New monocyclopentadienyl complexes of Tantalum(V) and Titanium(IV) with chelating pyrimidinethiolate and oxypyridine ligands - Molecular structure of [Cp*TaCl3(SC6H7N2)]

Article abstract of DOI:10.1002/ejic.200390070

New monocyclopentadienyl species of Ta^V, [Cp*TaL₃(XR)] (L = Cl, Me, X = O, S) bearing 4,6-dimethyl-2-pyrimidinethiolate (SR = SC₆H₇N₂) or 3-cyano-4,6-dimethyloxypyridine (OR = OC₈H₇N₂) ligands were prepared, namely [Cp*TaCl₃(SC₆H₇N₂)] (1), [Cp*TaCl₃(OC₆H₇N₂)] (2), [Cp*TaMe₃(SC₆H₇N₂)] (3). In addition, a bis(oxypyridine)titanium(IV) complex [Cp*TiMe₂(OC₈H₇ N₂)₂] was isolated. The X-ray structure analysis of 1 revealed that the thiolate group is bonded to the metal center through the sulfur atom and one of the nitrogen atoms in an η²-fashion. The reactivity of complex 3 with isocyanides (CNR), R = tBu, Xyl (Xyl = 2,6-dimethylphenyl) was also studied showing differences depending on the nature of R group. The reaction with 2,6-dimethylphenyl isocyanide gives the azatantalacyclobutane complex [Cp*TaMe[XylN=CC(Me₂)NXyl}(SC₆H₇ N₂)] (5) as the final product, whereas in the reaction with tert-butyl isocyanide the η²-imine-containing complex [Cp*Ta {tBuNC{Me₂)}{SC₆H₇N₂)] (6) is proposed to be formed. The dynamic behavior of [Cp*TaMe₃(SC₆H₇N₂)] (3) was also studied by variable-temperature ¹H NMR spectroscopy. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Full text of DOI:10.1002/ejic.200390070

FULL PAPER
New Monocyclopentadienyl Complexes of Tantalum(
V
) and Titanium(IV) with
Chelating Pyrimidinethiolate and Oxypyridine Ligands ؊ Molecular Structure
of [Cp*TaCl3(SC6H7N2)]
[a]
[a]
[b]
[c]
´
´
Rosa Fandos,* Carolina Hernandez, Antonio Otero,* Ana Rodrıguez,
[a]
[d]
´
´
Marıa Jose Ruiz, and Pilar Terreros
Keywords: N ligands / S ligands / Tantalum / Titanium / Cyclopentadienyl ligands
New monocyclopentadienyl species of TaV, [Cp*TaL3(XR)]
(L = Cl, Me, X = O, S) bearing 4,6-dimethyl-2-pyrimidine-
thiolate (SR = SC6H7N2) or 3-cyano-4,6-dimethyloxypyri-
dimethylphenyl) was also studied showing differences de-
pending on the nature of R group. The reaction with 2,6-di-
methylphenyl isocyanide gives the azatantalacyclobutane
complex [Cp*TaMe{XylN=CC(Me2)NXyl}(SC6H7N2)] (5) as
the final product, whereas in the reaction with tert-butyl iso-
dine (OR
[Cp*TaCl3(SC6H7N2)]
[Cp*TaMe3(SC6H7N2)] (3). In addition, a bis(oxypyridine)tit-
anium(IV) complex [Cp*TiMe2(OC8H7N2)2] was isolated. The {tBuNC(Me2)}(SC6H7N2)] (6) is proposed to be formed. The
=
OC8H7N2) ligands were prepared, namely
(1), [Cp*TaCl3(OC8H7N2)] (2),
cyanide
the
η2-imine-containing
complex
[Cp*Ta
X-ray structure analysis of 1 revealed that the thiolate group
is bonded to the metal center through the sulfur atom and
one of the nitrogen atoms in an η2-fashion. The reactivity of
complex 3 with isocyanides (CNR), R = tBu, Xyl (Xyl = 2,6-
dynamic behavior of [Cp*TaMe3(SC6H7N2)] (3) was also
studied by variable-temperature H NMR spectroscopy.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
1
Introduction
ganic chemistry due to their relevance to the structure,
bonding and function of biologically active reaction centers
such as nitrogenase or metalothioneins.[2,3]
Thiolate complexes also play an important role in differ-
ent reactions, such as the desulfurization of organosulfur
Ligand systems with two different donor atoms are at-
tracting increasing interest in the chemistry of metal com-
plexes. Under appropriate conditions, the remaining donor
atom can coordinate reversibly to the metal center and
eventually block a vacant coordination site.[1] In this field,
complexes that incorporate pyridinethiolate and pyrimidi-
nethiolate, as well as their alkoxide analogues, are interest-
ing for their ability to chelate and bridge transition metal
[4,5]
compounds
and metal-catalyzed synthetic reactions in-
volving CϪS bond cleavage and formation.[6] All of these
features, as well as the propensity of sulfur to form M(µ-
SR)MЈ bridges, has led to the widespread use of sulfur-con-
taining complexes as synthons for multinuclear transition
atoms, allowing access to both mono- and oligonuclear metal complexes.[7]
products. In addition, they contain functional groups that
are common in crude oils and nucleic acids. The thiolate
complexes are of particular interest in the field of bioinor-
Alkoxide and aryloxide ligands have been widely used to
stabilize high oxidation states of early transition metals[8]
and numerous studies have been reported concerning the
catalytic activity of their complexes in alkene metathesis
and, in particular, in alkene polymerization.[9]
A systematic study of the chemistry of mono- and bis(cy-
clopentadienyl) complexes of group-4 transition metals
bearing chelating pyrimidinethiolate ligands and analogous
oxygen derivatives has been carried out by our research
group in recent years.[10] The interesting coordination
modes and the reactivity observed along with the scarce
number of reported examples of this kind of compounds[11]
encouraged us to prepare analogous monocyclopentadienyl
complexes of group-5 metals. In particular, this paper will
focus on the synthesis, structural details and reactivity of
[a]
´
´
´
´
Departamento de Quımica Inorganica, Organica y Bioquımica,
Universidad de Castilla-La Mancha, Facultad de Ciencias del
Medio Ambiente
Avda. Carlos III, sn 45071 Toledo, Spain
[b]
´
´
´
´
Departamento de Quımica Inorganica, Organica y Bioquımica,
´
Universidad de Castilla-La Mancha, Facultad de Quımicas,
Campus de Ciudad Real, 13071 Ciudad Real, Spain
Fax: (internat.) ϩ 34-926/295318
E-mail: antonio.otero@uclm.es
[c]
´
´
´
´
Departamento de Quımica Inorganica, Organica y Bioquımica,
Universidad de Castilla-La Mancha, ETS Ingenieros
Industriales,
´
Avda. Camilo Jose Cela, 3, 13071 Ciudad Real, Spain
Instituto de Catalisis y Petroleoquımica, CSIC,
[d]
´
´
Cantoblanco, 28049 Madrid, Spain
Eur. J. Inorg. Chem. 2003, 493Ϫ498  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/03/0203Ϫ0493 $ 20.00ϩ.50/0
493

´
´
R. Fandos, C. Hernandez, A. Otero, A. Rodrıguez, M. J. Ruiz, P. Terreros
FULL PAPER
new monocyclopentadienyl complexes of tantalum() and
titanium() bearing chelating pyrimidinethiolate and oxy-
pyridine ligands.
Results and Discussion
The reaction of [Cp*TaCl4] (Cp* ϭ η5-C5H5) with 4,6-
dimethyl-2-mercaptopyrimidine (HSR, R ϭ C6H7N2) in the
presence of 1 equiv. of triethylamine proceeds at room tem-
perature in toluene to yield the complex [Cp*TaCl3(SR)] (1)
[Equation (1)]. Attempts to perform the substitution of a
second chlorine atom by a thiolate ligand were made under
a wide variety of conditions but no further reaction was
observed and in all cases the only isolated compound was 1.
(1)
Figure 1. ORTEP drawing of complex 1 with the atomic labeling
scheme; hydrogen atoms omitted for clarity; thermal ellipsoids are
at the 30% level of probability
˚
Table 1. Bond lengths [A] and angles [°] for 1
Complex 1 was isolated as an air-sensitive orange solid,
soluble in toluene and THF and less soluble in pentane or
Ta(1)ϪN(1)
Ta(1)ϪCl(3)
Ta(1)ϪCl(2)
Ta(1)ϪCl(1)
Ta(1)ϪC(14)
Ta(1)ϪC(11)
Ta(1)ϪS(1)
Ta(1)ϪC(13)
Ta(1)ϪC(10)
Ta(1)ϪC(12)
2.327(5)
2.393(2)
2.407(2)
2.407(2)
2.431(8)
2.447(7)
2.456(2)
2.463(8)
2.472(8)
2.484(7)
N(1)ϪTa(1)ϪCl(1)
N(1)ϪTa(1)ϪCl(2)
N(1)ϪTa(1)ϪCl(3)
Cl(2)ϪTa(1)ϪCl(1)
Cl(3)ϪTa(1)ϪCl(1)
Cl(3)ϪTa(1)ϪCl(2)
N(1)ϪTa(1)ϪS(1)
Cl(1)ϪTa(1)ϪS(1)
Cl(2)ϪTa(1)ϪS(1)
Cl(3)ϪTa(1)ϪS(1)
C(1)ϪS(1)ϪTa(1)
C(1)ϪN(1)ϪTa(1)
C(4)ϪN(1)ϪTa(1)
76.2(1)
76.3(2
1
Et2O. It was characterized by H and 13C NMR and IR
87.6(1)
151.37(8)
85.4(1)
85.5(1)
64.3(1)
87.87(8)
87.49(9)
151.96(7)
84.6(2)
99.5(4)
143.8(4)
spectroscopy as well as by elemental analysis (see Exp.
Sect.). The 1H and 13C NMR spectra indicate that the thiol-
ate ligand is bonded to the metal atom in a bidentate fash-
ion. For example, two resonances at δ ϭ 1.71 and 2.88 ppm
are present in the 1H MNR spectrum for the two non-
equivalent methyl groups of the thiolate ligand, in accord-
ance with the proposed η2-S,N coordination mode.
Crystals of 1, suitable for an X-ray crystal structure de-
termination, were obtained by slow diffusion of pentane
into a saturated solution of the complex in toluene. Figure 1
shows an ORTEP diagram of the molecule; selected bond
lengths and angles are given in Table 1.
as a yellow, air-sensitive solid which was sparingly soluble
in alkanes but soluble in toluene or THF.
The structure consists of discrete molecules separated by
van der Waals distances. The tantalum atom is bonded to
the cyclopentadienyl ring in an η5-mode, to three chlorine
atoms and to the thiolate ligand in the proposed chelate
fashion. In this way, the coordination around the metal
˚
atom is pseudo-octahedral, with the tantalum atom 0.59 A
out of the plane defined by the S(1), Cl(1), Cl(2) and Cl(3)
atoms. The nitrogen atom of the pyrimidinethiolate ligand
is located trans to the Cp* group. The Ta(1)ϪS(1) bond
(2)
˚
length [2.456(2) A] is as expected for tantalum() thiolate
complexes[12] and the Ta(1)ϪN(1) bond [2.327(5) A] is also
˚
in the normal range for pyridyltantalum() complexes.[13]
Finally, the Ta(1)ϪS(1)ϪC(1) angle [84.6(2)°] is in accord-
ance with others observed in this kind of complexes.[10,11]
The H and 13C NMR spectra for 2 are analogous to
1
When
3-cyano-2-hydroxy-4,6-dimethylpyridine
was those previously described for 1. For example, the 1H NMR
treated with [Cp*TaCl4] in the presence of Et3N in toluene spectrum exhibits two singlet resonances at δ ϭ 1.52 and
at room temperature [Equation (2)] complex 2 was isolated 2.49 ppm, attributable to the two nonequivalent methyl
494
Eur. J. Inorg. Chem. 2003, 493Ϫ498

Monocyclopentadienyl Complexes of Tantalum(V) and Titanium(IV)
FULL PAPER
groups of the alkoxide ligand. By analogy with the situation
for compound 1, a bidentate coordination mode for the al-
koxide ligand is proposed to be present in this complex.
Another general way to synthesize thiolate complexes is
to carry out the protonolysis of metalϪalkyl bonds with the
corresponding thiol. In this way, the reaction of Cp*TaMe4
with 2-mercapto-4,6-dimethylpyrimidine at 80 °C in toluene
yields [Cp*TaMe3(SR)] (3) as an orange solid which is sol-
uble in toluene and THF and scarcely soluble in pentane
[Equation (3)]. As in the case of the chlorinated complex 1,
all attempts to increase the number of thiolate ligands
around the metal atom were unsuccessful.
(4)
This compound was isolated as a red solid which is sol-
uble in toluene and THF but less soluble in pentane. The
1H NMR spectrum shows a singlet at δ ϭ 1.00 ppm, corres-
ponding to the methyl group bonded to the titanium atom
and a further singlet at δ ϭ 1.77 ppm for the Cp* methyl
groups. The pyridine ligands give rise to three signals, two
of them at δ ϭ 1.71 and 1.82 ppm are assigned to the
methyl groups bonded to the pyridine rings, and the other,
at δ ϭ 5.46 ppm, corresponds to the aromatic proton. It
can be inferred from these results that in complex 4 the two
pyridine ligands are in the same chemical environment, and
an η1-O coordination is proposed for both ligands.
(3)
Finally, the reactivity of 3 toward isocyanide ligands has
been considered. Compound 3 reacts readily in toluene at
room temperature with 2,6-dimethylphenyl isocyanide in a
1:2 molar ratio to give the azatantalacyclobutane complex
5 containing an iminoacyl fragment (Scheme 2).
1
The H NMR spectrum of 3 at room temperature shows
a broad resonance at δ ϭ 2.43 ppm that integrates for six
protons and which is assigned to the methyl groups of the
thiolate ligand. The broadness of the peak indicates a flux-
ional behavior through which both nitrogen atoms inter-
change their positions in the coordination sphere of the tan-
talum atom by rotation around the SϪC bond (Scheme 1).
Scheme 1
In order to study this fluxional behavior a variable-tem-
perature (VT) 1H NMR experiment was carried out. At
Ϫ40 °C the methyl groups are inequivalent and appear as
two signals at δ ϭ 2.74 and 2.04 ppm, indicating that rota-
tion around the CϪS bond is hindered for the thiolate li-
gand. When the temperature is raised, the peaks coalesce at
Scheme 2
1
The H NMR spectrum of compound 5 shows a singlet
Ϫ10 °C. The two site-exchange equations[14] and the coales- signal at δ ϭ 1.39 ppm which is assigned to the Cp* protons
cence temperature of 263 K can be used to estimate a value and nine singlet signals between δ ϭ 1.00 and 2.45 ppm,
for ∆G϶ of 12.0(2) kcal·molϪ1 for the process. This value each of them integrating for three protons, corresponding
is in accordance with that previously found for analogous to the methyl groups present in the molecule (see Exp.
systems, i.e. [Cp2ZrMe(SR)] (SR ϭ 4,6-dimethylpyrimidine- Sect.).
2-thiolate).[10a]
Furthermore, the 13C NMR spectrum shows, among
Complex 4 was synthesized in a similar way to 3, by reac- others, two signals at δ ϭ 230.0 and 86.7 ppm, which we
tion of [Cp*TiMe3] with 2 equiv. of 3-cyano-2-hydroxy-4,6- tentatively assign to an iminoacyl carbon atom and to the
dimethylpyridine in toluene [Equation (4)].
quaternary carbon atom of the TaϪNϪCϪC metallacycle.[15]
Eur. J. Inorg. Chem. 2003, 493Ϫ498
495

´
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R. Fandos, C. Hernandez, A. Otero, A. Rodrıguez, M. J. Ruiz, P. Terreros
FULL PAPER
We propose (see Scheme 2) that, initially, complex 3 re- mined by X-ray diffraction studies, shows a pseudo-octa-
acts with one molar equivalent of xylyl isocyanide by inser- hedral geometry around the tantalum atom with the thiol-
tion into one TaϪMe bond to form an η2-iminoacyl-con- ate ligand chelating two coordination positions. This struc-
taining complex. A second methyl migration would then tural situation can be considered to also be present in the
occur, forming an η2-imine-containing species. Finally, the related tantalum complexes 2 and 3, on the basis of spectro-
insertion of a second isocyanide molecule into the newly scopic data. We have also studied the reactivity of complex
formed TaϪC bond would lead to 5.
3 with xylyl and tert-butyl isocyanides. With the first re-
Recently, we reported a mechanism for the reaction of agent the azatantalacyclobutane complex 5 was isolated,
xylyl isocyanide with [Cp*TaMe2(SCH2CH2)2O] in which whereas with the second isocyanide the η2-imine-containing
the proposed η2-imine intermediate was isolated .[16] At- complex 6 was obtained.
tempts to isolate this type of intermediate in the reaction of
3 were unsuccessful.
Furthermore, compound 3 reacts readily with tert-butyl
isocyanide, at room temperature, in C6D6 on an NMR-tube
Experimental Section
scale, to give the η2-imine complex 6 as the only detectable
1
compound by H NMR spectroscopy (Scheme 3). Isolation
General Remarks: The preparation and handling of the described
compounds was performed with rigorous exclusion of air and mois-
ture under nitrogen using standard vacuum line and Schlenk tech-
niques. All solvents were dried and distilled under nitrogen. The
following reagents were prepared by literature procedures: [Cp*
TaCl4][18] [Cp*TaMe4][19] and [Cp*TiMe3].[20] The commercially
available compounds Cp*H, MeLi in diethyl ether, xylyl isocyanide,
tert-butyl isocyanide, 2-mercapto-4,6-dimethylpyrimidine and 3-cy-
ano-2-hydroxy-4,6-dimethylpyridine were used as received from Al-
drich. 1H and 13C NMR spectra were recorded with a 200 Mercury
Varian Fourier Transform spectrometer. Trace amounts of pro-
tonated solvents were used as reference, and chemical shifts are
reported in units of ppm relative to SiMe4. IR spectra were re-
corded in the region 4000Ϫ400 cmϪ1 with a Nicolet Magna-IR 550
spectrophotometer as Nujol mulls using PET cells.
of 6 on a preparative scale with an acceptable level of purity
was not possible.
Scheme 3
In contrast to the reactivity observed for complex 3 with [Cp*TaCl3(SC6H7N2)] (1): HSC6H7N2 (0.136 g, 0.97 mmol) and
Et3N (0.140 mL, 0.97 mmol) were added to a solution of Cp*TaCl4
(0.446 g, 0.97 mmol) in 5 mL of toluene. The mixture was stirred
at room temperature for 1 h. After filtration, the solid was washed
twice with 5 mL of THF. The resulting solution was concentrated
to dryness and the solid obtained was washed with diethyl ether to
give an orange solid, which was characterized as 1 (0.425 g, 78%).
IR (Nujol/PET): ν˜ ϭ 1591 cmϪ1 (s), 1558 (w), 1520 (s), 1342 (m),
xylyl isocyanide, no further reaction was observed when an
excess of tert-butyl isocyanide was added.
The 1H and 13C NMR spectroscopic data point to an η2-
coordination of the imine ligand, while the thiolate would
act as a monodentate ligand (see Exp. Sect.). The 1H NMR
spectroscopic data exhibit a singlet signal at δ ϭ 0.04 ppm
corresponding to the methyl group bonded to the tantalum
atom, a singlet at δ ϭ 1.31 ppm integrating for nine protons
assignable to the tert-butyl group and a broad signal at δ ϭ
1
1271 (s), 1021 (m), 956 (w), 848 (m). H NMR (200 MHz, C6D6):
δ ϭ 1.71 (s, 3 H, CH3), 2.24 (s, 15 H, Cp*), 2.88 (s, 3 H, CH3),
5.67 (s, 1 H, CH pyrimidine) ppm. 13C{1H} NMR (C6D6): δ ϭ
1.79 ppm due to the methyl groups of the thiolate ligand, 13.0 (Cp*), 23.7 (CH3), 24.8 (CH3), 119.6 (CH pyrimidine), 130.3
(Cp*), 165.5 (CϪCH3), 168.5 (CCH3), 172.2 (CS) ppm.
C16H22N2Cl3STa (561.73): calcd. C 34.17, H 3.91, N 4.98; found C
34.17, H 3.90, N 5.09.
indicating that a fluxional behavior similar to that described
for 3 takes place. The methyl groups bonded to the quatern-
ary carbon atom of the imine ligand appear as two singlets
at δ ϭ 1.66 and 1.99 ppm, respectively. The 13C NMR spec-
trum shows, as its outstanding feature, a signal at δ ϭ
68.1 ppm corresponding to the quaternary carbon atom of
the imine ligand. The high-field shift of this resonance
seems to confirm the η2-coordination of the imine group.[17]
[Cp*TaCl3(OC8H7N2)] (2): HOC8H7N2 (0.517 g, 3.49 mmol) and
Et3N (0.486 mL, 3.49 mmol) were added to a solution of [Cp*
TaCl4] (1.6 g, 3.49 mmol) in 25 mL of toluene. The mixture was
stirred at room temperature for 2 h. After filtration, the resulting
solution was concentrated to dryness and the solid obtained was
washed with pentane to give a yellow solid, which was character-
ized as 2 (1.465 g, 74%). IR (Nujol/PET): ν˜ ϭ 2216 cmϪ1 (s), 1666
(w), 1604 (ms), 1551 (s), 1304 (s), 1256 (m), 1026 (w), 651 (w), 570
(s). 1H NMR (200 MHz, C6D6): δ ϭ 1.52 (s, 3 H, CH3), 2.22 (s, 15
H, Cp*), 2.49 (s, 3 H, CH3), 5.49 (s, 1 H, CH pyridine) ppm.
13C{1H} NMR (C6D6): δ ϭ 12.6 (Cp*), 20.1 (CH3), 22.1 (CH3),
94.1 (CCN), 112.9 (CN), 118.7 (Cp*), 131.9 (CH pyridine), 155.9
(CCH3), 157.3 (CCH3), 168.3 (CO) ppm. C18H22N2Cl3OTa
(569.69): calcd. C 37.95, H 3.89, N 4.92; found C 38.14, H 3.75,
Conclusion
In this paper we report the synthesis of some new mono-
cyclopentadienyl-containing tantalum() and titanium()
complexes with chelating pyrimidinethiolate and oxypyrid-
ine ligands. These compounds were prepared by halide or
methyl displacement. The molecular structure of 1, as deter- N 4.66.
496
Eur. J. Inorg. Chem. 2003, 493Ϫ498

Monocyclopentadienyl Complexes of Tantalum(V) and Titanium(IV)
FULL PAPER
[Cp*TaMe3(SC6H7N2)] (3): Toluene (10 mL) was added to a mix-
ture of Cp*TaMe4 (0.379 g, 1.01 mmol) and HSC6H7N2 (0.141 g,
1.01 mmol). The solution was heated slowly to 80 °C and stirred
at this temperature for 1 h. After cooling, the mixture was filtered
and the solvent removed. The oil obtained was washed with 10 mL
of n-pentane to afford an orange solid (0.373 g, 75%) which was
characterized as 3. IR (Nujol/PET): ν˜ ϭ 1623 cmϪ1 (w), 1580 (s),
1532 (s), 1340 (s), 1274 (s), 1138 (m), 1026 (m) 955 (w) 844 (w),
814 (w). 1H NMR (200 MHz, [D8]toluene): δ ϭ 0.23 (s, 6 H,
CH3Ta), 0.34 (s, 3 H, CH3Ta), 2.04 (s, 15 H, Cp*), 2.43 (br. s, 6 H,
CH3 pyrimidine), 6.04 (s, 1 H, CH pyrimidine) ppm. 13C{1H}
NMR (C6D6): δ ϭ 11.6 (Cp*), 23.7 (CH3, pyrimidine), 45.6
(CH3Ta), 48.7 (CH3Ta), 119.1 (CH pyrimidine), 120.5 (Cp*), 165.8
(CCH3), 174.6 (CS) ppm. C19H31N2STa (500.48): calcd. C 45.60,
H 6.24, N 5.60; found C 45.39, H 5.82, N 5.61.
Table 2. Crystal data and structure refinement for 1
Empirical formula
Formula mass
Temperature
C16H22Cl3N2STa
561.71
293(2) K
0.71073 A
˚
Wavelength
Crystal system, space group
Unit cell dimensions
monoclinic, P21/c
a ϭ 13.328(4) A
˚
˚
b ϭ 8.596(3) A, β ϭ 90.74(3)°
˚
c ϭ 17.224(2) A
3
˚
Volume
1973.1(9) A
Z, calculated density
Absorption coefficient
F(000)
4, 1.891 Mg/m3
6.082 mmϪ1
1088
Crystal size
θ range for data collection
Limiting indices
0.3 ϫ 0.3 ϫ 0.2 mm
2.37Ϫ27.97°
Ϫ17 Յ h Յ 17, 0 Յ k Յ 11,
0 Յ l Յ 22
[Cp*TiMe(OC8H7N2)2] (4): Toluene (2 mL) was added to a mixture
of [Cp*TiMe3] (0.209 g, 0.92 mmol) and HOC8H7N2 (0.271 g,
1.83 mmol). The solution was stirred at room temperature for 5 h
and filtered. By addition of 4 mL of n-pentane and cooling to Ϫ30
°C a red solid (0.190 g, 42%) was obtained and characterized as 4.
IR (Nujol/PET): ν˜ ϭ 2218 cmϪ1 (s), 1560 (s), 1504 (s), 1221 (s),
1157 (m), 1098 (s), 783 (ms). 1H NMR (200 MHz, C6D6): δ ϭ 1.00
(s, 3 H, CH3-Ti), 1.71 (s, 6 H, CH3), 1.77 (s, 15 H, Cp*), 1.82 (s, 6
H, CH3), 5.46 (s, 2 H, CH pyridine) ppm. 13C{1H} NMR (C6D6):
δ ϭ 11.9 (Cp*), 20.0 (CH3), 20.9 (CH3), 63.8 (CH3Ti), 91.4 (CCN),
114.4 (CN), 115.0 (Cp*), 127.4 (CH pyridine), 155.1 (CCH3), 157.5
(CCH3), 171.0 (CO) ppm. C27H32N4O2Ti (492.44): calcd. C 65.85,
H 6.55, N 11.38; found calcd. C 65.57, H 6.88, N 11.72.
Reflections collected/unique
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I)]
R indices (all data)
9175/4747 [R(int) ϭ 0.0920]
4747/0/213
1.052
R1 ϭ 0.0351, wR2 ϭ 0.0859
R1 ϭ 0.0542, wR2 ϭ 0.1060
Ϫ3
˚
Largest diff. peak and hole
1.297 and Ϫ2.295 e A
X-ray Crystallographic Study: The crystallographic data and experi-
mental details are given in Table 2. Crystals of complex 1 suitable
for an X-ray diffraction study were obtained by slow diffusion of
pentane into a saturated solution of the complex in toluene. A pris-
matic crystal was selected, sealed in a Lindeman capillary under
dry nitrogen and used for data collection. Accurate unit-cell para-
meters were determined by least-squares refinement of the setting
angles of 25 randomly distributed and carefully centered
reflections. The data collection was performed with a NONIUS-
MACH3 diffractometer equipped with graphite-monochromated
[Cp*TaMe{XylN؍CC(Me2)NXyl}(SC6H7N2)] (5): Toluene (5 mL)
was added to
a mixture of [Cp*TaMe3(SC6H7N2)] (0.132 g,
0.26 mmol) and XylNϵC (0.70 g, 0.53 mmol). The solution was
stirred at room temperature for 30 min. After that, the mixture was
filtered and the solvent removed. The oil obtained was washed with
5 mL of cool n-pentane to afford a yellow solid (0.110 g, 54%)
which was characterized as 5. IR (Nujol/PET): ν˜ ϭ 1666 cmϪ1 (w),
1633 (m), 1593 (s), 1553 (m). 1H NMR (200 MHz, C6D6): δ ϭ 1.00
(s, 3 H, CH3-Ta), 1.29 (s, 3 H, CH3), 1.39 (s, 15 H, Cp*), 1.44 (s,
3 H, CH3), 1.76 (s, 3 H, CH3), 1.94 (s, 3 H, CH3), 2.11 (s, 3 H,
CH3), 2.15 (s, 3 H, CH3), 2.40 (s, 3 H, CH3), 2.45 (s, 3 H, CH3),
5.64 (s, 1 H, CH pyrimidine), 6.57Ϫ6.82 (m, 6 H, Xyl) ppm.
13C{1H} NMR (C6D6): δ ϭ 10.8 (Cp*), 19.6, 20.1, 21.8, 22.1, 22.3,
23.5, 23.8, 24.3 (CH3), 39.8 (CH3Ta), 86.7 (CMe2), 116.9 (CH pyri-
midine), 119.6 (Cp*), 119.6 (CH, Xyl), 125.0 (CH, Xyl), 127.1 (CH,
Xyl), 127.9 (CH, Xyl), 128.4 (CH, Xyl), 128.6 (CH, Xyl) 136.4
(CCH3, Xyl), 137.0 (CCH3, Xyl), 146.9 (CNϭC), 154.8 (CN), 164.9
(CCH3, pyrimidine), 165.8 (CCH3, pyrimidine), 176.7 (CS), 230.0
(CϭN) ppm. C37H49N4STa (762.83): calcd. C 58.26, H 6.47, N
7.34; found C 57.80, H 7.34, N 7.61.
˚
Mo-Kα radiation (λ ϭ 0.71073 A) using an ω/2θ scan technique to
a maximum value of 56°. Data were corrected for Lorentz and
polarization effects. The structure was solved by direct methods
(SIR92)[21] and refined first isotropically by full-matrix least
squares using SHELXL-97[22] program and then anisotropically by
blocked full-matrix least-squares techniques for all the non-hydro-
gen atoms. The hydrogen atoms were included in calculated
positions and refined as ‘‘riding’’ on their parent carbon atoms.
CCDC-189366 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; Fax: (internat.)
deposit@ccdc.cam.ac.uk].
ϩ 44-1223/336-033; E-mail:
Acknowledgments
The support of this work by the Direccion General de Ensen˜anza
[Cp*TaMe{tBuNC(Me2)}(SC6H7N2)]
(6):
tBuNϵC
(7µL,
´
0.06 mmol) was added to a solution of Cp*TaMe3(SC6H7N2)
(0.031 g, 0.06 mmol) in 0.7 mL of C6D6. The mixture was allowed
to react at room temperature in an NMR tube during 10 min to
yield the proposed complex 6 as only detectable compound. 1H
NMR (200 MHz, C6D6): δ ϭ 0.04 (s, 3 H, CH3Ta), 1.31 (s, 9 H,
tBu), 1.62 (s, 15 H, Cp*), 1.66 (s, 3 H, CH3), 1.79 (br, 6 H, CH3),
1.99 (s, 3 H, CH3), 5.79 (s, 1 H, CH pyrimidine) ppm. 13C{1H}
NMR (C6D6): δ ϭ 11.4 (Cp*), 23.6 (CH3 pyrimidine), 27.3, 32.8
(CH3CϭN), 31.5 (tBu), 45.9 (CH3Ta), 62.6 (CMe3), 68.1 (CMe2),
114.1 (CH pyrimidine), 116.3 (Cp*), 164.40 (CCH3), 182.4 (CS)
ppm.
´
´
Superior e Investigacion Cientıfica (Spain, Grant No. PB 98-0159-
C02-01) is gratefully acknowledged.
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