Article pubs.acs.org/Organometallics
Titanium-Catalyzed Hydrohydrazination of Carbodiimides Peter D. Schweizer, Hubert Wadepohl, and Lutz H. Gade* Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany S Supporting Information *
ABSTRACT: Hydrazinediido complexes of the type [Cp*Ti(NxylN)(NNR2)(L)] (R = Ph, Me; Ar, fluorene, L = tBuNH2, Py; 3a−e) have been synthesized and used as catalysts for the hydrohydrazination of a series of carbodiimides, yielding aminoguanidines or fluoreneiminoguanidines. The highest yields were obtained for diarylhydrazines and fluorenone hydrazone at temperatures between 80 and 105 °C. Stoichiometric reactions of hydrazinediido complexes with i PrNCNiPr led to an equilibrium with the resulting [2 + 2] cycloadducts 4a−f, which were characterized by 1H, 13C, and 15 N NMR spectroscopy as well as X-ray diffraction. The proposed mechanism, which is closely related to that previously established for the hydrohydrazination of alkynes and allenes, was found to be consistent with the results of a kinetic study. The dynamic structures of aminoguanidines and fluoreneiminoguanidines were characterized by NMR spectroscopy, and the minimum configurations were found to be stabilized by intramolecular hydrogen bonding.
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Hydrazinediido complexes of group 4 metals7,8 are known to be active catalysts in the catalytic addition of hydrazine N−H bonds across triple or cumulated double bonds,9 especially in the hydrohydrazination of alkynes.10,11 The related titanium imido complexes have been employed as catalysts for amination and CN bond metathesis of carbodiimides, and examples of the [2 + 2] cycloaddition products, proposed to be the key intermediates in the reaction mechanism, have been characterized and studied in some detail by Mountford, Richeson, and co-workers.12,13 For zirconium imido complexes, this type of chemistry has been studied extensively by Bergman.14 However, to our knowledge no catalytic hydrohydrazination of carbodiimides involving group 4 catalysts has been published to date. Herein we report a titanium-catalyzed synthesis of substituted aminoguanidines via hydrohydrazination of carbodiimides with various substituted hydrazines along with studies of the reaction mechanism.
INTRODUCTION Aminoguanidines (I) exhibit interesting physiological behavior as dopamine β-oxidase inhibitors and antihypertensives.1 Moreover, anti-HIV activity has been found for N-glycosylN′-(4-arylthiazolyl)aminoguanidines2 (II) and several Nhydroxy-N′-aminoguanidines (III) display antitumor activity.3 Whereas the underlying mechanisms for this activity remain to be established, they may well be related to their properties as radical scavengers and antioxidants, as studied recently by Tong et al.4 Further development of their chemistry requires efficient preparative protocols for N-aminoguanidines.
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RESULTS AND DISCUSSION Preparation and Structural Characterization of [Cp*Ti(NxylN)(NNR2)(L)]. The titanium hydrazinediido complexes 2a−d were prepared via imido/hydrazine exchange from the imido complex 1 as previously reported,10,15 and a series of new derivatives 3a−e were synthesized similarly as depicted in Scheme 1. Thus, the reaction of 1 with 1 equiv of diarylhydrazine and subsequent precipitation from hexane yielded 3a−d as green complexes, while the N-fluoreneiminoimido complex 3e was isolated as a diamagnetic deep red compound by reacting complex 1 with 1 equiv of fluorenone
An efficient and atom-economical way to synthesize substituted N-aminoguanidines is the catalytic addition of hydrazine N−H bonds to the carbodiimide heterocumulene unit, generally referred to as hydrohydrazination or aminoguanylation. While the catalytic amination of carbodiimides, or guanylation, has been explored for many transition metals, lanthanides, and even group 1 and 2 complexes as catalysts,5 we are only aware of one previous example of catalytic aminoguanylation, reported by Koller and Bergman in 2010.6 Using aluminum alkyl complexes as precatalysts, several substituted aminoguanidines were synthesized at elevated temperatures (120 °C). © 2013 American Chemical Society
Received: April 17, 2013 Published: June 24, 2013 3697
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Scheme 1. Synthesis of the Hydrazinediido Complexes 3a−e by Imido/Hydrazine Exchange
hydrazone and 2 equiv of pyridine. Compound 3e may also be viewed as an alkylidene hydrazide, and a systematic study of such species has been reported very recently by Mountford and co-workers.16 An X-ray crystal structure analysis of 3a revealed severe disorder in the coordination sphere of the titanium atom, which could be modeled by two components which essentially have the aminopyrrolinato and tert-butylamine ligands interchanged. The major component is depicted in Figure 1. Unfortunately, because of extensive overlap of atoms, the accuracy of the parts of the structure involved in this disorder is considerably reduced (see the Experimental Section for details).
Interestingly, the 2-aminopyrrolinato ligand in 3a does not attain the κ2 coordination found previously in 2b−d. In contrast, κ1 coordination with N(2) dangling freely is found for both disordered components, with one molecule of tertbutylamine coordinated to the titanium occupying the coordination site liberated by the dissociation of one Ndonor atom of the 2-aminopyrrolinato ligand. This aspect aside, the metric parameters of the complex were similar to those previously found10 for 2b−d and are consistent with a Ti−N double bond and a N−N single bond in the hydrazinediido group. Application of the Hydrazinediido Titanium Complexes as Catalysts for the Hydrohydrazination of Carbodiimides. The aminoguanylation of a series of carbodiimides was carried out at 80 or 105 °C employing titanium hydrazinediido complexes as catalysts or the imido complex 1 as precatalyst (Scheme 2). Both the use of the appropriate hydrazinediido complexes and their in situ generation from the catalyst precursor 1 gave similar yields. Generally, 5 mol % of the corresponding catalyst or precatalyst 1 was used, but the catalyst loading could be reduced to 2 mol % by employing higher temperatures or longer reaction times. For all substrates, complete conversion (or halt of conversion) was confirmed by GC-MS analysis. The yields listed in Scheme 2 refer to the isolated products after purification. As a control experiment, the different hydrazines and fluorenone hydrazone were heated with diisopropylcarbodiimide at 105 °C for 24 h without addition of catalyst. In each case, no conversion was observed. Among the different carbodiimides tested, iPrNCNiPr displayed the highest reactivity, followed by CyNCNCy (DCC). On the other hand, tBuNCNEt, TolNCNTol, and
Figure 1. Molecular structure of 3a. Only one of the two disordered sets of atoms is shown. Hydrogen atoms are omitted for clarity, and ellipsoids are drawn at 50% probability. Selected bond lengths (Å) and angles (deg): Ti−N(1A) = 2.01(1), Ti−N(3) = 1.738(2), Ti−N(5A) = 2.076(12), N(3)−N(4) = 1.364(2), N(1A)−C(4A) = 1.35(1), N(2A)−C(4A) = 1.298(5); N(2A)−C(4A)−N(1A) = 121.3(5), Ti− N(3)−N(4) = 165.1(1). 3698
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Scheme 2. Catalytic Aminoguanylationsa
Reaction conditions: 5 mol % catalyst for all reactions; (a) 2 mL of toluene, 18 h and 80 °C or 30 min and 105 °C; (b) 24 h and 105 °C; (c) 1 h and 105 °C; (d) 1,4-dioxane, 24 h, and 80 °C; (e) 1,4-dioxane, 24 h, and 100 °C. Yields refer to isolated products.
a
workup and purification, 1.92 equiv of aminoguanidine (96% overall yield) was isolated. Study of the Reaction Mechanism of the Ti-Catalyzed Hydrohydrazination of Carbodiimides: Characterization of Intermediates and Reaction Kinetics. The stoichiometric reaction of titanium17,18 and zirconium19 hydrazinediido complexes with alkynes, allenes, and heteroallenes has been extensively studied. These are thought to be key intermediates in various coupling reactions involving hydrazines. A cycloaddition product of a titanium imido complex with tolNCNtol was first reported by Mountford and co-workers7b,12 and characterized by NMR spectroscopy, while the Richeson group subsequently characterized two such cycloaddition products by X-ray crystallography.13 However, to the best of our knowledge, the cycloaddition of the hydrazinediido group to carbodiimides has not been studied to date. Upon addition of 1 equiv of iPrNCNiPr to 2a, the almost instantaneous formation of the cycloadduct 4a was observed, establishing an equilibrium between 2a and 4a in a ratio of 1:2 at room temperature. Upon addition of 3 equiv of carbodiimide, the equilibrium could be shifted completely to
especially (3-N,N-dimethylaminopropyl)ethylcarbodiimide were generally less reactive and demonstrated the limitations of the system. Finally, tBuNCNtBu did not react with any of the hydrazines under the conditions outlined above, probably due to steric hindrance. Notably, the best yields and broadest substrate scope were not found for Me2NNH2, as observed in the aluminum-catalyzed reaction, but for fluorenone hydrazone. For yields and activity, the trend Ar2NNH2 > MePhNNH2 > Me2NNH2 was observed, which is the opposite of the trend found by Bergman and co-workers. This may be rationalized by assuming that for the aluminum-catalyzed reaction, nucleophilicity of the hydrazine is important, while the titanium-catalyzed reaction is controlled by the NH acidity of the hydrazine. Overall, 21 new (and 3 previously known) aminoguanidines and fluoreneiminoguanidines were synthesized by Ti catalysis (Scheme 2). In order to investigate the lifetime of the catalyst, another 1 equiv of both the carbodiimide and the hydrazine was added after full consumption of the initial amount of diisopropylcarbodiimide and diphenylhydrazine (30 min at 105 °C), and the reaction mixture was heated again (30 min at 105 °C). After 3699
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Scheme 3. Molecular Structure of 4a in Comparison to Those of the Previously Reported Complexes 5a,b
the side of the cycloaddition product, which was then studied by 1H, 13C, and 15N NMR spectroscopy. Since the reaction is reversed upon removal of the excess of carbodiimide during workup, the pure complex could not be isolated in bulk quantities. The NMR spectra of 4a are consistent with the formation of a titanacycle. Four characteristic doublets at 2.07, 1.55, 1.25, and 0.56 ppm assigned to the diastereotopic methyl groups of the isopropyl groups were observed in the 1H NMR spectrum. The 15N NMR spectrum displayed the Nα resonance of the converted hydrazinediido group at 251.5 ppm and the imino N (CNiPr) of the diazatitanacycle at 225.7 ppm, and a signal was observed at 292.3 ppm for TiNiPr. The assignments are based on long-range N−H coupling to isopropyl CH and CH3 protons. The chemical shifts of the CNiPr and Nα resonances are comparable to the corresponding signals of the previously reported N,S-coordinated cycloadduct with phenyl isothiocyanate 5a (245.1 ppm and 266.2 ppm).17 The most characteristic 13 C NMR signal is that of the CNiPr group in the metallacyclic ring, which was detected at 148.8 ppm and was thus in a range similar to the corresponding signals in complexes 5a (154.9 ppm) and 5b (155.8 ppm) (Scheme 3). As indicated above, complex 4a could not be isolated in pure form in significant quantities due to its incomplete formation in the cycloaddition and it proved not to be possible to separate it from unconverted reactants. However, a few single crystals suitable for X-ray diffraction were obtained at −40 °C from a concentrated solution of tert-butylamine-free 2b in hexane after reaction with 3 molar equiv of iPrNCNiPr. The structural assignment based on spectroscopic methods described above thus could be confirmed (Figure 2). In the molecular structure of 4a the 2-aminopyrrolinato ligand is symmetrically κ2 coordinated to the titanium center, as previously found for other complexes bearing this type of ancillary ligand.10,15,17 While the exocyclic CN bond length is consistent with a double bond (C(13)−N(5) = 1.276(2) Å), both endocyclic CN bonds feature interatomic distances typical for single bonds (approximately 1.41 Å). Furthermore, both Ti−N bonds within the metallacycle have lengths consistent with (amido-type) single bonds (approximately 2.00 Å). All other bond lengths and angles are in good agreement with those found in related cycloaddition products reported previously.17 The equilibrium between 2a and iPrNCNiPr on the one side and 4a on the other was studied at variable temperature (Scheme 4). With increasing temperature, the equilibrium is shifted toward the reactant 2a, which is consistent with an exothermic cycloaddition step. A van’t Hoff analysis of the equilibrium constants determined between 23 and 70 °C gave the thermodynamic parameters ΔH0 = −74 ± 1 kJ mol−1 and ΔS0 = −210 ± 3 J mol−1 K−1 (Figure 3), indicating that the equilibrium is associative. This is consistent with the
Figure 2. Molecular structure of complex 4a. Hydrogen atoms are omitted for clarity, and ellipsoids are drawn at 50% probability. Selected bond lengths (Å) and angles (deg): Ti−N(1) = 2.140(1), Ti−N(2) = 2.108(1), Ti−N(3) = 2.005(1), Ti−N(4) = 1.978(1), N(3)−N(6) = 1.398(2), C(13)−N(5) = 1.276(2), N(4)−C(13) = 1.405(2), N(3)−C(13) = 1.409(2); N(1)−Ti−N(2) 63.14(4), C(13)−N(3)−Ti = 96.48(8), N(3)−Ti−N(4) = 65.41(5), N(3)− C(13)−N(4) = 99.8(1), C(13)−N(4)−Ti = 97.81(8).
observation that in an analogous experiment using complex 2b (without coordinated t-BuNH2) values of ΔH0 = −77 ± 2 kJ mol−1 and ΔS0 to be −212 ± 6 J mol−1 K−1 were found, which are essentially identical and indicate that tert-butylamine in 2a is coordinated very weakly, dissociates in solution, and therefore does not affect the equilibrium. Using CyNCNCy instead of iPrNCNiPr, a similar equilibrium was found. This cycloaddition product 4b was studied in situ by 1H and 13C NMR spectroscopy. Different sets of signals were observed for the two phenyl rings. In addition, for each of the cyclohexyl rings a set of signals consistent with diastereotopic CH2 groups was found. Apart from that, the spectra were similar to those of 4a. When equimolar amounts of both carbodiimides were added to 2a, an equilibrium of the two corresponding cycloadducts was established (ratio 2:3). Notably, no crossover exchange between the RC units of the carbodiimides was observed. Finally, neither tBuNCNEt nor t BuNCNtBu reacted with 2a or 2b to form a cycloadduct in a stoichiometric reaction, which reflects the very sluggish reactivity of the former and the unreactive nature of the latter in catalytic reactions described above. The N-methyl-N-phenylhydrazinediido complex 2c similarly formed an equilibrium of the corresponding cycloadduct 4c, as did the diarylhydrazinediido complexes 3a−d (Scheme 5). For all products, 1H and 13C spectra were similar to those of 4a; however, for 4d−f the formation of two conformers of the cycloaddition product was observed in each case. 3700
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Scheme 4. Equilibrium between 2a and 4a/4b
as catalysts,12,13 the mechanism of the catalytic cycle is proposed in Scheme 6. In the first step, a formal [2 + 2] cycloaddition of the hydrazinediido group with the carbodiimide leads to the cycloadduct, which establishes a rapid equilibrium with the hydrazinediido reactant. This is followed by attack of the hydrazine and subsequent hydrazinolysis as the rate-determining step. A proposed intermediate such as 6 has never been observed spectroscopically but thought to convert rapidly to the hydrazinediido (starting) complex with release of the aminoguanidine. This last step, which follows the rate-determining opening of the metallacycle 4a, will therefore not be reflected in the overall rate law for this conversion. The overall kinetics should therefore be the represented by the following sequence of steps for the catalytic cycle: Figure 3. Van’t Hoff plot of the equilibrium constants of the equilibrium between the reactants 2a and iPrNCNiPr and the product 4a determined between 23 and 70 °C.
i
PrNCNiPr + Cp*Ti(NxylN)(NNPh 2) k1
HooI Cp*Ti(NxylN){N(NPh 2)C(NiPr)NiPr} k −1
1
H NOESY NMR spectra displayed cross relaxation between the ortho protons of the substituted aryl ring and the C NCHMe2 proton of the imido group in the titanacycle, between the Cp* methyl protons, and between the NCH2 protons of the aminopyrrolinato ligand backbone, respectively. For the minor isomer, the same cross relaxation pattern was observed for the ortho protons of the unsubstituted aryl ring instead. These patterns are consistent with a mixture of two rotamers for the rotation around the NN bond of the hydrazido unit. The assignment of the major and minor isomers is given in Figure 4. This is supported by the observation that for the ortho and meta protons of the C6H4Br groups in 4g different resonances are found for the two aryl rings. In analogy to the titanium-catalyzed hydroamination using the corresponding imido complex 115 and to the proposed mechanism of the guanylation using titanium imido complexes
Cp*Ti(NxylN){N(NPh 2)C(NiPr)NiPr} + Ph 2NNH 2 k2
→ Cp*Ti(NxylN)(NNPh 2)+iPr NHC(NNPh 2)NHiPr
The reaction is represented by the following rate law: d[aminoguanidine] dt k1k 2[RNCNR][TiNNPh 2]0 [Ph 2NNH 2] = k1[RNCNR] + k −1 + k 2[Ph 2NNH 2]
Since k1 and k−1 ≫ k2, in the absence of a large excess of hydrazine the rate law simplifies to
Scheme 5. Formation of Cycloaddition Products for Different Hydrazinediido Complexes
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Figure 4. Mixture of rotamers in 4d−f.
Scheme 6. Proposed Mechanism for Titanium-Catalyzed Aminoguanylation
kJ/mol, ΔS⧧ = 31 ± 13 J/(mol K), and ΔG⧧328 = 116 ± 6 kJ/ mol (Figure 5). Properties of Aminoguanidines and Fluoreneiminoguanidines. As pointed out by Bergman and co-workers,6 substituted aminoguanidines feature an unsymmetric configuration reflected in their NMR spectra which is stabilized by an intramolecular hydrogen bond between one of the NH protons and N-d (Scheme 7). For unsymmetrically substituted aminoguanidines, two sets of signals for the two possible conformers were detected. In addition, different coupling constants 3J(NH-b,CHMe2-b) (8.0−9.0 Hz) in comparison to 3J(NH-a,CHMe2-a) (6.0−7.0 Hz) were found, indicating different dihedral torsion angles caused by the hydrogen-bonding interaction. This feature was also studied by 15N NMR, and for NH-a and NH-b different resonances featuring typical 1JNH coupling constants of 85 Hz
d[aminoguanidine] dt k1k 2[RNCNR][TiNNPh 2]0 [Ph 2NNH 2] = k1[RNCNR] + k −1
This should result in first-order dependence of the overall reaction rate with respect to the concentration of hydrazine and catalyst, and for low concentrations also for the carbodiimide. This was supported by a systematic kinetic study documented in the Supporting Information, which also established the expected saturation kinetics for high concentrations of the carbodiimide. Finally, the activation parameters of the rate-limiting step were determined by Eyring analysis of the reaction of equimolar amounts of diisopropylcarbodiimide and diphenylhydrazine in the presence of 2 mol % of catalyst 2a, giving ΔH⧧ = 126 ± 5 3702
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A single-crystal X-ray structure analysis of the fluoreneiminoguanidine derivative (tBu/Et) confirmed the structural arrangement of the N-aminoguanidines referred to above (Figure 6). The N(1)−H(4) hydrogen bond distance was
Figure 5. Eyring plot for the reaction of equimolar amounts of Ph2NNH2 and iPrNCNiPr with 2 mol % of 2a.
Scheme 7. Unsymmetrical Configurations of Aminoguanidines and Fluoreneiminoguanidines
Figure 6. Molecular structure of tBuNHC(NNfluorene)NHEt. Selected bond lengths (Å) and angles (deg): N(1)−C(1) = 1.301(1), N(1)−N(2) = 1.369(1), N(2)−C(14) = 1.345(1), N(3)− C(14) = 1.354(1), N(3)−C(15) = 1.473(1), N(4)−C(14) = 1.338(1), N(4)−C(19) = 1.454(1), N(4)−H(4) = 0.89(1), N(1)−H(4) = 2.152; N(2)−C(14)−N(4) = 123.70(9), N(2)−C(14)−N(3) = 119.33(9), N(3)−C(14)−N(4) = 116.96(9), N(1)−C(1)−C(13) = 120.69(9), N(1)−C(1)−C(2) = 132.62(9), C(13)−C(1)−C(2) = 106.30(8).
were found. An additional 3JNH coupling between N-a and NHb was detected, indicating a fixed trans conformation of NH-b to N-a. The strength of the hydrogen-bonding interaction correlates with the difference in the 1H NMR chemical shifts (Δδ) of the amino NH proton, which forms the hydrogen bridge, in comparison to the resonance of the non-H-bonded NH group. 20 In addition, the activation barriers for the interconversion of the two (equivalent) configurations were measured by determining the coalescence temperatures Tc for the 1H NMR spectra. These data are summarized in Table 1 and illustrate that there is no simple dependence of these inversion barriers on the strength of the intramolecular hydrogen bonding. This indicates that other structural factors influence the inversion kinetics.
measured as 2.152 Å. Similar CN and NN bond lengths (1.30− 1.35 Å) reflect extensive delocalization of the C−N π-bonding system. We note that, in contrast to this, the Bergman group found a localized NN single bond with a length of 1.464 Å for i PrNHC(NNMe2)NHiPr.6
Table 1. Coalescence Temperatures, Inversion Barriers, and Shifts of NH-b Protons for Diisopropyl Derivatives
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R3
R4
Tc (°C)
ΔG*
δ(NH-b)
Δδ
C6H4F C6H4Br Ph C6H4Me C6H4OMe Me Me fluorene
Ph C6H4Br Ph Ph Ph Ph Me fluorene
66 107 125 54 99 82 60 52
69.1 77.7 81.3 66.1 76.2 72.9 69.5 67.7
5.16 4.91 5.13 5.38 5.25 5.19 5.85 6.59
1.76 1.55 1.83 1.84 1.95 1.89 2.95 2.82
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CONCLUSIONS Titanium hydrazinediido complexes may act as catalysts for the hydrohydrazination of carbodiimides with a broad substrate range, and a number of previously unknown aminoguanidines and fluoreneiminoguanidines have been isolated and fully characterized. The reaction mechanism appears to be closely related to the mechanistic schemes proposed for the hydroamination and hydrohydrazination of alkynes and allenes and is supported by the characterization of intermediate [2 + 2] cycloadducts as well as the kinetics of the catalytic transformation. EXPERIMENTAL SECTION
All manipulations of air- and moisture sensitive species were carried out under an atmosphere of argon (Argon 5.0) using standard Schlenk and glovebox techniques (glovebox M. Braun Unilab 2000). Solvents were predried over molecular sieves and dried over Na/K alloy (pentane, diethyl ether), K (THF, hexane, toluene), or CaH2 (dichloromethane), distilled, or dried over activated alumina columns using a solvent purification system (M. Braun SPS 800); they were then stored over potassium mirrors (except for dichloromethane) or sodium mirror (THF) in Teflon valve ampules. Deuterated solvents were purchased from Deutero GmbH, dried over K (benzene-d6, 3703
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Organometallics
Article
C6H3Me2), 3.67 (m, 1 H, NCH2-a), 3.50 (m, 1 H, NCH2-b), 2.37 (m, 1 H, CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.15 (m, 1 H, CH2CNNb), 1.94 (s, 15 H, C5Me5), 1.54 (m, 2 H, CH2CH2CNN), 1.07 (s, 9 H, H2NCMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 170.0 (NCN), 159.3 (d, 1JC−F = 240.0 Hz, p-NNC6H4F), 152.0 (mC6H3Me2), 147.2 (ipso-NNC6H5), 142.7 (ipso-NNC6H4F), 138.2 (ipsoC6H3Me2), 128.9 (m-NNC6H5), 123.7 (d, 3JC−F = 7.1 Hz, o-C6H4F), 123.3 (p-C6H3Me2), 120.8 (p-NNC6H5), 120.7 (o-C6H3Me2), 118.4 (C5Me5), 117.6 (o-NNC6H5), 115.8 (d, 2JC−F = 22.6 Hz, mNNC6H4F), 56.0 (CH2N), 49.5 (H2NCMe3), 31.6 (H2NCMe3), 30.0 (CH2CNN), 25.0 (CH2CH2CNN), 21.7 (C6H3Me2), 11.5 (C5Me5) ppm. 19F NMR (benzene-d6, 376.27 MHz, 295 K): δ −120.4 (m) ppm. IR (KBr, cm−1): 3059 (w), 3021 (w), 2958 (m), 2911 (m), 2861 (m), 1594 (s), 1559 (s), 1501 (s), 1453 (m) 1375 (m), 1309 (m), 1276 (m), 1261 (m), 1216 (m), 1161 (m), 1081 (m), 1026 (w), 866 (w), 839 (m), 783 (s), 741 (m), 694 (m), 650 (w), 580 (w), 522 (w). Anal. Found (calcd for C38H50FN5Ti): C, 70.55 (70.90); H, 7.49 (7.83); N, 10.66 (10.88). [Cp*Ti(NxylN)(NN{C6H4OMe}{Ph})(NH2tBu)] (3c). A 321 mg amount (0.624 mmol) of 1 was dissolved in hexane (6 mL). A 163 mg amount (0.624 mmol) of (p-C6H4OMe)PhNNH2 was added. The solution immediately turned green, and a green solid started to precipitate. After 1.5 h, the supernatant solution was removed by filtration and the residue dried under reduced pressure to yield 249 mg (0.380 mmol, 61%) of a green solid. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.28 (d, 2 H, H ar), 7.24−7.17 (m, 4 H, H ar), 6.83− 6.77 (m, 3 H, H ar), 6.68 (s, 2 H, o-C6H3Me2), 6.62 (s, 1 H, pC6H3Me2), 3.71(broad m, 1 H, NCH2-a), 3.56 (broad m, 1 H, NCH2b), 3.32 (s, 3 H, C6H4OCH3), 2.42 (m, 2 H, CH2CNN), 2.27 (s, 6 H, C6H3Me2), 1.99 (s, C5Me5), 1.56 (m, 2 H, CH2CH2CNN), 1.07 (s, 9 H, H2NCMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 168.6 (NCN), 157.2 (p-C6H4OMe), 148.0 (C ar), 139.3 (C ar), 138.3 (C ar), 125.9 (C ar), 123.3 (C ar), 122.5 (p-C6H3Me2), 120.7 (C ar), 119.1 (o-C6H3Me2), 118.8 (C5Me5), 115.0 (C ar), 114.7 (C ar), 55.5 (CH2N), 55.0 (C6H4OMe), 49.0 (H2NCMe3), 31.8 (H2NCMe3), 30.0 (CH2CNN), 24.8 (CH2CH2CNN), 21.7 (C6H3Me2), 11.5 (C5Me5) ppm. IR (KBr, cm−1): 3011 (w), 2957 (m), 2910 (m), 1592 (s), 1541 (s), 1506 (s), 1458 (m), 1374 (m), 1309 (m), 1246 (s), 1180 (m), 1162 (m), 1125 (m), 1099 (m), 1035 (m), 989 (m), 896 (m), 859 (m), 836 (s), 783 (s), 740 (s), 694 (m), 628 (m), 588 (m), 530 (m), 506 (m), 480 (m). Anal. Found (calcd for C39H53N5OTi): C, 71.05 (71.43); H, 7.78 (8.15); N, 10.28 (10.68). [Cp*Ti(NxylN)(NN{C6H4Br}2)(NH2tBu)] (3d). A 257 mg amount (0.499 mmol) of 1 was dissolved in hexane (4 mL). A 171 mg amount (0.499 mmol) of (BrC6H4)2NNH2 was added. The red solution immediately turned green, and a dark green solid began to precipitate. The solution was stirred for 1 h, and then the supernatant solution was removed by filtration and the residue was dried under reduced pressure to yield 248 mg (0.317 mmol, 63%) of a dark green solid. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.25 (d, 4 H, 3JH−H = 6.7 Hz, m-NNC6H4Br), 6.90 (d, 4 H, 3JH−H = 7.9 Hz, o-C6H4Br), 6.63 (s, 2 H, o-C6H3Me2), 6.60 (s, 1 H, p-C6H3Me2), 3.61 (broad m, 1 H, CH2N-a), 3.47 (broad m, 1 H, CH2N-b), 2.36 (broad m, 1 H, CH2CNN-a), 2.26 (s, 6 H, C6H3Me2), 2.11 (broad m, 1 H, CH2CNNb), 1.86 (s, 15 H, C5Me5), 1.53 (broad m, 2 H, CH2CH2CNN), 1.02 (s, 9 H, CMe3) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 170.0 (NCN), 151.7 (ipso-C6H3Me2), 145.2 (ipso-NNC6H4Br), 138.3 (m-C6H3Me2), 132.0 (m-NNC6H4Br), 123.4 (p-C6H3Me2), 121.4 (oNNC6 H4 Br), 120.7 (o-C6 H3 Me 2 ), 118.9 (C 5Me 5 ), 114.4 (pNNC6H4Br), 55.9 (CH2N), 49.3 (CMe3), 31.7 (CMe3), 29.9 (CH2CNN), 25.0 (CH2CH2CNN), 21.7 (C6H3Me2), 11.6 (C5Me5) ppm. IR (KBr, cm−1): 3027 (w), 2959 (m), 2911 (m), 2859 (m), 1558 (s), 1477 (s), 1374 (s), 1321 (s), 1263 (s), 1157 (s), 1123 (m), 1068 (s), 1011 (m), 897 (m), 862 (m), 844 (m), 816 (s), 799 (s), 651 (m), 631 (m), 528 (m), 499 (m), 481 (m), 463 (m). Anal. Found (calcd for C38H49Br2N5Ti): C, 58.06 (58.25); H, 6.12 (6.30); N, 8.82 (8.94). [Cp*Ti(NxylN)(NNfluorenon)(py)] (3e). A 643 mg amount (1.249 mmol) of 1 was dissolved in 5 mL of hexane. First 0.20 mL of pyridine (2.498 mmol, 2 equiv) and then 243 mg (1.249 mmol) of 9fluorenone hydrazone were added. The red solution immediately
toluene-d8, THF-d8), vacuum-distilled, and stored under argon in Teflon valve ampules. Ph2NNH2 was prepared from the hydrochloride salt purchased from Acros and purified by column chromatography (over silica, dichloromethane) prior to use. 1 and 2a−c were prepared as described previously.7,9 All other chemicals were purchased from commercial sources (Acros/Thermo Fischer, ABCR/Strem, and Sigma-Aldrich). Carbodiimides were degassed and stored in a glovebox. Samples for NMR spectroscopy of moisture-sensitive compounds were prepared under argon in 5 mm Wilmad tubes equipped with J. Young Teflon valves. NMR spectra were recorded on Bruker DRX200, Bruker Avance II 400, and Bruker Avance III 600 (with QNP-CryoProbe) NMR spectrometers. NMR spectra are quoted in ppm and were referenced internally relative to the residual protio solvent (1H) or solvent (13C) resonances or externally to 15NH3 (15N) and C19FCl3 (19F). Where necessary, NMR assignments were confirmed by the use of two-dimensional 1H−1H, 1H−19F, and 1 H−13C correlation experiments. 13C spectra were recorded 1H broadband decoupled; multiplicities of the resonances were determined using DEPT-135 experiments. 15N data were obtained by twodimensional 1H correlated experiments or by direct detection using a cryogenically cooled direct-detection NMR probe (QNP CryoProbe). Microanalyses were performed by the microanalytical services in the chemistry department of the Universität Heidelberg on a vario MIKRO Cube (Elementar) or a Vario EL (Elementar) CHN analyzer. Mass spectra were recorded by the Institute of Organic Chemistry of the Universität Heidelberg as ESI spectra on a Finnigan TSQ-700, Finnigan LCQ quadrupole ion trap, or a Bruker apex-Qe hybrid 9.4 T FT-ICR (for HR-ESI) spectrometer. IR spectra were recorded on a Varian 3100 Exalibur FT-IR spectrometer as KBr plates or as a neat oil between NaCl plates. Infrared data are quoted in wavenumbers (cm−1). [Cp*Ti(NxylN)(NN{C6H4Me}{Ph})(NH2tBu)] (3a). To a solution of 1 (1.178 g, 2.29 mmol) in hexane ({p-Tol}{Ph})NNH2 was added (454 mg, 2.29 mmol). After the mixture was stirred for 1 h at room temperature, the supernatant solution was removed by filtration and the residue was dried under reduced pressure. The product could be isolated as a green powder (556 mg, 0.87 mmol, 38%). Crystals suitable for X-ray diffraction could be obtained from a concentrated toluene solution at −40 °C. 1H NMR (600.1 MHz, benzene-d6, 295 K): δ 1.08 (s, 9H, NH2C(CH3)3), 1.54 (br m, 2 H, CH2CH2CNN), 1.98 (s, 15 H, C5Me5), 2.13 (br m, 1H, CH2CNN-a), 2.15 (s, 3H, C6H4Me), 2.22 (br m, 1 H, CH2CNN-b), 2.27 (s, 6 H, C6H3Me2), 3.60 (br m, 1 H, CH2N-a), 3.66 (br m, 1 H, CH2N-b), 6.62 (s, 1 H, pC6H3Me2), 6.67 (s, 2 H, o-C6H3Me2), 6.81 (t, 3JH−H = 7.2 Hz, 1 H, pPh), 6.99 (d, 3JH−H = 7.8 Hz, 2 H, m-C6H4Me), 7.20−7.18 (m, 2H, mNNC6H5), 7.26 (d, 3JH−H = 8.6 Hz, 2 H, o-C6H4Me), 7.28 (d, 3JH−H = 8.2 Hz, 2 H, o-NNC6H5) ppm. 13C{1H} NMR (150.9 MHz, benzened6, 295 K): δ 11.5 (C5Me5), 20.9 (C6H4Me), 21.7 (C6H3Me2), 24.7 (CH2CH2CNN), 29.9 (CH2CNN), 31.9 (NH2C(CH3)3), 48.9 (NH2C(CH3)3), 55.3 (CH2N), 117.7 (C5Me5), 118.8 (o-C6H5), 120.5 (o-C6H3Me2), 120.6 (o-C6H4Me), 121.8 (p-C6H5), 123.5 (pC6H3Me2), 128.3 (m-C6H5), 128.8 (m-C6H4Me), 129.7 (p-C6H4Me), 138.2 (m-C6H3Me2), 147.7 (ipso-C6H5, ipso-C6H4Me, ipso-C6H3Me2), 168.4 (s, NCN) ppm. 15N NMR (60.8 MHz, benzene-d6, 295 K): δ 69.2 (H2NC(CH3)3), 188.5 (TiNN{Ph}{Tol}), 199.5 (NCNXyl ppm, TiNN{Ph}{Tol}), NCNXyl not observed. IR (KBr): 3026.8 (w), 2956.1 (m), 2915.6 (m), 2858.3 (m), 2365.6 (w), 1618.4 (s), 1594.8 (s), 1541 (s), 1507.2 (s), 1489.4 (s), 1465.9 (s), 1374.5 (m) 1363.8 (m), 1308.9 (m), 1261.7 (s). Anal. Found (calcd for C39H35N5Ti): C, 72.98 (73.33); H, 8.04 (8.35); N, 10.59 (10.95). [Cp*Ti(NxylN)(NN{C6H4F}{Ph})(NH2tBu)] (3b). A 415 mg amount (0.807 mmol) of 1 was dissolved in hexane (6 mL). A 163 mg amount (0.807 mmol) of (p-C6H4F)PhNNH2 was added. The solution immediately turned green, and a green solid started to precipitate. After 1.5 h, the supernatant solution was removed by filtration and the residue dried under reduced pressure to yield 229 mg (0.356 mmol, 44%) of a green solid. 1H NMR (600.1 MHz, benzene-d6, 295 K): δ 7.2−7.12 (m, 4 H, o- and m-NNC6H5), 7.10 (dd, 2 H, 3JH−H = 8.6 Hz, 4 JH−F = 5.3 Hz, o-C6H4F), 6.86−6.78 (m, 3 H, p-NNC6H5 and mNNC6H4F), 6.65 (broad s, 2 H, o-C6H3Me2), 6.61(s, 1 H, p3704
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709
Organometallics
Article
(CH2CH2)2CH2-a), 2.85−2.77 (m, 1 H, TiNCH(CH2CH2)2CH2-b), 2.49−2.43 (m, 1 H, CH2CNN-a), 2.40−2.34 (m, 1 H, CH2-Cy), 2.30 (s, 6 H, C6H3Me2), 2.31−2.28 (m, 1 H, CH2CNN-b), 2.09−2.03 (m, 1 H, CH2-Cy), 1.98−1.93 (m, 3 H, CH2-Cy), 1.88−1.85 (m, 4 H, CH2Cy), 1.84 (s, 15 H, C5Me5), 1.78−1.72 (m, 1 H, CH2-Cy), 1.72−1.67 (m, 1 H, CH2-Cy), 1.62−1.50 (m, 2 H, CH2-Cy, overlaps with DCC), 1.48−1.40 (m, 2 H, CH2-Cy), 1.26−1.14 (m, 2 H, CH2CH2CNN), 0.76−0.66 (m, 1 H, CH2-Cy), 0.65−0.59 (m, 1 H, CH2−Cy) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.4 (NCN), 148.6 (C NCy), 148.2 (ipso-C6H3Me2), 146.5 (ipso-Ph-a), 145.3 (ipso-Ph-b), 139.7 (m-C6H3Me2), 128.7, 128.6 (m-Ph-a and -b), 125.4 (C5Me5), 123.1 (p-C6H3Me2), 122.7 (o-Ph-a), 122.0 (p-Ph-a), 118.6 (p-Ph-b), 118.5 (o-C6H3Me2), 114.5 (o-Ph-b), 65.1 (TiNCH(CH2CH2)2CH2), 53.1 (CNCH(CH2CH2)2CH2), 52.6 (CH2N), 38.0 (CNCH(CH2CH2)2CH2-a), 35.9 (CH2−Cy), 34.6 (TiNCH(CH2CH2)2CH2a), 32.9 (TiNCH(CH2CH2)2CH2-b), 31.4 (CH2CNN), 28.3 (CH2Cy), 27.6 (CH2-Cy), 26.8 (CH2-Cy), 26.8 (CH2-Cy), 25.4 (C NCH(CH2CH2)2CH2-b), 24.9 (CH2−Cy), 24.3 (CH2CH2CNN), 21.9 (C6H3Me2), 12.2 (C5Me5) ppm. In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NMePh)C(NiPr)i N Pr}] (4b). A 10 mg portion (0.018 mmol) of 2c was dissolved in 0.5 mL of benzene-d6, and 2.7 μL (0.018 mmol) of iPrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded and an equilibrium was observed. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.30 (t, 2 H, 3 JH−H = 7.1 Hz, m-NNC6H5), 6.75 (t, 1 H, 3JH−H = 7.2 Hz, pNNC6H5), 6.71 (d, 2 H, 3JH−H = 7.6 Hz, o-NNC6H5), 6.60 (s, 2 H, oC6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.81 (sep, 1 H, 3JH−H = 6.5 Hz, TiNCHMe2), 3.83 (sep, 1 H, 3JH−H = 6.1 Hz, CNCHMe2), 3.37 (m, 1 H, CH2N-a, overlaid by iPrNCNCHMe2), 3.04 (s, 3 H, NNMe), 3.00−2.95 (m, 1 H, CH2N-b), 2.25 (s, 6 H, C6H3Me2), 2.23 (m, 1 H, CH2CNN), 2.03 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-a), 2.03−2.01 (m, 1 H, CH2CNN), 1.96 (s, 15 H, C5Me5), 1.53 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-b), 1.26 (d, 3 H, 3JH−H = 6.2 Hz, CNCHMe2-a), 1.05 (d, 3 H, 3JH−H = 6.2 Hz, CNCHMe2-b, overlaid by i PrNCNCHMe2) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.7 (NCN), 148.9, 148.8, 148.6 (CNCHMe2, ipso-C6H3Me2, ipso-NNC6H5), 138.2 (m-C6H3Me2), 128.8 (m-NNC6H5), 124.7 (C5Me5), 123.6 (p-NNC6H5), 119.5 (o-C6H3Me2), 115.5 (pC6H3Me2), 110.7 (o-NNC6H5), 54.6 (TiNCHMe2), 53.2 (CH2N), 45.1 (TiNCHMe2), 42.0 (NNMe), 30.9 (CH2CNN), 26.9 (C NCHMe2-a), 26.8 (CNCHMe2-b), 24.6 (TiNCHMe2-b), 24.1 (TiNCHMe2 -a), 23.1 (CH2CH2CNN), 21.6 (C 6H3 Me2), 12.4 (C5Me5) ppm. In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4F))C(NiPr)NiPr}] (4c). A 10 mg portion (0.016 mmol) of 3b was dissolved in 0.5 mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded and an equilibrium was observed. Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was added in order to shift the equilibrium to the side of the cycloadduct. After 15 min, NMR spectra were again recorded. The spectra indicated two isomers in a ratio of 1.3:1. Major isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.34 (dd, 2 H, 3JH−F = 8.9 Hz, 3JH−H = 5.0 Hz, m-NNC6H4F), 7.0 (t, 2 H, 3 JH−H = 8.0 Hz, m-NNC6H5), 6.95 (d, 2 H, 3JH−H = 8.0 Hz, oNNC6H5), 6.91 (m, 2 H, o-NC6H4F), 6.61 (t, 1 H, 7.2 Hz, pNNC6H5), 6.60 (s, 2 H, o-C6H3Me2), 6.59 (s, 1 H, p-C6H3Me2), 4.87 (quin, 1 H, 3JH−H = 6.5 Hz, TiNCHMe2), 3.97 (quin, 1 H, 3JH−H = 5.9 Hz, CNCHMe2), 3.50 (dt, 1 H, 2JH−H = 11.8 Hz, 3JH−H = 7.0 Hz, CH2N-a), 3.43 (dt, 1 H, 2JH−H = 11.8 Hz, 3JH−H = 7.0 Hz, CH2N-b), 2.43−2.35 (m, 1 H, CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b), 2.28 (s, 6 H, C6H3Me2), 2.05 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a), 1.80 (s, 15 H, C5Me5), 1.55 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-b), 1.42−1.31 (m, 2 H, CH2CH2CNN), 1.25 (d, 3 H, 3JH−H = 6.2 Hz, C NCHMe2-a), 0.58 (d, 3 H, 3JH−H = 6.0 Hz, CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.4 (NCN), 148.8 (C ar), 148.0 (C ar), 144.0 (d, 1JC−F = 155.5 Hz, p-NNC6H4F), 141.7 (C ar), 140.2 (d, 4JC−F = 3.1 Hz, ipso-NNC6H4F), 138.4 (m-C6H3Me2), 128.7 (m-NNC6H5), 126.5 (C5Me5), 123.9 (d, 3JC−F = 7.7 Hz, o-NNC6H4F),
turned deep red. The solution was stirred for 2 h at room temperature, and then the supernatant solution was removed by filtration and the residue was dried under reduced pressure. A 613 mg amount (0.955 mmol, 76%) of a dark red solid was obtained. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 8.94 (d, 1 H, 3JH−H = 7.6 Hz, H5), 7.82−7.72 (broad m, 2 H, o-C5H5N), 7.74 (d, 1 H, 3JH−H = 7.6 Hz, H2), 7.63 (d, 1 H, 3JH−H = 6.8 Hz, H11), 7.47 (t, 1 H, 3JH−H = 7.6 Hz, H4), 7.26 (t, 1 H, 3JH−H = 7.6 Hz, H3), 7.05 (m, 2 H, H9, H10), 6.51 (broad t, 1 H, 3 JH−H = 7.8 Hz, p-C5H5N), 6.39 (s, 2 H, o-C6H3Me2), 6.37 (s, 1 H, pC6H3Me2), 6.19 (broad m, 2 H, m-C5H5N), 3.83−3.63 (m, 2 H, CH2N), 2.51 (dt, 1 H, 2JH−H = 14.9 Hz, 3JH−H = 7.6 Hz, CH2CNN-a), 2.06 (s, C6H3Me2), 2.05 (m, CH2CNN-b), 1.95 (s, C5Me5), 1.80−1.71 (m, 1 H, CH2CH2CNN-a), 1.27 (dt, 1 H, 2JH−H = 13.1 Hz, 3JH−H = 6.9 Hz, CH2CH2CNN-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 170.6 (NCN), 166.2 (TiNNC), 150.6 (o-C6H5N), 138.8 (ipsoC6H3Me2), 137.7 (C12), 137.6 (C6), 137.1 (C7), 136.9 (p-C5H5N), 135.3 (C1), 126.9 (C4), 125.7 (C10), 125.6 (C3), 125.4 (C5), 124.4 (C9), 124.1 (m-C5H5N), 123.4 (p-C6H3Me2), 121.6 (C5Me5), 121.2 (o-C6H3Me2), 120.2 (C11), 119.9 (C2), 118.9 (C8), 53.1 (CH2N), 30.05 (CH2CNN), 23.2 (CH2CH2CNN), 21.5 (C6H3Me2), 11.8 (C5Me5) ppm. IR (KBr, cm−1): 3052 (w), 2946 (w), 2901 (w), 2841 (w), 1591 (m), 1531 (s), 1491 (s), 1444 (s), 1374 (m), 1338 (s), 1291 (s), 1259 (m), 1186 (s), 1150 (m), 1126 (s), 1069 (m), 1023 (m), 947 (m), 878 (w), 834 (m), 732 (s), 703 (m), 684 (s), 622 (s), 591 (s). Anal. Found (calcd for C40H43N5Ti): C, 74.83 (74.87); H, 6.78 (6.75); N, 10.76 (10.91). NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(NPh2)C(NiPr)NiPr}] (4a). A 40 mg amount (0.064 mmol) of 2a was dissolved in 0.5 mL of benzene-d6, and 25 μL (0.160 mmol) of iPrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded. Crystals suitable for X-ray analysis were obtained by adding 3 equiv (80 μL, 0.52 mmol) of i PrNCNiPr to a concentrated solution of 90 mg (0.16 mmol) of 2b in hexane. After several days at −40 °C, crystals began to grow. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.51 (d, 2 H, 3JH−H = 7.9 Hz, oNNC6H5-a), 7.27 (t, 2 H, 3JH−H = 7.9 Hz, m-C6H5-a), 7.05 (d, 2 H, 3 JH−H = 8.2 Hz, o-C6H5-b), 7.00 (t, 2 H, 3JH−H = 7.9 Hz, m-C6H5-b), 6.89 (t, 1 H, 3JH−H = 7.3 Hz, p-C6H5-a), 6.62 (t, 1 H, 3JH−H = 7.2 Hz, p-C6H5-b), 6.59 (s, 2 H, o-C6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.89 (1 H, quin, 3JH−H = 6.5 Hz, TiNCHMe2), 4.05 (1 H, quin, 3JH−H = 6.0 Hz, C=NCHMe2), 3.55 (dt, 1 H, 2JH−H = 11.6 Hz, 3JH−H = 7.4 Hz, NCH2-a), 3.42−3.37 (m, 1 H, NCH2-b), 2.44−2.38 (m, 1 H, CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b), 2.27 (s, 6 H, C6H3Me2), 2.07 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a), 1.83 (s, 15 H, C5Me5), 1.55 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-b), 1.25 (d, 3 H, 3 JH−H = 6.0 Hz, CNCHMe2-a), 0.56 (d, 3 H, 3JH−H = 6.0 Hz, C NCHMe2-b) ppm. 13C NMR (benzene-d6, 150.9 MHz, 295 K): δ 169.3 (NCN), 148.8 (CNiPr), 148.1 (ipso-C6H3Me2), 146.4 (ipsoC6H5-a), 145.3 (ipso-C6H5-b), 138.3 (m-C6H3Me2), 128.7, 128.6 (mC6H5-a and b), 125.4 (C5Me5), 123.3 (p-C6H3Me2), 122.5 (o-C6H5-a), 121.9 (p-C6H5-a), 118.8 (o-C6H3Me2), 118.6 (p-C6H5-b), 114.6 (oC6H5-b), 55.07 (TiNCHMe2), 52.8 (CH2N), 45.0 (CNCHMe2), 31.4 (CH2CNN), 27.5 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9 (TiNCHMe2-a), 24.1 (CH2CH2CNN), 23.7 (TiNCHMe2-b), 21.7 (C6H3Me2), 12.2 (C5Me5) ppm. 15N NMR (benzene-d6, 60.81 MHz, 295 K): δ 292.3 (TiNiPr), 251.5 (TiNNPh2), 225.7 (CNiPr), 206.6 (xylNCNCH2), 178.1 (xylNCNCH2), 104.9 (TiNNPh2) ppm. NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(NPh2)C(NCy)NCy}] (4b). A 10 mg amount (0.016 mmol) of 2a was dissolved in 0.5 mL of benzene-d6, and 9.9 mg (0.048 mmol) of CyNCNCy was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded. 1H NMR (benzene-d6, 600.1 MHz, 295 K): δ 7.51 (δ, 2 H, 3JH−H = 8.4 Hz, o-Ph-a), 7.24 (t, 2 H, 3JH−H = 7.5 Hz, m-Ph-a), 7.06 (d, 2 H, 3JH−H = 8.2 Hz, o-Ph-b), 7.02 (t, 2 H, 3JH−H = 7.9 Hz, m-Ph-b), 6.89 (t, 1 H, 3JH−H = 7.6 Hz, pPh-a), 6.64 (t, 1 H, 3JH−H = 7.0 Hz, p-Ph-b), 6.58 (s, 1 H, p-C6H3Me2), 6.57 (s, 2 H, o- C6H3Me2), 4.32 (tt, 1 H, 3JH−H = 11.2 Hz, 3JH−H = 2.8 Hz, TiNCH(CH2CH2)2CH2), 3.67 (m, 1 H, C NCH(CH2CH2)2CH2), 3.55 (dt, 1 H, 2JH−H = 11.8 Hz, 3JH−H = 7.4 Hz, CH 2 N-a), 3.45−3.37 (m, 2 H, CH 2 N-a and TiNCH3705
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709
Organometallics
Article
H, CH2CH2CNN-b), 1.28 (d, 3 H, 3JH−H = 6.2 Hz, CNCHMe2-a), 0.60 (d, 3 H, 3JH−H = 5.3 Hz, CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 148.7, 148.1, 146.6, 143.1 (CNCHMe2, ipso-C6H4Me, ipso-C6H5, ipso-C6H3Me2), 140.2 (m-C6H3Me2), 129.3 (p-C6H5), 128.6 (m-C6H4Me), m-C6H5 overlaid by solvent signal, 125.3 (C5Me5), 123.3 (o-C6H3Me2), 122.0 (o-C6H5), 118.3 (p-C6H3Me2), 114.9 (o-C6H4Me), 55.1 (TiNCHMe2), 52.8 (CH2N), 45.1 (CNCHMe2), 31.4 (CH2CNN), 27.5 (CNCHMe2a), 25.7 (CNCHMe2-b), 25.0 (TiNCHMe2-b), 24.5 (TiNCHMe2a), 23.7 (CH2CH2CNN), 21.7 (C6H3Me2), 20.5 (C6H4Me), 12.2 (C5Me5) ppm. In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4OMe))C(NiPr)NiPr}] (4e). A 10 mg (0.016 mmol) portion of 3c was dissolved in 0.5 mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded and an equilibrium was observed. Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was added in order to shift the equilibrium to the side of the cycloadduct. After 15 min, again NMR spectra were recorded. The spectra indicated two isomers in a ratio of 3:1. Major isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.47 (d, 2 H, 3JH−H = 8.6 Hz, m-NNC6H4OMe), 7.07−7.00 (m, 4 H, o- and mNNC6H5), 6.89 (d, 2 H, 3JH−H = 8.6 Hz, o-C6H4OMe), 6.70−6.64 (m, 1 H, p-NNC6H5), 6.63 (s, 2 H, o-C6H3Me2), 6.60 (s, 1 H, pC6H3Me2), 4.90 (quin, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.12 (quin, 1 H, 3JH−H = 5.9 Hz, CNCHMe2), 3.58 (dt, 1 H, 2JH−H = 11.7 Hz, 3 JH−H = 7.1 Hz, CH2N-a), 3.47−3.43 (m, 1 H, CH2N-b), 3.43 (s, 3 H, C6H4OMe), 2.49−2.42 (m, 1 H, CH2CNN-a), 2.36−2.29 (m, 1 H, CH2CNN-b), 2.28 (s, 6 H, C6H3Me2), 2.10 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-a), 1.85 (s, 15 H, C5Me5), 1.58 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-b), 1.42−1.34 (m, 2 H, CH2CH2CNN), 1.32 (d, 3 H, 3 JH−H = 6.1 Hz, CNCHMe2-a), 0.63 (d, 3 H, 3JH−H = 6.1 Hz, C NCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.5 (NCN), 155.5 (p-NNC6H4OMe), 148.5, 148.2, 145.9 (ipso-NNC6H5, ipso-C6H3Me2, CNCHMe2), 140.2 (ipso-NNC6H4OMe), 138.4 (mC 6 H 3 Me 2 ), 128.8 (m-NNC 6 H 5 ), 125.3 (C 5 Me 5 ), 124.2 (mNNC6H4OMe), 123.3 (p-C6H3Me2), 114.2 (p-NNC6H5), 114.0 (oNNC6H4OMe), 113.9 (o-NNC6H5), 55.2 (NNC6H4OMe), 55.1 (TiNCHMe 2 ), 52.8 (CH 2 N), 45.0 (CNCHMe 2 ), 31.3 (CH2CNN), 27.6 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9 (TiNCHMe2-b), 24.2 (CH2CH2CNN), 23.7 (TiNCHMe2-a), 21.7 (C6H3Me2), 12.2 (C5Me5) ppm. Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.50 (d, 2 H, 3JH−H = 8.5 Hz, o-NNC6H5), 7.26 (t, 2 H, 3JH−H = 7.6 Hz, mNNC6H5), 7.07−7.00 (m, 2 H, m-NNC6H4OMe), 6.86 (d, 1 H, 3JH−H = 7.3 Hz, p-NNC6H5), 6.70−6.64 (m, 2 H, o-NNC6H4OMe), 6.59 (s, 2 H, o-C6H3Me2), 6.57 (s, 1 H, p-C6H3Me2), 4.96 (quin, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.08 (quin, 1 H, 3JH−H = 6.1 Hz, CNCHMe2), 3.63 (dt, 1 H, 2JH−H = 11.8 Hz, 3JH−H = 7.3 Hz, CH2N-a), 3.47−3.43 (m, CH2N-b), 3.25 (s, 3 H, C6H4OMe), 2.49−2.42 (m, 1 H, CH2CNN-a), 2.42−2.36 (m, 1 H, CH2CNN-b), 2.27 (s, 6 H, C6H3Me2), 2.12 (d, 3 H, 3JH−H = 6.3 Hz, TiNCHMe2-a), 1.99 (s, 15 H, C5Me5), 1.64 (d, 3 H, 3JH−H = 6.6 Hz, TiNCHMe2-b), 1.42−1.34 (m, 2 H, CH2CH2CNN), 1.27 (d, 3 H, 3JH−H = 6.1 Hz, CNCHMe2-a), 0.66 (d, 3 H, 3JH−H = 6.1 Hz, CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 153.3 (pC6H4OMe), 149.5, 147.9, 146.7 (ipso-NNC6H5, ipso-C6H3Me2, C NCHMe2), 140.1 (ipso-NNC6H4OMe), 138.2 (m-C6H3Me2), 128.7 (m-NNC6H5), 125.3 (C5Me5), 123.2 (p-C6H3Me2), 121.4 (oNNC6H5), 120.9 (p-NNC6H5), 118.9 (o-NNC6H4OMe), 116.1 (mNNC6H4OMe), 55.2 (NNC6H4OMe), 55.1 (TiNCHMe2), 52.8 (CH2 N), 45.1 (CNCHMe2 ), 31.5 (CH2 CNN), 27.4 (C NCHMe2-a), 25.9 (CNCHMe2-b), 25.0 (TiNCHMe2-b), 24.1 (CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.7 (C 6H3 Me2), 12.2 (C5Me5) ppm. NMR Tube Scale Preparation of [Cp*Ti(NxylN){κ2-N(N(C6H4Br)2)C(NiPr)NiPr}] (4f). A 10 mg portion (0.013 mmol) of 3d was dissolved in 0.5 mL of benzene-d6, and 2.0 μL (0.013 mmol) of i PrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded and an
123.4 (p-C6H3Me2), 122.0 (o-NNC6H5), 118.9 (o-C6H3Me2), 115.5 (p-NNC6H5), 115.3 (d, 2JC−F = 22.0 Hz, m-NNC6H4F), 55.1 (TiNCHMe 2 ), 52.7 (CH 2 N), 45.0 (CNCHMe 2 ), 31.3 (CH2CNN), 27.5 (CNCHMe2-a), 25.7 (CNCHMe2-b), 24.9 (TiNCHMe2-b), 24.1 (CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.7 (C6H3Me2), 12.2 (C5Me5) ppm; 19F NMR (benzene-d6, 376.27 MHz, 295 K) δ −121.2 (m) ppm. Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.43 (d, 2 H, 3JH−H = 8.0 Hz, o-NNC6H5), 7.22 (t, 2 H, m-NNC6H5), 6.90− 6.86 (m, 3 H, p-NNC6H5 and o-NNC6H4F), 6.66 (t, 2 H, 8.8 Hz, mNNC6H4F), 6.57 (s, 1 H, p-C6H3Me2), 6.54 (s, 2 H, o-C6H3Me2), 4.90 (quin, 1 H, 3JH−H = 6.6 Hz, TiNCHMe2), 3.97 (quin, 1 H, 3JH−H = 5.9 Hz, CNCHMe2), 3.39−3.33 (m, 2 H, CH2N), 2.43−2.35 (m, 1 H, CH2CNN-a), 2.34−2.29 (m, 1 H, CH2CNN-b), 2.26 (s, 6 H, C6H3Me2), 2.08 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-a), 1.81 (s, 15 H, C5Me5), 1.59 (d, 3 H, 3JH−H = 6.5 Hz, TiNCHMe2-b), 1.42−1.31 (m, 2 H, CH2CH2CNN), 1.27 (d, 3 H, 3JH−H = 6.2 Hz, CNCHMe2-a), 0.58 (d, 3 H, 3JH−H = 6.0 Hz, CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.3 (NCN), 148.5 (C ar), 147.9 (C ar), 146.4 (C ar), 144.0 (d, 1JC−F = 155.5 Hz, p-C6H4F), 141.7 (C ar), 140.1 (d, 4JC−F = 3.1 Hz, ipso-C6H4F), 138.4 (m-C6H3Me2), 128.8 (m-C6H5), 125.6 (C5Me5), 123.9 (d, 3JC−F = 7.8 Hz, o-C6H4F), 123.4 (p-C6H3Me2), 121.8 (o-C6H5), 118.7 (o-C6H3Me2), 115.6 (pNNC 6 H 5 ), 115.1 (d, 2 J C−F = 22.0 Hz, m-NNC6 H 4 F), 55.1 (TiNCHMe 2 ), 52.7 (CH 2 N), 45.0 (CNCHMe 2 ), 31.4 (CH2CNN), 27.4 (CNCHMe2-a), 25.6 (CNCHMe2-b), 24.9 (TiNCHMe2-b), 24.1 (CH2CH2CNN), 23.6 (TiNCHMe2-a), 21.6 (C6H3Me2), 12.1 (C5Me5) ppm’ 19F NMR (benzene-d6, 376.27 MHz, 295 K) δ −126.3 (m) ppm. In Situ Preparation of [Cp*Ti(NxylN){κ2-N(NPh(C6H4Me))Ci (N Pr)NiPr}] (4d). A 10 mg portion (0.016 mmol) of 3a was dissolved in 0.5 mL of benzene-d6, and 2.4 μL (0.016 mmol) of iPrNCNiPr was added. The color immediately changed from light to deep dark green. After 15 min, NMR spectra were recorded and an equilibrium was observed. Then, an additional 4.8 μL (0.032 mmol) of iPrNCNiPr was added in order to shift the equilibrium to the side of the cycloadduct. After 15 min, NMR spectra were again recorded. The spectra indicated two isomers in a ratio of 3:2. Major isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.46 (d, 2 H, 3JH−H = 8.2 Hz, o-C6H5), 7.07 (d, 2 H, 3JH−H = 8.3 Hz, m-C6H5), 7.04−7.00 (m, 3 H, p-C6H5 and o-C6H4Me), 6.81 (d, 2 H, 3JH−H = 8.3 Hz, m-C6H4Me), 6.64−6.61 (m, 1 H, p-C6H3Me2), 6.59 (s, 2 H, oC6H3Me2), 4.91 (sep, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.08 (sep, 1 H, 3JH−H = 6.1 Hz, CNCHMe2), 3.62−3.58 (m, 1 H, CH2N-a), 3.48−3.42 (m, 1 H, CH2N-b), 2.42 (m, 1 H, CH2CNN-a), 2.34−2.30 (m, 1 H, CH2CNN-b), 2.28 (s, 6 H, C6H3Me2), 2.23 (s, 3 H, C6H4Me), 2.10(d, 3 H, 3JH−H = 6.2 Hz, TiNCHMe2-a), 1.85 (s, 15 H, C5Me5), 1.59 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-b), 1.41−1.34 (m, 1 H, CH2CH2CNN-a), 1.34−1.28 (m, 1 H, CH2CH2CNN-b), 1.30 (d, 3 H, 3JH−H = 5.8 Hz, CNCHMe2-a), 0.61 (d, 3 H, 3JH−H = 5.3 Hz, CNCHMe2-b) ppm; 13C NMR (benzene-d6, 150.9 MHz, 295 K) δ 169.4 (NCN), 149.1, 148.1, 145.6, 144.1 (CNCHMe2, ipsoC6H4Me, ipso-C6H5, ipso-C6H3Me2), 138.3 (m-C6H3Me2), 131.1 (pC6H4Me), 129.2 (p-C6H5), 128.8 (m-C6H4Me), m-C6H5 overlaid by solvent signal, 125.4 (C5Me5), 123.3 (o-C6H3Me2), 122.6 (o-C6H5), 118.9 (p-C6H3Me2), 114.4 (o-C6H4Me), 55.1 (TiNCHMe2), 52.8 (CH2N), 45.0 (CNCHMe2), 31.4 (CH2CNN), 27.5 (CNCHMe2a), 25.6 (CNCHMe2-b), 24.9 (TiNCHMe2-b), 24.1 (TiNCHMe2a), 23.7 (CH2CH2CNN), 21.7 (C6H3Me2), 20.9 (C6H4Me), 12.2 (C5Me5) ppm. Minor isomer: 1H NMR (benzene-d6, 600.1 MHz, 295 K) δ 7.54 (d, 2 H, 3JH−H = 8.3 Hz, o-C6H5), 7.25 (t, 2 H, 3JH−H = 7.6 Hz, m-C6H5), 7.04−7.00 (m, 2 H, o-C6H4Me), 6.88 (t, 1 H, 3JH−H = 7.3 Hz, p-C6H5), 6.64−6.61 (m, 5 H, o- and p-C6H3Me2 and m-C6H4Me), 4.94 (sep, 1 H, 3JH−H = 6.4 Hz, TiNCHMe2), 4.09 (sep, 1 H, 3JH−H = 6.1 Hz, C NCHMe2), 3.66−3.62 (m, 1 H, CH2N-a), 3.42−3.38 (m, 1 H, CH2Nb), 2.45 (m, 1 H, CH2CNN-a), 2.37−2.34 (m, 1 H, CH2CNN-b), 2.29 (s, 6 H, C6H3Me2), 2.11 (d, 3 H, 3JH−H = 6.0 Hz, TiNCHMe2-a), 2.06 (s, 3 H, C6H4Me), 1.84 (s, 15 H, C5Me5), 1.64 (d, 3 H, 3JH−H = 6.4 Hz, TiNCHMe2-b), 1.41−1.33 (m, 1 H, CH2CH2CNN), 1.34−1.28 (m, 1 3706
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709
Organometallics
Article
Table 2. Details of the Crystal Structure Determinations of 3a, 4a, and tBuNHC(NNfluorene)NHEt formula Mr cryst syst space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z F000 dc/Mg m−3 μ/mm−1 max, min transmissn factors θ range/deg index ranges (indep. set) h,k,l no. of rflns measd no. of unique rflns (Rint) no. of obsd rflns (I ≥ 2σ(I)) no. of params refined GOF on F2 R indices (F > 4σ(F)): R(F), Rw(F2) R indices (all data): R(F), Rw(F2) difference density/e Å−3: max, min
tBuNHC(NNfluorene)NHEt
3a
4a
C39H53N5Ti 639.76 triclinic P1̅ 12.0332(3) 13.2330(3) 13.8121(3) 102.414(2) 101.959(2) 116.935(3) 1793.95(9) 2 688 1.184 2.264 0.822, 0.750 3.5−72.0 −14 to +14, −16 to +16, −16 to +17 55551 6862 (0.0418)] 6497 556 1.104 0.0434, 0.1067 0.0457, 0.1080 0.277, −0.288
C41H54N6Ti 678.80 triclinic P1̅ 11.6307(2) 12.6815(2) 13.1652(2) 82.306(1) 78.514(1) 82.948(1) 1876.53(5) 2 728 1.201 2.202 0.884, 0.686 3.4−72.0 −14 to +14, −15 to +15, −16 to +16 137282 7221 (0.0575) 6879 512 1.070 0.0313, 0.0844 0.0331, 0.0857 0.273, −0.329
equilibrium was observed. Then, an additional 4.0 μL (0.026 mmol) of i PrNCNiPr was added in order to shift the equilibrium to the side of the cycloadduct. After 15 min, NMR spectra were again recorded. 1H NMR (600.1 MHz, benzene-d6, 295 K): δ 0.56 (d, 3JH−H = 6.1 Hz, 3 H, CNCHMe2-a), 1.19 (d, 3JH−H = 6.1 Hz, 3 H, CNCHMe2-b), 1.27 (br m, 2 H, CH2CH2CNN), 1.55 (d, 3JH−H = 6.4 Hz, 3 H, TiNCHMe2-a), 1.73 (s, 15 H, C5Me5), 2.01 (d, 3JH−H = 6.4 Hz, 3 H, TiNCHMe2-b), 2.18 (t, 3JH−H = 7.3 Hz, 2 H, CH2CNN), 2.25 (s, 6 H, C6H3Me2), 3.28 (br m, 2H, CH2N), 3.76 (sep, 3JH−H = 6.4 Hz, 1 H, CNCHMe2), 4.82 (sep, 3JH−H = 6.4 Hz, 1 H, TiNCHMe2), 6.50 (s, 2 H, o-C6H3Me2), 6.56 (s, 1 H, p-C6H3Me2), 6.69 (d, 3JH−H = 8.8 Hz, 2 H o-C6H4Br), 7.07 (d, 3JH−H = 8.8 Hz, 2 H m-C6H4Br), 7.14 (d, 3 JH−H = 8.6 Hz, 2 H, o-C6H4Br), 7.28 (d, 3JH−H = 8.6 Hz, 2 H, mC6H4Br) ppm. 13C{1H} NMR (150.9 MHz, benzene-d6, 295 K): δ 12.2 (C 5 Me 5 ), 21.6 (C 6 H 3 Me 2 ), 23.5 (TiNCHMe 2 ), 24.1 (CH2CH2CNN), 24.9 (TiNCHMe2) 25.7 (CNCHMe2), 27.4 (CNCHMe2), 31.2 (CH2CNN), 45.0 (CNCHMe2), 52.6 (CH2N), 55.0 (TiNCHMe2), 110.7 (p-C6H4Br), 114.1 (p-C6H4Br), 116.6 (o-C6H4Br), 118.7 (o-C6H3Me2), 123.7 (p-C6H3Me2), 125.9 (C5Me5), 128.4 (m-C6H4Br), 131.5 (m-C6H4Br), 131.7 (o-C6H4Br), 138.5 (m-C6H3Me2), 143.8 (ipso-C6H4Br), 145.02 (ipso-C6H4Br), 147.6 (ipso-C6H3Me2), 148.2 (CNCHMe2), 169.2 (NCN) ppm. Reaction Kinetics. Details of the kinetic study are provided in the Supporting Information. In order to determine activation parameters for the reaction of equimolar amounts of Ph2NNH2 and iPrNCNiPr, catalyzed by 2 mol % of 2a, a solution of [Cp*Ti(NxylN)(NNPh2)(tBuNH2)] (2.5 mg, 4 μmol), Ph2NNH2 (36.8 mg, 200 μmol), i PrNCNiPr (31 μL, 200 μmol), and 1,4-dimethoxybenzene (2.8 mg, 20 μmol) in benzene-d6 was transferred to a J. Young NMR tube and heated to 50, 53, 55, 57, or 59 °C in the spectrometer. 1H NMR spectra (200 MHz) were recorded every 10 min over a period of 12 h. The rate constants kobs were determined from the slope of the curves plotting ln([Ph2NNH2]/[Ph2NNH2]0) against time. Line fitting of the Eyring plot was conducted with error-weighted regression.21 General Procedure for Catalytic N-Aminoguanidine Synthesis. A 0.05 mmol amount of catalyst (1 or the corresponding hydrazinediido complex 2a−d or 3a−e) were dissolved in 1 mL of
C20H24N4 320.43 monoclinic P21/c 12.04507(12) 7.06049(8) 20.7577(3) 100.421(1) 1736.20(4) 4 688 1.226 0.577 0.961, 0.908 3.7−72.0 −14 to +14, −8 to +8, −23 to +19 37772 3333 (0.0339) 3082 290 1.038 0.0323, 0.0824 0.0348, 0.0847 0.180, −0.227
toluene (or 0.5 mL of 1,4-dioxane if 9H-fluoren-9-one hydrazone was used). A 1.0 mmol amount of carbodiimide and 1.1 mmol of hydrazine were dissolved in 1 mL of toluene (or 1.5 mL of 1,4-dioxane if 9Hfluoren-9-one hydrazone was used), and the solutions were combined, which usually resulted in an immediate change of color. The reaction was monitored by GC-MS until no further conversion occurred. The reaction mixture was then diluted with 120 mL of diethyl ether and filtrated through a pad of alumina, the solvent was removed under reduced pressure, and the crude product was purified by column chromatography (for Ar2NNH2 and 9H-fluoren-9-one hydrazone) or subjected to high vacuum (for Me2NNH2 and MePhNNH2). X-ray Crystal Structure Determinations. Crystal data and details of the structure determinations are given in Table 2. Full shells of intensity data were collected at low temperature (115 K) with an Agilent Technologies Supernova-E CCD diffractometer (Cu Kα radiation, microfocus tube, multilayer mirror optics, λ = 1.54184 Å). Data were corrected for air and detector absorption, Lorentz, and polarization effects; absorption by the crystal was treated analytically.22 The structures were solved by the charge flip procedure23 and refined by full-matrix least-squares methods based on F2 against all unique reflections.24 All non-hydrogen atoms were given anisotropic displacement parameters. Hydrogen atoms were generally input at calculated positions and refined with a riding model. When justified by the quality of the data, the positions of some hydrogen atoms were taken from difference Fourier syntheses and refined. In the structure of 3a large parts of the molecule were found to be disordered, which leads to extensive overlay of atoms belonging to different disordered parts. To achieve stable refinement and sensible bond parameters, geometry and adp restraints had to be applied extensively, and the accuracy of the derived parameters is correspondingly reduced.
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ASSOCIATED CONTENT
S Supporting Information *
Text, figures, and CIF files giving characterization data of the aminoguanidines and fluoreniminoguanidines obtained in the 3707
dx.doi.org/10.1021/om400323p | Organometallics 2013, 32, 3697−3709
Organometallics
Article
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catalysis, crystallographic data for compounds 3a, 4a, and t BuNHC(NNfluorene)NHEt, and details of the kinetics study. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS We thank the Deutsche Forschungsgemeinschaft for funding (SFB 623) and Ludger Schöttner for help with catalyst synthesis and the catalysis studies.
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REFERENCES
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