ARTICLE pubs.acs.org/Organometallics
Reactions of [Ti(η5-C5Me4SiMe2Cl)Cl3] with Diamines, a Suitable Approach to Prepare Mono- and Dinuclear Cyclopentadienylsilyl-amido Titanium Complexes with Constrained and Unstrained Structures Cristina Paniagua, Marta E. G. Mosquera,‡ Tomas Cuenca,* and Gerardo Jimenez* Departamento de Química Inorganica, Universidad de Alcala, Campus Universitario, 28871 Alcala de Henares. Spain
bS Supporting Information ABSTRACT:
Complex [Ti(η5-C5Me4SiMe2Cl)Cl3] (1) reacts with NH2(CH2)nNH2 (n = 3, 4), under appropriate reaction conditions, to yield the corresponding di- and mononuclear constrained-geometry cyclopentadienyl-silyl-amido complexes [Ti{η5-C5Me4SiMe2κ-N(CH2)n/2}Cl2-]2 (n = 3, 2a; 4, 2b) and [Ti{η5-C5Me4SiMe2-κ-N(CH2)nNH2}Cl2] (n = 3, 3a; 4, 3b). Complexes 2a and 2b are obtained as pure compounds when the reaction is carried out in a 1(Ti):1.5(diamine) molar ratio, while the derivatives 3 cannot be selectively prepared. Treatment of 1 with NH2(CH2)5NH2 gives the dinuclear derivative [Ti{η5-C5Me4SiMe2-κ-N(CH2)2.5-}Cl2]2 (2c) as a single complex, regardless of the reaction stoichiometry. On monitoring these reactions by NMR spectroscopy, the formation of the transient asymmetrical dinuclear complexes [TiCl2{η5-C5Me4SiMe2-κ-N(CH2)nNH-η5-C5Me4SiMe2}TiCl3] (n = 3, 4a; 4, 4b; 5, 4c) is observed. The analogue dinuclear complex [TiCl2{η5-C5Me4SiMe2-κ-N(CH2)3NMe-η5C5Me4SiMe2}TiCl3] (6) is synthesized, on a preparative scale, by treatment of 1 with an equimolar amount of N-methylpropylenediamine, which is transformed into the mononuclear derivative [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NHMe}Cl2] (7) upon addition of a further equivalent of the diamine. However, treatment of 1 with 1 equiv of N-methylpropylenediamine proceeds with the formation of the mononuclear constrained-geometry compound [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NHMe 3 HCl}Cl2] (5). The reaction of 1 with 2 equiv of NH2(CH2)3NMe2 or NHMe(CH2)3NMe2 specifically affords, respectively, a mononuclear cyclopentadienyl-silyl-amido derivative with constrained geometry, [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NMe2}Cl2] (8), or unconstrained geometry, [Ti{η5-C5Me4SiMe2NMe(CH2)3-κ-NMe}Cl2] (9). When the reaction with NHMe(CH2)3NHMe is monitored by NMR spectroscopy, the mononuclear intermediate [Ti{η5-C5Me4SiMe2NMe(CH2)3NHMe}Cl3] (11) and the dinuclear complex [Ti{η5-C5Me4SiMe2NMe(CH2)1.5-}Cl3]2 (12) are observed. The dinuclear complex [Ti{η5-C5Me4SiMe2NMe(CH2)3-} Cl3]2 (13) is synthesized by treatment of 1 with 1 equiv of NHMe(CH2)6NHMe. All the reported compounds were characterized by the usual analytical and spectroscopic methods, and the crystal structure of 9 has been determined by X-ray diffraction methods.
’ INTRODUCTION The chemistry of transition metal compounds bearing ancillary polydentate ligands is a continuously developing research field,16 which fosters the study of new generations of polymerization catalyst precursors with novel and excellent performance.715 Hence, bifunctional cyclopentadienyl ligands, incorporating neutral r 2011 American Chemical Society
or anionic appended donor substituents, constitute a prominent class of this type of ligand system,1619 as inferred from the numerous reviews recently published in this research area.1,17,18,20 Received: February 3, 2011 Published: May 06, 2011 2993
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Scheme 1
This field has largely been stimulated by the remarkable success of group 4 metal “constrained-geometry” complexes as alternative catalysts to the classical bis(cyclopentadienyl) systems2124 (MCp2X2) for R-olefin polymerization processes, due to their high activity and the unique properties of the polymers and copolymers obtained.25,26 One of our ongoing research lines has been focused on a feasible alternative approach to prepare transition metal complexes containing a bifunctional cyclopentadienyl ligand,27 based on protonolysis reactions of MCl and SiCl bonds from chlorosilyl-substituted cyclopentadienyl compounds, corresponding to the general formula [M(η5-C5R4SiMe2Cl)Cln] (M = group 4 metal, n = 3, R = H, Me;28,29 M = group 5 metal, n = 4, R = H30).3135 We are particularly interested in developing a systematic investigation into the factors that drive these reactions in order to attain greater control of the process. We initially studied the behavior of [Nb(η5-C5H4SiMe2Cl)Cl4] in reactions with primary mono- and diamines, specifically concluding that such reactions proceed with initial aminolysis of a NbCl bond, rendering an amido transient that eventually gives imido, amido-amino, or cyclopentadienyl-silyl-amido-amino derivatives.35 In contrast, the behavior exhibited by the analogous titanium compounds in similar aminolysis processes is markedly different.31,32 The reaction of the titanium derivatives with ethylendiamines seems to proceed with the preferential rupture of the SiCl bond, preventing the formation of amido-amino or imido derivatives.35 Herein, we report the results of extending our reactivity studies of the chlorosilyl-substituted tetramethylcyclopentadienyl titanium complex [Ti(η5-C5Me4SiMe2Cl)Cl3] (1) with longer chain diamines NHR(CH2)nNR0 R00 (n g 3) under various working conditions.
’ RESULTS Reactions of [Ti(η5-C5Me4SiMe2Cl)Cl3] (1) with Diamines NHR(CH2)nNR0 R00 (n g 3). Treatment of 1 with an equimolar
amount of diamine NH2(CH2)nNH2 (n = 3, 4), in aromatic solvents and in the presence of 2 equiv of NEt3, resulted in the formation of the tethered dimetallic cyclopentadienyl-silyl-amido complexes [Ti{η5-C5Me4SiMe2-κ-N(CH2)n/2-}Cl2]2 (n = 3, 2a; 4, 2b) along with a small amount (in a molar ratio < 10%, as revealed by NMR) of the corresponding mononuclear cyclopentadienyl-silyl-amido derivatives [Ti{η5-C5Me4SiMe2κ-N(CH2)nNH2}Cl2] (n = 3, 3a; 4, 3b) with a pendant amino functionality (Scheme 1). This result is in sharp contrast to that
achieved using different shorter carbon chain ethylenediamines, H2N(CH2)2NRR0 , where the corresponding mononuclear constrained-geometry complexes are regioselectively formed.35 The presence of NEt3 along with the corresponding diamine reagent in the reaction mixture yields products that are difficult to purify. Titanium amido complexes of greater purity were achieved when these reactions were performed in the absence of NEt3 using the diamine as the sole captor of HCl. As assessed by NMR spectroscopy, the molar ratio of the mononuclear complex 3 decreases as the diamine-carbon chain lengthens. Indeed, when the same reaction was carried out with the pentamethylenediamine, the corresponding mononuclear compound was never observed and the reaction regioselectively afforded the dinuclear constrained-geometry derivative [Ti{η5-C5Me4SiMe2-κ-N(CH2)2.5-}Cl2]2 (2c) as an analytically pure yellow solid (Scheme 1). The reaction of both diamine ends is favored in terms of enthalpy, and only the increase of steric repulsion between the two metal-based molecular fragments, as the chain becomes shorter, reverses the preference for the dinuclear disposition. Such an observation follows the previous trend observed in the reactions toward analogous diamines.35 In an attempt to selectively produce complexes 2 or 3, an extensive series of experiments, which either reduced or increased the molar ratio of the corresponding diamine, was performed. By halving the amount of the diamine, the dinuclear complexes 2 were formed in high yield and isolated as analytically pure samples. However, on raising the diamine ratio, the mononuclear compounds were not selectively obtained, even though the mixture was enriched up to ca. 2.5(3a):1(2a) and 2(3b): 1(2b). All attempts to isolate complexes 3 in a pure form were unfruitful due to their high instability with respect to hydrolysis,35 although their structural disposition was clearly assigned from the spectroscopic analysis of a sample containing both compounds 2 and 3. To gain insight into the chemical background of these processes, the reaction using 1(Ti):1(diamine) was conducted in a Teflon-valved NMR tube and monitored by 1H NMR spectroscopy. Upon incomplete consumption of 1, spectroscopic analysis initially revealed the formation of the new asymmetric dimetallic derivative [TiCl2{η5-C5Me4SiMe2-κ-N(CH2)nNHη5-C5Me4SiMe2}TiCl3] (n = 3, 4a; 4, 4b; 5, 4c), in which each metal-based molecular fragment occupies a different coordination sphere. Over a period of time (2 h), 4 was transformed into 2, indicating the former is a transient intermediate in the stepwise formation process of the latter (Scheme 2), which confirms again that this kind of reaction initially proceeds with the aminolysis of 2994
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Scheme 2
the SiCl bond, while the rupture of the TiCl bond takes place in a following step. The spectroscopic behavior of compounds 24 supports the proposed structures. Both the 1H and 13C NMR spectra of complexes 2 and 3 show a unique set of resonances for the “C5Me4SiMe2” moieties, exhibiting one and two singlets for the SiMe2 and C5Me4 methyl groups, respectively. The methylene protons of the N(CH2)nN chain appear as two multiplets for complexes 2a and 2b, three resonances for compounds 2c and 3a, and four multiplets for derivative 3b. These data are consistent with either a symmetric dinuclear (overall C2h symmetry) disposition or a mononuclear (Cs symmetry) disposition for complexes 2 and 3, respectively. In contrast with the C2h symmetry shown by the dinuclear compounds 2, the NMR data of complexes 4 are in agreement with Cs symmetry as inferred from the inequivalence of their two metal-based molecular extremes. Thus, the 1H and 13C NMR spectra of complexes 4 exhibit a doubling of resonances for the C5Me4SiMe2 moieties and distinct multiplets for all of the methylene groups of the linking chain. However, the most striking NMR feature of the 1H NMR spectra of complexes 4 is the broad signal at δrange ≈ 0.760.93, integrating for one proton, assigned to the remaining SiNH proton.32 As expected with a constrained-geometry disposition, compounds 2 and 3 show the typical upfield shifted resonance for the cyclopentadienyl ipso-carbon (δ < 110), with respect to the rest of the ring carbon atoms.35,36 The 13C NMR spectra of complexes 4 feature two clearly separated resonances for the cyclopentadienyl ipso-carbon (δ < 105 and >140), confirming the very different structural dispositions of both ends of the molecule. The silicon and nitrogen chemical shifts of the resonances of the “CpSiMe2N” fragment provide a suitable tool to determine its coordination mode.35,36 Thus, the spectroscopic behavior of 2 shows a unique upfield resonance (δaverage ≈ 17) in its 29Si NMR spectrum and a downfield signal (δaverage ≈ 350) in its 15N NMR spectrum, confirming the suggested symmetry of these compounds with a constrained-geometry disposition in their metal-based molecular fragments. In contrast, the spectroscopic behavior of 4 shows two well-separated resonances at δ ≈ 6 and 17 in its 29Si NMR spectrum, indicating that the two “CpSiMe2N” moieties occupy very different bonding environments. The 29Si NMR spectra of complexes 3 exhibit one silicon resonance at δ ≈ 18. To further verify the structure of complex 4, the reaction of 1 with N-methylpropylendiamine was explored in detail. Considering that, in this case, one of the nitrogen substituents contained a methyl group, it was reasonable to propose that the aminolysis process would end once the analogue asymmetric dinuclear complex was formed. The reaction in a molar ratio of 1(Ti):1(N-methylpropylendiamine) was initially conducted in an NMR tube and monitored by 1H NMR spectroscopy. Thus, within a few minutes after the experiment began, along with resonances
assigned to the starting complex 1, a symmetric set of resonances was observed attributed to the intermediate [Ti{η5C5Me4SiMe2-κ-N(CH2)3NHMe 3 HCl}Cl2] (5). On monitoring the reaction for a long period of time (4 h), the resonance pattern of 5 gradually disappeared, initially accompanied by an increase in the intensity of the peaks corresponding to the expected compound [TiCl2{η5-C5Me4SiMe2-κ-N(CH2)3NMeη5-C5Me4SiMe2}TiCl3] (6), which was isolated as an analytically pure sample in modest yield. With the aim of forcing the complete transformation of 1 into 6, a further equivalent of diamine was added to the aforementioned reaction mixture, giving a new mononuclear constrained-geometry complex, [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NHMe}Cl2] (7), in quantitative yield. The formation of 7 entails the rupture of the SiNMe bond from 6, caused by the HCl produced from the reaction of residual complex 1 with the additional diamine. The specific attachment through the SiNMe bond may be justified on the basis of the higher basicity of this nitrogen atom, considering that the other nitrogen is bonded to two acidic centers (titanium and silicon atoms). Complex 7 was quantitatively generated by directly treating 1 with a 2-fold quantity of N-methylpropylenediamine (Scheme 3). Complex 5 was conveniently formed, on a preparative scale, and isolated as a pure substance in high yield when the reaction of 1 with 1 equiv of NH2(CH2)3NHMe was stopped after five minutes. On the basis of its structural analysis, complex 5 was formulated as a mononuclear constrained-geometry complex bearing an unexpected pendant ammonium group. The quaternization of the pendant amine nitrogen in this type of derivative has not been previously observed. In contrast with that observed in the process discussed above, the treatment of 1 with N,N-dimethylpropylenediamine directly afforded the corresponding constrained-geometry complex [Ti{η5-C5Me4SiMe2-κ-N(CH2)3NMe2}Cl2] (8), regardless of the reaction stoichiometry or the working conditions (Scheme 3). The NMR spectroscopic features of compound 6 are in accordance with those previously analyzed for complex 4a, revealing an analogous molecular disposition. Likewise, the 1H, 13 C, and 29Si NMR data of complexes 5, 7, and 8 are substantially comparable to those of derivative 3a, indicating a related isostructural relationship. The differences are obviously evident in the distinct nature of the pendant amine nitrogen substituents. The key feature of the 1H NMR spectrum of compound 5 is the broad signal centered at δ 7.80 with an integration for two protons, assigned to the hydrogens attached to the pendant quaternized nitrogen. Likewise, the downfield shift observed in the 15N NMR spectrum of 5 for the pendant nitrogen functionality (δ = 38.3), compared with the corresponding resonance observed for 7 (δ = 25.5), appears in the normal range reported for ammonium nitrogen, revealing the quaternization of this nitrogen atom. 2995
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Scheme 3
Scheme 4
Encouraged by the aforementioned findings, we extended the study to the reactions of 1 with propylenediamines exhibiting different degrees of substitution (N,N0 -dimethyl- and the N,N, N0 -trimethylpropylenediamine). Complex 1 reacted with 2 equiv of these diamines to give, regioselectively, the mononuclear derivatives [Ti{η5-C5Me4SiMe2NMe(CH2)3-κ-NMe}Cl2] (9) and [Ti{η5-C5Me4SiMe2NMe(CH2)3NMe2}Cl3] (10), respectively, both isolated in high yield as red crystalline solids. However, when the amount of diamine was reduced by half, while the reaction with N,N,N0 -trimethylpropylenediamine gave the same final compound, 10, the reaction with NHMe(CH2)3NHMe was perceptively different, as along with 9 a new symmetric dinuclear compound, [Ti{η5-C5Me4SiMe2NMe(CH2)1.5-}Cl3]2 (12), was observed. Monitoring the latter reaction by NMR spectroscopy revealed, within 10 minutes, the formation of a mixture of products containing the mononuclear unstrained 9, compound 12, and a new mononuclear
transient species, [Ti{η5-C5Me4SiMe2NMe(CH2)3NHMe}Cl2] (11). On maintaining this reaction mixture for one hour at room temperature, complex 11 completely disappeared, transforming into 9. However, all attempts to isolate 11 and 12 as pure products were unfruitful (Scheme 4). In view of these results, it is reasonable to assume that complex 9 is the product of thermodynamic control, due to the additional entropic stability conferred by the chelating ligand, and only the presence of a large excess of 1 in the reaction mixture favors the intermolecular reaction between 11 and 1 to give 12. In fact, when this reaction was performed using a significantly longer diamine as the N,N0 -dimethylhexalenediamine, the final product was invariably the dinuclear derivative [Ti{η5-C5Me4SiMe2NMe(CH2)3-}Cl3]2 (13) (Scheme 5). Compounds 9, 10, and 13 were characterized on the basis of NMR spectroscopy and elemental analysis, while the molecular structure of 9 was also determined by X-ray diffraction analysis. 2996
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Scheme 5
the titanium atom of a piano stool.3741 The diamino fragment clearly connects the silicon and titanium atoms, giving rise to a puckered eight-membered (CpSiNCCCNTi) metallacycle. In contrast with its behavior in solution, it is a chiral species due to the helical conformation adopted by a linking chain around the CpTi axis.
Figure 1. Molecular structure of 9, shown with 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity. Representative bond lengths (Å) and angles (deg): Ti(1)N(1) 1.889(3); Ti(1)Cl(1) 2.3238(10); Ti(1)Cl(2) 2.3151(10); Si(1)N(2) 1.730(3); Cl(1)Ti(1)Cl(2) 102.72(4); N(1)Ti(1)Cl(1) 101.77(9); N(1)Ti(1)Cl(2) 104.56(10).
The structures of 11 and 12 were unequivocally established by NMR spectroscopy. The 1H NMR spectra of these compounds show a unique set of resonances for the C5Me4SiMe2 moieties, comprising one singlet for the silicon methyl protons and two singlets for the ring methyl protons. These data are in agreement with Cs symmetry for 9, 10, and 11 and C2h symmetry for 12 and 13. The main spectroscopic differences of the spectra relate to the resonances due to the diamine fragment. In the case of complexes 10 and 11 the differences come from the distinct nature of the substituent on the amine nitrogen. Additionally, the two methyl and the three methylene groups of the chain are inequivalent, consistent with the structure proposed, where both nitrogen atoms show different coordination environments. Likewise, the 1H NMR spectrum of 9 shows a set of five resonances for the protons of MeNCH2CH2CH2NMe. In contrast, the spectra of 12 and 13 feature a unique resonance for both of the methyl groups on nitrogen and two and three resonances for the methylene groups, integrating for 4:2 and 4:4:4 protons, respectively, in agreement with their symmetric binuclear structures. The 13C NMR data show similar behavior. The 29Si and 15N NMR data are also in accordance with the structures proposed for these complexes. In all cases, the silicon chemical shifts (δ ≈ 3) clearly reveal the conversion of the SiCl bond into a SiN bond. In addition, whereas the 15N NMR spectrum of 9 shows two well-separated resonances, the spectra of 12 and 13 feature only one. The molecular structure of 9 is depicted in Figure 1. Compound 9 is mononuclear with a coordination geometry around
’ CONCLUDING REMARKS The reactions of the chlorosilyl-substituted cyclopentadienyl titanium compound [Ti(η5-C5Me4SiMe2Cl)Cl3] with longchain diamines NHR(CH2)nNR0 R00 (n g 3) are studied. New mononuclear and dinuclear cyclopentadienyl-silyl-amido derivatives with constrained-geometry or unstrained structures can be selectively synthesized under appropriate reaction conditions. Transient species in the corresponding aminolysis processes have been observed by NMR spectroscopic studies. These experimental findings allow us to make more convincing the case for the preferential rupture of the SiCl bond in the pathway followed by titanium compounds in these reactions, highlighting clear behavioral differences compared to analogous niobium complexes.3335 ’ EXPERIMENTAL SECTION General Considerations. All manipulations were performed under argon using Schlenk and high-vacuum line techniques or in a glovebox, model HE-63. The solvents were dried and purified with an MBraun solvent purification system. Deuterated solvents were stored over activated 4 Å molecular sieves and degassed by several freezethaw cycles. NEt3 (Aldrich) was distilled before use and stored over 4 Å molecular sieves. Diamines were purchased from commercial sources (Aldrich) and used without further purification. [Ti(η5-C5Me4SiMe2Cl)Cl3]29 was prepared by a known procedure. C, H, and N microanalyses were performed on a Perkin-Elmer 240B and/or Heraeus CHN-O-Rapid microanalyzer. NMR spectra, at 25 °C, were recorded on a Bruker AV400 (1H NMR at 400 MHz, 13C NMR at 100.6 MHz, 29Si NMR at 79.5 MHz, 15 N NMR at 40.5 MHz). Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)1.5-}Cl2]2 (2a). A toluene solution (10 mL) of NH2(CH2)3NH2 (0.06 mL, 0.72 mmol) and NEt3 (0.40 mL, 2.90 mmol) was added to a dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.53 g, 1.44 mmol) in toluene (30 mL) at room temperature. The reaction mixture was stirred for 4 h, the white solid formed was collected by filtration, and the volatiles were removed under vacuum. The residue was washed with n-hexane (2 10 mL) to afford 2a in 50% yield (0.24 g, 0.36 mmol). Anal. Calcd for C25H42Cl4N2Si2Ti2: C, 45.20; H, 6.37; N, 4.22. Found: C, 45.09; H, 6.81; N, 4.43. 1H NMR (400 MHz, CDCl3): δ 0.62 (s, 12H, SiMe2), 1.84 (m, 2H, CH2), 2.11, 2.21 (s, 2 12H, C5Me4), 4.11 (m, 4H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 2.7 (SiMe2), 13.0, 16.0 (C5Me4), 34.3 (CH2), 54.0 (TiNCH2), 103.2, 136.1, 141.2 (C5Me4). 29 Si NMR (79.5 MHz, CDCl3): δ 16.8 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 349.9 (TiNCH2). 2997
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Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)2-}Cl2]2 (2b). A method similar to that described for 2a was adopted by using NH2(CH2)4NH2 (0.072 mL, 0.72 mmol) to give 2b as a reddish-brown solid. Yield: 57% (0.28 g, 0.41 mmol). Anal. Calcd for C26H44Cl4N2Si2Ti2: C, 46.03; H, 6.54; N, 4.13. Found: C, 46.11; H, 6.96; N, 4.02. 1H NMR (400 MHz, CDCl3): δ 0.61 (s, 12H, SiMe2), 1.52 (m, 4H, CH2), 2.10, 2.20 (s, 2 12H, C5Me4), 4.17 (m, 4H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 2.9 (SiMe2), 13.0, 16.0 (C5Me4), 30.5 (CH2), 55.4 (TiNCH2), 102.8, 136.0, 141.0 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.2 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 353.6 (TiNCH2). Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)2.5-}Cl2]2 (2c). A method similar to that described for 2a was adopted by using NH2(CH2)5NH2 (0.17 mL, 1.45 mmol) to give 2b as a yellowish-brown solid. Yield: 88% (0.88 g, 1.27 mmol). Anal. Calcd for C27H46Cl4N2Si2Ti2: C, 46.83; H, 6.71; N, 4.05. Found: C, 46.51; H, 6.62; N, 4.01. 1H NMR (400 MHz, CDCl3): δ 0.62 (s, 12H, SiMe2), 1.33, 1.49 (m, 2H, 4H, CH2), 2.11, 2.20 (s, 2 12H, C5Me4), 4.14 (m, 4H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 2.9 (SiMe2), 13.0, 16.0 (C5Me4), 24.8, 31.8 (CH2), 55.3 (TiNCH2), 102.8, 135.9, 141.0 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.1 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 355.2 (TiNCH2).
Synthesis of [Ti{η -C5Me4SiMe2-K-N(CH2)3NH2}Cl2] (3a). 5
A toluene solution (10 mL) of NH2(CH2)3NH2 (0.34 mL, 4.08 mmol) was added to a dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.50 g, 1.36 mmol) in toluene (30 mL) at room temperature. The reaction mixture was stirred for 3 h, and the white solid formed was collected by filtration. The solvent was completely removed from the resulting solution, and the residue was washed with n-hexane (2 15 mL). The yellow solid obtained was a mixture of 3a and 2a in a ratio 2.5:1. 3a: 1 H NMR (400 MHz, CDCl3): δ 0.55 (s, 6H, SiMe2), 1.71 (m, 2H, CH2), 2.17, 2.19 (s, 2 6H, C5Me4), 3.02 (m, 2H, CH2NH2), 3.99 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 2.1 (SiMe2), 13.0, 16.3 (C5Me4), 32.7 (CH2), 40.5 (CH2NH2), 53.0 (TiNCH2), 103.9, 135.9, 139.0 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 19.8 (SiMe2).
Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)4NH2}Cl2] (3b).
A method similar to that described for 3a was adopted, by using NH2(CH2)4NH2 (0.41 mL, 4.08 mmol), obtaining a mixture of 3b and 2b in a ratio of 2:1. 3b: 1H NMR (400 MHz, CDCl3): δ 0.61 (s, 6H, SiMe2), 1.45, 1.50 (m, 2 2H, CH2), 2.12, 2.21 (s, 2 6H, C5Me4), 2.70 (m, 2H, CH2NH2), 4.15 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 2.9 (SiMe2), 13.0, 16.0 (C5Me4), 29.7, 31.2 (CH2), 42.2 (CH2NH2), 55.3 (TiNCH2), 107.7, 136.0, 140.9 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.0 (SiMe2).
Spectroscopic Observation of [TiCl2{η5-C5Me4SiMe2-K-N(CH2)nNH-η5-C5Me4SiMe2}TiCl2] (4). A 0.08 mmol amount of
NH2(CH2)nNH2 was syringed into a solution of [Ti(η5-C5Me4 SiMe2Cl)Cl3] (0.08 mmol) in CDCl3 (0.5 mL), and the resulting solution was transferred to an NMR tube. A spectroscopic analysis of the sample indicated the formation of complexes 4. 4a: 1H NMR (400 MHz, CDCl3): δ 0.44, 0.60 (s, 2 6H, SiMe2), 0.93 (brs, 1H, SiNH), 1.55 (m, 2H, CH2), 2.10, 2.21, 2.32, 2.54 (s, 4 6H, C5Me4), 2.76 (m, 2H, CH2NHSi), 4.15 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 1.1, 2.8 (SiMe2), 13.0, 14.0, 16.0, 16.3 (C5Me4), 34.3 (CH2), 39.0 (CH2NHSi), 53.0 (TiNCH2), 102.0, 124.3, 136.1, 141.0, 142.2, 145.0 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 16.9 (TiN), 5.7 (SiN). 4b: 1H NMR (400 MHz, CDCl3): δ 0.44, 0.61 (s, 2 6H, SiMe2), 0.80 (brs, 1H, SiNH), 1.40, 1.49 (m, 2 2H, CH2), 2.11, 2.21, 2.32, 2.54 (s, 4 6H, C5Me4), 2.76 (m, 2H, CH2NHSi), 4.12 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 1.9, 2.9 (SiMe2), 13.0, 14.1, 16.0, 17.4 (C5Me4), 29.6, 32.1 (CH2), 41.7 (CH2NHSi), 55.3 (TiNCH2), 102.8, 125.1, 136.1, 141.0, 141.1, 142.2 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.3 (TiN), 6.2 (SiN). 4c: 1H NMR (400 MHz, CDCl3): δ 0.43, 0.61
(s, 2 6H, SiMe2), 0.76 (brs, 1H, SiNH), 1.30, 1.40, 1.45 (m, 3 2H, CH2), 2.11, 2.21, 2.32, 2.54 (s, 4 6H, C5Me4), 2.72 (m, 2H, CH2NHSi), 4.12 (m, 2H, TiNCH2). 29Si NMR (79.5 MHz, CDCl3): δ 17.3 (TiN), 6.3 (SiN).
Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)3NHMe 3 HCl}Cl2] (5). NH2(CH2)3NHMe (0.14 mL, 1.36 mmol) was syringed into a
dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.50 g, 1.36 mmol) in dichloromethane (30 mL), and the mixture was stirred at room temperature for 5 min. The solvent was removed from the resulting solution under vacuum, and the residue was washed with n-hexane (5 15 mL) to afford 5 in 38% yield (0.22 g, 0.52 mmol). Anal. Calcd for C15H29Cl3N2SiTi: C, 42.92; H, 6.98; N, 6.67. Found: C, 43.02; H, 6.40; N, 6.78. 1H NMR (400 MHz, CDCl3): δ 0.65 (s, 6H, SiMe2), 1.99 (m, 2H, CH2), 2.13, 2.21 (s, 2 6H, C5Me4), 2.56 (m, 3H, CH2NH2Me), 2.84 (m, 2H, CH2NH2Me), 4.16 (m, 2H, TiNCH2), 7.80 (brs, 2H, CH2NH2Me). 13 C{1H} NMR (100.6 MHz, CDCl3): δ 2.8 (SiMe2), 13.0, 16.4 (C5Me4), 30.6 (CH2), 35.0 (CH2NH2Me), 48.6 (CH2NH2Me), 52.9 (TiNCH2), 103.3, 136.1, 141.5 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 16.2 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 38.3 (CH2NH2Me), 345.0 (TiNCH2).
Synthesis of [TiCl2{η5-C5Me4SiMe2-K-N(CH2)3NMe-η5C5Me4SiMe2}TiCl2] (6). A solution of NH2(CH2)3NHMe (0.28 mL,
2.72 mmol) in toluene (10 mL) was added to a stirred solution of [Ti(η5C5Me4SiMe2Cl)Cl3] (1.00 g, 2.72 mmol) in toluene (35 mL) at room temperature. After the reaction mixture was stirred for 4 h, the white solid formed was collected by filtration, and the solvent was removed from the residual solution under reduced pressure. The residue was washed with cold n-hexane (3 10 mL) and extracted into toluene (2 15 mL), and the resulting solution cooled to 20 °C to give 6 in 21% yield (0.20 g, 0.28 mmol). Anal. Calcd for C26H45Cl5N2Si2Ti2: C, 43.68; H, 6.36; N, 3.92. Found: C, 43.72; H, 6.42; N, 3.78. 1H NMR (400 MHz, CDCl3): δ 0.50, 0.60 (s, 2 6H, SiMe2), 1.57 (m, 2H, CH2), 2.10, 2.20, 2.32, 2.50 (s, 4 6H, C5Me4), 2.44 (m, 3H, NMeSi), 2.73 (m, 2H, CH2NMeSi), 4.02 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 0.9, 2.8 (SiMe2), 13.0, 14.2, 16.0, 17.5 (C5Me4), 31.1 (CH2), 34.8 (CH2NMeSi), 48.9 (CH2NMeSi), 53.5 (TiNCH2), 103.0, 124.4, 136.0, 141.0, 142.3, 144.9 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.1 (TiN), 3.8 (SiN). 15 N NMR (40.5 MHz, CDCl3): δ 14.5 (SiNCH2), 351.7 (TiNCH2).
Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)3NHMe}Cl2] (7).
A toluene solution (10 mL) of NH2(CH2)3NHMe (0.28 mL, 2.72 mmol) was added to a dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.50 g, 1.36 mmol) in toluene (30 mL), and the mixture was stirred at room temperature for 3 h. The orange solution was filtered off, the solvent was removed under vacuum, and the residue was washed with nhexane (2 15 mL). The solid was redissolved in toluene (30 mL) and the solution cooled at 20 °C. The precipitated solid was collected by filtration, and the solution was concentrated under vacuum (15 mL) and recooled at 20 °C to afford 7 in 38% yield (0.20 g, 0.52 mmol). Anal. Calcd for C15H28Cl2N2SiTi: C, 47.00; H, 7.38; N, 7.30. Found: C, 46.99; H, 7.42; N, 6.99. 1H NMR (400 MHz, CDCl3): δ 0.61 (s, 6H, SiMe2), 1.69 (m, 2H, CH2), 2.11, 2.20 (s, 2 6H, C5Me4), 2.40 (m, 3H, CH2NHMe), 3.59 (m, 2H, CH2NHMe), 4.18 (m, 2H, TiNCH2). 13 C{1H} NMR (100.6 MHz, CDCl3): δ 2.8 (SiMe2), 13.0, 16.0 (C5Me4), 32.6 (CH2), 36.6 (CH2NHMe), 49.8 (CH2NHMe), 53.4 (TiNCH2), 102.9, 136.1, 141.0 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 17.1 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 25.5 (CH2NHMe), 350.9 (TiNCH2).
Synthesis of [Ti{η5-C5Me4SiMe2-K-N(CH2)3NMe2}Cl2] (8).
Following the procedure for the synthesis of 7, using NH2(CH2)3NMe2 (0.34 mL, 2.72 mmol), compound 8 was obtained in 78% yield. Anal. Calcd for C16H30Cl2N2SiTi: C, 48.37; H, 7.61; N, 7.05. Found: C, 48.36; H, 7.58; N, 7.01. 1H NMR (400 MHz, C6D6): δ 0.36 (s, 6H, SiMe2), 1.71 (m, 2H, CH2), 1.97, 2.00 (s, 2 6H, C5Me4), 2.07 (m, 6H, CH2NMe2), 2.17 (m, 2H, CH2NMe2), 4.31 (m, 2H, TiNCH2). 13C{1H} 2998
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NMR (100.6 MHz, C6D6): δ 2.4 (SiMe2), 12.6, 15.8 (C5Me4), 30.8 (CH2), 45.3 (CH2NMe2), 53.8 (TiNCH2), 57.3 (CH2NMe2), 102.6, 135.6, 140.3 (C5Me4). 29Si NMR (79.5 MHz, C6D6): δ 17.9 (SiMe2). 15 N NMR (40.5 MHz, C6D6): δ 23.8 (CH2NMe2), 347.2 (TiNCH2).
Synthesis of [Ti{η5-C5Me4SiMe2NMe(CH2)3-K-NMe}Cl2] (9).
A toluene solution (10 mL) of NHMe(CH2)3NHMe (0.69 mL, 5.44 mmol) was added to a dark red solution of [Ti(η5-C5Me4Si Me2Cl)Cl3] (1.00 g, 2.72 mmol) in toluene (30 mL), and the mixture was stirred at room temperature for 4 h. The solution was filtered off, the solvent was removed under vacuum, and the residue was washed with cold n-hexane (2 15 mL). The red solid was recrystallized from n-hexane/ toluene at 20 °C to give 9 as a microcrystalline red solid in 87% yield (0.94 g, 2.37 mmol). Anal. Calcd for C16H30Cl2N2SiTi: C, 48.37; H, 7.61; N, 7.05. Found: C, 48.44; H, 7.75; N, 6.89. 1H NMR (400 MHz, CDCl3): δ 0.30 (s, 6H, SiMe2), 1.51 (m, 2H, CH2), 2.10, 2.31 (s, 2 6H, C5Me4), 2.55 (s, 3H, SiNMe), 2.66 (m, 2H, SiNCH2), 3.71 (s, 3H, TiNMe), 4.01 (m, 2H, TiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 1.1 (SiMe2), 13.6, 16.4 (C5Me4), 25.2 (CH2), 33.9 (SiNMe), 42.7 (TiNMe), 45.3 (SiNCH2), 61.4 (TiNCH2), 126.6, 136.2, 136.3 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 2.7 (SiMe2). 15N NMR (40.5 MHz, C6D6): δ 5.6 (SiNMe), 326.9 (TiNMe).
Synthesis of [Ti{η5-C5Me4SiMe2NMe(CH2)3NMe2}Cl3] (10). A solution of NHMe(CH2)3NMe2 (0.25 mL, 1.63 mmol) in toluene (10 mL) at room temperature was added to a dark red solution of [Ti(η5C5Me4SiMe2Cl)Cl3] (0.30 g, 0.82 mmol) in toluene (15 mL) at room temperature. The reaction mixture was stirred for 3 h, the solid formed was collected by filtration, and the solvent was completely removed from the residual solution. The resulting solid was washed with cold n-hexane (2 10 mL) to give 10 as a red solid. Yield: 57% (0.21 g, 0.47 mmol). Anal. Calcd for C17H33Cl3N2SiTi: C, 44.60; H, 7.43; N, 6.26. Found: C, 44.53; H, 7.18; N, 6.46. 1H NMR (400 MHz, CDCl3): δ 0.48 (s, 6H, SiMe2), 1.55 (m, 2H, CH2) 2.13 (m, 2H, CH2NMe2), 2.16 (m, 6H, CH2NMe2), 2.31, 2.50 (s, 2 6H, C5Me4), 2.42 (s, 3H, SiNMe), 2.71 (m, 2H, SiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 0.9 (SiMe2), 14.1, 17.4 (C5Me4), 26.9 (CH2), 34.8 (SiNMe), 45.5 (CH2NMe2), 48.7 (SiNCH2), 57.5 (CH2NMe2), 142.1, 143.2, 144.7 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 3.9 (SiMe2). 5
Spectroscopic Observation of [Ti{η -C5Me4SiMe2NMe(CH2)3NHMe}Cl3] (11). A 0.01 mL amount of NHMe(CH2)3NHMe
(0.08 mmol) was syringed into a solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.08 mmol) in C6D6 (0.5 mL), and the resulting solution was transferred to an NMR tube. A spectroscopic analysis of the sample indicated the formation of complex 11. 1H NMR (400 MHz, CDCl3): δ 0.48 (s, 6H, SiMe2), 1.63 (m, 2H, CH2), 2.32, 2.49 (s, 2 6H, C5Me4), 2.42 (m, 3H, SiNMe), 2.49 (brs, 3H, CH2NHMe), 2.52 (m, 2H, CH2NHMe), 2.76 (m, 2H, SiNCH2), 4.01 (brs, 1H, CH2NHMe). 13 C{1H} NMR (100.6 MHz, CDCl3): δ 1.0 (SiMe2), 14.1, 17.5 (C5Me4), 26.4 (CH2), 33.9 (SiNMe), 34.7 (CH2NHMe), 46.8 (CH2NHMe), 48.6 (SiNCH2), 142.0, 142.9, 144.7 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 3.9 (SiMe2).
Spectroscopic Observation of [Ti{η5-C5Me4SiMe2NMe(CH2)1.5-}Cl3]2 (12). A solution of NHMe(CH2)3NHMe (0.17 mL,
1.36 mmol) in toluene (10 mL) at room temperature was added to a dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.50 g, 1.36 mmol) in toluene (15 mL), and the mixture was stirred for 3 h at room temperature. The solid formed was collected by filtration, the solvent was removed from the residual solution under vacuum, and the resulting solid was washed with n-hexane (2 10 mL). The solid obtained was a mixture of 9 and 12. Complex 12: 1H NMR (400 MHz, CDCl3): δ 0.45 (s, 12H, SiMe2), 1.51 (m, 2H, CH2), 2.32, 2.49 (s, 2 12H, C5Me4), 2.41 (m, 6H, SiNMe), 2.66 (m, 4H, SiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 0.9 (SiMe2), 14.2, 17.4 (C5Me4), 27.9 (CH2), 34.8 (SiNMe), 48.6 (SiNCH2), 142.2, 143.3, 144.6 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 3.7 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 14.2 (SiNMe).
Synthesis of [Ti{η5-C5Me4SiMe2NMe(CH2)3-}Cl3]2 (13). A solution of NHMe(CH2)6NMe2 (0.25 mL, 1.36 mmol) in toluene (10 mL) at room temperature was added to a dark red solution of [Ti(η5-C5Me4SiMe2Cl)Cl3] (0.50 g, 1.36 mmol) in toluene (15 mL), and the mixture was stirred for 3 h at room temperature. The solid formed was collected by filtration, and the solvent removed from the residual solution under vacuum. The resulting solid was washed with cold n-hexane (2 10 mL) to give 13 as a brown solid. Yield: 32% (0.18 g, 0.22 mmol). Anal. Calcd for C30H54Cl6N2Si2Ti2: C, 44.63; H, 6.74; N, 3.47. Found: C, 44.54; H, 6.98; N, 3.86. 1H NMR (400 MHz, CDCl3): δ 0.46 (s, 12H, SiMe2), 1.16, 1.38 (m, 2 2H, CH2), 2.31, 2.49 (s, 2 12H, C5Me4), 2.40 (m, 6H, SiNMe), 2.66 (m, 4H, SiNCH2). 13C{1H} NMR (100.6 MHz, CDCl3): δ 0.9 (SiMe2), 14.2, 17.4 (C5Me4), 27.0, 28.9 (CH2), 34.7 (SiNMe), 50.7 (SiNCH2), 142.2, 143.3, 144.6 (C5Me4). 29Si NMR (79.5 MHz, CDCl3): δ 4.3 (SiMe2). 15N NMR (40.5 MHz, CDCl3): δ 13.7 (SiNMe).
Single-Crystal X-ray Structure Determination of Compound 9. Crystal data and details of the structure determination are presented in the Supporting Information. Suitable single crystals of 9 for the X-ray diffraction study were selected, covered with perfluorinated polyether oil, and mounted on a Bruker-Nonius Kappa CCD singlecrystal diffractometer. Data collection was performed at 200(2) K. The structures were solved, using the WINGX package,42 by direct methods (SHELXS-97) and refined by using full-matrix least-squares against F2 (SHELXL-97).43 All non-hydrogen atoms were anisotropically refined, and hydrogen atoms were geometrically placed and left riding on their parent atoms. Full-matrix least-squares refinements were carried out by minimizing ∑w(Fo2 Fc2)2 with the SHELXL-97 weighting scheme and stopped at shift/err < 0.001. Crystallographic data for 9: C16H30Cl2N2SiTi, M = 397.31. Monoclinic, space group P21/c, a = 8.6281(17) Å, b = 28.265(3) Å, c = 9.2586(18) Å, R = 90°, β = 115.094(14)°, γ = 90°, V = 2044.8(6) Å3. Z = 4, Dc = 1.291 g cm3, F(000) = 840, λ(Mo KR) = 0.71069 Å. At the conclusion of the refinement, wR2 = 0.1389 and R1 = 0.0799 for all 4688 reflections.
’ ASSOCIATED CONTENT
bS
Supporting Information. Tables of crystallographic data, including fractional coordinates, bond lengths and angles, anisotropic displacement parameters, and hydrogen atom coordinates in CIF format for complex 9. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author ‡
Correspondence concerning the crystallography data should be addressed to this author. E-mail:
[email protected]. *Tel: 34918854767 and 34918854655. Fax: 34 918854683. E-mail:
[email protected] [email protected].
’ ACKNOWLEDGMENT Financial support for this research by Direccion General de Investigacion Científica y Tecnica (Project MAT2010-14965) and Comunidad Autonoma de Madrid (Project S-0505-PPQ/ 0328-02) is gratefully acknowledged. C.P.P. acknowledges Comunidad Autonoma de Madrid for a fellowship. ’ REFERENCES (1) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283–315. (2) Gendler, S.; Zelikoff, A. L.; Kopilov, J.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2008, 130, 2144–2145. 2999
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