(C6H5), 126.5 (C6H5), 124.5 (C5H4), 122.2 (Ci, C5H4),
114.4 (C5H4), 2.5 (SiMe2). Anal. Calc. for
C13H15Cl3NNbSi: C, 37.84; H, 3.66; N, 3.39. Found:
C, 37.12; H, 3.49; N, 3.46%.
3.4. [Nb(g5-C5H4SiMe2-g1-NAr)Cl(NAr)] (Ar = 2,
6-Me2C6H3, 3a)
A solution of 2a (1.06 g, 2.40 mmol) in diethylether
(30 mL) was treated dropwise with a solution of LiN-
HAr (Ar = 2,6-Me2C6H3) (0.91 g, 7.21 mmol) in diethy-
lether (30 mL) and the mixture was stirred for 16 h at
room temperature. After addition of hexane (30 mL),
the solution was filtered and the solvents were removed
under vacuum to ca. 30 mL. The remaining solution was
cooled to ꢀ38 ꢁC to give complex 3a as a yellow crystal-
3.1. [Mg(NAr)(THF)]6 (Ar = 2,6-Me2C6H3, 1a)
1
line solid (0.70 g, 60% yield). Data for 3a: H NMR:
Compound 1a was isolated as a white solid following
the procedure reported for [Mg(NPh)(THF)]6 (1b) [29],
from ArNH2 (5.00 g, 41.25 mmol) and [MgBu2] (41.25
mmol) in THF (8.45 g, 95% yield). Data for 1a: 1H
NMR: 6.71 (d, J = 7.6 Hz, 2H, Me2C6H3), 6.62 (t,
J = 7.6 Hz, 1H, Me2C6H3), 3.55 (m, 4H, OCH2), 2.34
(s, 6H, Me2C6H3), 1.40 (m, 4H, CH2).
6.96–6.69 (m, 6H, Me2C6H3), 6.46 (m, 2H, C5H4), 6.33
(m, 1H, C5H4), 6.23 (m, 1H, C5H4), 2.23 (s, 3H,
Me2C6H3), 2.12 (s, 6H, Me2C6H3), 1.94 (s, 3H,
Me2C6H3), 0.28 (s, 3H, SiMe2), 0.07 (s, 3H, SiMe2).
13C NMR: 132.1, 130.1, 124.3, 121.1, 118.2, 112.3,
112.0 and 109.5 (Me2C6H3 and C5H4, Cipso not ob-
served), 19.4 (Me2C6H3), 19.3 (Me2C6H3), 17.5

1278
R. Arteaga-Mu¨ller et al. / Polyhedron 24 (2005) 1274–1279
(Me2C6H3), 0.2 (SiMe2), ꢀ1.3 (SiMe2). Anal. Calc. for
C23H28ClN2NbSi: C, 56.50; H, 5.77; N, 5.73. Found:
C, 55.90; H, 5.43; N, 5.59%.
least-squares refinement based on 5271 reflections and
253 parameters converged to final values of
R1(F2 > 2r(F2)) = 0.0388, wR2(F2 > 2r (F2)) = 0.0927,
R1(F2) = 0.0668, wR2(F2) = 0.1014 and goodness-of-
fit = 1.011. Final difference Fourier maps showed no
peaks higher than 0.513 nor deeper than ꢀ0.453
3.5. [{NbCl2(NAr)}2{(g5-C5H4)2(Me2SiOSiMe2)}]
(Ar = 2,6-Me2C6H3, 4a)
e Aꢀ3. Geometrical calculations were made with PLATON
˚
Distilled water (0.02 mL, 1.20 mmol) was added to a
mixture of 2a (1.06 g, 2.40 mmol) and NEt3 (0.33 mL,
2.40 mmol) in toluene (60 mL). After stirring for 24 h
at room temperature, the solution was filtered and the
volatiles removed under vacuum to give 4a as a brown
[42]. The crystallographic plots were made with OR-
TEP-3. All calculations were made at the University
´
of Alcala.
1
solid (0.40 g, 40% yield). Data for 4a: H NMR: 6.78
4. Supplementary material
(m, 4H, Me2C6H3), 6.73 (m, 2H, Me2C6H3), 6.35 (m,
4H, C5H4) 5.91 (m, 4H, C5H4), 2.39 (s, 12H, Me2C6H3),
0.37 (s, 12H, SiMe2). Anal. Calc. for C30H38Cl4N2Nb2O-
Si2: C, 43.60; H, 4.63; N, 3.39. Found: C, 42.91; H, 4.29;
N, 3.05%.
Crystallographic data for the structural analysis for
3a have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC No. 259073. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44 1223 366 033; e-mail: deposit@ccdc.
cam.ac.uk or http://www.ccdc.cam.ac.uk).
3.6. [{NbCl2(NAr)}2{(g5-C5H4)2(Me2SiOSiMe2)}]
(Ar = C6H5, 4b)
This compound was prepared as above from 2b (1.00
g, 2.42 mmol), NEt3 (0.34 mL, 2.42 mmol) and distilled
water (0.02 mL, 1.21 mmol) to yield 4b (0.37 g, 40%).
Data for 4b: 1H NMR: 6.92–6.70 (m, 10H, C6H5),
6.40 (m, 4H, C5H4) 5.96 (m, 4H, C5H4), 0.33 (s, 12H,
SiMe2). Anal. Calc. for C26H30Cl4N2Nb2OSi2: C,
40.54; H, 3.93; N, 3.64. Found: C, 39.88; H, 3.81; N,
3.47%.
Acknowledgments
We gratefully acknowledge the Ministerio de Edu-
´
cacion
y Ciencia (Project MAT2004-02614) and
DGUI-Comunidad de Madrid (Project GR/MAT/
0622/2004) (Spain) for financial support. R.A.-M.
acknowledges MCyT for a fellowship.
3.7. X-ray crystallographic study of 3a
Suitable single crystals for the X-ray diffraction study
were grown by standard techniques from a saturated
solution of 3a (C23H28ClN2NbSi) in diethylether. A
light yellow crystal, 0.31 · 0.30 · 0.16 mm, monoclinic,
space group P21/n was used. Data collection were per-
formed at 200 K on a Kappa-CCD area detecting dif-
fraction system using a Mo Ka radiation. The unit
cell dimensions were determined from 110 reflections
between h = 3.102ꢁ and 21.448ꢁ. Unit cell parameters
References
[1] T. Cuenca, P. Royo, Coord. Chem. Rev. 195 (1999) 447.
[2] M. Antberg, H. Luker, L. Bo¨hm, Eur. Patent. Appl. EP
¨
293815A1, Hoechst, 1998.
[3] G.G. Hlatky, Chem. Rev. 100 (2000) 1347.
[4] R.M. Kasi, E.B. Coughlin, Organometallics 22 (2003) 1534.
[5] K.Q. Yu, M.W. McKittrick, C.W. Jones, Organometallics 23
(2004) 4089.
´ ´
[6] S. Ciruelos, T. Cuenca, R. Gomez, P. Gomez-Sal, A. Manzanero,
P. Royo, Organometallics 15 (1996) 5577.
[7] R. Go´mez, P. Go´mez-Sal, A. Mart´ın, A. Nu´n˜ez, P.A. del Real, P.
Royo, J. Organomet. Chem. 564 (1998) 93.
˚
˚
˚
were a = 8.3381(5) A, b = 21.597(2) A, c = 12.751(1) A,
3
˚
b = 92.549(7)ꢁ, V = 2294.0(3) A , Z = 4. X-ray data
were collected within the h-range of 3.01ꢁ < h < 27.51ꢁ
to a completeness of 0.998. An empirical absorption
correction was applied, and symmetry equivalent and
multiple measured reflections were averaged with the
program SORTAV [40]. A total of 19118 reflections were
collected and merged (Rint = 0.0688) to give 5271 unique
reflections of which 3884 were observed with I > 2r(I).
The crystal structure was solved by direct methods
and refined using full-matrix least squares on F2 [41].
All non-hydrogen atoms were anisotropically refined.
Hydrogen atoms were geometrically placed and left rid-
ing on their parent atoms. The final cycle of full-matrix
´ ´
[8] S. Ciruelos, A. Sebastian, T. Cuenca, P. Gomez-Sal, A. Manzan-
ero, P. Royo, J. Organomet. Chem. 604 (2000) 103.
´ ´ ´
[9] G. Jimenez, E. Rodrıguez, P. Gomez-Sal, P. Royo, T. Cuenca,
M. Galakhov, Organometallics 20 (2001) 2459.
´
[10] G. Jimenez, P. Royo, T. Cuenca, E. Herdtweck, Organometallics
21 (2002) 2189.
[11] M.I. Alcalde, M.P. Gomez-Sal, P. Royo, Organometallics 18
(1999) 546.
´
[12] A.L. McKnight, R.M. Waymouth, Chem. Rev. 98 (1998) 2587.
[13] H.G. Alt, A. Reb, W. Milius, A. Weis, J. Organomet. Chem. 628
(2001) 169.
[14] V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283.
[15] N. Guo, L.T. Li, T.J. Marks, J. Am. Chem. Soc. 126 (2004)
6542.

R. Arteaga-Mu¨ller et al. / Polyhedron 24 (2005) 1274–1279
1279
[16] J. Okuda, T. Eberle, Half-sandwich Complexes as Metallocene
Analogues in Metallocenes: Synthesis, Reactivity, Applications,
vol. 1, Wiley–VCH, Weinheim, 1998.
[29] W.J. Grigsby, M.M. Olmstead, P.P. Power, J. Organomet. Chem.
513 (1996) 173.
´
[30] S. Ciruelos, T. Cuenca, P. Gomez-Sal, A. Manzanero, P. Royo,
[17] J. Cano, P. Royo, M. Lanfranchi, M.A. Pellinghelli, A. Tiripic-
chio, Angew. Chem. Int. Ed. 40 (2001) 2495.
Organometallics 14 (1995) 177.
[31] B. Royo, P. Royo, L.M. Cadenas, J. Organomet. Chem. 551
(1998) 293.
[18] J. Cano, P. Royo, H. Jacobsen, O. Blacque, H. Berke, E.
Herdtweck, Eur. J. Inorg. Chem. (2003) 2463.
´
[32] O. Buitrago, G. Jimenez, T. Cuenca, J. Organomet. Chem. 683
(2003) 70.
[19] M. Sudupe, J. Cano, P. Royo, E. Herdtweck, Eur. J. Inorg.
Chem. (2004) 3074.
´
[33] A.B. Vazquez, P. Royo, E. Herdtweck, J. Organomet. Chem. 683
[20] F. Hannig, R. Fro¨hlich, K. Bergander, G. Erker, J.L. Petersen,
Organometallics 23 (2004) 4495.
(2003) 155.
[34] J.M. Benito, E.d. Jesu´s, F.J.d.l. Mata, J.C. Flores, R. Gomez, P.
´
Gomez-Sal, J. Organomet. Chem. 664 (2002) 258.
´
[21] D.N. Williams, J.P. Mitchell, A.D. Poole, U. Siemeling, W.
Clegg, D.C.R. Hockless, P.A. OÕNeil, V.C. Gibson, J. Chem.
Soc., Dalton Trans. (1992) 739.
´
´
[35] M.V. Galakhov, M. Gomez, G. Jimenez, M.A. Pellinghelli, P.
Royo, A. Tiripicchio, Organometallics 13 (1994) 1564.
[36] D.W. Carpenetti, L. Kloppenburg, J.T. Kupec, J.L. Petersen,
Organometallics 15 (1996) 1572.
[22] M.C.W. Chan, J.M. Cole, V.C. Gibson, J.A.K. Howard, C.
Lehmann, A.D. Poole, U. Siemeling, J. Chem. Soc., Dalton
Trans. (1998) 103.
[37] M.J. Humphries, M.L.H. Green, M.A. Leech, V.C. Gibson, M.
Jolly, D.N. Williams, M.R.J. Elsegood, W. Clegg, J. Chem. Soc.,
Dalton Trans. (2000) 4044.
[23] D.E. Wigley, Prog. Inorg. Chem. 42 (1994) 239.
[24] W.A. Herrmann, W. Baratta, J. Organomet. Chem. 506 (1996) 357.
[25] S.G. Feng, G.R. Roof, E.Y.X. Chen, Organometallics 21 (2002)
832.
[38] J. Okuda, T. Eberle, T.P. Spaniol, Chem. Ber.-Recl. 130 (1997)
209.
[26] M.J. Humphries, M.L.H. Green, R.E. Douthwaite, L.H. Rees, J.
Chem. Soc., Dalton Trans. (2000) 4555.
´ ´
[27] M.I. Alcalde, P. Gomez-Sal, A. Martın, P. Royo, Organometallics
[39] J. Gavenonis, T.D. Tilley, Organometallics 23 (2004) 31.
[40] R.H. Blessing, Acta Crystallogr. 51 (1995) 33.
[41] G.M. Sheldrick, SHELXL-97, University of Gottingen, Gottingen,
1997.
17 (1998) 1144.
[28] M.I. Alcalde, M.P. Gomez-Sal, P. Royo, Organometallics 20
(2001) 4623.
´
[42] A.L. Spek, PLATON, Utrecht University, Utrecht, The Netherlands,
2000.