Chloro- and alkyltitanium complexes of a new dianionic ancillary ligand: A linked amidinate-amide

Article abstract of DOI:10.1002/ejic.200390059

The lithium amidinate [Me₃SiNC(Ph)N(CH₂)₃N(Me) SiMe₃]-Li(THF) (2), with a pendant methyl(trimethylsilyl)amine functionality, was prepared and found to react with [TiCl₄(THF)₂] to give the titanium amidinate-amide dichloride complex [η²,η¹-Me₃SiNC(Ph) N(CH₂)₃NMe]TiCl₂ (3) by elimination of LiCl and Me₃SiCl. The elimination of Me₃SiCl from the cyclopentadienyl derivative Cp[η²-Me₃SiNC(Ph)N (CH₂)₃N(-SiMe₃)Me]TiCl₂ (5) to give Cp[η²,η¹-Me₃SiNC(Ph)N- (CH₂)₃NMe]TiCl (4) is much less favorable, and was found to be readily reversible. Dialkyltitanium complexes [η²,η¹-Me₃SiNC(Ph)N (CH₂)₃NMe]Ti(CH₂R)₂ [R = Ph (6), SiMe₃ (7)] were prepared, but could not be activated for catalytic ethene polymerization. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200390059

FULL PAPER
Chloro- and Alkyltitanium Complexes of a New Dianionic Ancillary Ligand:
A Linked Amidinate؊Amide[‡]
Wouter J. van Meerendonk,[a] Kai Schröder,[a] Edward A. C. Brussee,[a] Auke Meetsma,[a]
Bart Hessen,*[a] and Jan H. Teuben[a]
Keywords: N ligands / Tridentate ligands / Titanium / Alkyl complexes
The lithium amidinate [Me3SiNC(Ph)N(CH2)3N(Me)SiMe3]-
(CH2)3NMe]TiCl (4) is much less favorable, and was found
Li(THF) (2), with a pendant methyl(trimethylsilyl)amine func- to be readily reversible. Dialkyltitanium complexes [η2,η1-
tionality, was prepared and found to react with [TiCl4(THF)2] Me3SiNC(Ph)N(CH2)3NMe]Ti(CH2R)2 [R = Ph (6), SiMe3 (7)]
to give the titanium amidinate−amide dichloride complex
[η2,η1-Me3SiNC(Ph)N(CH2)3NMe]TiCl2 (3) by elimination of
LiCl and Me3SiCl. The elimination of Me3SiCl from the
cyclopentadienyl derivative Cp[η2-Me3SiNC(Ph)N(CH2)3N(-
were prepared, but could not be activated for catalytic
ethene polymerization.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
SiMe3)Me]TiCl2 (5) to give Cp[η2,η1-Me3SiNC(Ph)N- Germany, 2003)
Introduction
Results and Discussion
Amidinate monoanions [RC(NRЈ)2]Ϫ (R ϭ aryl, alkyl;
RЈ ϭ aryl, alkyl, SiMe3) form a group of versatile ancillary
ligands (binding predominantly in an N,NЈ-bidentate fash-
ion) that have been employed extensively in main-group and
transition-metal coordination chemistry, organometallic
chemistry and catalysis.[1Ϫ5] They can also be incorporated
as a functionality in polydentate ligand systems. Examples
have been reported recently of the synthesis and com-
plexation chemistry of monoanionic tridentate amidinate
Lewis base[6Ϫ9] and dianionic tetradentate bis(amidinate)
ligands.[10Ϫ12] One way to prepare amidinate-based polyd-
entate ligands is the reaction of functionalized trimethylsily-
lamides with nitriles.[6,8,9,12] Here we report the use of this
method to prepare the amidinate [Me3SiNC(Ph)N-
(CH2)3N(SiMe3)Me]Ϫ with a pendant alkyl(trimethylsilyl)a-
mine functionality. Reaction of the Li salt of this amidinate
with titanium chlorides leads to the formation of titanium
complexes of the new dianionic amidinateϪamide trident-
ate ligand [Me3SiNC(Ph)N(CH2)3NMe]2Ϫ by sequential
salt metathesis and Me3SiCl elimination reactions. The syn-
thesis, structure and reactivity of two of these titanium
complexes, [Me3SiNC(Ph)N(CH2)3NMe]TiCl2 and Cp-
[Me3SiNC(Ph)N(CH2)3NMe]TiCl, are described.
The Li salt of an amidinate with a pendant alkyl(trimeth-
ylsilyl)amine group, [Me3SiNC(Ph)N(CH2)3N(SiMe3)Me]Ϫ,
was prepared by the deprotonation of the diamine Me3Si-
N(H)(CH2)3N(Me)SiMe3 (1) with nBuLi/hexane in THF,
followed by reaction with benzonitrile (Scheme 1). After
recrystallization from pentane, the resulting Li amidinate
was obtained analytically pure as its THF solvate [Me3Si-
NC(Ph)N(CH2)3N(Me)SiMe3]Li(THF) (2) in 55% isolated
yield. The presence of THF in 2 probably indicates that
the pendant methyl(trimethylsilyl)amine functionality is not
coordinated to the Li ion, in contrast to the THF-free Li
amidinateϪamine [Me3SiNC(Ph)N(CH2)3NMe2]Li, which
was found to adopt a dimeric structure with a coordinated
amine functionality.[9]
[‡]
Netherlands Institute for Catalysis Research (NIOK)
Scheme 1
publication RUG 02-04-05
[a]
Center for Catalytic Olefin Polymerization, Stratingh Institute
for Chemistry and Chemical Engineering, University of
Groningen,
The Li amidinate 2 reacts with [TiCl4(THF)2] in THF to
give the titanium amidinateϪamide complex [η2,η1-Me3Si-
NC(Ph)N(CH2)3NMe]TiCl2 (3) by elimination of LiCl and
Nijenborgh 4, 9747 AG Groningen, The Netherlands
Fax: (internat.) ϩ 31-50/363-4315
E-mail: hessen@chem.rug.nl
Eur. J. Inorg. Chem. 2003, 427Ϫ432  2003 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 1434Ϫ1948/03/0203Ϫ0427 $ 20.00ϩ.50/0
427

B. Hessen et al.
FULL PAPER
Me3SiCl (Scheme 2). After recrystallization from diethyl
ether, complex 3 was obtained as orange-red crystals, ana-
lytically pure, in 56% yield.
Figure 1. Molecular structure of compound 3; thermal ellipsoids
are drawn at the 50% probability level; TiϪCl(1) 2.2464(6),
TiϪCl(2) 2.2954(7), TiϪN(1) 2.077(2), TiϪN(2) 2.059(2), TiϪN(3)
˚
1.863(2) A; Cl(1)ϪTiϪCl(2) 107.26(2), N(1)ϪTiϪN(2) 64.03(6),
Scheme 2
N(1)ϪTiϪN(3) 139.40(7), N(2)ϪTiϪN(3) 84.08(7), N(3)ϪTiϪ
Cl(1) 107.72(6), N(3)ϪTiϪCl(2) 100.83(6), TiϪN(3)ϪC(13)
137.0(2), TiϪN(3)ϪC(14) 110.2(2)°
A single-crystal X-ray structure determination of 3 (Fig-
ure 1) showed that the amidinate moiety of the ligand is
N,NЈ-dihapto bound to the metal center [TiϪN(1) ϭ leads to a thermodynamically favored elimination of
˚
˚
2.077(2) A and TiϪN(2) ϭ 2.059(2) A]. The TiϪN distance Me3SiCl and formation of the metalϪamide bond in 3.
to the amido nitrogen atom is significantly shorter
The reaction of [CpTiCl3] with the Li amidinate 2 in
˚
[TiϪN(3) ϭ 1.863(2) A] than those to the amidinate nitro- THF, followed by extraction with, and crystallization from,
gen atoms, probably in response to an amide N(p) π-dona- diethyl ether, resulted only in a low isolated yield (13%) of
tion to Ti(d). The amidinate nitrogen atom linked to the the corresponding amidinateϪamide complex Cp[η2,η1-
alkylamide moiety deviates somewhat from planarity [the Me3SiNC(Ph)N(CH2)3NMe]TiCl (4), which was character-
sum of the angles around N(2) is 353.8°], but this deviation ized by single-crystal X-ray diffraction (vide infra). Workup
is not as pronounced as in the vanadium amidinateϪamine of the reaction mixture was made more difficult by the pres-
complex [η2,η1-Me3SiNC(Ph)N(CH2)2NMe2]VCl2(THF) in ence of a substantial amount of an orange oil, which ap-
which the sum of the angles around N is 336.4°[6] and where peared to be the major product of the reaction, but which
the amidinateϪamine tridentate ligand clearly adopts a fac defied crystallization. Investigation of the reaction between
coordination geometry. The amide nitrogen atom in 3 is [CpTiCl3] and 2 in [D8]THF at ambient temperature ini-
planar [the sum of the angles around N(3) is 360.0°], again tially showed rapid formation of a primary product, identi-
indicative of efficient amide-to-metal π-donation. The fied as Cp[η2-Me3SiNC(Ph)N(CH2)3N(SiMe3)Me]TiCl2 (5)
angles around this atom show significant asymmetry, with from its NMR characteristics (which are identical to those
the TiϪNϪC angle within the six-membered ring of the orange oil observed in the reaction on preparative
[TiϪN(3)ϪC(13) ϭ 137.0(2)°] being significantly larger scale). This initial reaction is followed by slow release of
than the TiϪNϪC(Me) angle [TiϪN(3)ϪC(14)
ϭ
Me3SiCl
and
concomitant
formation
of
the
110.2(2)°]. The solution NMR spectra of 3 are consistent amidinateϪamide complex 4 (Scheme 2). Characteristic for
with Cs symmetry, indicating that the amidinateϪamide the latter are the significant downfield shift of the NMR
acts as a meridional-type ligand, and that the six-membered resonances associated with the NMe group (1H: δ ϭ
TiN2C3 ring, which adopts a boat-like conformation in the 3.21 ppm; 13C: δ ϭ 51.0 ppm) relative to those in 5 (1H:
crystal structure, readily inverts.
The rapid formation in high yield of the can be accelerated by increasing the reaction temperature
amidinateϪamide complex in the reaction of (50Ϫ80 °C), but this is then accompanied by the formation
TiCl4(THF)2 with the Li amidinate 2 indicates that the of unidentified degradation products. The Me3SiCl elimina-
Me3SiCl elimination reaction from
[η2-Me3Si- tion reaction appears to be noticeably faster when the reac-
δ ϭ 2.29 ppm; 13C: δ ϭ 35.3 ppm). The secondary reaction
3
NC(Ph)N(CH2)3N(SiMe3)Me]TiCl3, the likely primary tion is performed in C6D6 rather than in the Lewis basic
product of the salt metathesis reaction, is facile. The reverse solvent [D8]THF, proceeding readily at ambient temper-
reaction Ϫ formation of group-4 metal chlorides by reac- ature. The reaction was observed to reach an equilibrium
tion of group-4 metal amides with an excess of Me3SiCl Ϫ (in C6D6 and 25 °C within 30 min), suggesting that the reac-
was reported as a clean, salt-free route to generate group-4 tion is readily reversible in the mono(cyclopentadienyl)tit-
metallocene dichlorides from their corresponding anium system. Indeed, upon addition of Me3SiCl to C6D6
bis(amides).[13Ϫ15] Apparently, in our case the chelate effect solutions of the amidinateϪamide complex 4 the formation
428
Eur. J. Inorg. Chem. 2003, 427Ϫ432

Chloro- and Alkyltitanium Complexes of a New Dianionic Ancillary Ligand
FULL PAPER
of 5 could be observed. Examination of C6D6 solutions of the dialkyl complexes [η2,η1-Me3SiNC(Ph)N(CH2)3NMe]-
4 of known concentration to which 1, 2 or 3 equiv. of Ti(CH2R)2 [R ϭ Ph (6), SiMe3 (7); Scheme 3]. Compound
Me3SiCl were added allowed a determination of the equilib- 6 was obtained in 74% yield as yellow crystals by crystal-
rium constant at 25 °C of the equilibrium of 4 ϩ Me3SiCl lization from pentane, whereas 7 is an extremely soluble oil
with 5 as K ϭ [5]/([4] ϩ [Me3SiCl]) ϭ 32(3) L molϪ1. Com- that only gradually solidifies on standing. The compounds
pound 4 was also prepared independently, in 38% isolated are thermally rather labile, and are best handled and stored
yield, by the reaction of the dichloride 3 with CpLi, in below 0 °C. Their solution NMR spectra are consistent
which this equilibrium is avoided. This reaction appears to with an average Cs symmetry, and each show two doublets
suffer from some reduction of the metal center, as seen from for the diastereotopic alkyl methylene protons in the 1H
the dark residue left after extraction of the reaction mixture NMR spectrum (6: δ ϭ 2.75 and 3.09 ppm, 2JH,H ϭ 9.0 Hz;
2
with hexane and the relatively modest isolated yield.
7: δ ϭ 1.56 and 1.86 ppm, JH,H ϭ 11.0 Hz).
The molecular structure of 4 (Figure 2) shows a fully
symmetrically bound η5-cyclopentadienyl ligand and an
η2,η1-amidinateϪamide ligand in which the TiN2C3 ring
now adopts a twisted conformation. The amidinate nitro-
gen atom attached to the alkylamide moiety is significantly
less planar [sum of the angles around N(2) is 340.6°] than
in 3. The angles around the (planar) amide nitrogen atom
are again highly asymmetric, but in the opposite direction
than in 3: the TiϪNϪC angle within the six-membered ring
[TiϪN(1)ϪC(7) ϭ 105.6(2)°] is now significantly smaller
than the TiϪNϪC(Me) angle [TiϪN(1)ϪC(6) ϭ 141.6(2)°].
This is probably in response to the twisted conformation of
the six-membered ring. It also reduces the steric interaction
of the amide methyl group with the cyclopentadienyl ligand,
towards which it is pointing. Overall, the metalϪligand dis-
tances in 4 are larger than those in 3 [especially the TiϪCl
Scheme 3
The dibenzyl complex 6 was treated with the Lewis acid
B(C6F5)3 in C6D6 and in [D5]bromobenzene solvents in or-
der to effect the abstraction of a benzyl anion. As the ligand
system is sterically not very demanding, the formation of a
contact ion pair with an η6-PhCH2B(C6F5)3 interaction
might be anticipated, as was observed recently for titanium
in the reaction of [(2,6-diphenylphenoxide)2Ti(CH2Ph)2]
with B(C6F5)3.[16,17] However, in both solvents rapid de-
composition to a mixture of unidentified products was ob-
served, even when the reaction in [D5]bromobenzene was
performed at Ϫ20 °C. Attempts at catalytic ethene poly-
merization (5 bar of ethene, 150 mL of toluene solvent, 50
°C, 15 µmol of Ti) by treating 6 with B(C6F5)3 or 7 with
[PhNMe2H][B(C6F5)4] in the presence of monomer did not
result in ethene uptake, suggesting that the decomposition
of the cationic species generated is rapid. It is likely that the
present amidinateϪamide ligand is either reactive itself and/
or provides insufficient steric protection to the highly elec-
tron-deficient metal center.
˚
distance of 2.4038(7) A, compared to 2.2464(6) and
˚
2.2954(7) A in 3] but the metalϪamide distances are similar
˚
˚
[1.887(2) A in 4, 1.863(2) A in 3], indicating the importance
of the amide-to-metal π-donation.
Conclusion
Titanium complexes of the new dianionic η2,η1-
amidinateϪamide ligand can be prepared by sequential salt
metathesis and Me3SiCl elimination reactions that occur
upon combining titanium chlorides with a lithium amidin-
Figure 2. Molecular structure of compound 4; thermal ellipsoids
are drawn at the 50% probability level; TiϪCl 2.4038(7), TiϪN(1)
˚
1.887(2), TiϪN(2) 2.095(2), TiϪN(3) 2.170(2) A; N(1)ϪTiϪN(2)
85.12(7), N(1)ϪTiϪN(3) 128.61(7), N(2)ϪTiϪN(3) 61.96(6),
N(1)ϪTiϪCl 93.96(6), TiϪN(1)ϪC(6) 141.6(2), TiϪN(1)ϪC(7)
105.6(2)°
ate containing
a pendant (trimethylsilyl)amide func-
tionality. The Me3SiCl elimination reaction forming the
titaniumϪamide bond is thermodynamically favored by its
The amidinateϪamide dichloride 3 may be converted intramolecular nature, but it is reversible, and the equilib-
into the corresponding dialkyltitanium amidinateϪamide rium is dependent on what is probably a combination of
complexes, which are precursors to cationic monoalkyl electronic and steric factors. The formation of the TiN2C3
species that are interesting as potential olefin polymeriz- six-membered ring is clearly less favorable in the more elec-
ation catalysts. Reaction of 3 with 2 equiv. of either tron-rich and sterically more encumbered [Cp(amidinate)-
PhCH2MgBr or Me3SiCH2Li results in the formation of TiCl2] species 5 than in the (amidinate)TiCl3 intermediate
Eur. J. Inorg. Chem. 2003, 427Ϫ432
429

B. Hessen et al.
FULL PAPER
Si(CH3)3], Ϫ0.03 [s, 9 H, Si(CH3)3], 1.28 (m, 4 H, THF β-H), 1.58
proposed in the formation of 3. The dialkyltitanium deriv-
atives [η2,η1-Me3SiNC(Ph)N(CH2)3NMe]Ti(CH2R)2 (R ϭ
Ph, SiMe3) are readily prepared but are thermally rather
labile, and could not be converted into well-defined cationic
alkyl compounds that are active in catalytic olefin poly-
merization. Possibly the present substitution pattern of the
ligand (SiMe3 on the amidinate nitrogen atom, Me on the
amido nitrogen atom) renders it incapable of stabilizing
such highly reactive species, and sterically more demanding
substituents may be required for catalytic activity.
3
(m, 2 H, CH2CH2CH2), 2.44 (s, 3 H, NCH3), 2.47 (t, JH,H
ϭ
3
7.0 Hz, 2 H, NCH2), 2.98 [t, JH,H ϭ 7.3 Hz, 2 H, N(Me)CH2],
3.58 (m, 4 H, THF α-H), 7.0Ϫ7.2 (m, 5 H, Ph) ppm. 13C{1H}
NMR (50 MHz, C6D6): δ ϭ Ϫ0.9 and 3.6 [Si(CH3)3], 25.7 (THF
β-C), 32.6 (CH2CH2CH2), 34.3 (NCH3), 48.4 and 49.3 (NCH2),
68.3 (THF α-C), 126.9, 127.8, 128.1 (Ph CH), 143.3 (Ph C), 177.5
(NCN) ppm. C21H40N3LiOSi2 (413.68): calcd. C 60.97, H 9.75, N
10.16; found C 61.17, H 9.60, N 10.45.
Synthesis of [Me3SiNC(Ph)N(CH2)3NMe]TiCl2 (3): A solution of
2 (2.45 g, 5.93 mmol) and TiCl4(THF)2 (1.98 g, 5.93 mmol) in
70 mL of THF was stirred overnight at room temperature. The
dark red solution was stirred for another 8 h, during which the
flask was periodically briefly evacuated. The volatiles were removed
in vacuo, and the residue was freed of residual THF by stirring
twice with diethyl ether (15 mL), which was subsequently removed
in vacuo. The residue was extracted three times with diethyl ether
(30 mL) after which the extract was concentrated and cooled to
Ϫ80 °C, yielding microcrystalline orange-red 3 (1.26 g, 3.31 mmol,
56%). Crystals suitable for X-ray diffraction were obtained by cool-
ing a solution of 3 in diethyl ether to Ϫ20 °C. 1H NMR (300 MHz,
C6D6): δ ϭ 0.24 [s, 9 H, Si(CH3)3], 1.35 (m, 2 H, CH2CH2CH2),
2.60 (m, 2 H, NCH2), 2.99 (m, 2 H, MeNCH2), 3.74 (s, 3 H,
NCH3), 6.93Ϫ6.99 (m, 5 H, Ph) ppm. 13C{1H} NMR (75 MHz,
C6D6): δ ϭ 0.2 [Si(CH3)3], 31.8 (CH2CH2CH2), 43.0 (NCH2), 46.6
(NCH3), 61.8 (NCH2), 126.8, 127.7, 130.4 (Ph CH), 132.7 (Ph C)
ppm; NCN signal not observed. C14H23Cl2N3SiTi (380.23): calcd.
C 44.22, H 6.10, N 11.05, Ti 12.60; found C 44.36, H 6.03, N 11.12,
Ti 12.50.
Experimental Section
General Remarks: All experiments were carried out under purified
dinitrogen using standard Schlenk and glove-box techniques. Solv-
ents were distilled from Na/K alloy (THF, diethyl ether, pentane,
hexane) or sodium (toluene) under nitrogen before use. Deuterated
solvents were either dried with Na/K alloy and vacuum-transferred
˚
before use (C6D6, [D8]THF) or degassed and stored over 4-A mo-
lecular sieves ([D5]bromobenzene). [TiCl4(THF)2][18] and
[CpTiCl3],[19] were prepared according to published procedures.
Benzonitrile, nBuLi/hexane, Me3SiCl and MeNH(CH3)3NH2 were
purchased and used as received. NMR spectra were recorded with
Varian Gemini 200, VXR 300 and Unity 500 spectrometers. The
1H NMR spectra were referenced to the resonances of residual pro-
tons in the deuterated solvent. Chemical shifts (δ) are given relative
to tetramethylsilane (downfield shifts are positive). Elemental ana-
lyses were performed at the Microanalytical Department of the
University of Groningen. All values are the average of at least two
independent determinations.
Synthesis of Cp[Me3SiNC(Ph)N(CH2)3NMe]TiCl (4). Method 1: A
solution of 2 (1.07 g, 2.56 mmol) in 40 mL of THF was cooled to
Ϫ80 °C, after which CpTiCl3 (0.57 g, 2.59 mmol) was added. The
solution was allowed to warm to room temperature, during which
time the color changed from yellow to orange-red. After stirring
for 2 h, the volatiles were removed in vacuo and the residual THF
was removed by stirring the mixture in pentane, which was sub-
sequently pumped off. The residue was extracted twice with diethyl
ether (20 mL). Concentrating and cooling the extract to Ϫ20 °C
yielded red crystalline 4 (0.14 g, 0.34 mmol, 13%). Crystals suitable
for X-ray diffraction were obtained by cooling a concentrated solu-
tion of 4 in diethyl ether from room temperature to 7 °C. Method
2: Hexane (15 mL) was condensed onto a mixture of solid 3 (0.11 g,
0.28 mmol) and CpLi (20 mg, 0.28 mmol), frozen in liquid nitro-
gen. The mixture was allowed to thaw and warm to room temper-
ature. After stirring for one more hour, the suspension was filtered
and the volatiles were removed from the filtrate in vacuo. Extrac-
tion of the residue with hexane, and concentrating and cooling the
extract to Ϫ20 °C, yielded microcrystalline 4 (54 mg, 0.13 mmol,
38%). 1H NMR (500 MHz, C6D6): δ ϭ 0.17 [s, 9 H, Si(CH3)3],
Synthesis of Me3SiN(H)(CH2)3N(Me)SiMe3 (1): This compound
was prepared according to a modification of a published proced-
ure.[20] A 2.5  solution of nBuLi in hexane (160 mL, 0.40 mol)
was slowly added to a solution of MeNH(CH3)3NH2 (20.9 mL,
0.20 mol) in 50 mL of hexane. After refluxing for 2.5 h, Me3SiCl
(50.5 mL, 0.40 mol) was added dropwise, and the mixture was sub-
sequently refluxed for one more hour. From the resulting deep or-
ange suspension, the volatiles were flash-distilled at 90 °C and
0.05 Torr. Subsequent vacuum distillation of this liquid (14 Torr)
yielded the product as a spectroscopically pure colorless liquid at
1
98Ϫ101 °C (29.3 g, 0.126 mol, 63%). H NMR (300 MHz, C6D6):
δ ϭ 0.09 (s, 18 H, SiMe3), 1.46 (m, 2 H, CH2CH2CH2), 2.39 (s, 3
H, NCH3), 2.70 (t, 3JH,H ϭ 7.7 Hz, 2 H, HNCH2), 2.64 (t, 3JH,H ϭ
7.0 Hz, 2 H, MeNCH2) ppm. 13C{1H} NMR (75 MHz, C6D6): δ ϭ
0.2 [Si(CH3)3], 34.0 (CH2CH2CH2), 34.1 (NCH3), 39.8 (HNCH2),
49.0 (MeNCH2) ppm. IR (neat, KBr): ν˜ ϭ 3420 (br. w), 2969 (s),
2854 (m), 2795 (w), 1453 (w), 1400 (m), 1375 (w), 1330 (w), 1253
(s), 1189 (w), 1144 (m), 1110 (m), 1020 (w), 980 (w), 943 (w), 835
2
1.13, 1.33 (m, 1 H each, CH2CH2CH2), 2.43 (ddd, JH,H ϭ 12.4,
(s), 746 (m), 677 (m) cmϪ1
.
3JH,H ϭ 8.8, 5.7 Hz, 1 H, NCHH), 2.65 (ddd, 2JH,H ϭ 14.8, 3JH,H ϭ
6.2, 4.4 Hz, 1 H, MeNCHH), 3.03 (ddd, overlapped, 1 H, NCHH),
Synthesis of [Me3SiNC(Ph)N(CH2)3N(Me)SiMe3]Li(THF) (2): A
solution of 1 (4.2 mL, 18 mmol) in 50 mL of THF was cooled to
Ϫ80 °C after which a 2.5  solution of nBuLi in hexane (8 mL,
20 mmol) was added dropwise. The solution was allowed to warm
to room temperature and was subsequently stirred for 2 h. The light
yellow mixture was cooled to Ϫ80 °C and benzonitrile (1.8 mL,
17 mmol) was added, after which the mixture was allowed to warm
to room temperature. The volatiles from the orange-yellow mixture
were removed in vacuo, and the solid residue was recrystallized
twice from pentane. Yield: 4.13 g (9.93 mmol, 55%) of a light yel-
2
3.04 (s, 3 H, NCH3), 3.38 (ddd, JH,H ϭ 14.8, 3JH,H ϭ 7.6, 4.3 Hz,
1 H, NCHH), 6.24 (s, 5 H, C5H5), 6.98Ϫ7.03 (m, 5 H, Ph) ppm.
13C{1H} NMR (126 MHz, C6D6): δ ϭ 2.6 [Si(CH3)3], 29.8
(CH2CH2CH2), 44.8 (MeNCH2), 49.8 (NCH3), 58.6 (NCH2), 114.5
(C5H5), 127.0, 128.6, 129.3 (Ph CH), 135.0 (Ph C), 174.3 (NCN)
ppm. C19H28ClN3SiTi (409.89): calcd. C 55.68, H 6.89, N 10.25;
found C 55.10, H 6.89, N 9.75.
Reaction of [CpTiCl3] with 2 in [D8]THF: Separately prepared solu-
tions of [CpTiCl3] (17 mg, 0.08 mmol) and 2 (33 mg, 0.08 mmol),
low solid. 1H NMR (300 MHz, C6D6): δ ϭ Ϫ0.08 [s, 9 H, each in 0.4 mL of [D8]THF, were mixed at ambient temperature,
430
Eur. J. Inorg. Chem. 2003, 427Ϫ432

Chloro- and Alkyltitanium Complexes of a New Dianionic Ancillary Ligand
FULL PAPER
resulting in a rapid color change from light yellow to orange, and
the mixture was added into an NMR tube, equipped with a Teflon
valve. The 1H and 13C NMR spectra indicated formation of
Synthesis of [Me3SiNC(Ph)N(CH2)3NMe]Ti(CH2Ph)2 (6): A solu-
tion of 3 (0.316 g, 0.83 mmol) in 30 mL of diethyl ether was cooled
to Ϫ100 °C and a 1.56  solution of PhCH2MgBr in diethyl ether
Cp[Me3SiNC(Ph)N(CH2)3N(Me)SiMe3]TiCl (5). 1H NMR (1.07 mL, 1.66 mmol) was slowly added. The solution was allowed
(300 MHz, [D8]THF): δ ϭ Ϫ0.11, Ϫ0.05 [s, 9 H each, Si(CH3)3],
1.66 (m, 2 H, CH2), 2.29 (s, 3 H, NCH3), 2.52 (t, JH,H ϭ 6.8 Hz, for 2 h. During workup the temperature of the mixture was kept at
to warm to Ϫ15 °C, at which temperature the mixture was stirred
3
2 H, MeNCH2), 3.03 (m, 2 H, NCH2), 6.83 (s, 5 H, C5H5), 7.33
or below Ϫ15 °C. The volatiles were removed in vacuo and the
(m, 2 H, Ph m-H), 7.45 (m, 3 H, Ph o-H and p-H) ppm. 13C(APT) mixture was stirred twice with 10 mL of precooled pentane, which
NMR (75 MHz, [D8] THF): δ ϭ 0.4, 3.3 [Si(CH3)3], 31.6 (CH2), was subsequently pumped off. The residue was extracted with pent-
35.3 (NCH3), 49.8, 52.2 (NCH2), 122.0 (C5H5), 128.7, 130.4, 131.5 ane, after which the extract was concentrated and cooled to Ϫ60
1
(Ph CH), 135.2 (Ph C), 172.2 (NCN) ppm. Upon standing at ambi-
°C. This yielded crystalline 6 (0.302 g, 0.62 mmol, 74%). H NMR
ent temperature or 50 °C, gradual formation of 4 and Me3SiCl was (300 MHz, C6D6): δ ϭ 0.26 [s, 9 H, Si(CH3)3], 1.07 (m, 2 H,
observed. At 50 °C a maximum conversion of 34% was reached
CH2CH2CH2), 2.63 (m, 2 H, NCH2), 2.75, 3.09 (d, 2JH,H ϭ 9.0 Hz,
(after 24 h, with concomitant formation of some degradation prod- 2 H each, TiCH2), 3.80 (s, 3 H, NCH3), 6.9Ϫ7.2 (m, 15 H, Ph)
ucts). 1H NMR (300 MHz, [D8]THF, characteristic resonances): ppm. 13C{1H} NMR (75 MHz, C6D6): δ ϭ 3.0 [Si(CH3)3], 31.2
δ ϭ Ϫ0.11 [s, Si(CH3)3], 3.21 (s, 3 H, NCH3), 6.30 (s, 5 H, C5H5) (CH2CH2CH2), 40.8 (MeNCH2), 45.4 (NCH3), 59.9 (NCH2), 84.5
ppm. 13C(APT) NMR (75 MHz, [D8]THF): δ ϭ 51.0 (NCH3),
116.1 (C5H5) ppm.
(TiCH2), 122.2, 126.5, 127.2, 128.6, 128.8, 129.3 (Ph CH), 134.6
(Ph C), 144.4 (CH2Ph C), 177.4 (NCN) ppm. C28H37N3SiTi
(491.59): calcd. C 68.41, H 7.59, N 8.55; found C 68.32, H 7.53,
N 8.44.
Reaction of 4 with Me3SiCl: Three NMR tubes were charged each
with a solution of 4 in C6D6 to which measured amounts of a stock
solution of Me3SiCl in C6D6 was added. Initial concentrations of
[4]/[Me3SiCl] in the three tubes were: 0.030:0.035, 0.029:0.069 and
Synthesis of [Me3SiNC(Ph)N(CH2)3NMe]Ti(CH2SiMe3)2 (7): Pent-
ane (30 mL) was condensed into a vessel containing a solid mixture
0.029:0.100 mol LϪ1. After 30 min at 25 °C, the relative amounts of 3 (0.31 g, 0.81 mmol) and Me3SiCH2Li (0.15 g, 1.63 mmol) that
of 4, 5 and Me3SiCl were determined by 1H NMR spectroscopy. was frozen in liquid nitrogen. The solution was allowed to thaw
Observed ratios after 1 h were the same, indicating that equilibrium
had been reached. Values determined for K ϭ [5]/([4] ϩ [Me3SiCl])
were 32, 33 and 33(2) L molϪ1, respectively, for the three samples.
and warm to Ϫ15 °C, at which temperature it was stirred for 2 h.
The solution was filtered and the residue was extracted with 30 mL
of pentane. From the combined filtrates the volatiles were removed
Cp[Me3SiNC(Ph)N(CH2)3N(Me)SiMe3]TiCl2 (5): 1H NMR in vacuo to leave 7 as a yellow oil that slowly solidified on standing.
(500 MHz, C6D6): δ ϭ Ϫ0.04 [s, 9 H, Si(CH3)3], 0.04 [s, 9 H,
Attempts to recrystallize this material from pentane were unsuc-
Si(CH3)3], 1.63 (m, 2 H, CH2CH2CH2), 2.27 (s, 3 H, NCH3), 2.49 cessful due to the extreme solubility of the product. The yield of
3
(t, JH,H ϭ 7.3 Hz, 2 H, NCH2), 3.22 (m, 2 H, NCH2), 6.55 (s, 5
H, C5H5), 6.70Ϫ6.95 (m, 5 H, Ph) ppm.
the material (Ͼ 95% pure by NMR spectroscopy) was essentially
quantitative. 1H NMR (300 MHz, C6D6): δ ϭ 0.18 [s, 18 H,
Table 1. Crystallographic data for compounds 3 and 4
3
4
Empirical formula
Molecular mass
Temperature [K]
C14H23Cl2N3SiTi
380.21
130
C19H28ClN3SiTi
409.86
130
˚
Wavelength [A]
0.71073
0.71073
Crystal system
Space group
Unit cell dimensions
monoclinic
P21/n
a ϭ 11.570(1) A
b ϭ 8.992(1) A
monoclinic
P21/c
a ϭ 12.130(1) A
b ϭ 15.168(1) A
˚
˚
˚
˚
˚
˚
c ϭ 18.177(1) A
c ϭ 12.278(1) A
β ϭ 94.129(5)°
β ϭ 112.607(6)°
3
3
˚
˚
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
1886.2(3) A
4
2805.4(3) A
4
1.339 Mg/m3
1.305 Mg/m3
0.8 mmϪ1
0.6 mmϪ1
792
864
Crystal size
θ range for data collection
Index ranges
0.25 ϫ 0.30 ϫ 0.61 mm
1.12Ϫ28.0°
Ϫ15 Յ h Յ 1
0 Յ k Յ 11
Ϫ23 Յ l Յ 23
5514
4529
4529/0/282
1.012
0.08 ϫ 0.38 ϫ 0.50 mm
1.34Ϫ27.0°
Ϫ14 Յ h Յ 10
0 Յ k Յ 19
Ϫ15 Յ l Յ 0
4934
4531
4531/0/338
1.067
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices
R1 ϭ 0.0352, wR2 ϭ 0.1012
0.59 and Ϫ0.51(7)
R1 ϭ 0.0326, wR2 ϭ 0.0827
0.42 and Ϫ0.27(5)
Ϫ3
˚
Largest difference peak and hole [e A
]
Eur. J. Inorg. Chem. 2003, 427Ϫ432
431

B. Hessen et al.
FULL PAPER
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[I02390]
432
Eur. J. Inorg. Chem. 2003, 427Ϫ432