Synthesis and characterization of g5-cyclopentadienyl-silylallyl niobium and tantalum complexes

Article abstract of DOI:10.1016/j.ica.2004.09.017

Reaction of the disilylcyclopentadiene 1,1-[SiMe₂(CH ₂CHCH₂)]₂C₅H₄ with NbCl₅ gave the new allylsilyl-substituted monocyclopentadienyl niobium complex [Nb{η⁵-C₅

Full text of DOI:10.1016/j.ica.2004.09.017

Inorganica Chimica Acta 358 (2005) 1494–1500
www.elsevier.com/locate/ica
Synthesis and characterization of
g5-cyclopentadienyl–silylallyl niobium and tantalum complexes
*
´
Pilar Nicolas, Pascual Royo
´ ´ ´
Departamento de Quımica Inorganica, Facultad de Ciencias, Universidad de Alcala, Campus Universitario,
´
E-28871 Alcala de Henares, Spain
Received 16 July 2004; accepted 6 September 2004
Available online 21 November 2004
Dedicated to Professor F.G.A. Stone in recognition of his outstanding contribution to organometallic chemistry
Abstract
Reaction of the disilylcyclopentadiene 1,1-[SiMe2(CH2CH@CH2)]2C5H4 with NbCl5 gave the new allylsilyl-substituted monocy-
clopentadienyl niobium complex [Nb{g5-C5H4SiMe2(CH2CH@CH2)}Cl4]. This compound was reacted with LiNHtBu or NH2tBu
to give the imido derivative [Nb{g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)Cl2], which was further alkylated to the imido alkyl com-
plexes [Nb{g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)R2] (R = Me, CH2Ph) and [Nb{g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)Cl
(CH2Ph)]. Reaction of the imido complexes with the corresponding lithium cyclopentadienides gave the dicyclopentadienyl-imido
complexes [M(g5-C5R5){g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)Cl] (M = Nb, Ta; R = H, Me). Metallocene dichlorides [M(g5-
C5R5){g5-C5H4SiMe2(CH2CH@CH2)}Cl2] (M = Nb, Ta; R = H, Me) were easily prepared by reduction with Na/Hg and simulta-
neous transmetallation of [Ta(g5-C5R5)Cl4] with Li[C5H4SiMe2(CH2CH@CH2)] and of [Nb{g5-C5H4SiMe2(CH2CH@CH2)}Cl4]
with Li(C5R5). All of the new compounds have been characterized by elemental analysis, and IR and NMR spectroscopy.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Niobium; Tantalum; Imido; Cyclopentadienyl
1. Introduction
contribution from the polarized olefinic system. These
results encouraged us to prepare similar group 5 metal
derivatives, which would allow comparison of the nature
of the metal–olefin interaction of the related d0 and d2
metal complexes. The weakly coordinating properties
reported [3] for the dicyclopentadienyl [MCp2R2]+ ca-
tions, which are stabilized by strong a-agostic interac-
tions [4], recommended the isolobal analogs [5–8],
cyclopentadienyl imido compounds (a), as better models
for d0, whereas the neutral dicyclopentadienyl metal(III)
(b) derivatives were the most suitable models for d2 spe-
cies, as shown in Scheme 1. The results of these studies
have been reported [9] separately.
Important efforts have been made to elucidate the
behavior of the alkene-alkyl cationic species responsible
for the catalytic activity of group 4 metallocene com-
plexes in Ziegler–Natta type polymerization of a-olefins
[1]. With this aim, we synthesized olefin-tethered group 4
metallocene complexes [2] containing the allylsilylcyclo-
pentadienyl ligand and studied the coordination of its
olefinic moiety. The metal–olefin interaction in these
d0 metal compounds is essentially due to the weak r-
donation from the olefin p-bonding MO to the cationic
metal center strengthened by a significant electrostatic
Both (a)- and (b)-type complexes may be easily acces-
sible from the half-sandwich niobium and tantalum com-
plexes [M{g5-C5H4SiMe2(CH2CH@CH2)}Cl4] through
*
Corresponding author. Tel.: +34 91 8854765; fax +34 91 8854683.
E-mail address: pascual.royo@uah.es (P. Royo).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.09.017

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P. Nicolas, P. Royo / Inorganica Chimica Acta 358 (2005) 1494–1500
1495
Me
Si
80% yield as a red solid identified by analytical data
and NMR spectroscopy. However, the same reaction
using TaCl5 was not successful and the related tantalum
derivative could not be isolated.
Me
Me
Si
Me
+
M
M
Transformation of monocyclopentadienyl metal(V)
compounds into metallocene dichlorides was achieved
by reaction with the corresponding lithium cyclopenta-
dienides in the presence of 1 equiv of Na/Hg in toluene
(see Scheme 3). In this way, reaction of 1 with Li(C5H5)
afforded [Nb(g5-C5H5){g5-C5H4SiMe2(CH2CH@CH2)}
Cl2] 2 and similar reactions of [Ta(g5-C5R5)Cl4]
(R = H [16], Me [17]) with Li[C5H4SiMe2(CH2CH@
CH2)] gave the related tantalum compounds [Ta(g5-
C5R5){g5-C5H4SiMe2(CH2CH@CH2)}Cl2] (R = H 3,
Me 4). The paramagnetic compounds 2–4 were isolated
in 60–70% yields as brown (2, 3) and green (4) air sensi-
tive solids which can be stored indefinitely under inert
atmosphere. The compounds, which were very soluble
in toluene and THF, and partially soluble in hexanes,
were identified by elemental analysis.
R
tBuN
R
(b)
(a)
Scheme 1.
conversion into the imido derivatives [M{g5-C5H4-
and into the
SiMe2(CH2CH@CH2)}Cl2(NtBu)]
dicyclopentadienyl metal(IV) compounds [M(g5-
C5H5){g5-C5H4SiMe2(CH2CH@CH2)}Cl2], followed by
further reduction by alkylation and reductive elimination
of alkane. Here, we report the synthesis and structural
characterization of these precursor chloro complexes
and their alkylated derivatives.
2. Results and discussion
Reaction of complex 1 with 1 equiv of LiNHtBu in
the presence of 1 equiv of NEt3 takes place with elimina-
tion of the lithium and ammonium salts to give the
imido complex [Nb{g5-C5H4SiMe2(CH2CH@CH2)}-
(NtBu)Cl2] 5 in 70% yield (see Scheme 4). The same
transformation can also be carried out using 3 equiv
of NH2tBu or 1 equiv of NH2tBu and 2 equiv of
NEt3, although the resulting yields were lower. Complex
5 was isolated as a yellow solid after cooling its concen-
trated hexane solution at ꢀ30 ꢁC and was identified by
elemental analysis and NMR spectroscopy.
2.1. Synthetic results
Desilylation of silylcyclopentadienes by reaction with
electrophilic metal halides is a convenient method [10] to
prepare silylcyclopentadienyl niobium [11], tantalum
[12] and group 6 metal [13] complexes. The selectivity
of this reaction, when two different silyl groups are
bound to the ring, is not only dependent on the nature
of the silyl substituents but also on the metal halide.
The reaction of NbCl5 with [1-SiMe2(CH2CH@
CH2)](1-SiMe3)C5H4] [2] gave a mixture containing a
1/1 molar ratio of the already reported [Nb(g5-C5H4Si-
Me3)Cl4] [14] and [Nb{g5-C5H4SiMe2(CH2CH@CH2)}-
Cl4] 1 regardless of the solvent or the reaction conditions
used. Compound 1 could be separated by repeated
recrystallization from toluene but always in low yield
(< 30%) and containing small amounts of the other com-
ponent. The same reaction with TaCl5 took place with
selective elimination of SiClMe2(CH2CH@CH2) afford-
ing pure [Ta(g5-C5H4SiMe3)Cl4] [15]. For this reason,
we decided to use the symmetric disilylated cyclopentad-
iene 1,1-[SiMe2(CH2CH@CH2)]2C5H4 [9]. As shown in
Scheme 2, this compound reacted easily with NbCl5 to
give the desired monocyclopentadienyl derivative 1 in
Alkylation of complex 5 with 2 equiv of MgClR
(R = Me, CH2Ph) resulted in substitution of both chloro
ligands to give the corresponding dialkyl derivatives
[Nb{g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)R2]
(R =
Me 6, CH2Ph 7) in 70% and 80% yield, respectively,
whereas the same reactions using 1 equiv of the alkylat-
ing agent gave unresolvable mixtures of mono- and
di-alkyl compounds in different molar ratios. However
the mono-benzyl complex [Nb{g5-C5H4SiMe2(CH2-
CH@CH2)}(NtBu)Cl(CH2Ph)] 8 could be isolated as a
Me
Me
Si
Me Me
Si
Nb
Cl
Cl
Cl
Li+
Na/Hg
Cl
1
Cl
Cl
M
R
R
R
Na/Hg
Me Me
R
R
R
R
Me2Si
Me2Si
SiMe2
+
Cl
M = Nb, R=H 2
M = Ta, R = H 3, Me 4
NbCl5
R
R
ClMe2Si
Nb
Si
R
Cl
Li+
Ta
Cl
Cl
Cl
Cl
Cl
1
Cl
Scheme 2.
Scheme 3.

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1496
Me
Me
Me
Me
Me
two doublets for the olefinic methylene group and one
multiplet due to the internal olefinic proton. The ring
proton resonances are shifted upfield for imido com-
plexes (5–8) compared with the tetrachloro niobium
derivative 1, whereas the resonances due to SiMe2, Si–
CH2 and olefinic CH@CH2 protons of the dimethylsilyl-
allyl group are shifted low field, the Si–CH2 being the
most sensitive signals. These displacements are related
to the stronger r–p-donating character of the imido lig-
and, causing the metal to require less electron density
from the aromatic ring. The same behavior can be ob-
served in the 13C NMR spectra, although smaller differ-
ences are found. The electron donating capacity of the
imido ligand can be inferred [19] from the Dd = d(qua-
ternary C) ꢀ d(methyl C) differences observed for the
tert-butyl group in the 13C NMR spectra which are be-
tween 33.0 (6) and 39.7 (5), in the range accepted for a
substantial p-donating contribution (see Table 1). The
1H and 13C NMR spectra of complex 8 show similar
resonances for the tert-butyl and olefin groups although
the chiral character of the metal center makes all of the
other substituents non-equivalent. Therefore, it shows
two singlets for the methyl–silyl groups, two overlapped
doublets for the methylene–silyl protons and two dou-
blets for the methylene–benzyl protons. Consequently,
there are four 1H multiplets and five 13C resonances
for the silyl-substituted ring.
Ta
Cl
tBuN
Cl
Me2
Si
Me2
Si
Li+
LiNHtBu
1
NEt3
Nb
Me2
Si
Cl
LiC5R5
tBuN
Cl
5
Cl
NtBu
2 MgClR
M
R
+ 7
120ºC
R
R
R
Me2
Si
Me2
Si
R
M = Nb; R=H 9, Me 10
M = Ta; R= Me 11
Nb
Nb
CH2Ph
R
tBuN
tBuN
Cl
R
8
R=Me 6, CH2Ph 7
Scheme 4.
unique component in 90% yield by a redistribution reac-
tion when an equimolar mixture of 5 and 7 was heated
in toluene at 120 ꢁC. The alkyl complexes 6–8 were iso-
lated as waxy brown air sensitive solids, very soluble in
all organic solvents including hexanes. They were char-
acterized by elemental analyses and NMR spectroscopy.
Similar alkylation using 1 equiv of Li(C5R5) (R = H,
Me) gave the dicyclopentadienyl imido complexes
[Nb(g5-C5R5){g5-C5H4SiMe2(CH2CH@CH2)}(NtBu)-
Cl] (R = H 9, Me 10) isolated in 75% yield as yellow and
waxy brown solids, respectively. The related tantalum
All of the dicyclopentadienyl imido complexes 9–11
are chiral asymmetric molecules which show the ex-
1
pected similar pattern observed for 8 in their H and
complex
[Ta(g5-C5Me5){g5-C5H4SiMe2(CH2CH@
13C NMR spectra. The nature of these apparently 20-
electron compounds has been reported [20] previously
for similar group 5 and 6 metal derivatives, which show
nearly linear M–N–R imido ligands with the sp hybrid-
ized nitrogen acting as a four-electron donor ligand.
Theoretical investigation of the bonding in compounds
of this type showed that the surplus electron pair is lo-
cated in an essentially cyclopentadienyl-based orbital.
We were not able to isolate single crystals appropriate
for X-ray diffraction studies. Nevertheless, the p-donor
capacity of the imido ligand in complexes 9–11 can be
estimated by the Dd values observed in their 13C NMR
spectra for the tert-butyl substituent.
CH2)}(NtBu)Cl] 11 was isolated as a brown waxy solid
in 70% yield by a similar reaction of the corresponding
[Ta(g5-C5Me5)(NtBu)Cl2] [18] with the lithium salt of
the allylsilylcyclopentadienyl ligand. Complexes 9–11
were very soluble in all usual organic solvents including
hexanes. They were identified by elemental analyses and
NMR spectroscopy.
2.2. Structural studies
The metal(IV) complexes 2–4 are paramagnetic com-
pounds with effective magnetic moments lef = 1.7–1.8
BM at 298 K similar to those found for related
compounds.
As shown in Table 1, complex 9 shows a value of Dd
(40.0), even higher than that found for complex 5, indi-
cating the strong p-bonding contribution of the imido
ligand. As expected, this contribution is lower for the
niobium complex 10 (Dd = 38.5) and even lower for
the tantalum complex 11 (Dd = 33.7) with its more
donating Cp* ligand.
All of the other metal(V) compounds were studied by
1H and 13C NMR spectroscopy and selected data are
shown in Section 3. The tetrachloro (1), dichloro-imido
(5) and dialkyl-imido (6–7) complexes are Cs symmetry
1
molecules which show the expected H NMR spectra
corresponding to an AA0BB0 spin system for the ring
protons. The typical spectral pattern of the allyl–
dimethylsilyl group consists of two high field signals ob-
served as one singlet for both equivalent silicon methyl
groups and one doublet for the methylene silicon-bound
group, together with three low field signals appearing as
3. Experimental
Standard Schlenk procedures were used for all syn-
theses and sample manipulations. The solvents were

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1497
3.2. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)} (g5-C5H5)Cl2] (2)
Table 1
13C{1H} NMR data in C6D6 for the tert-butyl-imido group in
compounds 5–11
Compound
dCMe3
dCMe3
Dd
Toluene (150 ml) was added to a mixture of 1 (1.38 g,
3.4 mmol) and Li(C5H5) (0.25 g, 3.4 mmol). This sus-
pension was added to a 10% sodium amalgam (0.08 g,
3.4 mmol). The mixture was stirred for 16 h at room
temperature. The resulting brown suspension was dec-
anted and filtered through Celite, and the filtrate was
concentrated to ca. 15 ml and cooled to ꢀ40 ꢁC to give
2 as a dark brown solid. Yield: 0.93 g, 2.37 mmol (70%).
IR (cmꢀ1): 3074w, 1461m, 1050s, 804m, 1251s, 576m,
1627s, 960w, 489s, 285s. Elemental Anal. Calc. for
C15H20Cl2NbSi (392.22): C, 45.93; H, 5.14. Found: C,
45.78; H, 5.10%.
5
30.4
32.2
31.9
31.1
29.9
31.3
32.8
70.1
65.2
66.5
68.0
69.9
69.8
66.5
39.7
33.0
34.6
36.9
40.0
38.5
33.7
6
7
8
9
10
11
dried by standard methods (hexane over Na/K alloy,
toluene and THF over sodium) and distilled under ar-
gon before use. Na, Hg, C5H6, SiMe2(CH2CH@CH2)Cl,
SiMe3Cl, LinBu (1.6 M in hexane), TaCl5, NbCl5,
NH2tBu, NEt3, MgCl(CH2Ph) (2 M in THF) and
MgClMe (3 M in THF) were obtained from Aldrich
and used without further purification. Na(C5H5) [21], Si-
3.3. Preparation of [Ta{g5-C5H4SiMe2(CH2CH@
CH2)} (g5-C5R5)Cl2] (R = H, 3; Me, 4)
Toluene (150 ml) was added to a mixture of [Ta(g5-
C5R5)Cl4], (R = H, 1.68 g, 4.35 mmol; R = Me, 2.0 g,
4.35 mmol) and Li[C5H4SiMe2(allyl)] (0.74 g, 4.35
mmol). This suspension was added to a 10% sodium
amalgam (0.1 g, 4.35 mmol). The mixture was stirred
for 16 h at room temperature. The resulting brown or
green suspension was decanted and filtered through Cel-
ite, and the filtrate was concentrated to ca. 15 ml and
cooled to ꢀ40 ꢁC to give 3 as a dark brown solid or 4
as dark green crystals.
Data for compound 3: Yield: 1.46 g, 3,04 mmol
(70%). IR (cmꢀ1): 3095w, 1461m, 1017s, 824s, 1250s,
1627s, 899m, 400w, 274s. Elemental Anal. Calc. for
C15H20Cl2SiTa (480.26): C, 37.51; H, 4.20. Found: C,
37.65; H, 4.32%.
Me3(C5H5) [22], LiNHtBu, [Ta(g5-C5H5)Cl4] [23],
1
Li(C5H5) [24], [Ta(g5-C5Me5)CI4] [25] and [Ta(g5-
C5Me5)Cl2(NtBu)] [26] were prepared as described
previously.
IR spectra were recorded on a Perkin–Elmer 583
spectrophotometer (4000–200 cmꢀ1) as Nujo1 mulls be-
tween CsI pellets. 1H and 13C{H} NMR spectra were re-
corded on a Varian VXR-300 Unity instrument in C6D6
solution at 300 K and chemical shifts are reported in d
units relative to the solvent signals (dH 7.15, dC
128.00). C, H and N analyses were performed with a
Perkin–Elmer 240 microanalyzer.
3.1. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)}Cl4] (1)
Data for compound 4: Yield: 1.79 g, 3.25 mmol
(75%). IR(cmꢀ1): 3080w, 1461s, 1029s, 1051s, 821m,
1243s, 574w, 1628s, 918m, 444m, 274s. Elemental Anal.
Calc. for C20H30Cl2SiTa (550.40): C, 43.64; H, 5.49.
Found: C, 43.68; H, 5.65%.
A solution of 1,1-[SiMe2(allyl)]2C5H4 (3.5 ml, 22.4
mmol) was added to a toluene suspension (75 ml) of
NbCl5 (3 g, 11.1 mmol) and the mixture was vigorously
stirred for 12 h at room temperature. The red suspension
was filtered and the red solid was washed twice with n-
hexane (2 · 15 ml), dried in vacuo and identified as 1.
3.4. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)}Cl2(NtBu)] (5)
1
Yield: 3.5 g, 8.8 mmol (80%). H NMR (C6D6): d 0.17
3
(s, 6H, SiMe2), 1.40 (d, J = 8.1 Hz, 2H, SiCH2), 4.65
A hexane solution (50 ml) of LiNHtBu (0.3 g, 3.7
mmol) was added at ꢀ78 ꢁC to a toluene suspension
(50 ml) of 1 (1.5 g, 3.7 mmol) and NEt3 (0.52 ml, 3.7
mmol). The mixture was stirred for 15 h at room tem-
perature. The resulting brown suspension was concen-
trated under reduced pressure and hexane (50 ml) was
added. The suspension was filtered through Celite and
the filtrate was concentrated to ca. 10 ml and cooled
to ꢀ40 ꢁC to give 5 as a yellow solid. Yield: 1.00 g,
3
3
(d, Jtrans = 16.1 Hz, 1H, CH@CH2), 4.78 (d, Jcis = 9.9
Hz, 1H, CH@CH2), 5.41 (m, 1H, CH@CH2), 6.31 (m,
2H, C5H4), 6.44 (m, 2H, C5H4). 13C NMR (C6D6): d-
3.4 (SiMe 2), 24.0 (SiCH2), 113.1 (CH@CH2), 133.1
(CH@CH2), 115.1 (C5H4), 127.8 (C5H4). IR(cmꢀ1):
3030w, 1460m, 1048s, 803m, 1255s, 579m, 1627s,
994w, 489s, 349m. Elemental Anal. Calc. for
C10H15Cl4NbSi (398.03): C, 30.18; H, 3.80. Found: C,
30.32; H, 3.91%.
2.51 mmol (70%). 1H NMR (C6D6): d 0.29 (s, 6H,
3
SiMe ), 1.06 (s, 9H, CMe3), 1.66 (d, J = 8.0 Hz, 2H,
2
SiCH2), 4.85 (m, 2H, CH@CH2), 5.62 (m, 1H,
CH@CH2), 6.09 (m, 2H, C5H4), 6.35 (m, 2H, C5H4);
1
Quantitative yield by reaction of NH2t Bu with LinBu.

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P. Nicolas, P. Royo / Inorganica Chimica Acta 358 (2005) 1494–1500
1498
13C NMR (C6D6): d-2.8 (SiMe2), 24.1 (SiCH2), 30.4
(CMe3), 70.1 (CMe3), 114.3 (CH@CH2), 134.1
(CH@CH2), 110.3 (C5H4), 122.6 (C5H4), 124.5 (C5H4,
Ci). IR (cmꢀ1): 2964m, 1450m, 1036s, 824m, 1256s,
1368s, 570m, 1626s, 925w, 425w, 374w. Elemental Anal.
Calc. for C14H24Cl2NNbSi (398.25): C, 42.22; H, 6.07;
N, 3.52. Found: C, 42.26; H, 6.07; N, 3.67%.
(C6D6): d 0.26 (s, 3H, SiMe2), 0.29 (s, 3H, SiMe2),
1.12 (s, 9H, CMe3), 1.67 (d, J = 8.0 Hz, 2H, SiCH2),
3
2
2
2.84 (d, J = 8.0 Hz, 1H, NbCH2Ph), 3.22 (d, J = 8.0
Hz, 1H, NbCH2Ph), 4.93 (m, 2H, CH@CH2), 5.70 (m,
1H, C5H4), 5.76 (m, 1H, CH@CH2), 5.88 (m, 2H,
3
C5H4), 6.05 (m, 1H, C5H4), 6.87 (d, J = 7.7 Hz, 2Ho,
C6H5), 7.05 (t, 3J = 7.7 Hz, 2Hm, C6H5), 7.22 (t,
3J = 7.7 Hz, 2Hp C6H5); 13C NMR (C6D6): d-2.4
(SiMe2), ꢀ2.5 (SiMe2), 24.8 (SiCH2), 31.1 (CMe3), 68.0
(CMe3), 51.6 (NbCH2Ph), 113.7 (CH@CH2), 106.3
(C5H4), 134.7 (CH@CH2), 109.7 (C5H4), 111.8 (C5H4),
119.7 (C5H4), 118.5 (C5H4, Ci), 128.5; 128.7, 129.9;
131.5 (C6H5) IR (cmꢀ1): 3074s, 1449m, 1046m, 819m,
1247s, 1356s, 548m, 1620s, 929m, 431m, 353w, 375w.
Elemental Anal. Calc. for C22H27ClNbSi (447.90): C,
59.00; H, 6.08. Found: C, 59.14; H, 6.21%.
3.5. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)}R2(NtBu)] R = Me, 6; CH2Ph, 7
A THF solution of MgClR (R = Me, 2.3 ml, 6.8
mmol; R = CH2Ph, 3.4 ml, 6.8 mmol) was added at
ꢀ78 ꢁC to a hexane solution (50 ml) of 5 (1.37 g, 3.4
mmol). The mixture was stirred for 2 h at room temper-
ature. The resulting brown suspension was decanted and
filtered through Celite, and the filtrate was concentrated
under reduced pressure to give 6 (reddish) and 7 (brown)
as viscous products.
3.7. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)}(g5-C5H5)Cl(NtBu)] (9)
Data for compound 6: Yield: 0.85 g, 2.38 mmol
1
(70%). H NMR (C6D6): d 0.19 (s, 6H, SiMe2), 0.55 (s,
6H, NbMe2), 1.32 (s, 9H, CMe3), 1.63 (d, J = 7.9 Hz,
Hexane (50 ml) was added to a mixture of 5 (0.4 g, 1.0
mmol) and LiC5H5 (0.072 g, 1.0 mmol) cooled to ꢀ78
ꢁC. After stirring overnight at room temperature, the
yellow suspension was decanted and filtered through
Celite. The filtrate was concentrated to ca. 10 ml and
cooled to ꢀ40 ꢁC to give 9 as a yellow solid. Yield:
3
2H, SiCH2), 4.88 (m, 2H, CH@CH2), 5.73 (m, 1H,
CH@CH2), 5.75 (m, 2H, C5H4), 6.05 (m, 2H, C5H4).
13C NMR (C6D6): d-2.4 (SiMe2), 24.8 (SiCH2), 32.2
(CMe3), 65.2 (CMe3), 113.9 (CH@CH2), 134.5
(CH@CH2), 108.0 (C5H4), 114.1 (C5H4), 117.8 (C5H4,
Ci). IR (cmꢀ1): 2966s, 1450m, 1045s, 816s, 1252s,
1354s, 546m, 1629s, 931m, 433w, 401w. Elemental Anal.
Calc. for C16H30NNbSi (357.41): C, 53.77; H, 8.46; N,
3.92. Found: C, 53.94; H, 8.59; N, 3.74%.
1
0.32 g, 0.75 mmol (75%). H NMR (C6D6): d 0.33 (s,
3H, SiMe2), 0.40 (s, 3H, SiMe2), 0.97 (s, 9H, CMe3),
1.74 (m, 2H, SiCH2), 4.95 (m, 2H, CH@CH2), 5.76
(m, 1H, C5H4), 5.80 (m, 1H, CH@CH2), 5.84 (m, 1H,
C5H4), 5.90 (s, 5H, C5H5), 6.22 (m, 1H, C5H4), 6.28
(m, 1H, C5H4); 13C NMR (C6D6): d-2.3 (SiMe2), ꢀ2.2
(SiMe2), 25.0 (SiCH2), 29.9 (CMe3), 69.9 (CMe3),
114.6 (CH@CH2), 105.3 (C5H4), 135.0 (CH@CH2),
113.6 (C5H4), 111.9 (C5H5), 121.7(C5H4), 125.6
(C5H4), 118.9 (C5H4, Ci). IR (cmꢀ1): 3078m, 1450m,
1046s, 805w, 1243s, 1357s, 575w, 1628s, 897m, 433m,
319w. Elemental Anal. Calc. for C19H29ClNNbSi
(427.89): C, 53.33; H, 6.83; N, 3.27. Found: C, 53.51;
H, 6.97; N, 3.41%.
Data for compound 7: Yield: 1.38 g, 2.71 mmol
1
(80%). H NMR (C6D6): d 0.23 (s, 6H, SiMe2), 1.12 (s,
9H, CMe3), 1.62 (d, J = 8.0 Hz, 4H, NbCH2Ph), 1.91
2
3
(d, J = 8.0 Hz, 2H, SiCH2), 4.91 (m, 2H, CH@CH2),
5.52 (m, 2H, C5H4), 5.70 (m, 1H, CH@CH2), 5.82 (m,
2H, C5H4), 6.86–7.04 (m, 10H, C6H5); 13C NMR
(C6D6): d-2.3 (SiMe2), 25.4 (SiCH2), 31.9 (CMe3), 66.5
(CMe3), 41.5 (NbCH2Ph), 113.9 (CH@CH2), 107.3
(C5H4), 134.6 (CH@CH2), 113.3 (C5H4), 113.0 (C5H4,
Ci), 124.9, 128.7, 130.3 (C6H5), 140.1 (C6H5, Ci) IR
(cmꢀ1): 3057m, 1417m, 1085s, 819s, 1210s, 1354s,
549m, 1629s, 960m, 436m, 377w. Elemental Anal. Calc.
for C28H38NNbSi (509.61): C, 65.99; H, 7.52; N, 2.75.
Found: C, 65.67; H, 7.39; N, 2.71%.
3.8. Preparation of [Nb{g5-C5H4SiMe2(CH2CH@
CH2)}(g5-C5Me5)Cl(NtBu)] (10)
THF (30 ml) was added to a mixture of 5 (0.5 g, 1.3
mmol) and Li(C5Me5) (0.18 g, 1.3 mmol) cooled to ꢀ78
ꢁC. The mixture was stirred for 15 h at room tempera-
ture and the solvent was removed under vacuum. The
residue was treated with hexane and after filtration the
solution was concentrated under vacuum to give 10 as
a brown viscous solid. Yield: 0.45 g, 0.90 mmol (70%).
1H NMR (C6D6): d 0.42 (s, 3H, SiMe2), 0.50 (s, 3H,
3.6. Preparation of [Nb(g5-C5H5){g5-C5H4SiMe2(CH2-
CH@CH2)}(CH2Ph)Cl] (8)
Toluene (50 ml) was added to a mixture of 5 (2.0 g,
5.02 mmol) and 7 (2.56 g, 5.02 mmol). The mixture
was heated to 120 ꢁC for 5 h and the solvent was evap-
orated under reduced pressure. The residue was treated
with hexane (30 ml) and the solution was filtered and
concentrated under vacuum to give 8 as a brown viscous
product. Yield: 2.0 g, 4.47 mmol (90%). 1H NMR
3
SiMe2), 1.09 (s, 9H, CMe3), 1.80 (d, J = 8.0 Hz, 2H,
SiCH2), 1.80 (s, 15 H, C5Me5), 4.95 (m, 2H, CH@CH2),
5.54 (m, 1H, C5H4), 5.86 (m, 1H, C5H4), 5.86 (m, 1H,
CH@CH2), 6.14 (m, 1H, C5H4), 6.39 (m, 1H, C5H4);

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P. Nicolas, P. Royo / Inorganica Chimica Acta 358 (2005) 1494–1500
1499
13C NMR (C6D6): d-2.5 (SiMe2), ꢀ2.4 (SiMe2), 12.7
(C5Me5), 25.3 (SiCH2), 31.3 (CMe3), 69.8 (CMe3),
120.5 (C5Me5), 113.3 (CH@CH2), 108.8 (C5H4), 110.0
(C5H4), 135.5 (CH@CH2), 112.6 (C5H4), 114.3 (C5H4),
130.1 (C5H4, Ci). IR (cmꢀ1): 3075s, 1447m, 1049s,
812m, 1248s, 1354s, 572w, 1629s, 931m, 432m, 377w.
Elemental Anal. Calc. for C24H39ClNNbSi (498.03): C,
57.88; H, 7.89; N, 2.81. Found: C, 58.01; H, 7.95; N,
2.93%.
[3] E.Y.-X. Chen, K.A. Abboud, Organometallics 19 (2000) 5541.
[4] K.S. Cook, W.E. Piers, S.J. Rettig, R. McDonald, Organometal-
lics 19 (2000) 2243.
[5] J.K. Cockroft, V.C. Gibson, J.A.K. Howard, A.D. Poole, U.
Siemeling, C. Wilson, Chem. Commun. (1992) 1668.
[6] 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.
[7] M.J. Humphries, M.L.H. Green, R.E. Douthwaite, L.H. Rees,
Dalton (2000) 4555.
[8] G.I. Nikonov, P. Mountford, L.G. Kuzmina, J.A.K. Howard,
D.A. Lemenovskii, D.M. Roitershtein, J. Organomet. Chem.
628 (2001) 25.
3.9. Preparation of [Ta{g5-C5H4SiMe2(CH2CH@
CH2)}(g5-C5Me5)Cl(NtBu)] (11)
´
[9] P. Nicolas, P. Royo, M.V. Galakhov, O. Blacque, H. Jacobsen,
H. Berke, Dalton Trans. (2004) 2943.
[10] T. Cuenca, P. Royo, Coord. Chem. Rev. 193–195 (1999) 447.
A THF solution (10 ml) of LiC5H4SiMe2(allyl) (0.18
g, 1.09 mmol) was added at ꢀ78 ꢁC to a hexane solution
(50 ml) of [Ta(g5-C5Me5)Cl2(NtBu)] (0.50 g, 1.09
mmol). After stirring overnight, the orange suspension
was decanted and filtered through Celite. The filtrate
was concentrated under vacuum to give 11 as a brown
´
[11] (a) M.I. Alcalde, M.P. Gomez-Sal, P. Royo, Organometallics 20
(2001) 4623;
(b) M.I. Alcalde, M.P. Go´mez-Sal, P. Royo, Organometallics 18
(1999) 546.
´ ´
[12] (a) M.V. Galakhov, M. Gomez, G. Jimenez, M.A. Pellinghelli, P.
Royo, A. Tiripicchio, Organometallics 13 (1994) 1564;
´
´ ´
(b) M. Gomez, P. Gomez-Sal, M.P. Nicolas, P. Royo, J.
Organomet. Chem. 491 (1995) 121;
1
viscous product. Yield: 0.42 g, 0.72 mmol (70%). H
NMR (C6D6): d 0.36 (s, 3H, SiMe2), 0.42 (s, 3H, SiMe2),
1.12 (s, 9H, CMe3), 1.80 (d, J = 8.0 Hz, 2H, SiCH2),
´ ´
(c) M.V. Galakhov, M. Gomez, G. Jimenez, P. Royo, Organo-
3
metallics 14 (1995) 2843;
´
´
J. Sanchez-Nieves, Organometallics 15 (1996) 3579;
´
´ ´
(d) M. Gomez, P. Gomez-Sal, G. Jimenez, A. Martın, P. Royo,
1.88 (s, 15 H, C5Me5), 4.90 (m, 2H, CH@CH2), 5.60
(m, 1H, C5H4), 5.80 (m, 1H, C5H4), 5.80 (m, 1H,
CH@CH2), 6.15 (m, 1H, C5H4), 6.40 (m, 1H, C5H4);
13C NMR (C6D6): d-2.5 (SiMe2), ꢀ2.4 (SiMe2), 12.7
(C5Me5), 25.4 (SiCH2), 32.8 (CMe3), 66.5 (CMe3),
119.0 (C5Me5), 113.2 (CH@CH2), 107.3 (C5H4), 108.5
(C5H4), 135.4 (CH@CH2), 112.5 (C5H4), 119.7 (C5H4),
114.0 (C5H4, Ci). IR (cmꢀ1): 3076s, 1450m, 1047s,
821m, 1245s, 1357s, 574w, 1629s, 921m, 431m, 376w.
Elemental Anal. Calc. for C24H39ClNSiTa (586.07): C,
49.19; H, 6.71; N, 2.39. Found: C, 48.98; H, 6.74; N,
2.29%.
´ ´
(e) A. Castro, M.V. Galakhov, M. Gomez, P. Gomez-Sal, A.
´
Martın, P. Royo, J. Organomet. Chem. 554 (1998) 185;
´
(f) P. Royo, J. Sanchez-Nieves, M.A. Pellinghelli, A. Tiripicchio,
J. Organomet. Chem. 563 (1998) 15;
´
(g) P. Royo, J. Sanchez-Nieves, J. Organomet. Chem. 597 (2000)
61;
(h) J. Sanchez-Nieves, P. Royo, M.A. Pellinghelli, A. Tiripicchio,
Organometallics 19 (2000) 3161;
´
´
(i) J. Sanchez-Nieves, P. Royo, J. Organomet. Chem 621 (2001)
299.
[13] (a) F. Amor, P. Gomez-Sal, E. de Jesus, A. Martın, Ana. I.
´ ´
Perez, P. Royo, A. Vazquez de Miguel, Organometallics 15 (1996)
´
´
´
2103;
(b) T. Pedraz, M.A. Pellinghelli, P. Royo, A. Tiripicchio, A.
´
Vazquez de Miguel, J. Organomet. Chem. 534 (1997) 27;
´
(c) P. Gomez-Sal, I. Jimenez, A. Martın, T. Pedraz, P. Royo, A.
Selle´s, A. Va´zquez de Miguel, Inorg. Chim. Acta 273 (1998) 270;
´
´
Acknowledgment
´
(d) F.J. de la Mata, J. Gomez, P. Royo, J. Organomet. Chem. 564
(1998) 277.
[14] A.M. Andreu, F.A. Jalon, A. Otero, P. Royo, A.M. Manotti
Lanfredi, A. Tiripicchio, J. Chem. Soc., Dalton Trans. (1987) 953.
Financial support of our work by MCyT (Project
MAT2001-1309) is gratefully acknowledged.
´
´
[15] M. Gomez, P. Royo, J.M. Selas, J. Organomet. Chem. 314 (1986)
131.
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