Alkyl chloro, dialkyl and mixed alkyl derivatives of imido(pentamethylcyclopentadienyl) tantalum(V). X-ray crystal structure of [TaCp*Cp′Cl{N(2,6-Me2C6H3)}], (Cp′=η5-C5H4SiMe3]

Article abstract of DOI:10.1016/S0022-328X(97)00724-9

[TaCp*Cl₂{N(2,6-Me₂C₆H ₃)}] (Cp=η⁵-C₅Me₅) reacts with one equivalent of LiR (R=CH₂SiMe₃, CH₂CMe₂Ph, CH₂CMe₃, 2-(CH₂NMe₂)C₆H₄, C₅H₄SiMe₃) or 0.5 equivalents of Mg(CH₂C₆H₅)₂(THF)₂ to give the alkyl chloro complexes [TaCp*ClR{N(2,6-Me₂C₆H₃)}],(R=CH ₂SiMe₃, 1; CH₂CMe₂Ph, 2; CH₂CMe₃, 3; CH₂C₆H₅, 4; 2-(CH₂NMe₂)C₆H₄, 5; C₅H₄SiMe₃, 6). When the same reaction was carried out with two equivalents of lithium or one equivalent of magnesium reagent, the corresponding dialkyl derivatives [TaCp*R₂{N(2,6-Me₂C₆H ₃)}],(R=CH₂SiMe₃, 7; CH₂CMe₂Ph, 8; C₆H₅, 9; CH₂C₆H₅, 10; CH₂CMe₃, 11) were obtained. The mixed alkyl derivatives [TaCp*MeR{N(2,6-Me₂C₆H₃)}], (R=CH₂SiMe₃, 12; CH₂CMe₂Ph, 13; C₆H₅, 14; CH₂CMe₃, 15; 2-(CH₂NMe₂)C₆H₄, 16; CH₂C₆H₅, 17; C₅H₄SiMe₃, 18) have been prepared by treatment of solutions containing [TaCp*ClMe{N(2,6-Me₂C₆H₃)}] with one equivalent of lithium or 0.5 equivalents of magnesium reagent. All the new complexes were characterized by the usual IR and NMR spectroscopic methods. The crystal structure of 6 was determined by X-ray diffraction studies. Crystals of 6 are monoclinic, space group P2₁/c, with Z=4 in a unit cell of dimensions a=12.597(3), b=11.338(2), c=18.297(4) A and β=96.53(3)°. The structure was solved from diffractometer data by a combination of direct and Fourier methods and refined by full-matrix least squares fit on the basis of 4846 observed reflections to R₁ and wR² values of 0.0224 and 0.0574, respectively.

Full text of DOI:10.1016/S0022-328X(97)00724-9

Journal of Organometallic Chemistry 554 (1998) 185–194
Alkyl chloro, dialkyl and mixed alkyl derivatives of
imido(pentamethylcyclopentadienyl) tantalum(V). X-ray crystal
structure of [TaCp*Cp%Cl{N(2,6-Me2C6H3)}], (Cp%=p5-C5H4SiMe3]1
Aurora Castro, Mikhail V. Galakhov, Manuel Go´mez, Pilar Go´mez-Sal 2, Avelino Mart´ın,
Pascual Royo *
Departamento de Qu´ımica Inorganica, Uni6ersidad de Alcala´ de Henares, Campus Uni6ersitario, 28871 Alcala de Henares, Spain
Received 22 September 1997
Abstract
[TaCp*Cl2{N(2,6-Me2C6H3)}] (Cp*=p5-C5Me5) reacts with one equivalent of LiR (R=CH2SiMe3, CH2CMe2Ph, CH2CMe3,
2-(CH2NMe2)C6H4, C5H4SiMe3) or 0.5 equivalents of Mg(CH2C6H5)2(THF)2 to give the alkyl chloro complexes
[TaCp*ClR{N(2,6-Me2C6H3)}],(R=CH2SiMe3, 1; CH2CMe2Ph, 2; CH2CMe3, 3; CH2C6H5, 4; 2-(CH2NMe2)C6H4, 5;
C5H4SiMe3, 6). When the same reaction was carried out with two equivalents of lithium or one equivalent of magnesium reagent,
the corresponding dialkyl derivatives [TaCp*R2{N(2,6-Me2C6H3)}],(R=CH2SiMe3, 7; CH2CMe2Ph, 8; C6H5, 9; CH2C6H5, 10;
CH2CMe3, 11) were obtained. The mixed alkyl derivatives [TaCp*MeR{N(2,6-Me2C6H3)}], (R=CH2SiMe3, 12; CH2CMe2Ph, 13;
C6H5, 14; CH2CMe3, 15; 2-(CH2NMe2)C6H4, 16; CH2C6H5, 17; C5H4SiMe3, 18) have been prepared by treatment of solutions
containing [TaCp*ClMe{N(2,6-Me2C6H3)}] with one equivalent of lithium or 0.5 equivalents of magnesium reagent. All the new
complexes were characterized by the usual IR and NMR spectroscopic methods. The crystal structure of 6 was determined by
X-ray diffraction studies. Crystals of 6 are monoclinic, space group P21/c, with Z=4 in a unit cell of dimensions a=12.597(3),
˚
b=11.338(2), c=18.297(4) A and i=96.53(3)°. The structure was solved from diffractometer data by a combination of direct
and Fourier methods and refined by full-matrix least squares fit on the basis of 4846 observed reflections to R1 and wR2 values
of 0.0224 and 0.0574, respectively. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Tantalum; alkyl imido pentamethylcyclopentadienyl complexes
cyclopentadienyl ligands [4,5] allows the isoelectronic
[MCp2] group 4 and the [MCp(NR)] group 5 metal
1. Introduction
fragments to generate two groups of related complexes
due to their similar stereochemical properties. The easy
modification of the steric and electronic properties of
High-valent early transition metal complexes con-
taining cyclopentadienyl ligands and strong y-donor
oxo and organoimido substituents are being intensively
the cyclopentadienyl ligand by the introduction of ap-
studied in relation to their many potential applications
propriate ring-substituents and also of the imido ligand
in catalytic and stoichiometric processes [1–3].
by the modification of its alkyl moiety make this type
The isolobal relationship between the imido and the
of compound very versatile. For all these reasons a rich
chemistry of imido group 5 metal complexes containing
* Corresponding author. Tel.: +34
1 8854765; fax: +34 1
mono-functional [6,7], tetradentate triamidoamine [8,9]
and cyclopentadienyl ligands in mono- [10–14] and
di-cyclopentadienyltype [15–18] complexes has been re-
ported in recent years. Protonated lithium amides [12]
8854683; e-mail; proyo@enorg.alcala.es
1 Dedicated to Prof. P.M. Maitlis on the occasion of his 65th
birthday.
2 X-ray diffraction studies.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00724-9

186
A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
Scheme 1.
have been extensively used to generate the imido ligand
but other synthetic strategies have also been applied
such as those based on the deprotonation of cyclopen-
tadiene by metal amides [10,15], i-hydrogen elimina-
tion of amides and amines coordinated to metal(III)
compounds [16,18] and oxidation of metal(III) com-
plexes with azides [17]. Related alkoxylimido and hy-
drazido(2-) derivatives have been reported [19–21]
more recently.
Although the chemistry of imido pentamethylcy-
clopentadienyl tantalum halides is well established, the
alkyl compounds are less known even though such
complexes have significant potential applications. Fol-
lowing our recent work on the dichloro- and chloro-
methyl derivatives [Ta(p5-C5Me5)Cl2(NAr)], (Ar=2,6-
Me2C6H3; 2,4,6-Me3C6H2) [22], [Ta(p5-C5Me5)XY
{N(2,6-Me2C6H3)}],(X=Y=Me; X=Cl, OC6H3Me2,
Y=Me) [23] we report herein a systematic study of the
reactivity of monocyclopentadienyl arylimido tantalum
complexes [Ta(p5-C5Me5)XY{N(2,6-Me2C6H3)}], (X=
Y=Cl; X=Cl, Y=Me) towards alkylating reagents
and the X-ray molecular structure of the [Ta(p5-
C5Me5)(p5-C5H4SiMe3) Cl{N(2,6-Me2C6H3)}] complex.
2. Results and discussion
2.1. Alkyl chloro and dialkyl imido pentamethylcyclopen-
tadienyl tantalum(V) compounds
The direct alkylation of [TaCp*Cl2{N(2,6-
Me2C6H3)}] (Cp*=p5-C5Me5) with an appropriate
amount of the alkylating reagent leads to the forma-
tion of the half-sandwich alkyl chloro imido
[TaCp*ClR{N(2,6-Me2C6H3)}] (1–6) and dialkyl imido
[TaCp*R2{N(2,6-Me2C6H3)}] (7–11) complexes, as
shown in Scheme 1.
Treatment of the starting dichloro imido complex
with one equivalent of LiPh gives a 1:1 mixture of

A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
187
Table 1
Kinetic parameters of Berry pseudorotation for complexes 2, 3 and 4
Complex
log A
Ea
DHc
DSc
DGc298 K
kcal mol−1
13.5
kcal mol−1
12.890.39
12.990.15
12.890.30
kcal mol−1
12.890.30
12.390.16
12.890.25
e.u.
2
12.290.31
12.890.12
12.290.30
−2.591.2
−2.090.5
−2.591.1
R=CH2CMe2Ph
3
R=CH2CMe3
4
12.9
12.0
R=CH2C6H5
chloro phenyl and diphenyl complexes, but the diphenyl
complex 9 is the only product formed when two equiv-
alents of LiPh are used in the reaction. Several attempts
to prepare the bis-2-[(dimethylamino)methyl]phenyl
imido compound were unsuccessful, probably due to
steric factors, and in all cases a mixture of monoalkyl
derivative 5 and the excess alkylating reagent were
obtained.
increases from the smallest (R=CH2C6H5) to bulkiest
substituent (R=CH2CMe2Ph). We suggest that this
dynamic process does not take place by rotation
around the Ta–N–Ci(aryl) axis hindered by the steric
requirement of the pentamethylcyclopentadienyl and
2,6-dimethylphenyl groups, but involves in a Berry
pseudorotation with negligible variation of DSc [27] in
a solvated pentacoordinate species present in solution.
The 2-[(dimethylamino)methyl]phenyl ligand is able
to form cyclometalated complexes [28] containing a
five-membered chelate ring by coordination of the ni-
trogen to electron-deficient metal centers, leading to a
distorted peudo-square pyramidal geometry as has been
reported for similar alkylated tantalum compounds
[29]. However the NMR data for complex 5 (Section 3)
show that the Me2N protons and carbons are equiva-
lent, consistent with a singly coordinated aryl ligand
with non-coordinated amine functionality.
Crystals of complex 6 suitable for X-ray diffraction
studies were obtained by cooling its toluene solution to
−40°C. An ORTEP drawing of 6 based on the X-ray
structural analysis with the atomic labeling scheme is
shown in Fig. 1. Selected bond distances and angles are
given in Table 2.
The molecular structure of 6 shows a typical bent-
metallocene geometry, with the chlorine atom and the
imido group lying in the equatorial plane. Although the
two cyclopentadienyl (Cp) rings are different the dis-
tance from the tantalum atom to both centroids is the
same and the mean distance Ta–C does not show any
All of the complexes 1–11 are soluble in aromatic
and saturated hydrocarbons, chlorinated solvents, di-
ethyl ether and tetrahydrofuran. They are air- and
moisture-sensitive, and rigorously dried solvents and
handling under dry inert atmosphere were found to be
imperative for successful preparations.
1
The analytical, IR, and H and 13C{1H} NMR spec-
troscopic data (Section 3) for compounds 1–11 are
consistent with their formulation. The new imido com-
plexes show the w(TaꢀN) [13,24] IR absorption at ca. 1320
cm−1
.
1
The H NMR spectra show an AB spin system for
the h-CH2 protons of the alkyl groups of complexes
1–4 with a chiral metal center, and of the h-CH2
protons of complexes 7, 8, 10 and 11 with a prochiral
1
metal center. In addition, the H and 13C{1H} NMR
spectra of 2 and 8 show the expected two resonances
for the inequivalent methyl substituents of the i-CMe2
groups. Complex 6 shows four proton and five carbon
resonances for the silyl-substituted cyclopentadienyl
ring.
1
The H NMR spectra of complexes 2, 3 and 4 in
CD2Cl2 or CDCl3 solutions at room temperature show
slightly broad signals for the o-methyl(phenyl) groups
of the imido ligand, whereas the 13C{1H} NMR spec-
trum of 3 displays a very broad signal for the same
˚
˚
significant difference (2.50 A in Cp1 and 2.49 A in
Cp2). The equatorial plane is defined by Ta1, Cl1, N1
and C41. The two Cp centroids are equidistant from it
˚
1
with distances of 1.98 and 1.93 A for Cp1 and Cp2,
groups. The H NMR study at variable temperature
respectively. The angles between the equatorial plane
and the mean Cp planes are also equivalent. All these
features indicate that the bonding of both Cp rings to
the metal centre is very similar. The Ta–N distance of
indicates typical dynamic behaviour involving the ex-
change of two equally populated signals [25,26]. The
kinetic parameters of this dynamic process which were
calculated using the 1H DNMR data and DNMR5
program (see Table 1) are consistent with an in-
tramolecular process (log A:12). The free Gibbs en-
ergy (DGc) found for complexes 2, 3 and 4 depends on
the steric requirement of the alkyl substituent and
˚
1.803(4) A is very similar to those found in the closely
related compounds TaCp2*Cl(ꢀNPh), (Ta–N 1.799(4)
˚
˚
A) [18] and TaCp*H(ꢀNPh), (Ta–N 1.831(10) A) [30].
2
Likewise, although slightly more closed, the Ta–N–

188
A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
consistent with an 18-electron configuration at the
metal centre and an sp hybridized nitrogen atom with
a lone pair of electrons, involved in bonding with the
phenyl substituent, centred on it. These data are con-
sistent with a tantalum–nitrogen bond order of about
2. The phenyl ring occupies its sterically more fa-
voured position fairly parallel to the equatorial plane
at an angle of 15.4° with it, thus facilitating maximun
overlap with the nitrogen centered p orbital.
One remarkable difference between our structure
and the two structures previously reported is the situ-
ation of the ligands in the equatorial plane with re-
spect to the Cp(centroid)–Ta–Cp(centroid) plane. In
the reported compounds the imido nitrogen donor
atom lies closer to this plane at 38 and 21° and the
chloro and the hydrido ligands are located at 57 and
61°, respectively, whereas in complex 6 the chloro
moiety is nearer to that plane, making an angle of
28.5° with it and the imido nitrogen is located at 53°,
thus avoiding any unfavourable steric interaction with
the –SiMe3 ring-substituent located practically in that
plane. The SiMe3 fragment is bent away from the
corresponding Cp plane and the Si atom is located at
Fig. 1. ORTEP view of the molecular structure of [Ta(p5-C5Me5)(p5-
C5H4SiMe3)Cl{N(2,6-Me2C6H3)}], 6, with the atom-numbering
scheme.
˚
0.28 A from it. All of the Ta–Cl, C–C and C–Si
distances are normal.
2.2. Alkyl methyl imido pentamethylcyclopentadienyl
tantalum(V) compounds
C41 angle of 174.6(3)° is almost linear. This disposi-
tion is in accordance with the MO explanation re-
ported for complexes of this type [31] and is
When one equivalent of LiR or 0.5 equivalents of
dibenzyl magnesium is added to a toluene solution of
the starting chloro methyl imido complex, a yellow
solution is obtained, which after manipulation affords
the mixed alkylated complexes 12–18 in good yields,
as shown in Scheme 2.
All of the complexes 12–18 are air- and moisture-
sensitive, very soluble in alkanes, aromatic hydrocar-
bons and chlorinated solvents.
The structures of complexes 12–18 in the solid
have not been determined but the compounds are as-
sumed to be monomers, pseudotetrahedral and
isostructural with other half-sandwich imido Group 5
metal derivatives [13,32]. Their formulation as mixed
alkylated imido complexes is supported by analytical
and spectroscopic data (Section 3) which show the
behaviour expected for such chiral species.
The IR spectra of complexes 12–18 display a
strong band at ca. 1326 cm−1 which can be assigned
to the wTaꢀN stretching vibration [l3,24]. The 1H and
13C{1H} NMR spectra of complexes 12–18 show the
expected signals for the pentamethylcyclopentadienyl
ring and also for the equivalent ortho-methyl phenyl
imido groups except for complex 18 which shows two
signals for both ortho-methylphenyl imido sub-
stituents due to slow rotation of the phenyl ring
around the Ta–N–Ci(phenyl) axis. In addition, four
Table 2
˚
Bond lengths [A] and angles [°] for 6
Ta(1)ꢁN(1)
Ta(1)ꢁC(14)
Ta(1)ꢁC(23)
Ta(1)ꢁC(13)
Ta(1)ꢁC(25)
Ta(1)ꢁC(24)
Si(1)ꢁC(27)
Si(1)ꢁC(21)
N(1)ꢁC(41)
Ta(1)ꢁCp(2)
N(1)ꢁTa(1)ꢁCl(1)
1.803(4) Ta(1)ꢁCl(1)
2.432(4) Ta(1)ꢁC(22)
2.444(4) Ta(1)ꢁC(12)
2.484(4) Ta (1)ꢁC(21)
2.544(4) Ta(1)ꢁC(11)
2.549(5) Ta(1)ꢁC(15)
1.847(6) Si(1)ꢁC(26)
1.873(5) Si(1)ꢁC(28)
1.372(6) Ta(1)ꢁCp(1)
2.190
2.426(1)
2.433(5)
2.487(4)
2.506(4)
2.559(5)
2.570(5)
1.849(6)
1.863(5)
2.202
98.5(1)
C(41)ꢁN(1)ꢁTa(1)
174.6(3)
102.5
102.4
Cp(1)ꢁTa(1)ꢁCp(2) 126.2
Cp(1)ꢁTa(1)ꢁN(1) 110.1
Cp(2)ꢁTa(1)ꢁN(1) 112.3
Cp(1)ꢁTa(1)ꢁCl(1)
Cp(2)ꢁTa(1)ꢁCl(1)
Cp(1) and Cp(2) are the centroids of the C5Me5 and C5H4SiMe3,
respectively.

A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
189
Scheme 2.
3. Experimental section
and five resonances for the trimethylsilylcyclopentadi-
enyl ring protons and carbons are observed. The h-
CH2 protons of the alkyl groups of complexes 12,
13, 15, 16 and 17 appear as an AB spin system and
in the case of 13 two resonances are observed for
the inequivalent methyl substituents of the alkyl
group.
3.1. General considerations
All manipulations were carried out under an atmo-
sphere of argon using conventional Schlenk-tube and
glove-box techniques.

190
A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
Solvents were purified by distillation from an appro-
to −40°C to give the chloro methyl imido derivative as
priate drying agent diethyl ether and tetrahydrofuran
(Na/benzophenone), n-hexane (Na/K alloy) and
toluene (Na).Reagent grade iodobenzene, LinBu (1.6 M
in hexanes) and ZnMe2 (2 M in toluene) were pur-
chased from Aldrich Chemical and were used without
further purification. Alkyl lithium LiR (R=CH2SiMe3
[33], CH2CMe2Ph [33], CH2CMe3 [33], C6H5 [34], 2-
(CH2NMe2)C6H4 [35], C5H4SiMe3 [36]), benzyl magne-
sium Mg(CH2C6H5)2(THE)2 [37] and the starting
materials [TaCp*X2{N(2,6-Me2C6H3)}], (X=Cl [38],
Me [23]), [TaCp*ClMe{N(2,6-Me2C6H3)}] [23] and
[TaCp*Me{N(2,6 - Me2C6H3)}{N(2,6 - Me2C6H3(CMeꢀ
CMe2)}] [38] were prepared as described previously.
Infrared spectra were recorded on a Perkin–Elmer
583 spectrophotometer (4000–200 cm−1) as Nujol
mulls between CsI or polyethylene pellets. 1H and
13C{1H} NMR spectra were recorded on Varian Unity
300 and Varian Unity 500 Plus spectrometers and
orange crystals. Yield 0.60 (90%).
3.3. Synthesis of [TaCp*ClR{N(2,6-Me2C6H3)}] (R=
CH2SiMe3, 1; CH2CMe2Ph, 2; CH2–CMe3, 3;
CH2C6H5, 4; 2-(CH2NMe2)C6H4, 5; C5H4SiMe3, 6)
1–5. [TaCp*Cl2{N(2,6-Me2C6H3)}] (0.70 g, 1.38
mmol) and LiR (1.38 mmol; R=CH2SiMe3, 0.13 g;
CH2CMe2Ph, 0.19 g; CH2–CMe3, 0.11 g; 2-
(CH2NMe2)C6H4, 0.20 g) or Mg(CH2C6H5)2(THF)2
(0.24 g, 1.38 mmol) were stirred in toluene (50 ml) at
room temperature for 12 h. The resulting suspension
was evaporated to dryness and the residue extracted
into n-hexane (2×10 ml). Subsequently, the resulting
solution was filtered, concentrated to ca. 10 ml and
cooled to −40°C overnight to give 1–5 as yellow
microcrystalline solids.
The data for 1 follow. Yield 0.64 g (70%). IR (Nujol
mull, w cm−1): 1642 (w), 1327 (vs), 1241 (vs), 1095 (m),
1023 (m), 966 (m), 897 (m), 850 (m), 761 (m), 526 (w),
1
chemical shifts were measured relative to residual H
and 13C resonances in the deuterated solvents C6D6(l
7.15), CDCl3(l 7.24) and C6D6(l 128), CDCl3(l 77),
respectively. C, H and N analyses were carried out with
a Perkin–Elmer 240C microanalyzer.
1
353 (m). H NMR (l ppm, in chloroform-d): 6.95 (d,
2H), 6.62 (t, 1H, H3C6Me2N), 2.34 (s, 6H, Me2C6H3N),
2.04 (s, 15H, C5Me5), 0.73av (AB, 2H, JH–H=12.5 Hz,
2
H2CSiMe3), 0.02 (s, 9H, Me3SiCH2). 13C{1H} NMR (l
ppm, in chloroform-d): 152.33, 134.08, 122.00, 118.10
(Ci, Cp, Co, Cm, C6H3Me2N), 126.81 (C5Me5), 56.34
(CH2SiMe3), 19.02 (Me2C6H3N), 11.27 (C5Me5), l.95
(Me3SiCH2). Anal. Found: C, 47.55; H, 6.24; N, 2.62.
C22H35ClNSiTa. Calc.: C, 47.35; H, 6.32; N, 2.51%.
The data for 2 follow. Yield 0.54 g (65%). IR (Nujol
mull, w cm−1): 1590 (w), 1326 (vs), 1169 (m), 1096 (m),
1027 (m), 983 (m), 763 (s), 722 (m), 696 (m), 608 (w),
3.2. Synthesis of starting materials
Starting
materials
[TaCp*Cl2−xMex{N(2,6-
Me2C6H3)}] (x=0 [38], 1 [23]) were recently prepared
and described by our research group, but in the case of
the chloro methyl imido derivative, we here report two
new synthetic methods with better yield.
1
548 (w), 392 (w), 348 (s). H NMR (l ppm, in chloro-
3.2.1. Method A
form-d): 7.34 (d, 2H), 7.20 (t, 2H), 7.06 (t, 1H,
H5C6CMe2CH2), 7.00 (d, 2H), 6.68 (t, 1H, H3C6Me2N),
2.33 (br, 6H, Me2C6H3N), 2.02 (s, 15H, C5Me5), 1.53 (s,
3H, H2CCMe2Ph), 1.46 (AB, 2H, 2JH–H=14.5 Hz,
H2CCMe2Ph), 1.43 (s, 3H, H2CCMe2Ph). 13Cl{1H}
NMR (l ppm, in chloroform-d): 155.20, 127.72, 127.00,
125.45 (Ci, Co, Cp, Cm, C6H5Me2CCH2), 152.00, 128.20,
124.80, 122 20(Ci, Cp, Co, Cm, C6H3Me2N), 118.60
(C5Me5), 83.20(H2CCMe2Ph), 40.11 (H2CCMe2Ph),
33.26, 32.42 (H2CCMe2Ph), 19.00(br, Me2C6H3N),
11.25 (C5Me5). Anal. Found: C, 55.94; H, 6.26; N, 2.38.
C28H37ClNTa. Calc.: C, 55.68; H, 6.17; N, 2.32%.
The data for 3 follow. Yield 0.52 g (70%). IR (Nujol
mull, w cm−1): 1587 (m), 1326 (vs), 1213 (s), l095 (s),
1022 (m), 984 (s), 760 (vs), 565 (m), 505 (w), 429 (m),
A
mixture
of
equimolar
amounts
of
[TaCp*Cl2{N(2,6-Me2C6H3)}](0.60 g, 1.18 mmol) and
[TaCp*Me2{N(2,6-Me2C6H3)}] (0.55 g, 1.18 mmol) in
toluene (25 ml) was heated at 100°C for 3 days in a
sealed ampoule. After the ampoule was opened, the
solution was evaporated to dryness and the residue
washed with cold n-hexane (3×5 ml). The orange
microcrystalline solid obtained was identified as
[TaCp*ClMe{N(2,6-Me2C6H3)}] by analytical and
1
spectroscopic (IR, H NMR) methods. The data coin-
cide with those previously reported [7]. Yield 0.54 g
(95%).
3.2.2. Method B
A 2 M solution of ZnMe2 in toluene (0.70 ml, 1.38
mmol) was added at room temperature to a red solu-
tion of [TaCp*Cl2{N(2,6-Me2C6H3)}] (0.70 g, l.38
mmol) in toluene (50 ml) and the mixture was stirred
for 12 h. The solvent was removed in vacuo and the
residue extracted into n-hexane (3×15 ml). The solu-
tion was filtered, concentrated to ca. 10 ml and cooled
1
391 (m), 349 (vs). H NMR (l ppm, in chloroform-d):
6.97 (d, 2H), 6.65 (t, 1H, H3C6Me2N), 2.37 (s, 6H,
Me2C6H3N), 2.20, 1.10 (AB, 2H, 2JH–H=13.7 Hz,
H2C–CMe3), 2.03 (s, 15H, C5Me5), 1.03 (s, 9H, Me3C–
CH2). 13C{1H} NMR (l ppm, in chloroform-d):
152.20, 127.00, 122 04(Ci, Cp, Cm, C6H3Me2N). 118.41

A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
191
(C5Me5), 83.75(CH2–CMe3), 34.74 (Me3C–CH2), 33.70
(Me3C–CH2), 19.40 (br, Me2C6H3N), 11.20 (C5Me5).
Anal. Found: C, 54.92; H, 6.07; N, 2.46. C27H35ClNTa
Calc.: C, 54.97; H, 5.98; N, 2.37%.
125.95, 120.60 (C2, 5, C5H4SiMe3), 125.04, 120.95 (Co,
C6H3Me2N), 118.76 (C5Me5), 118.70(Cp,C6H3Me2N),
109.21, 105.23 (C3,4
,
C5H4SiMe3), 19.7, 18.8
(Me2C6H3N), 12.00 (C5Me5), −0.44 (Me3SiC5H4).
Anal. Found: C, 51.12; H, 6.01; N, 2.30.
C26H37ClNSiTa. Calc.: C, 51.35; H, 6.13; N, 2.30%.
The data for 4 follow. Yield 0.47 g (60%). IR (Nujol
mull, w cm−1): 1591 (m), 1324 (vs), 1196 (m), 1096 (m),
1065 (m), 1027 (s), 984 (m), 895 (m), 794 (m), 760 (s),
1
749 (s), 692 (m), 546 (w), 393 (m), 347 (s), 228 (m). H
NMR (l ppm, in chloroform-d): 7.20 (t, 1H), 7.08 (t,
2H), 7.00 (d, 2H, H5C6CH2), 6.94(d, 2H), 6.64 (t, 1H,
H3C6Me2N), 3.08, 2.40 (AB, 2H, 2JH–H=11 Hz,
H2CC6H5), 2.36 (s, 6H, Me2C6H3N), 2.03 (s, 15H,
C5Me5) 13C{1H} NMR (l ppm, in chloroform-d):
152.35–122.33 (several phenyl for C6H5CH2 and
C6H3Me2N), 117.01 (C5Me5), 62.00 (H2C–C6H5), 19.20
(Me2C6H3N), 11.24 (C5Me5). Anal. Found: C, 53.20; H,
5.45; N, 2.47. C25H31ClNTa Calc.: C, 53.43; H, 5.56; N,
2.49%.
3.4. Synthesis of [TaCp*R2{N(2,6-Me2C6H3)}], (R=
CH2 SiMe3, 7; CH2CMe2Ph, 8; C6H5, 9; CH2C6H5, 10;
CH2CMe3, 11)
A solution of LiR (2.76 mmol; R=CH2SiMe3, 0.26
g; CH2CMe2Ph, 0.39 g; C6H5, 0.23 g; CH2CMe3, 0.21 g)
or Mg (CH2C6H5)2(THF)2 (0.48 g; 1.38 mmol) in
toluene or n-hexane(11) (25 ml) was added at room
temperature to
a
solution of [TaCp*Cl2{N(2,6-
Me2C6H3)}] (0.70 g; 1.38 mmol) in toluene or n-hex-
ane(11) (25 ml) and the mixture was stirred for 12 h.
The solvent was removed in vacuo and the residue
extracted into n-hexane (3×15 ml). The solution was
concentrated to ca. 20 ml and cooled to −40°C to give
7–11 as brown (7 ,8, 11), red–orange (9) and yellow
(10) microcrystalline solids.
The data for 5 follow. Yield 0.58 g (70%). IR (Nujol
mull, w cm−1): 1585 (w), 1407 (m), 1309 (vs), 1101 (m),
1019 (m), 981 (m), 845 (m), 761 (m), 740 (m), 516 (w),
1
331 (s). H NMR (l ppm, in chloroform-d): 7.66 (m,
1H), 7.05 [m, 3H, H4C6-2-(CH2NMe2)], 6.86 (d, 2H),
2
6.55 (t, 1H, H3C6Me2N), 4.22, 3.46 [AB, 2H, JH–H
=
14.1 Hz, 2-(CH2NMe2)C6H4], 2.66 [s, 6H, 2-
(CH2NMe2)C6H4], 2.28 (s, 6H, Me2C6H3N), 2.00 (s,
15H, C5Me5). 13C{1H} NMR (l ppm, in chloroform-
d): 191.26 [Ci, H4C6-2-(CH2NMe2)], 144.60, 142.75 [Co,
The data for 7 follow. Yield 0.59 g (70%). IR (Nujol
mull, w cm−1): 1588(m), 1320 (vs), 1243 (vs), 1159 (m),
1096 (m), 1025 (m), 965 (s), 908 (s), 850 (vs), 758 (vs),
1
683 (s), 523 (w), 471 (w), 348 (s). H NMR (l ppm, in
H4C6-2-(CH2NMe2)].
127.24
[H4C6-2-(CH2NMe2)]
chloroform-d): 6.96 (d, 2H), 6.62 (t, 1H, H3C6Me2N),
2.33 (s, 6H, Me2C6H3N), 1.49 (s, 15H, C5Me5), 0.40,
−0.84 (AB, 4H, JH–H=7.69 Hz, H2CSiMe3), 0.021 (s,
126.02, 125.05 [Cm, H4C6-2-(CH2NMe2)], 153.92,
134.78, 123.20, 121.87 (Ci, Cp, Cm, Co, C6H3Me2),
119.66 (C5Me5), 72.94 [2-(CH2NMe2)C6H4], 50.73 [2-
(CH2NMe2)C6H4] 20.30(Me2C6H3N), 12.37(C5Me5).
Anal. Found: C, 53.52; H, 6.17; N, 4.70.
C27H36ClN2Ta. Calc.: C, 53.60; H, 6.00; N, 4.63%.
Compound 6. A solution of LiC5H4SiMe3 (0.28 g,
1.97 mmol) in 10 ml of THF was slowly added at room
temperature to a stirred freshly prepared solution of
[TaCp*Cl2{N(2,6-Me2C6H3)}] (1.00 g, 1.97 mmol) in 30
ml of THF. The mixture was stirred for 12 h to give an
orange solution. Volatiles were removed in vacuo and
the residue was extracted into toluene (3×20 ml). The
resulting orange solution was filtered, the solvent evap-
orated to dryness and the orange solid washed with
cold n-hexane (2×5 ml), dried in vacuo and identified
as 6.
2
18H, Me3SiCH2). 13C{1H} NMR (l ppm, in chloro-
form-d): 154.1 (Ci, C6H3Me2N), 133.31 (Cp,
C6H3Me2N), 127.00 (C5Me5), 120.64 (Cm, C6H3Me2N),
115.71 (Co, C6H3Me2N), 61.85 (CH2SiMe3), 20.01
(Me2C6H3N), 11.22 (C5Me5), 2.50 (Me3SiCH2). Anal.
Found: C, 51.42; H, 7.64; N, 2.41. C26H46NSi2Ta.
Calc.: C, 51.21; H, 7.60; N, 2.30%.
The data for 8 follow. Yield 0.68 g (70%). IR (Nujol
mull, w cm−1): 1593 (s), 1317 (vs), 1162 (s), 1125 (m),
1099 (s), 1066 (s), 1028 (s), 980 (s), 761 (vs), 699 (vs),
1
550 (m), 345 (s). H NMR (l ppm, in chloroform-d):
7.20 (m, 10 H, H5C6Me2CCH2), 7.12 (d, 2H), 6.80 (t,
1H, H3C6Me2N), 2.57 (s, 6H, Me2C6H3N), 2.00 (s, 15H,
C5Me5), 1.67 (s, 6H, Me2PhCCH2), 1.47 (s, 6H,
2
Me2PhCCH2), 1.40, −0.25 (AB, 4H, JH–H=13.2 Hz,
The data for 6 follow. Yield 0.78 g (65%). IR (Nujol
mull, w cm−1): 1584 (w), 1407 (m), 1323 (vs), 1243 (m),
1094 (m), 1022 (m), 959 (m), 838 (m), 801 (m), 752 (m),
H2CCMe2Ph). 13C{1H} NMR (l ppm, in chloroform-
d):
154.10
(Ci,
C6H3Me2N),
153.32
(Ci,
C6H5Me2CCH2), 133.77 (Cp, C6H5Me2CCH2), 127.73
(Co, C6H5Me2CCH2), 127.34 (Cm, C6H5Me2CCH2),
125.52 (C5Me5), 124.81 (Cm, C6H3Me2N), 121.17 (Cp,
1
727 (m), 324 (w). H NMR (l ppm, in chloroform-d):
6.90 (d, 1H), 6.80 (d,1H), 6.40 (t, 1H, H3C6Me2N), 6.42
(m, 1H), 6.30 (m, 1H), 6.00 (m, 1H), 5.76 (m, 1H,
H4C5SiMe3), 2.32 (s, 3H, Me2C6H3N), 2.00 (s, 15H,
C5Me5), 0.064 (s, 9H, Me3SiC5H4). 13C{1H} NMR (l
ppm, in chloroform-d): 130.51 (Ci, C6H3Me2N), 128.55
(C1, C5H4SiMe3), 127.04, 126.84 (Cm, C6H3Me2N),
C6H3Me2N),
115.46
(Co,
C6H3Me2N),
95.40
(CH2CMe2Ph), 42.80 (CH2CMe2Ph), 35.87, 32.20
(CH2CMe2Ph), 20.71 (Me2C6H3N), 11.05 (C5Me5).
Anal. Found: C, 64.92; H, 7.08; N, 2.03. C38H50NTa.
Calc.: C, 65.04; H, 7.18; N, 2.00%.

192
A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
The data for 9 follow. Yield 0.63 g (70%). IR (Nujol
evaporated to dryness and the residue extracted into
n-hexane (2×10 ml). The solution was concentrated to
ca. 10 ml and cooled to −40°C to yield 12–17 as
yellow microcrystalline solids.
mull, w cm−1): 1586 (m), 1317 (vs), 1157 (m), 1095 (m),
1062 (m), 1020 (m), 985 (m), 761 (vs), 725 (vs), 698 (vs),
1
578 (m), 455 (m), 395 (m), 350 (s). H NMR (l ppm, in
chloroform-d): 7.60 (d, 4H), 7.12 (t, 4H), 7.03 (t, 2H,
H5C6), 6.82 (d, 2H), 6.53 (t, 1H, H3C6Me2N), 2.28 (s,
6H, Me2C6H3N), 1.93 (s, 15H, C5Me5). 13C{1H} NMR
(l ppm, in chloroform-d): 153.64(Ci, C6H3Me2N),
141.93 (Ci, C6H5), 130.15 (Cp, C6H3Me2N), 128.80 (Cp,
C6H5), 127.55 (Co,C6H5), 127.01(C5Me5), 125.63 (Cm,
C6H5), 121.50 (Cm, C6H3Me2N), 114.87 (Co,
C6H3Me2N), 20.01 (Me2C6H3), 11.63 (C5Me5). Anal.
Found: C, 64.84; H, 5.30; N, 2.11. C35H34NTa. Calc.:
C, 64.71; H, 5.27; N, 2.15%.
The data for 12 follow. Yield 0.46 g (60%). IR (Nujol
mull, w cm−1): 1588 (m). 1333 (vs), 1243 (vs), 1158 (m),
1096 (m), 1025 (m), 959 (s), 887 (s), 852 (vs), 758 (vs),
1
682 (s), 610 (m), 485 (m), 350 (s). H NMR (l ppm, in
chloroform-d): 6.96 (d, 2H), 6.61 (t, 1H, H3C6Me2N),
2.31 (s, 6H, Me2C6H3N), 1.96 (s, 15H, C5Me5), 0.23,
2
−0.14 (AB, 2H, JH–H=11 Hz, H2CSiMe3), 0.08 (s,
3H, Me–Ta), −0.03 (s, 9H, Me3SiCH2). 13C{1H}
NMR (l ppm, in chloroform-d): 153.97, 133.65, 120.60,
115.88 (Ci, Cp, Co, Cm, C6H3Me2N), 126.73 (C5Me5),
60.97 (CH2SiMe3), 49.24 (Me–Ta), 19.23 (Me2C6H3N),
11.05 (C5Me5), 2.26 (Me3SiCH2). Anal. Found: C,
51.30; H, 7.12; N, 2.58. C23H38NSiTa. Calc.: C, 51.38;
H, 7.12; N, 2.60%.
The data for 10 follow. Yield 0.60 g (70%). IR (Nujol
mull, w cm−1): 1588 (m), 1312 (vs), 1199 (m), 1096 (m),
1063 (m), 1028 (m), 980 (m), 799 (m), 741 (s), 693 (s),
1
533 (w), 502 (w), 443 (w), 362 (s). H NMR (l ppm, in
chloroform-d): 7.09 (m, 8H), 6.80 (m, 2H, H5C6CH2),
6.90 (d, 2H), 6.60 (t, 1H, H3C6Me2N), 2.40, 1.45 (AB,
4H, 2JH–H=12.45 Hz, H2CC6H5), 2.02 (s, 6H,
Me2C6H3), 1.97 (s, C5Me5). 13C{1H} NMR (l ppm, in
chloroform-d): 152.86 (Ci, C6H3Me2N), 147.42 (Cp,
C6H5), 133.82 (Ci, C6H5), 128.16 (Co,C6H5), 127.53
(C5Me5), 126.49 (Cm,C6H5), 122.58 (Cm, C6H3Me2N),
121.02 (Cp, C6H3Me2N), 115.56 (Co, C6H3Me2N), 74.25
(CH2C6H5), 18.53 (Me2C6H3), 10.56 (C5Me5). Anal.
Found: C, 62.17; H, 6.18; N, 2.24. C32H38NTa. Calc.:
C, 62.23; H, 6.20; N, 2.27%.
The data for 13 follow. Yield 0.50 g (60%). IR (Nujol
mull, w cm−1): 1587 (m), 1327 (vs), 1169 (m), 1095 (m),
1027 (m), 981 (m), 763 (s), 696 (m), 551 (w), 486 (m),
1
349 (m). H NMR (l ppm, in chloroform-d): 7.28 (d,
2H), 7. 17 (t, 2H), 7.05 (t, 1H, H5C6CMe2CH2), 7.00 (d,
2H), 6.66 (t, 1H, H3C6Me2N), 2.30 (s, 6H, Me2C6H3N),
1.92 (s, 15H, C5Me5), 1.49 (s, 3H, Me2PhCCH2), 1.44
2
(s, 3H, Me2PhCCH2), 0.91, 0.60 (AB, 2H, JH–H=14.5
Hz, H2CCMe2Ph), −0.30 (s, 3H, Me–Ta). 13C{1H}
NMR (l ppm, in chloroform-d): 154.35 (Ci,
C6H3Me2N), 140.00 (Ci, C6H5CMe2CH2), 133.84 (Co,
C6H3Me2N), 127.70 (Cm, C6H5CMe2CH2), 126.87 (Cm,
C6H3Me2N), 125.53 (Co, C6H5CMe2CH2), 124.78
(Cp,C6H5CMe2CH2), 120.90 (Cp, C6H3Me2N), 116.10
(C5Me5), 91.23 (CH2CMe2Ph), 50.99 (Me–Ta), 40.08
(CH2CMe2Ph), 35.60, 32.11 (CH2CMe2Ph), 19.48
(Me2C6H3N), 10.97 (C5Me5). Anal. Found: C, 59.61; H,
6.97; N, 2.41. C29H40NTa Calc.: C, 59.70; H, 6.91; N,
2.40%.
The data for 11 follow. Yield 0.56 g (70%).IR (Nujol
mull, w cm−1): 1586 (w), 1308 (s), 1212 (m), 1098 (m),
1
1024 (m), 980 (m), 758 (s), 488 (m), 346 (m). H NMR
(l ppm, in chloroform-d): 6.97 (d, 2H), 6.63 (t, 1H,
H3C6Me2N), 2.42 (s, 6H, Me2C6H3N), 1.89 (s, 15H,
C5Me5), 1.76, −0.62 (AB, 4H, 2JH–H=13.04 Hz,
CH2CMe3), 1.07 (s, 9H, CH2CMe3). 13C{1H} NMR (l
ppm, in chloroform-d): 154.23 (Ci, C6H3Me2N), 133.53
(Cp, C6H3Me2N), 127.15 (Cm, C6H3Me2N), 120.80 (Co,
C6H3Me2N), 115.12 (C5Me5), 96.97 (CH2CMe3), 35.68
(CH2CMe3), 34.41 (CH2CMe3), 20.36 (Me2C6H3N),
11.00 (C5Me5). Anal. Found: C, 58.12; H, 7.87; N,
2.31.C28H46NTa. Calc.: C, 58.22; H, 8.03; N, 2.42.
The data for 14 follow. Yield 0.46 g (60%). IR (Nujol
mull, w cm−1): 1586 (m) 1328 (vs), 1158 (m), 1095 (m),
1066 (m), 1025 (m), 982 (m), 762 (s), 726 (s), 700 (m),
1
592 (m), 484 (m), 347 (s). H NMR (l ppm, in chloro-
form-d): 7.33 (d, 2H), 7.27 (t, 2H), 7.12 (t, 1H, H5C6),
6.97 (d, 2H), 6.62 (t, 1H, H3C6Me2N), 2.45 (s, 6H,
Me2C6H3N), 1.94 (s, 15H, C5Me5), 0.69 (s, 3H, Me–
Ta). 13C{1H} NMR (l ppm, in chloroform-d): 200.36
(Ci, C6H5), 153.90 (Ci, C6H3Me2N), 135.18 (Cm,
C6H3Me2N), 134.36 (Cp, C6H5), 128.23 (Co,
C6H3Me2N), 127.38 (Cm, C6H5), 126.92 (Co, C6H5),
121.40 (Cp, C6H3Me2N), 117.90 (C5Me5), 49.60 (Me–
Ta), 19.75 (Me2C6H3N), 11.14 (C5Me5). Anal. Found:
C, 57.98; H, 4.38; N, 2.69. C25H32NTa. Calc.: C, 58.03;
H, 4.30; N, 2.71%.
3.5. Synthesis of [TaCp*MeR{N(2,6-Me2C6H3)}], (R=
CH2SiMe3, 12; CH2CMe2Ph, 13; C6H5, 14; CH2–
CMe3, 15; 2-(CH2NMe2)C6H4, 16; CH2C6H5, 17; C5H4
SiMe3, 18)
12–17. In a standard vacuum line, LiR (1.44 mmol;
R=CH2SiMe3, 0.13 g; CH2CMe2Ph, 0.20 g; C6H5, 0.12
g; CH2–CMe3, 0.11 g; 2-(CH2NMe2)C6H4, 0.20 g) or
Mg(CH2C6H5)2(THF)2 (0.25 g; 0.72 mmol) was added
to a toluene (50 ml) solution of [TaCp*ClMe{N(2,6-
Me2C6H3)}] (0.70 g; 1.44 mmol) under rigorously anhy-
drous conditions and the reaction mixture stirred for 12
h. The resulting suspension was filtered, the solvent
The data for 15 follow. Yield 0.45 g (60%). IR (Nujol
mull, w cm−1): 1587 (m), 1324 (vs), 1261 (m), 1216 (m),
1158 (m), 1095 (m), 1025 (m), 982 (m), 803 (m), 758 (s),
1
532 (m), 471 (m), 349 (s), 253 (m). H NMR (l ppm, in

A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
193
The data for 18 follow. Yield 0.51 g (60%). IR (Nujol
mull, w cm−1): 1585 (m), 1328 (vs), 1243 (vs), 1179 (m),
1094 (s), 1024 (s), 955 (s), 835 (s), 753 (s), 693 (s), 633
(s), 597 (m), 560 (m), 476 (m), 417 (s), 338 (vs), 253 (m).
1H NMR (l ppm, in chloroform-d): 6.85 (d, 1H), 6.74
(d, 1H), 6.32 (t, 1H, H3C6Me2N), 6.10 (m, 1H), 6.07 (m,
1H), 6.04 (m, 1H), 5.24 (m, 1H, H4C5SiMe3), 2.35 (s,
3H, Me2C6H3N), 1.869 (s, 3H, Me2C6H3N), 1.863 (s,
15H, C5Me5), 0.45 (s, 3H, Me–Ta), −0.09 (s, 9H,
Me3SiC5H4). 13C{1H} NMR (l ppm, in chloroform-d):
156.63 (Ci, C6H3Me2N), 128.56 (C1, C5H4SiMe3),
126.82, 126.78 (Cm, C6H3Me2N), 122.43 (C5Me5),
chloroform-d): 7.00 (d, 2H), 6.65 (t, 1H, H3C6Me2N),
2.36 (s, 6H, Me2C6H3N), 1.95 (s, 15H, C5Me5), 1.00 (s,
9H, Me3CCH2), 0.70, −0.015 (AB, 2H, JH–H=14.65
2
Hz, H2CCMe3), 0.11 (s, 3H, Me–Ta). 13C{1H} NMR
(l ppm, in chloroform-d): 153.87, 127.73, 126.84,
120.69 (Ci, Cp, Co, Cm, C6H3Me2N), 115.95 (C5Me5),
93.64 (CH2CMe3), 49.32 (Me–Ta), 34.84 (CH2CMe3),
33.66 (CH2CMe3), 20.10, 19.56 (Me2C6H3N), 10.95
(C5Me5). Anal. Found: C, 55.27; H, 7.30; N, 2.64.
C24H38NTa Calc.: C, 55.27; H, 7.34; N, 2.68.
The data for 16 follow. Yield 0.57 g (60%). IR (Nujol
mull, w cm−1): 1586 (m), 1317 (vs), 1165 (m), l099 (m),
1015 (m), 981 (s), 865 (m), 841 (s), 737 (s), 578 (m), 510
(m), 461 (m), 334 (m). 1H NMR (l ppm, in chloroform-
d): 7.98 (m, 1H),7.11 (m, 1H), 7.03 [m, 2H, H4C6-2-
(CH2NMe2)], 6.87 (d, 2H), 6.57 (t, 1H, H3C6Me2N),
3.95, 3.36 [AB, 2H, 2JH–H=13.5 Hz, H4C6-2-
(CH2NMe2)], 2.35 [s, 6H, H4C6-2-(CH2NMe2)], 2.35 (s,
6H, Me2C6H3N), 1.85 (s, 15H, C5Me5), 0.24 (s, 3H,
Me–Ta). 13C{1H}NMR (l ppm, in chloroform-d):
124.74, 117.55 (Co, C6H3Me2N), 116.93, 115.40 (C2,5
,
C5H4SiMe3), 114.49 (Cp, C6H3Me2N), 106.11, 105.31
(C3,4, C5H4SiMe3), 19.54, 19.02 (Me2C6H3N), 11.60
(C5Me5), 0.46 (Me3SiC5H4). Anal. Found: C, 55.14; H,
6.83; N, 2.40. C27H40NSiTa Calc.: C, 55.19; H, 6.86; N,
2.38.
Table 3
194.00[C1,
C6H4-2-(CH2NMe2)],
155.15
(Ci,
Crystal data and structure refinement for 6
C6H3Me2N), 144.63, 144.26 [C2,6, C6H4-2-(CH2NMe2)],
134.21 (Cp, C6H3Me2N), 127.26 [C4, C6H4-2-
(CH2NMe2)]. 124.85, 124.56 [C3,5, C6H4-2-(CH2NMe2)],
123.04(Cm, C6H3Me2N), 120.10(Co, C6H3Me2N), 116.10
(C5Me5), 74.30 [C6H4-2-(CH2NMe2)], 50.00 [C6H4-2-
(CH2NMe2)], 35.10 (Me–Ta), 20.48 (Me2C6H3N),
11.87(C5Me5). Anal. Found: C, 61.97; H, 6.31; N, 4.28.
C28H39N2Ta Calc.: C, 62.00; H, 6.27; N, 4.25.
The data for 17 follow. Yield 0.47 g (60%). IR (Nujol
mull, w cm−1): 1585 (w), 1326 (vs), 1200 (w), 1165 (m),
1091 (m), 1024 (m), 979 (m), 795 (m), 755 (s), 691 (m),
497 (m), 455 (m), 352 (m). 1H NMR (l ppm, in
Empirical formula
Formula weight
Temperature (K)
C26H37ClNSiTa
608.06
293(2)
˚
Wavelength (A)
0.71073
Crystal system
Space group
Monoclinic
P21/c
Unit cell dimensions
˚
a (A)
12.597(3)
11.338(2)
18.297(4)
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
90
96.53(3)
90
2596.3(10)
4
1.556
4.395
3
˚
chloroform-d): 7.06 (d, 2H), 6.76 (t, 1H, H3C6Me2N),
Volume (A )
Z
2
6.89 (vbr, 5H, H5C6CH2), 3.17, 1.95 (AB, 2H, JH–H
=
dcalc (g cm−3
)
9.5 Hz, H2CC6H5), 2.49 (s, 6H, Me2C6H3N), 1.70 (s,
15H, C5Me5), −0.38 (s, 3H, Me–Ta). 13C{1H}NMR
(l ppm, in chloroform-d): 154.02 (Ci, C6H3Me2N),
134.12 (Ci, C6H5CH2), 132.70 (Cp, C6H5CH2) 130.76
(Co, C6H3Me2N), 129.14 (Cm, C6H5CH2), 126.82 (Co,
C6H5CH2). 126.22 (Cm, C6H3Me2N), 120.85 (Cp,
C6H3Me2N), 114.23 (C5Me5), 61.34 (CH2C6H5), 33.58
(Me–Ta), 19.27 (Me2C6H3N), 11.02 (C5Me5). Anal.
Found: C, 57.72; H, 6.27; N, 2.56. C26H34NTa. Calc.:
C, 57.67; H, 6.33; N, 2.58.
18. A solution of LiC5H4SiMe3 (0.21 g; 1.44 mmol) in
THF (10 ml) was added dropwisely at room tempera-
ture to a stirred orange solution of [TaCp*ClMe{N(2,6-
Me2C6H3)}] (0.70 g; 1.44 mmol) in THF (30 ml). The
mixture was stirred for 12 h. Subsequently, the suspen-
sion was evaporated to dryness and the residue ex-
tracted into toluene (2×10 ml). The solution was
concentrated to ca. 10 ml, n-hexane (5 ml) added and
cooled to −40°C overnight to give a microcrystalline
brown–orange solid identified as 18.
Absorption coeffficient (mm−1
F(000)
)
1216
Crystal size (mm)
q range for data collection
Index ranges
0.35×0.33×0.28
3.17–24.98°
−15BhB0, −13BkB0,
−21BlB21
Reflections collected
4846
Independent reflections
Observed reflections [F\4|(F)]
Absorption correction
4546 (Rint=0.0163)
3931
C Scan
Max. and min. transmission
Refinement method
0.278 and 0.238
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2|(I)]
R indices (all data)
4537/0/271
0.908
R1=0.0224, wR2=0.0574
R1=0.0422, wR2=0.1382
w=1/[|2(F2o)+(0.0365P)2
Weighting scheme (calc.)
+6.4510P]
where P=(F2o+2Fc2)/3
Largest difference peak and hole 0.449 and −0.798
−3
˚
(e A
)

194
A. Castro et al. / Journal of Organometallic Chemistry 554 (1998) 185–194
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3.6. X-ray data collection, structure determination and
refinement for compound 6
Crystallographic and experimental details of the crys-
tal structure determination are given in Table 3. A
suitable crystal of complex 6 was mounted on an
Enraf–Nonius CAD-4 automatic four-circle diffrac-
tometer with bisecting geometry, equipped with a
graphite-oriented monochromator and Mo–Kh radia-
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˚
tion (u=0.71073 A). Data were collected at room
temperature. Intensities were corrected for Lorentz and
polarization effects in the usual manner. Absorption
was corrected by C scans technique (max. and min.
transmission factors 0.278 and 0.238, respectively). No
extinction correction was made.
The structure was solved by direct methods
(SHELXS 90) [39] and refined by full-matrix least-
squares against F2 (SHELXL 93) [40]. All non-hydro-
gen atoms were refined anisotropically. In the last cycle
of refinement, the hydrogen atoms were positioned
geometrically and refined using a riding model with
fixed thermal parameters.
Calculations were carried out on an ALPHA AXP
(Digital) workstation.
4. Supplementary material available
Tables of positional parameters of all atoms (Table
S1, 1 page), anisotropic displacement parameters ex-
pressions (Table S2, 1 page), complete bond distances
and angles (Table S3, 1 page), hydrogen coordinates
(Table S4, 1 page) and structure factors (Table S5, 11
pages) for complex 6 are available. Ordering informa-
tion is given on any current masthead page.
[28] G.R. Newkome, W.E. Puckett, V.K. Gupta, G.E. Kiefer, Chem.
Rev. 86 (1986) 451 and references therein.
Acknowledgements
[29] I. de Castro, M.V. Galakhov, M. Go´mez, P. Go´mez-Sal, P. Royo,
Organometallics 15 (1996) 1362.
[30] G. Parkin, A. van Asselt, D.J. Leahy, L. Whinnery, N.G. Hua,
R.W. Quan, L.M. Henling, W.P. Schaefer, B.D. Santarsiero, J.E.
Bercaw, lnorg. Chem. 31 (1992) 82.
We are grateful to DGICYT (Project PB-92-0178-C)
and to Universidad de Alcala´ (Project E001/97) for
financial support of this research.
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