Reaction of Pentafulvene Titanium and Zirconium Complexes with

Article Cite This: Organometallics XXXX, XXX, XXX−XXX

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Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles Tim Oswald, Malte Fischer, Niclas Struckmann, Marc Schmidtmann, and Rüdiger Beckhaus* Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany

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ABSTRACT: The reaction of penta- and benzofulvene complexes of group 4 (M = Ti, Zr) with different phosphorus ylides is reported. Employing the bis(η5:η1-pentafulvene)titanium complexes Ti1a and Ti1b, the reactions with the corresponding phosphorus ylides Y1−5 result in a spontaneous single C−H bond activation and metallocene ylide complexes Ti2a−e can be isolated in good yields. On the basis of these results, this reactivity pattern has been extended to the mono(η5:η1-pentafulvene) and -benzofulvene complexes Ti3, Zr1a,b, and Zr1a,b-benzo. Transferring this to the titanium complex Ti3, an additional equilibrium between the reaction product (η5-C5Me5)(η5-CpAd)Ti(Cl)CHPPh3 (Ti4a) and the corresponding “tuck-in” complex (η5:η1-C5Me4CH2)(η5CpAd)TiCl (Ti4b) can be observed. In Ti4b, a methyl group of the Cp*-ligand is activated by the coordinated phosphorus ylide. Using this intramolecular C−H activation, Ti4b can be synthesized by catalytic amounts (3 mol %) of the phosphorus ylide Y1 in quantitative yield. Subsequently, the reaction of Ti4b with different carbonyl and nitrile compounds has been investigated. In both cases, an insertion of the functional group into the newly formed Ti−CH2 bond is observed, and the insertion products Ti5−9 are isolated in good yields. Using a sterically demanding nitrile, the titanium-imine complex Ti7 is isolated. Upon heating of Ti7, a thermally induced subsequent nonreversible 1,3-H-shift can be observed, forming the titaniumenamine complex Ti7a. With reduced steric demand of the appropriate nitrile, this shift directly takes place even under mild reaction conditions with no observation of the titanium-imine species. By utilization of acetonitrile as substrate, a dimeric titanium-imine-enamine complex Ti10 is formed, due to an occurring subsequent C−C bond formation reaction.

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INTRODUCTION Catalytic C−H bond activation processes allow step-economical synthetic protocols in many types of organic synthesis.1−4 Particularly, the detailed understanding of different reaction steps,5,6 involving C−H−metal interactions like agostic effects,7 are helpful for the development of hydrocarbon chemistry.8,9 However, the C−H bond activation chemistry is extended to a large variety of substrates, e.g., employing early transition metal catalysts in hydroaminoalkylation of olefins using secondary amines.10−13 Additionally, in different metal initiated attacks on the coordinated ligands, tuck-in complexes are found as C−H bond activation products. For example, thermolysis reactions of Cp*-complexes lead from η5-C5Me5 to η5:η1-C5Me4CH2 ligands.14 In the past years, we have developed a direct access to such early transition metal complexes with an η5:η1 coordination mode employing different suitable pentafulvene ligands.15 Generally, using α- and β-C−H bond activation processes, the formation of carbene16 as well as olefin17,18 complexes becomes understandable. Especially carbene and carbyne complexes of transition metals in high oxidation states are of general interest, which are used in different catalytic chemical reactions.17,19−27 Phosphorus ylides provide an efficient access © XXXX American Chemical Society

to such complexes, due to the fact that they can be described as dipolar carbenes as well as neutral molecules. This polarization of the phosphorus−carbon bond results in high Brønsted basicity of the carbon atom and exceptional donor character (Scheme 1).28,29 Scheme 1. Resonance Structure of Phosphorus Ylides

Li and co-workers reported on a synthesis of a titanoceneylide complex, which requires 2 equiv of the corresponding ylide. In this case, the second equivalent serves as a base to deprotonate the ylide in the first step (Scheme 2).30 In previous works, we investigated the reactivity of bis(FvR2Ti) and monofulvene (Cp*FvRMCl) complexes of group 4 transition metals. Due to the electronic properties of the fulvene moiety, a large variety of element−hydrogen or Received: November 12, 2018

A

DOI: 10.1021/acs.organomet.8b00831 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

remaining anionic CHylide group connects to the metal center.34,37,34 Although there is a second pentafulvene ligand to react with, only single reactions with the phosphorusylide are observed, regardless of the stoichiometry. Attempts to vary the substituents of the phosphorus ylide to increase the Brønsted acidic character also shows no significant effects. After purification, the complexes Ti2a−e can be isolated in good yields. Compounds Ti2a−e were characterized by NMR spectroscopy. Table 1 summarizes selected 1H, 13C, and 31P NMR data compared to a selection of the used free ylides.

Scheme 2. Synthesis of a Titanocene-Ylide Complex Using 2 equiv of Ylide

element−element bond activation reactions under mild conditions can be approached (Scheme 3).31−35 Scheme 3. Penta- and Benzofulvene Complexes of Group 4 Transition Metals Exhibiting a Polar M−C Bond (M = Ti, Zr, Hf)

Table 1. Selected NMR Parameters of Complexes Ti2a−e and the Ylides Y1, Y2, and Y5 (C6D6, rt, ppm) 1

H CHylide (2JPH)

Ti2a Ti2b Ti2c Ti 2d Ti2e Y1 Y2 Y539

We recently reported on the reaction of bis(η5:η1-pentafulvene)titanium complexes FvR2Ti with an allyl-substituted phosphorusylide without an additional base. In this case, a spontaneous double C−H bond activation, accompanied by C−C bond formation, resulting in a titanocene-stabilized hexapentaene is observed (Scheme 4).36

6.43 (12.4 Hz) 5.99 (16.9 Hz) 6.77 6.67 (12.4 Hz) 6.92 0.79 (7.3 Hz) −0.38 (6.0 Hz) 0.01

13

Cylide (1JPC)

119.9 (15.4 Hz) 127.0 (10.0 Hz) 126.6 (18.2 Hz) 123.4 (16.4 Hz) 151.0 (62.7 Hz) −4.24 (99.3 Hz) −17.6 (83.1 Hz) −1.4

31

P (1JPC)

13.0 25.5 10.9 12.1 56.6 20.6 31.9 67.2

(78 Hz) (46 Hz)

(84.1 Hz) (48.7 Hz)

Characteristic of all compounds are the 1H and 13C NMR shifts of the α-CHylide group connected to the metal center. Those are significantly shifted to lower fields, compared to the free ylides, and are in good comparison to known complexes.39−42 It is noticeable that the 1H NMR shift of the CHylide group correlates with the substituent of the phosphorus ylide. By increasing the electron donating character from cyclohexyl- to diethylamino-substituents, the signal is shifted to lower fields from δ = 5.99 to 6.92 ppm, indicating a higher Brønsted acidic character of the proton. Nevertheless, as mentioned above, a second C−H activation could not be observed. Single-crystal X-ray diffraction confirmed the molecular structure of Ti2b. Suitable crystals were obtained from a saturated n-hexane solution at 5 °C. Ti2b crystallizes as red-orange plates in the triclinic space group P1; the molecular structure is shown in Figure 1. The Ct−Ti distances (ca. 2.1 Å) are within the expected ranges of known complexes.31,43,31 The newly formed Ti−C31 bond with 2.0441(18) Å corresponds to a shortened single bond; the C31−P1 bond (1.7156(19) Å) is also shorter than comparable C−P single bonds.30,45,30 These values indicate a partial double bond character of the C−P as well as the Ti−C bond. Additionally, the sum of angles around C31 (∑ 360.01°) shows an sp2-configuration of the carbon atom, while the Ti1− C31−P1 angle (157.31(12)°) is significantly different from the expected 120°. On the basis of these data, an explicit assignment to one of the resonance structures A or B is not possible. Therefore, the bonding situation of Ti2b can better be described by the resonance structure C (Scheme 6).47 Due to the fact that only one fulvene ligand is involved in the previously mentioned reaction with ylides, the next step is to investigate the reaction toward monofulvene complexes Zr1a/b and Zr1a/b-benzo (Scheme 7). Reacting the pentafulvene (Zr1a, Zr1b) and benzofulvene complexes (Zr1a-benzo, Zr1b-benzo) with the ylides Y1 and Y2 under mild conditions, the compounds Zr2a−Zr2c can be isolated as yellow solids in moderate to good yields.

Scheme 4. Bond Activation Cascade Resulting in Titanocene-Hexapentaene Complexes

Employing this reactivity, double C−H bond activation of methylene substituted ylides using pentafulvene metal complexes is conceivable. Here we report on the reaction of pentafulvene titanium as well as benzofulvene zirconium complexes with different substituted phosphorus ylides.

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RESULTS AND DISCUSSION Reacting the bis(η5:η1-pentafulvene)titanium complexes Ti1a and Ti1b with the corresponding phosphorus ylides Y1−Y5 results in a spontaneous C−H activation of the methylene group under mild conditions (Scheme 5). On this occasion, the exocyclic carbon atom (Cexo) is protonated while the Scheme 5. Synthesis of Complexes Ti2a−e

B


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by the arenes anisotropy cone. In the solid-state structure of Zr2b-benzo, the CHylide proton is located directly above the six-membered ring (Figure 4). Therefore, this proton is effectively shielded and its resonance shows an unusual upfield shift.48 Additionally, single crystal X-ray diffraction confirmed the molecular structures of Zr2b, Zr2a-benzo, and Zr2b-benzo; in all cases, suitable crystals were obtained from a saturated nhexane solution. Zr2a-benzo crystallizes as yellow rods in the triclinic space group P1̅, while Zr2b-benzo crystallizes as yellow plates in the monoclinic space group P21/n. The molecular structures are shown in Figures 2−4.

Figure 1. Molecular structure of complex Ti2b. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H31 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−C31 2.0441(18), Ti1−Ct1 2.089, Ti1−Ct2 2.026, C1−C6 1.514(3), C16−C21 1.439(2), P1−C31 1.7156(19), Ct1−Ti1−Ct2 134.616, Ti1−C31−P1 157.31(12), (Ct1 = centroid of C1−C5, Ct2 = centroid of C16−C20).

Scheme 6. Different Resonance Structures of the Ti−C−P Unit

Figure 2. Molecular structure of complex Zr2b. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H31 are omitted for clarity. Selected bond lengths [Å] and angles [deg]: Zr1−C31 2.1380(29), Zr1−Cl1 2.4947(8), Zr1−Ct1 2.2623, Zr1−Ct2 2.2589, C31−P1 1.6854(30), C11−C16 1.4973(38), Ct1− Zr1−Ct2 132.47, C31−Zr1−Cl1 98.04(78), P1−C31−Zr1 141.1(1), (Ct1 = centroid of C1−C5, Ct2 = centroid of C11−C15).

Scheme 7. Synthesis of Complexes Zr2a and Zr2b and the Analogue Benzoannulated Complexes Zr2a-benzo and Zr2b-benzo

Compounds Zr2a−c were characterized by NMR spectroscopy (Zr2a-benzo is insoluble in common deuterated solvents); Table 2 summarizes selected 1H, 13C, and 31P NMR data. Similar to the complexes Ti2a−e, the characteristic NMR shifts of the CH exo31,36,31 and CHylide group can be observed.27,39−41 Compared to the other 1H NMR chemical shifts of the CHylide group, the signal for Zr2b-benzo is noticeably shifted to higher fields. This phenomenon is caused Table 2. Selected NMR Parameters of Complexes Zr2a−c and Zr2b-benzo (C6D6, rt, ppm) 1

H CHylide (2JPH)

Zr2a Zr2b Zr2c Zr2b-benzo

5.08 5.20 5.71 2.72

(11.3 (12.5 (17.2 (22.1

Hz) Hz) Hz) Hz)

13

C CHylide (1JPC)

104.5 105.7 111.1 103.9

(34.5 (33.1 (23.7 (40.2

Hz) Hz) Hz) Hz)

Figure 3. Molecular structure of complex Zr2a-benzo. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H30 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Zr1−C30 2.1215(17), Zr1−Cl1 2.5313(4), Zr1−Ct1 2.285, Zr1−Ct2 2.311, C11−C20 1.511(2), P1−C30 1.7147(17), Ct1−Zr1−Ct2 134.611, Cl1−Zr1−C30 98.84(5), Zr1−C30−P1 148.040(10), (Ct1 = centroid of C1−C5, Ct2 = centroid of C11− C14, C19).

31

P (1JPC)

16.6 16.5 26.7 5.92

(81 Hz) (81 Hz) (46.4 Hz) (81 Hz) C


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Figure 5. 1H NMR (500 MHz, benzene-d6, rt) spectra of Ti4a. # indicates a second species Ti4b.

Figure 4. Molecular structure of complex Zr2b-benzo. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H35 and solvent molecules are omitted for clarity. Selected bond lengths (Å) and angles (deg): Zr1−C35 2.130(5), Zr1−Cl1 2.4867(12), Zr1−Ct1 2.239, Zr1−Ct2 2.356, C11−C20 1.511(6), P1−C35 1.695(5), Ct1−Zr1−Ct2 129.304, Cl1−Zr1−C35 99.18(12), Zr1−C35−P1 156.4(3), (Ct1 = centroid of C1−C5, Ct2 = centroid of C11−C14, C19).

This mixture turns out to be a thermodynamic equilibrium. By increasing the temperature to 60 °C, the equilibrium can be moved completety in favor of the second species Ti4b, which can be identified as a “tuck-in” complex (Scheme 9). Scheme 9. Reversible Formation of Ti4b at 60 °C with the Release of the Ylide Y1

In all three complexes, the metal center is in a tetrahedral distorted coordination environment, owing to the Ct1−Zr1− Ct2 (129.3−134.6°) and Cl1−Zr1−C30/C31/C35 angles (99.2−98.8°).49−51 The Ct−Zr distances as well as the Zr− Cl distances are within the expected.44 The newly formed Zr1−C30/C31/C35 bonds with 2.1215(17) Å, 2.1380(29) Å, and 2.130(5) Å are in accordance with shortened single bonds;28,44 the P1−C30/C31/C35 distances of 1.7147(17) Å, 1.6854(30) Å, and 1.695(5) Å are shortened as well.30,46 Considering the sums of angles around C30 (Zr2a-benzo, ∑∠ 357.9°), C31 (Zr2b, ∑∠ 359.1°), and C35 (Zr2b-benzo, ∑∠ 358.3°), these are characteristic for an sp2-configurated carbon atom, while the Zr1−C30/C31/C35−P1 angles (156.4− 148.0°) differ from the expected 120°. These parameters are similar to those in Ti2b and indicate again the aforementioned resonance structure C (Scheme 6). Furthermore, the C11− C20, respectively, C11−C16 bond lengths of approximately 1.50 Å correspond to a typical single bond (1.51 Å52), due to the protonation of the Cexo atom. Reaction of Ti3 with Y1. If titanium is used as central atom instead of zirconium, a different reaction behavior can be observed. Reacting the mono(η5:η1-pentafulvene)titanium complex Ti3 with 1 equiv of the phenylsubstituted ylide Y1 in n-hexane at room temperature, the desired complex Ti4a can be obtained (Scheme 8). Though, subsequent NMR spectroscopic investigations show the fomation of a second species Ti4b next to Ti4a in a 1:1 ratio (Figure 5).

The generation of such complexes is known and described in the literature, but often requires higher temperatures, longer reaction times, or complex ligands.53−58 In contrast, the generation of Ti4b is facilitated by an intramolecular hydrogen transfer, in which the ylide serves as a transfer agent. Due to the C−H activation of a methyl group of the Cp*-ligand, the ylide is released and a methylene group is generated and coordinates to the metal center. Using temperature dependent 1 H NMR experiments, it could be demonstrated that the C−H activation is a reversible process (Figure 6).

Scheme 8. Synthesis of Ti4a Next to a Second Species Ti4b

Figure 6. Temperature-dependent 1H NMR (500 MHz, toluene-d8) spectra of Ti4a (red) and Ti4b (blue). D


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to a typical carbon−phosphorus single bond.30,45,30 The sum of angles around C26 (∑∠ 360.5°) indicates again an sp2configuration of the carbon atom and the Ti1−C26−P1 angle with 141.53(17)° differs again from the expected 120°. Catalytic Synthesis and Reactivity of Ti4b. In order to show that higher temperatures favor the thermodynamic equilibrium toward compound Ti4b, the reaction of the just mentioned complex with acetone was investigated. Reactions of pentafulvene complexes with different substrates are wellknown in our workgroup.15,34,37,38 The free ylide should react in a Wittig-type reaction, resulting in the formation of triphenylphosphine and iso-butene. For the reaction, Ti3 was suspended in n-hexane and 1 equiv of the ylide Y1 was added. The resulting mixture was stored at 60 °C for 16 h. Afterward, an excess of acetone was added and the reaction mixture was once again stored at 60 °C. Employing the reactivity of the newly formed Ti−C bond in Ti4b, the C−O double bond of the acetone undergoes an insertion reaction. The liberated ylide reacts in a Wittig-type reaction, resulting in the formation of iso-butene and triphenylphosphine oxide (Scheme 10). Acetone proved to

Both compounds Ti4a and Ti4b can be characterized by NMR spectroscopy. In accordance to the previous complexes, typical signals for the CHexo groups can be identified (δ = 3.19 and 3.27 ppm). While the signals of the ring protons of the Cpligands cannot be differentiated, the Cp*-ligands show a characteristic difference. Caused by the free rotation in Ti4a, all five methyl groups are magnetically equivalent, resulting in a single signal at δ = 2.04 ppm. Contrary to this, the coordinating methylene group in Ti4b prevents such a rotation, generating four magnetically inequivalent methyl groups (δ = 0.93, 1.29, 1.74, 2.12 ppm). Additionally, the proton of the α-CHylide group shows a chemical shift of δ = 9.01 ppm, which is in accordance with known complexes.30,59 Furthermore, the signals of the protons of the methylene group (δ = 2.13 and 2.65 ppm) show higher multiplicity, caused by the diastereotopic environment in Ti4b, though one of the signals is superposed by the signal of a methyl group. Contrary to expectations, no signals of the methylene group of the free ylide can be detected, which are expected in high fields (δ = 0.79 ppm).30 In 31P NMR, also only one signal for the coordinated ylide can be detected at room temperature. This indicates that the hydrogen transfer is a very fast process and therefore not visible at the chosen temperature. By reducing the temperature, this process can be slowed down and a signal for the free ylide is observed at approximately 20 ppm.60 Single crystal X-ray diffraction confirmed the structure of Ti4a. Suitable crystals were obtained from a saturated n-hexane solution at 5 °C. The compound crystallizes as red rods in the monoclinic space group P21/n; the molecular structure is shown in Figure 7.

Scheme 10. Synthesis of Ti5

be suitable for this reaction, as the resulting gaseous iso-butene could be simply removed in vacuo. After an additional 16 h, depositing triphenylphosphine oxide was removed from the reaction mixture by decanting and identified by single crystal X-ray diffraction.64 Additionally, compound Ti5 was isolated as a yellow solid in good yield (63%) and characterized by NMR spectroscopy and single crystal X-ray diffraction (vide infra). As the ylide Y1 merely serves as a reagent for the H-transfer, we investigated the reaction with catalytic amounts (3.0 mol %) of the ylide. After 16 h at 60 °C, the tuck-in complex Ti4b could be isolated in quantitative yield (Scheme 11).

Figure 7. Molecular structure of complex Ti4a. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H26 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−C26 2.032(3), Ti1−Cl1 2.4303(9), Ti1−Ct1 2.142, Ti1−Ct2 2.1120, C11−C16 1.518(4), P1−C26 1.701(3), Ct1−Ti1−Ct2 131.384, Cl1−Ti1−C26 95.42(9), Ti1−C26−P1 141.53(17), (Ct1 = centroid of C1−C5, Ct2 = centroid of C11−C15).

Scheme 11. Synthesis of Ti4b Using Catalytic Amounts of Y1

Compound Ti4a shows similar crystallographic features like the aforementioned complexes. The metal center is again in a tetrahedral distorted coordination environment, owing to the Ct1−Ti1−Ct2 angle of 131.4° and the Cl1−Ti1−C26 angle of 95.42(9)°.61−63 The Ct−Ti distances of 2.1 Å are comparable to those in Ti2b and are within the expected range.31,43,31 The newly formed Ti−C26 bond with a length of 2.032(3) Å can also be described as a shortened single bond. The C26−P1 bond length of 1.701(3) Å is shortened as well in comparison E


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Organometallics Using the catalytic generation of a methylene group at the Cp*-ligand, we found an elegant access to a sterically less demanding pentafulvene ligand. Such small ligands are favored in the synthesis of ansa-metallocenes,65−67 which are used in stereoselective polymerization reactions.68,69 To further investigate the reactivity of the new titanium−carbon bond, Ti4b was generated in situ and reacted with ferrocenealdehyde (Scheme 12). The reaction mixture was stored at 60 °C for 16 Scheme 12. Synthesis of Ti6

Figure 9. Molecular structure of complex Ti6. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H11 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−O1 1.8884(10), Ti1−Cl1 2.3888(4), Ti1−Ct1 2.0879, Ti1−Ct2 2.0952, C22A−C27A 1.512(3), C1−C10 1.4943(19), O1−C11 1.4161(15), C10−C11 1.5416(18), C11−C12 1.5020(19), Ct1− Ti1−Ct2 136.795, Cl1−Ti1−O1 95.44(3), O1−C11−C10 108.46(10), (Ct1 = centroid of C1−C5, Ct2 = centroid of C22A− C27A).

h, after which red crystals separated from the solution. Those were characterized by NMR spectroscopy and singly crystal Xray diffraction and clearly identified as complex Ti6. Complex Ti5 crystallizes as yellow blocks with the monoclinic space group P21/c; Ti6 crystallizes as red blocks with the monoclinic space group P21/n. The molecular structures are shown in Figures 8 and 9. Both metal centers

Scheme 13. Synthesis of Ti7

the nearby double bond. The 13C NMR chemical shift of the CN group is also moved to lower field (δ = 196 ppm in Ti7 vs 124 ppm in Ph3CCN72), caused by the repeal of the triple bond, and is in good comparison to known complexes.73−75 Using 1H, 15N NMR correlation experiments, a signal for the coordinating nitrogen atom with a chemical shift of δ = 123 ppm can be observed, which is within the expected range.35 Heating a solution of Ti7 in n-hexane, an immediate color change from turquoise to red is observed. Subsequent NMR spectroscopic experiments show the quantitative formation of the titanium-enamine complex Ti7a (Scheme 14).

Figure 8. Molecular structure of complex Ti5. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−O1 1.8469(5), Ti1−Cl1 2.3894(2), Ti1−Ct1 2.0738, Ti1−Ct2 2.1017, C14−C19 1.5080(9), C1−C10 1.4958(10), O1−C11 1.4294(8), C10−C11 1.5679(11), C11−C12 1.5280(11), C11−C13 1.5267(11), Ct1−Ti1−Ct2 132.636, Cl1−Ti1−O1 96.73(2), O1−C11−C10 108.90(6), (Ct1 = centroid of C1−C5, Ct2 = centroid of C14−C18).

Scheme 14. Rearrangement from Ti7 to Ti7a via 1,3-H-Shift

show a tetrahedral distorted geometry, owing to the Ct1−Ti− Ct2 (132.6° and 136.8°) and Cl−Ti−O angles (96.73(2)° and 95.4(3)°). The Ti−O distances are similar to 1.8469(5) Å and 1.8884(10) Å and are within range of a single bond37,44,70 as well as the new C10−C11 bonds with 1.5679(11) Å and 1.5416(18) Å, respectively.52,71 Reactivity of Ti4b toward Triple Bond Substrates. In comparison to the reaction with carbonyls, the reactivity toward triple bond substrates was explored next. Reacting Ti4b with the steric high demanding tritylnitrile in n-hexane at room temperature (Scheme 13), the former red solution turns into a turquoise suspension. After purification, the titanium-imine complex Ti7 was isolated as a turquoise solid. Similar to the aforementioned complexes Ti5 and Ti6, an insertion reaction takes place which leads to the formation of a new Ti−N bond. In 1H NMR spectra, the characteristic signals for the methyl and methylene groups of the Cp*-ligand are observed. The latter is shifted to lower field compared to Ti5 and Ti6 due to

The same reaction takes place using toluene or cyclohexane, even at lower temperatures. This complex is the result of a 1,3H-shift between the methylene group of the Cp*-ligand and the nitrogen atom of the CN group, which has also been observed in a previous work.75 The signal of the new CH group is significantly shifted to lower fields (δ = 5.37 ppm), while 1H, 15N NMR correlation experiments assign the proton signal of the NH function to a chemical shift of δ = 8.79 ppm. Additionally, the 13C NMR chemical shift of the CN group changes as well, being shifted about 22 ppm to higher fields (δ = 174 ppm in Ti7a vs 196 ppm in Ti7) due to the increased F


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1,3-H-shift occurs already at room temperature; the formation of a titanium-imine species similar to Ti7 could not be observed. In 1H and 13C NMR spectra, chemical shifts similar to Ti7a were observed for the CH−, NH−, and CN− groups as well as for the coordinating nitrogen atom in 1H, 15N NMR correlation experiments (summarized in Table 3).

electron density at the carbon atom. Furthermore, the signal of the nitrogen atom is significantly shifted to lower fields (δ = 290 ppm in Ti7a vs 123 ppm in Ti7), owing to the change in substitution. Single crystal X-ray diffraction confirmed the molecular structure of Ti7a (Figure 10). The complex crystallizes as orange plates with the monoclinic space group P21/c.

Table 3. Selected NMR Parameters of Complexes Ti7−Ti9 (C6D6, rt, ppm) 1

H CH

Ti7 Ti7a Ti8 Ti9

5.37 5.37 5.36

1

H NH 8.79 9.25 9.00

15

N NH

123.0 289.9 277.6 267.9

13

C CN

196.0 174.1 167.2 167.6

Single crystal X-ray diffraction confirmed the molecular structures of Ti8 and Ti9 displayed in Figures 11 and 12. Both compounds crystallize as red blocks with the triclinic space group P1. Table 4 summarizes the structural parameters together with those of complex Ti7.

Figure 10. Molecular structure of complex Ti7a. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H10 and H1 and solvent molecules are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−N1 1.9676(12), Ti1−Cl1 2.3776(5), Ti1−Ct1 2.0689, Ti1−Ct2 2.0756, C31−C36 1.515(2), C1−C10 1.471(2), N1−C11 1.3902(18), C10−C11 1.343(2), C11− C12 1.536(2), Ct1−Ti1−Ct2 137.031, Cl1−Ti1−N1 96.58(4), N1− C11−C10 115.65(13), (Ct1 = centroid of C1−C5, Ct2 = centroid of C31−C35).

The metal center is again in a tetrahedral distorted coordination environment, defined by the Ct1−Ti−Ct (137.0°) and Cl−Ti−N (96.58(4)°) angle. The Ti−N distance with 1.9676(12) Å is within the expected range of a single bond,43,76−79 while the N1−C11 bond length of 1.3902(18) Å indicates a shortened single bond.52,71,80 Additionally, the sums of angle arounds N1 (∑∠ 360.0°) indicate an sp2-configuration as well as around C11 (∑∠ 359.9°). Considering the C10−C11 bond, its length of 1.343(2) Å can be described as a double bond.52,71 As suspected earlier, based on the 13C NMR chemical shift, these parameters indicate a delocalized double bond system across the C10−C11−N1 unit. To gather more information about the 1,3-H-shift, the reaction of Ti4b was repeated with two sterically less demanding substrates. Contrary to the synthesis of Ti7, in both cases, the direct formation of a red suspension was observed (Scheme 15). After purification, the titaniumenamine complexes Ti8 and Ti9 were isolated as red solids and characterized by NMR spectroscopy. It was found that the

Figure 11. Molecular structure of complex Ti8. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H10 and H1 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−N1 1.9856(18), Ti1−Cl1 2.4353(7), Ti1−Ct1 2.0705, Ti1−Ct2 2.0694, C22−C27 1.511(3), C1−C10 1.478(3), N1−C11 1.375(3), C10−C11 1.377(3), C11−C12 1.469(3), Ct1−Ti1−Ct2 134.61, Cl1−Ti1−N1 95.20(6), N1−C11−C10 116.24(18), (Ct1 = centroid of C1−C5, Ct2 = centroid of C31−C35).

The size of the used substrate seems to play an important role. Only the reaction with the sterically high demanding tritylnitrile oppresses a 1,3-H-shift at room temperature; by increasing the temperature, this shift can be purposefully induced. Reducing the size of the substrate, the 1,3-H-shift takes place even at room temperature. Regarding these results, Ti4b was reacted with acetonitrile at room temperature. Similar to Ti8 and Ti9, the formation of a red suspension is observed. While NMR spectroscopic investigations reveal the formation of a complex mixture of compounds, single crystals suitable for X-ray diffraction could be obtained from a solution of the reaction mixture in n-hexane at 5 °C. Ti10 crystallizes as red plates with the triclinic space group P1; the molecular structure is shown in Figure 13. In contrast to the previous complexes, Ti10 is set up as a dimer with a newly formed C−C bond (Scheme 16).

Scheme 15. Synthesis of Ti8 and Ti9

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Organometallics Scheme 16. Structure of Ti10a

a

Considering the Ti−N bond lengths, the Ti1−N1 bond with 1.9946 Å is longer than the Ti2−N2 bond 1.9243 Å. Additionally the sums of angles around N2 (∑∠ 358.9°) indicate a sp2-configuration, and the reduced distance to the metal center refers to partial double bond character.75,81 This N(pπ)→Ti(dπ) interaction is promoted by the Ti2−Cl2 distance (2.4432(5) Å), which is noticeably prolonged compared to the Ti1−Cl1 distance (2.3699(6) Å), owing to a decrease of the Cl(d π )→Ti(d π ) bond interactions. Furthermore, the N1−C11 bond (1.391(2) Å) is significantly shortened compared to the N2−C38 bond (1.469(2) Å), which reflects the configuration of the carbon atoms. While C11 shows sp2-configuration (∑∠ 356.0°), C38 experiences a tetrahedral geometry and is therefore sp3-configurated. The formation of Ti10 could be explained by 1,3-H-shifts, involving the CH2-fulvene unit as well as one CH3− nitrile group.75 Comparable reactions involving C−C bond formation of imines are known for samarocene or titanocene complexes (Scheme 17).82,83

Figure 12. Molecular structure of complex Ti9. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms except for H10 and H1 are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−N1 1.9843(10), Ti1−Cl1 2.4017(4), Ti1−Ct1 2.0676, Ti1−Ct2 2.0829, C18−C23 1.5186(15), C1−C10 1.4725(15), N1− C11 1.3834(15), C10−C11 1.3550(16), C11−C12 1.4806(15), Ct1−Ti1−Ct2 135.88, Cl1−Ti1−N1 97.81(3), N1−C11−C10 116.23(10), (Ct1 = centroid of C1−C5, Ct2 = centroid of C18− C22).

Table 4. Structural Parameters of Ti7a, Ti8, and Ti9 (Å, deg) Ti7a Ti8 Ti9

Ti−N

N−C11

∑∠ N

C10−C11

∑∠ C11

1.9676(12) 1.9856(18) 1.9843(10)

1.3902(18) 1.375(3) 1.3834(15)

360.0 359.9 356.0

1.343(2) 1.377(3) 1.355(16)

359.9 356.0 356.0

Newly formed C−C bond in red.

Scheme 17. Metallocene-Mediated C−C Bond Formation of Imines

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CONCLUSION Overall, this work showed the diverse reactivity of η5:η1pentafulvene metal complexes with ylides under mild conditions. Using the pentafulvene ligands as intramolecular bases, an efficient access to group 4 organometallic ylides Ti2a−e, Zr2a−c, and Zr2a/b-benzo is presented. Known syntheses of such compounds usually require the presence of an additional base. Furthermore, the ylide proves to be a catalytic and reversible hydrogen transfer reagent in the generation of the smallest substituted pentafulvene ligand and formation of the tuck-in complex Ti4b. On the basis of this, the reactivity of Ti4b toward different substrates has been studied. Using different carbonyl and nitrile compounds, an insertion into the new formed Ti−C bond and formation of complexes Ti5−10 is observed. When using sterically demanding nitriles, the titanium-imine complex Ti7a can be isolated, which undergoes a subsequent 1,3-H-shift to form the titanium-enamine species Ti7a upon heating. Reducing the steric demand, the titanium-enamine complexes Ti8 and Ti9 are directly formed. Using acetonitrile even leads to the generation of the dimeric titanium-imine-enamine complex Ti10 including a C−C bond formation.

Figure 13. Molecular structure of complex Ti10. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms and solvent molecules are omitted for clarity. Selected bond lengths (Å) and angles (deg): Ti1−N1 1.9946(16), Ti2−N2 1.9243(15), Ti1−Cl1 2.3699(6), Ti2−Cl2 2.4332(5), Ti1−Ct1 2.0861, Ti1−Ct2 2.1051, Ti2−Ct3 2.0811, Ti2−Ct4 2.0887, C13−C18 1.516(3), C40−C45 1.512(2), C1−C10 1.469(2), C28−C37 1.494(2), N1−C11 1.391(2), N2−C38 1.469(2), C10−C11 1.346(2), C37−C38 1.552(2), C11−C12 1.505(2), C38−C12 1.556(3), Ct1−Ti1−Ct2 134.593, Ct3−Ti2−Ct4 133.694, Cl1−Ti1−N1 101.53(5), Cl2− Ti2−N2 95.20(5), N1−C11−C10 116.01(16), N2−C38−C37 106.69(14), (Ct1 = centroid of C1−C5, Ct2 = centroid of C13− C17, Ct3 = centroid of C28−C32, Ct4 = centroid of C40−C44).

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decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.301 g (0.41 mmol, 72%) of Ti2a as a red solid, mp 115 °C. Single crystals suitable for X-ray diffraction were obtained from a saturated solution of Ti2b in n-hexane at 5 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.07−2.61 (Ad + Cy), 3.12 (s, 1 H, CHexo), 4.36 (m, 1 H, C5H4), 5.21 (m, 1 H, C5H4), 5.32 (m, 1 H, C5H4), 5.43 (m, 1 H, C5H4), 5.66 (m, 1 H, C5H4), 5.99 (d, 2JPH = 16.9 Hz, 1 H, CHylide), 6.08 (m, 1 H, C5H4), 6.38 (m, 1 H, C5H4), 6.45 (m, 1 H, C5H4) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 26.8 (CH2), 27.7 (CH2), 27.8 (CH2), 27.9 (CH2), 28.1 (CH2), 28.3 (CH2), 28.5 (CH), 28.7 (CH), 29.5 (CH), 30.0 (CH), 32.4 (CH2), 32.6 (CH), 33.9 (CH), 35.7 (CH), 36.1 (CH), 36.3 (CH), 37.6 (CH2), 38.6 (CH2), 39.2 (CH2), 39.4 (CH), 39.4 (CH2), 40.1 (CH2), 44.0 (CH2), 45.1 (CHexo), 45.1 (CH2), 98.7 (C5H4), 103.0 (C5H4), 106.7 (C5H4), 107.2 (C5H4), 107.8 (C5H4), 107.8 (C5H4), 108.2 (C5H4), 108.4 (C5H4), 111.4 (Cexo Fv), 121.6 (CipsoFv or CipsoCp), 121.7 (CipsoFv or CipsoCp), 127.0 (d, 10.0 Hz, CHylide) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 25.5 (1JPC = 46 Hz) ppm. IR (ATR, 16 scans): ṽ = 2924, 2899, 2849, 1632, 1445, 1353, 1259, 1174, 1128, 1098, 1060, 1045, 1000, 942, 886, 847, 829, 801, 785, 772, 745, 725, 687, 581, 562 cm−1. Synthesis of Ti2c. Ti1a (0.250 g, 0.56 mmol) and Y3 (0.206 g, 0.56 mmol) were placed in a Schlenk tube and a small amount of nhexane was added. The former blue suspension turns ochre and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.312 g (0.39 mmol, 68%) of Ti2c as an ochre solid, mp 74 °C (dec.). 1H NMR (500 MHz, C6D6, 305 K): δ = 1.52−2.45 (Ad), 3.17 (s, 1 H, CHexo), 3.23 (s, 9 H, OCH3), 4.33 (m, 1 H, C5H4), 5.18 (m, 1 H, C5H4), 5.20 (m, 1 H, C5H4), 5.36 (m, 1 H, C5H4), 5.38 (m, 1 H, C5H4), 6.07 (m, 1 H, C5H4), 6.18 (m, 1 H, C5H4), 6.50 (m, 1 H, C5H4), 6.77 (m, 1 H, CHylide), 6.77 (m, 6 H, Anisol3P), 7.64 (m, 6 H, Anisol3P) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 28.5 (Ad CH), 28.6 (Ad CH), 29.5 (Ad CH), 30.0 (Ad CH), 32.3 (Ad CH), 32.5 (2 × Ad CH2), 33.4 (Ad CH), 36.1 (Ad CH), 37.5 (Ad CH2), 38.5 (Ad CH2), 39.1 (Ad CH2), 39.2 (Ad CH2), 39.4 (Ad CH2), 39.5 (Ad CH2), 39.6 (Ad CH), 44.2 (Ad CH2), 45.1 (Ad CH2), 45.1 (CHexo), 54.8 (OCH3), 100.1 (C5H4), 103.3 (C5H4), 107.1 (C5H4), 107.3 (C5H4), 107.4 (C5H4), 108.2 (C5H4), 110.0 (C5H4), 110.4 (C5H4), 113.1 (CexoFv), 113.8 (d, J = 11.6 Hz, Anisol3P), 122.9 (Cipso Fv), 123.4 (Cipso Cp), 126.6 (d, 1JPC = 18.2 Hz, CHylide), 126.7 (d, 1JPC = 84 Hz, Anisol3P), 135.1 (d, J = 10.3 Hz, Anisol3P), 161.9 (d, J = 2.4 Hz, Anisol3P) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 10.9 ppm. IR (ATR, 16 scans): ṽ = 2961, 2899, 2847, 1634, 1594, 1568, 1504, 1448, 1411, 1353, 1295, 1260, 1181, 1114, 1097, 1059, 1023, 932, 984, 875, 797, 721, 690, 675, 627, 579 cm−1. Synthesis of Ti2d. Ti1a (0.250 g, 0.56 mmol) and Y4 (0.358 g, 1.12 mmol) were placed in a Schlenk tube and a small amount of nhexane was added. The former blue suspension turns ochre and was stirred at room temperature overnight. The reaction mixture was filtrated to remove excessive ylide; subsequent drying in vacuo afforded 0.366 g (0.48 mmol, 85%) of Ti2d as an ochre solid, mp 96 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.53−2.46 (28 H, Ad), 2.02 (s, 9 H, CH3), 3.19 (s, 1 H, CHexo), 4.30 (m, 1 H, C5H4), 5.14 (m, 1 H, C5H4), 5.18 (m, 1 H, C5H4), 5.35 (m, 1 H, C5H4), 5.37 (m, 1 H, C5H4), 6.05 (m, 1 H, C5H4), 6.08 (m, 1 H, C5H4), 6.48 (m, 1 H, C5H4), 6.67 (d, 2JPH = 12.4 Hz, 1 H, CHylide), 6.96−6.98 (m, 6 H, pTol3P), 7.61−7.65 (m, 6 H, pTol3P) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 21.3 (CH3), 28.5 (Ad CH), 28.6 (Ad CH), 29.5 (Ad CH), 30.0 (Ad CH), 32.4 (Ad CH), 32.5 (2 × Ad CH2), 33.5 (Ad CH), 36.1 (Ad CH), 37.5 (Ad CH2), 38.5 (Ad CH2), 39.1 (Ad CH2), 39.2 (Ad CH2), 39.4 (Ad CH2), 39.4 (Ad CH), 39.5 (Ad CH2), 44.2 (Ad CH2), 45.1 (Ad CH2), 45.1 (CHexo), 100.1 (C5H4), 103.5 (C5H4), 107.4 (C5H4), 107.4 (C5H4), 107.5 (C5H4), 108.2 (C5H4), 110.3 (2 × C5H4), 113.4 (Cexo Fv), 122.9 (Cipso Fv), 123.4 (d, 1JPC = 16.4 Hz, CHylide), 123.7 (Cipso Cp), 129.0 (d, J = 11.1 Hz, pTol3P), 132.3 (d, 1JPC = 80 Hz, pTol3P), 133.5 (d, J = 9.3 Hz, pTol3P), 140.9 (d, J = 2.7 Hz, pTol3P) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 12.1 ppm. IR (ATR, 16 scans): ṽ = 2960, 2899,

EXPERIMENTAL SECTION

General Considerations. All reactions were carried out under an inert atmosphere of argon or nitrogen with rigorous exclusion of oxygen and moisture using standard gloveboxes or Schlenk techniques. The glass equipment was stored in an oven at 120 °C and evacuated prior to use. Solvents were dried according to standard procedures over Na/K alloy with benzophenone as indicator and distilled under a nitrogen atmosphere. The bis(η5:η1-pentafulvene)titanium complexes Ti1a/b as well as the mono(η5:η1-pentafulvene)metal complexes Ti3, Zr1a/a-benzo, and Zr1b/b-benzo were synthesized according to literature procedures.48,84−86 The ylides Y1−Y5 were prepared using the corresponding phosphonium salts according to standard procedures.39,87,39 The phosphonium salts either are commercially available or can be prepared by a Grignard reaction of an aryl- or alkyl halide and subsequent methylation using methyl iodide.88 Further exact details of the individually synthesized products, crystallographic data, and NMR spectra are given in the Supporting Information. NMR spectra were recorded on Bruker Avance 300, Bruker Avance 500, and Bruker Avance III 500 spectrometers. 1H NMR spectra were referenced to the residual solvent resonance as internal standard (benzene-d6 (C6D6), δ(1H) C6D5H 7.16 ppm) and 13C NMR spectra by using the central line of the solvent signal (benzene-d6 (C6D6), δ(13C{1H}) C6D6 128.06 ppm). Given chemical shifts of 15N resulted from 1H, 15N-HMBC or -HMQC NMR experiments with nitromethane as external standard (δ = 378.9 vs NH3). Infrared spectra were performed on a Bruker Tensor 27 spectrometer with a MKII Reflection Golden Gate Single Diamond ATR system. Elemental analyses were carried out on a EuroEA 3000 Elemental Analyzer. The carbon value in the elemental analysis is often lowered by carbide formation. The hydrogen value is found in some cases to be higher due to residual traces of solvents. Although in some cases satisfactory elemental analysis could not be obtained, the data are included to demonstrate the best results to date. The combustion analysis of group 4 organometallics is known to be difficult.89,90 Melting points were determined using a “Mel-Temp” apparatus by Laboratory Devices, Cambridge, U.K. Further exact details of the individually synthesized products, crystallographic data, and NMR spectra are given in the Supporting Information. Synthesis of Ti2a. Ti1a (0.500 g, 1.13 mmol) and Y1 (0.311 g, 1.13 mmol) were placed in a Schlenk tube and 10 mL of n-hexane was added. The former blue suspension turns red and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.711 g (0.99 mmol, 88%) of Ti2a as a red-brown solid, mp 140 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.49−2.89 (Ad), 3.11 (s, 1 H, CHexo), 4.27 (m, 1 H, C5H4), 5.10 (m, 1 H, C5H4), 5.14 (m, 1 H, C5H4), 5.23 (m, 1 H, C5H4), 5.31 (m, 1 H, C5H4), 5.98 (m, 1 H, C5H4), 6.03 (m, 1 H, C5H4), 6.43 (d, 2JPH = 12.4 Hz, 1 H, CHylide), 6.44 (m, 1 H, C5H4), 7.07−7.09 (m, 9 H, PPh3), 7.60−7.64 (m, 6 H, PPh3) ppm. 13 C NMR (125 MHz, C6D6, 305 K): δ = 28.5 (Ad CH), 28.6 (Ad CH), 29.4 (Ad CH), 29.9 (Ad CH), 32.4 (Ad CH), 32.5 (2 × Ad CH2), 33.4 (Ad CH), 36.1 (Ad CH), 37.5 (Ad CH2), 38.5 (Ad CH2), 39.1 (Ad CH2), 39.2 (Ad CH2), 39.3 (Ad CH), 39.4 (Ad CH2), 39.4 (Ad CH2), 44.1 (Ad CH2), 45.1 (Ad CH2), 45.2 (CHexo), 100.4 (C5H4), 103.6 (C5H4), 107.5 (C5H4), 107.8 (C5H4), 107.9 (C5H4), 108.4 (C5H4), 110.4 (C5H4), 110.6 (C5H4), 114.0 (Cexo Fv), 119.9 (d, 1 JPC = 15.4 Hz, CHylide), 122.9 (Cipso Fv), 123.9 (Cipso Cp), 128.2 (d, J = 10.7 Hz, PPh3), 130.7 (d, J = 2.8 Hz, PPh3), 133.4 (d, J = 8.9 Hz, PPh3), 135.6 (d, 1JPC = 78 Hz, PPh3) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 13.0 (1JPC = 78 Hz) ppm. IR (ATR, 16 scans): ṽ = 3055, 2899, 2847, 2668, 1634, 1589, 1482, 1467, 1448, 1437, 1353, 1261, 1196, 1117, 1099, 1060, 1027, 998, 930, 874, 705, 775, 742, 720, 692, 627, 597, 580 cm−1. Synthesis of Ti2b. Ti1a (0.250 g, 0.56 mmol) and Y2 (0.166 g, 0.56 mmol) were placed in a Schlenk tube and a small amount of nhexane was added. The former blue suspension turns red and was stirred at room temperature overnight. The mother liquor was I


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Organometallics

quantitative yield, mp 125 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 0.92 (s, 3 H, C5Me4), 1.28 (s, 3 H, C5Me4), 1.61−2.46 (14 H, Ad), 1.74 (s, 3 H, C5Me4), 2.12 (s, 4 H, C5Me4, CH2), 2.65 (d, 2J = 3.4 Hz, 1 H, CH2), 3.19 (s, 1 H, CHexo), 5.08 (m, 1 H, C5H4), 5.14 (m, 1 H, C5H4), 5.94 (m, 1 H, C5H4), 6.47 (m, 1 H, C5H4) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 10.9 (C5Me4), 11.8 (C5Me4), 13.5 (C5Me4), 14.5 (C5Me4), 28.4 (Ad CH), 28.6 (Ad CH), 32.5 (Ad CH), 32.8 (Ad CH2), 32.9 (Ad CH2), 33.1 (Ad CH), 38.4 (Ad CH2), 39.0 (Ad CH2), 39.1 (Ad CH2), 45.3 (CHexo), 75.4 (CH2), 106.8 (C5H4), 109.7 (C5H4), 111.4 (C5H4), 118.7 (C5H4), 121.2 (C5Me4), 126.5 (C5Me4), 128.6 (C5Me4), 130.2 (C5Me4), 133.7 (CipsoCp), 135.6 (C5Me4) ppm. IR (ATR, 16 scans): ṽ = 2963, 2902, 2848, 1468, 1449, 1377, 1260, 1089, 1061, 1017, 874, 795, 745, 693, 619, 603, 580 cm−1. Synthesis of Ti5. Ti3 (0.500 g, 1.2 mmol) and Y1 (0.331 g, 1.2 mmol) were placed in a Schlenk tube and 10 mL of n-hexane was added. The resulting red suspension was stirred for 8 h at room temperature and subsequently an excess acetone was added. After storing at 60 °C overnight, the resulting yellow suspension was filtrated to remove triphenylphosphine oxide (0.196 g, 0.7 mmol, 59%). The solvent was evaporated and the resulting yellow solid dried in vacuo, yielding 0.361 g (0.76 mmol, 63%) of Ti5, mp 156 °C. Single crystals suitable for X-ray diffraction could be obtained from a saturated solution of Ti5 in n-hexane at 5 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.23 (s, 3 H, OC(CH3)2), 1.48 (s, 3 H, OC(CH3)2), 1.50−2.41 (14 H, Ad), 1.53 (s, 3 H, C5Me4), 1.69 (s, 3 H, C5Me4), 1.72 (s, 3 H, C5Me4), 2.33 (d, 3JCH = 13.2 Hz, 1 H, CH2), 2.36 (s, 3 H, C5Me4), 2.70 (d, 3JCH = 13.2 Hz, 1 H, CH2), 3.21 (s, 1 H, CHexo), 5.53 (m, 1 H, C5H4), 5.59 (m, 1 H, C5H4), 5.84 (m, 1 H, C5H4), 6.49 (m, 1 H, C5H4) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 11.5 (C5Me4), 12.8 (C5Me4), 13.1 (C5Me4), 14.2 (C5Me4), 28.5 (2 × Ad CH), 32.0 (OC(CH3)2), 32.0 (Ad CH), 32.6 (Ad CH), 33.0 (Ad CH2), 33.0 (Ad CH2), 34.5 (OC(CH3)2), 38.4 (CH2), 38.7 (CH2), 39.1 (CH2), 39.3 (CH2), 44.1 (CHexo), 108.6 (OC(CH3)2), 109.7 (C5H4), 111.9 (C5H4), 114.9 (C5H4), 115.6 (C5Me4), 116.4 (C5Me4), 121.1 (C5H4), 121.8 (C5Me4), 132.1 (C5Me4), 138.2 (CipsoCp), 140.8 (C5Me4) ppm. IR (ATR, 16 scans): ṽ = 2965, 2902, 2875, 2849, 1488, 1449, 1377, 1359, 1292, 1255, 1194, 1143, 1113, 1100, 1058, 1023, 965, 909, 852, 806, 778, 691, 608, 595, 572 cm−1. Anal. Calcd for C28H39ClOTi: C 70.81, H 8.28; found C 71.05, H 8.38. Synthesis of Ti6. Ti3 (0.250 g, 0.6 mmol) and Y1 (0.166 g, 0.6 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The resulting red suspension was stirred for 8 h at room temperature and subsequently ferrocenealdehyde (0.128 g, 0.6 mmol) was added. After storing at 60 °C overnight, single crystals suitable for X-ray diffraction could be obtained from the reaction mixture. The mother liquor was decanted and the red crystals dried in vacuo, yielding 0.104 g (0.16 mmol, 27%) of Ti6, mp 135 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.49−2.44 (14 H, Ad), 1.55 (s, 3 H, C5Me4), 1.69 (s, 3 H, C5Me4), 1.72 (s, 3 H, C5Me4), 2.44 (s, 3 H, C5Me4), 2.47 (dd, 2JCH = 12.8, 3JCH = 10.3 Hz, 1 H, CH2), 3.07 (dd, 2JCH = 12.9 Hz, 3 JCH = 6.1 Hz, 1 H, CH2), 3.29 (s, 1 H, CHexo), 4.01 (m, 2 H, FcC5H4), 4.11 (s, 5 H, FcC5H5), 4.12 (m, 2 H, FeC5H4), 5.58 (m, 1 H, C5H4), 5.72 (m, 1 H, C5H4), 5.93 (m, 1 H, C5H4), 6.28 (dd, 3JCH = 10.3 Hz, 6.1 Hz, 1 H, FcCHO), 6.47 (m, 1 H, C5H4) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 11.4 (C5Me4), 12.7 (C5Me4), 12.9 (C5Me4), 13.6 (C5Me4), 28.4 (Ad CH), 28.5 (Ad CH), 32.0 (Ad CH), 32.5 (Ad CH), 33.0 (Ad CH2), 33.4 (CH2), 38.4 (Ad CH2), 38.8 (Ad CH2), 39.0 (Ad CH2), 43.7 (CHexo), 66.6 (FcCH), 67.8 (FcCH), 67.9 (FcCH), 68.0 (FcCH), 69.0 (FcCH), 92.9 (FcC), 97.4 (FcCHO), 110.6 (C5H4), 112.7 (C5H4), 115.7 (C5H4), 116.2 (C5Me4), 117.7 (C5Me4), 120.1 (C5H4), 121.3 (C5Me4), 131.5 (C5Me4), 138.5 (Cipso C5Me4), 139.4 (CipsoCp) ppm. IR (ATR, 16 scans): ṽ = 3094, 2902, 2846, 1487, 1467, 1448, 1411, 1378, 1354, 1332, 1293, 1260, 1105, 1058, 1035, 1015, 1002, 972, 955, 933, 883, 850, 827, 806, 781, 721, 690, 685, 646, 632, 604, 586 cm−1. Anal. Calcd for C36H43ClFeOTi: C 68.54, H 6.87; found C 70.63, H 6.29. Synthesis of Ti7. Ti3 (0.250 g, 0.6 mmol) and catalytic amounts of Y1 were placed in a Schlenk tube and 7 mL of n-hexane was added.

2846, 1600, 1500, 1448, 1399, 1353, 1311, 1260, 1212, 1195, 1096, 1059, 1033, 1019, 930, 883, 801, 753, 729, 710, 688, 676, 646, 628, 609, 579 cm−1. Anal. Calcd for C52H59PTi: C 81.87, H 7.80; found C 71.36, H 7.74. Synthesis of Ti2e. (NEt2)3PCH3I (0.517 g, 1.33 mmol) and NaH (0.048 g, 1.99 mmol) were placed in a Schlenk tube, tetrahydrofuran (10 mL) was added, and the resulting suspension was refluxed for 4 h. After cooling to room temperature, the suspension was filtered into a Schlenk tube containing a solution of Ti1b (0.500 g, 0.89 mmol) in 2 mL of tetrahydrofuran. The former blue solution turns brown and was stirred overnight at room temperature. Evaporation of the solvent and drying in vacuo afforded Ti2e in quantitative yield as a dark redbrown solid, mp 83 °C (dec.). 1H NMR (500 MHz, C6D6, 305 K): δ = 0.85−0.88 (m, 18 H, CH3), 2.08 (s, 3 H, CH3), 2.11 (s, 3 H, CH3), 2.15 (s, 6 H, CH3), 2.67−2.75 (m, 6 H, CH2), 2.82−2.91 (m, 6 H, CH2), 4.43 (m, 1 H, C5H4), 4.76 (m, 1 H, C5H4), 4.80 (m, 1 H, C5H4), 4.83 (m, 1 H, C5H4), 5.12 (s, 1 H, CHexo), 5.56 (m, 1 H, C5H4), 6.47 (m, 1 H, C5H4), 6.70 (m, 1 H, C5H4), 6.82−6.84 (m, 3 H, C5H4 + pTol CH), 6.92 (m, 1 H, CHYlid), 6.94 (m, 6 H, pTol CH), 7.11 (d, J = 7.6 Hz, 2 H, pTol CH), 7.23 (d, J = 7.7 Hz, 2 H, pTol CH), 7.59 (d, J = 7.8 Hz, 2 H, pTol CH), 7.65 (d, J = 7.6 Hz, 2 H, pTol CH) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 14.2 (NCH2CH3), 14.3 (NCH2CH3), 21.0 (CH3Tol), 40.2 (NCH2CH3), 40.2 (NCH2CH3), 52.1 (CHexo), 105.1 (C5H4), 105.1 (C5H4), 106.2 (C5H4), 107.5 (C5H4), 107.5 (C5H4), 108.6 (Fv Cexo), 109.2 (C5H4), 110.0 (C5H4), 111.4 (C5H4), 113.4 (C5H4), 123.3 (pTol C), 123.3 (Cipso Cp), 127.1 (pTol CH), 127.5 (pTol CH), 128.6 (pTol CH), 129.0 (pTol CH), 129.0 (pTol CH), 129.2 (pTol CH), 129.5 (pTol CH), 132.4 (pTol C), 132.6 (pTol CH), 133.0 (pTol C), 135.3 (pTol C), 135.6 (pTol C), 142.7 (pTol C), 144.2 (pTol C), 145.2 (pTol C), 147.1 (pTol C), 151.0 (d, 1JPC = 62.7 Hz, CHylide) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 56.6 ppm. IR (ATR, 16 scans): ṽ = 2969, 2921, 2870, 1508, 1455, 1379, 1295, 1260, 1203, 1172, 1054, 1017, 946, 924, 864, 796, 762, 737, 688, 638, 569 cm−1. Synthesis of Ti4a and Ti4b. Ti3 (0.500 g, 1.2 mmol) and Y1 (0.331 g, 1.2 mmol) were placed in a Schlenk tube and n-hexane (10 mL) was added. The former blue suspension turns red and was stirred at room temperature overnight. Subsequently, the mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo only afforded a mixture of two products being subject to a reversible thermodynamic equilibrium. In this, the two compounds Ti4a and Ti4b are present in the ratio of 1:1. Increasing the temperature (353 K), the equilibrium can be influenced in favor of compound Ti4b. Combined data for Ti4a and Ti4b were as follows. 1 H NMR (500 MHz, C6D6, 303 K): δ = 0.93 (s, 3 H, C5Me4), 1.29 (s, 3 H, C5Me4), 1.47−2.47 (Ad), 1.74 (s, 3 H, C5Me4), 2.04 (s, 15 H, C5Me5), 2.12 (s, 3 H, C5Me4), 2.13 (m, 1 H, CH2), 2.65 (d, 2J = 3.5 Hz, 1 H, CH2), 3.19 (s, 1 H, CHexo), 3.27 (s, 1 H, CHexo), 4.77 (m, 1 H, C5H4), 5.08 (m, 1 H, C5H4), 5.14 (m, 1 H, C5H4), 5.19 (m, 1 H, C5H4), 5.72 (m, 1 H, C5H4), 5.95 (m, 2 H, C5H4), 6.48 (m, 1 H, C5H4), 7.02−7.11 (m, 18 H, C6H5), 7.71−7.75 (m, 12 H, C6H5), 9.01 (d, 2JPH = 4.8 Hz, CH) ppm. 13C NMR (125 MHz, C6D6, 303 K): δ = 10.9 (C5Me4), 11.8 (C5Me4), 13.5 (Cp*), 13.5 (C5Me4), 14.5 (C5Me4), 28.4 (Ad CH), 28.6 (Ad CH), 28.6 (Ad CH), 28.6 (Ad CH), 32.4 (Ad CH2), 32.5 (Ad CH2), 32.8 (Ad CH2), 32.9 (Ad CH2), 33.0 (Ad CH), 33.0 (Ad CH2), 33.1 (Ad CH), 33.2 (Ad CH2), 38.4 (Ad CH2), 38.7 (Ad CH2), 39.0 (Ad CH2), 39.1 (Ad CH2), 39.2 (Ad CH2), 39.3 (Ad CH2), 44.1 (CHexo), 45.9 (CHexo), 75.4 (CH2), 104.9 (C5H4), 106.8 (C5H4), 107.7 (C5H4), 108.4 (C5H4), 19.7 (C5H4), 111.4 (C5H4), 112.5 (C5H4), 118.7 (C5H4), 119.7 (C5Me5), 121.2 (C5Me4), 126.5 (C5Me4), 128.4 (d, J = 12.7 Hz, PPh3), 128.54 (d, J = 11.3 Hz, PPh3), 130.2 (C5Me4), 130.6 (d, J = 2.6 Hz, PPh3), 131.0 (d, J = 2.8 Hz, PPh3), 132.7 (d, J = 9.0 Hz, PPh3), 133.7 (d, J = 9.3 Hz, PPh3), 133.7 (CipsoCp), 134.3 (d, 1JPC = 80.0 Hz, PPh3), 135.3 (d, 1JPC = 84.1 Hz, PPh3), 135.5 (Cipso Cp), 136.1 (C5Me4), 173.5 (d, 1 JPC = 29.1 Hz, CHylide) ppm. Synthesis of Ti4b. Ti3 (1 g, 2.4 mmol) and Y1 (0.020 g, 0.072 mmol) were placed in a Schlenk tube, 10 mL of n-hexane was added, and the resulting red suspension was stored at 60 °C overnight. Evaporation of the solvent and drying in vacuo afforded Ti4b in J


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Organometallics The resulting red suspension was stored at 60 °C overnight; subsequent addition of tritylnitrile (0.162 g, 0.6 mmol) and stirring at room temperature overnight results in a turquoise suspension. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.304 g (0.35 mmol, 58%) of Ti7 as a turquoise solid, mp 125 °C (dec.). 1H NMR (500 MHz, C6D6, 305 K): δ = 1.27−2.47 (14 H, Ad), 1.46 (s, 3 H, C5Me4), 1.60 (s, 3 H, C5Me4), 1.64 (s, 3 H, C5Me4), 2.34 (s, 3 H, C5Me4), 2.89 (d, 3JCH = 17.5 Hz, 1 H, CH2), 3.15 (s, 1 H, CHexo), 3.69 (d, 3JCH = 17.5 Hz, 1 H, CH2), 5.27 (m, 1 H, C5H4), 5.49 (m, 1 H, C5H4), 5.69 (m, 1 H, C5H4), 6.54 (m, 1 H, C5H4), 7.01 (t, 3JCH = 7.3 Hz, 3 H, p-C6H5), 7.13−7.14 (m, 6 H, m-C6H5), 7.51 (d, 3JCH = 7.4 Hz, 6 H, o-C6H5) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 12.1 (C5Me4), 12.2 (C5Me4), 12.3 (C5Me4), 13.4 (C5Me4), 28.3 (Ad CH), 28.6 (Ad CH), 31.4 (Ad CH), 32.7 (Ad CH), 32.8 (Ad CH2), 33.2 (Ad CH2), 38.3 (CH2), 38.4 (CH2), 38.5 (CH2), 38.5 (CH2), 43.3 (CHexo), 71.1 (CPh3), 108.8 (C5H4), 112.0 (C5H4), 113.7 (C5H4), 118.5 (C5Me4), 119.3 (C5Me4), 121.6 (C5Me4), 123.6 (C5H4), 126.5 (p-C6H5), 127.9 (m-C6H5), 130.0 (C5Me4), 131.3 (o-C6H5), 136.5 (C5Me4), 139.4 (Cipso Cp), 146.1 (Cipso C6H5), 196.0 (C=N) ppm. 15N NMR (51 MHz, C6D6, 305 K): δ = 123.0 ppm. IR (ATR, 16 scans): ṽ = 3063, 3019, 2928, 2895, 2846, 1606, 1594, 1489, 1447, 1263, 1099, 1050, 1030, 876, 828, 804, 781, 768, 740, 701, 648, 632, 600, 556 cm−1. Anal. Calcd for C45H48ClNTi: C 78.77, H 7.05, N 2.04; found C 75.86, H 6.95, N 2.05. Synthesis of Ti7a. By heating a solution of Ti7 in n-hexane, a color change from turquoise to red can be observed, affording Ti7a in quantitative yield, mp 165 °C. Single crystals suitable for X-ray diffraction could be obtained from a saturated solution of Ti7a in nhexane at 5 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.29−2.60 (14 H, Ad), 1.43 (s, 3 H, C5Me4), 1.65 (s, 3 H, C5Me4), 1.72 (s, 3 H, C5Me4), 2.50 (s, 3 H, C5Me4), 3.03 (s, 1 H, CHexo), 5.04 (m, 1 H, C5H4), 5.20 (m, 2 H, C5H4), 5.37 (s, 1 H, C5Me4CH), 6.51 (m, 1 H, C5H4), 7.04 (t, 3JCH = 7.3 Hz, 3 H, p-C6H5), 7.16−7.18 (m, 6 H, mC6H5), 7.49 (d, 3JCH = 7.5 Hz, 6 H, o-C6H5), 8.79 (s, 1 H, NH) ppm. 13 C NMR (125 MHz, C6D6, 305 K): δ = 11.5 (C5Me4), 12.0 (C5Me4), 12.3 (C5Me4), 14.0 (C5Me4), 28.2 (Ad CH), 28.3 (Ad CH), 31.9 (Ad CH), 32.1 (Ad CH2), 32.2 (Ad CH), 32.2 (Ad CH2), 38.3 (Ad CH2), 38.7 (Ad CH2), 38.8 (Ad CH2), 43.5 (CHexo), 66.2 (CPh3), 105.1 (C5H4), 105.7 (C5Me4CH), 107.4 (C5H4), 113.6 (C5H4), 119.5 (C5Me4), 119.7 (C5Me4), 125.6 (C5Me4), 126.8 (p-C6H5), 127.1 (C5H4), 128.1 (m-C6H5), 131.3 (o-C6H5), 141.1 (Cipso Cp), 144.1 (C5Me4), 144.9 (C5Me4), 145.6 (Cipso C6H5), 174.1 (CNH) ppm. 15N NMR (51 MHz, C6D6, 305 K): δ = 289.9 ppm. IR (ATR, 16 scans): ṽ = 3354, 3057, 2963, 2904, 2849, 1595, 1492, 1448, 1318, 1260, 1152, 1088, 1016, 866, 795, 753, 743, 724, 699, 644, 622, 584, 568 cm−1. Synthesis of Ti8. Ti3 (0.250 g, 0.6 mmol) and catalytic amounts of Y1 were placed in a Schlenk tube and 7 mL of n-hexane was added. The resulting red suspension was stored at 60 °C overnight and subsequently ferrocenenitrile (0.127 g, 0.6 mmol) was added. After stirring the suspension at room temperature overnight, the mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.204 g (0.32 mmol, 54%) of Ti8 as a redbrown solid, mp 183 °C. Single crystals suitable crystals for X-ray diffraction could be obtained by slowly cooling a hot saturated solution of Ti8 in n-hexane. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.53−2.60 (14 H, Ad), 1.57 (s, 3 H, C5Me4), 1.75 (s, 3 H, C5Me4), 1.76 (s, 3 H, C5Me4), 2.45 (s, 3 H, C5Me4), 3.45 (s, 1 H, CHexo), 4.08 (s, 2 H, FcC5H4), 4.23 (s, 5 H, FcC5H5), 4.29 (s, 1 H, FcC5H4), 4.45 (s, 1 H, FcC5H4), 5.26 (m, 1 H, C5H4), 5.37 (s, 1 H, C5Me4CH), 5.63 (m, 1 H, C5H4), 5.68 (m, 1 H, C5H4), 6.46 (m, 1 H, C5H4), 9.25 (s, 1 H, NH) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 11.5 (C5Me4), 12.1 (C5Me4), 12.5 (C5Me4), 13.9 (C5Me4), 28.3 (Ad CH), 28.3 (Ad CH), 32.4 (Ad CH2), 32.4 (Ad CH2), 32.6 (Ad CH), 33.5 (Ad CH), 38.3 (Ad CH2), 38.9 (Ad CH2), 39.1 (Ad CH2), 44.4 (CHexo), 65.3 (FcC5H4), 66.5 (FcC5H4), 68.7 (FcC5H4), 69.3 (FcC5H4), 69.9 (FcC5H5), 81.8 (FcC), 97.1 (C5Me4CH), 107.9 (C5H4), 110.3 (C5H4), 112.1 (C5H4), 119.7 (C5Me4), 120.0 (C5Me4), 123.1 (C5H4), 126.9 (C5Me4), 130.8 (Cipso Cp), 144.13 (C5Me4), 147.0

(Cipso C5Me4), 167.2 (FcCNH) ppm. 15N NMR (51 MHz, C6D6, 305 K): δ = 277.6 ppm. IR (ATR, 16 scans): ṽ = 3379, 2900, 2846, 1660, 1600, 1487, 1467, 1448, 1375, 1338, 1314, 1261, 1100, 1057, 1030, 926, 889, 827, 810, 732, 691, 662, 645, 621, 595 cm−1. Anal. Calcd for C36H42ClFeNTi: C 68.86, H 6.74, N 2.23; found C 67.01, H 6.58, N 2.29. Synthesis of Ti9. Ti3 (0.250 g, 0.6 mmol) and catalytic amounts of Y1 were placed in a Schlenk tube and 7 mL of n-hexane was added. The resulting red suspension was stored at 60 °C overnight and subsequently p-chlorobenzonitrile (0.083 g, 0.6 mmol) was added. After stirring the suspension at room temperature overnight, the mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.215 g (0.39 mmol, 65%) of Ti9 as a red solid, mp 160 °C. Single crystals suitable for X-ray diffraction could be obtained by slowly cooling a hot saturated solution of Ti9 in n-hexane. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.45−2.38 (14 H, Ad), 1.57 (s, 3 H, C5Me4), 1.76 (s, 3 H, C5Me4), 1.78 (s, 3 H, C5Me4), 2.42 (s, 3 H, C5Me4), 3.26 (s, 1 H, CHexo), 5.26 (m, 1 H, C5H4), 5.36 (s, 1 H, C5Me4CH), 5.51 (m, 1 H, C5H4), 5.74 (m, 1 H, C5H4), 6.34 (m, 1 H, C5H4), 7.16 (m, C6D6 + 2 H C6H4), 7.18 (m, 2 H, C6H4), 9.00 (s, 1 H, NH) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 11.5 (C5Me4), 12.1 (C5Me4), 12.5 (C5Me4), 13.7 (C5Me4), 28.2 (Ad CH), 28.2 (Ad CH), 32.3 (2 × Ad CH2), 32.5 (Ad CH), 33.2 (Ad CH), 38.2 (Ad CH2), 38.7 (Ad CH2), 38.8 (Ad CH2), 44.2 (CHexo), 99.3 (C5Me4CH), 108.4 (C5H4), 111.8.4 (C5H4), 112.2 (C5H4), 119.9 (C5Me4), 120.8 (C5Me4), 121.3 (C5H4), 126.9 (C6H4), 126.9 (C5Me4), 128.9 (C6H4), 132.6 (Cipso Cp), 134.1 (C6H4), 136.9 (C6H4), 144.3 (C5Me4), 146.6 (C5Me4), 167.6 (CNH) ppm. 15N NMR (51 MHz, C6D6, 305 K): δ = 267.9 ppm. IR (ATR, 16 scans): ṽ = 2904, 2847, 1601, 1586, 1566, 1486, 1447, 1397, 1381, 1328, 1292, 1262, 1212, 1168, 1087, 1061, 1012, 982, 953, 873, 852, 824, 802, 732, 694, 661, 644, 623, 604, 590, 567 cm−1. Anal. Calcd for C32H37Cl2NTi: C 69.32, H 6.73, N 2.53; found C 69.26, H 6.91, N 2.44. Synthesis of Ti10. Ti3 (0.250 g, 0.6 mmol) and catalytic amounts of Y1 were placed in a Schlenk tube and 7 mL of n-hexane was added. The resulting red suspension was stored at 60 °C overnight and subsequently acetonitrile (0.53 mL, 0.60 mmol, 1.14 M in toluene) was added dropwise. After storing at 60 °C overnight, a red suspension has been formed, which was decanted and the red solid dried in vacuo. NMR experiments indicate a complex mixture of multiple compounds. However, few single crystals suitable for X-ray diffraction could be obtained from a hot saturated solution of the reaction product in n-hexane at 60 °C. Synthesis of Zr2a. Zr1a (0.110 g, 0.24 mmol) and Y1 (0.066 g, 0.24 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The former red solution turns into a yellow suspension and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.077 g (0.11 mmol, 46%) of Zr2a as a yellow solid, mp 145 °C (dec.). 1H NMR (500 MHz, C6D6, 305 K): δ = 1.45−2.31 (14 H, Ad), 2.07 (s, 15 H, C5Me5), 3.31 (s, 1 H, CHexo), 5.06 (m, 1 H, C5H4), 5.08 (d, 2JPH = 11.3 Hz, 1 H, CHylide), 5.47 (m, 2 H, C5H4), 5.92 (m, 1 H, C5H4), 7.10 (m, 9 H, PPh3), 7.10 (m, 6 H, PPh3) ppm. 13 C NMR (125 MHz, C6D6, 305 K): δ = 12.8 (C5Me5), 28.5 (Ad CH), 32.0 (Ad CH), 32.6 (Ad CH2), 33.3 (Ad CH), 38.6 (Ad CH2), 39.2 (Ad CH2), 39.2 (Ad CH2), 43.8 (CHexo), 104.4 (C5H4), 104.5 (d, 1JPC = 34.5 Hz, CHylide), 107.4 (C5H4), 110.0 (C5H4), 110.8 (C5H4), 118.1 (C5Me5), 128.4 (d, J = 11.3 Hz, PPh3), 130.7 (d, J = 2.7 Hz, PPh3), 133.5 (d, J = 9.2 Hz, PPh3), 133.8 (CipsoCp), 135.6 (d, 1 JPC = 81 Hz, PPh3) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 16.6 (1JPC = 81 Hz) ppm. IR (ATR, 16 scans): ṽ = 3058, 2907, 2848, 1482, 1435, 1261, 1185, 1095, 1062, 1044, 1023, 998, 852, 813, 748, 706, 692, 595 cm−1. Anal. Calcd for C44H49ClPZr: C 71.85, H 6.72; found C 68.80, H 6.91. Synthesis of Zr2b. Zr1b (0.250 g, 0.48 mmol) and Y1 (0.133 g, 0.48 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The former red solution turns into a yellow suspension and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in K


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Organometallics

mp 193 °C (dec.). 1H NMR (500 MHz, C6D6, 305 K): δ = 1.0−1.91 (30 H, PCy3), 1.97 (s, 15 H, C5Me5), 2.07 (s, 3 H, CH3), 2.12 (s, 3 H, CH3), 5.71 (d, 2JPH = 17.2 Hz, 1 H, CHylide), 5.13 (m, 1 H, C5H4), 5.48 (m, 1 H, C5H4), 6.06 (m, 1 H, C5H4), 6.10 (s, 1 H, CHexo), 6.89 (m, 1 H, C5H4), 6.98 (d, J = 7.9 Hz, 2 H, pTol CH), 7.04 (d, J = 7.8 Hz, 2 H, pTol CH), 7.43 (d, J = 8.0 Hz, 2 H, pTol CH), 7.61 (d, J = 8.0 Hz, 2 H, pTol CH) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 12.8 (C5Me5), 21.0 (pTol CH3), 21.1 (pTol CH3), 26.7 (CH2), 27.7 (CH2), 28.0 (CH2), 36.8 (d, 1JPC = 47.0 Hz, Cy CH), 51.6 (CHexo), 102.5 (C5H4), 107.5 (C5H4), 109.5 (C5H4), 109.7 (C5H4), 111.1 (d, 1 JPC = 23.7 Hz, CHylide), 117.5 (C5Me5), 129.2 (pTol CH), 129.2 (pTol CH), 129.8 (pTol CH), 130.4 (pTol CH), 135.0 (Cp Cipso), 135.1 (pTol C), 135.5 (pTol C), 142.5 (pTol C), 144.8 (pTol C) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 26.7 (1JPC = 46.4 Hz) ppm. IR (ATR, 16 scans): ṽ = 3021, 2929, 2854, 1627, 1510, 1447, 1376, 1313, 1260, 1181, 1110, 1022, 1007, 929, 909, 851, 807, 763, 690, 593, 576 cm−1.

vacuo afforded 0.248 g (0.31 mmol, 65%) of Zr2b as a yellow solid, mp 153 °C (dec.). Single crystals suitable for X-ray diffraction were obtained from a saturated solution of Zr2a-benzo in n-hexane at 5 °C. 1 H NMR (500 MHz, C6D6, 305 K): δ = 1.97 (s, 15 H, C5Me5), 2.05 (s, 3 H, CH3), 2.10 (s, 3 H, CH3), 4.79 (m, 1 H, C5H4), 5.04 (m, 1 H, C5H4), 5.20 (d, 2JPH = 12.5 Hz, 1 H, CHylide), 5.41 (m, 1 H, C5H4), 5.96 (s, 1 H, CHexo), 6.27 (m, 1 H, C5H4), 6.86 (d, J = 7.9 Hz, 2 H, pTol CH), 7.00−7.06 (m, 11 H, pTol CH + PPh3), 7.20 (d, J = 8.0 Hz, 2 H, pTol CH), 7.50 (d, J = 8.0 Hz, 2 H, pTol CH), 7.68−7.72 (m, 6 H, PPh3) ppm. 13C NMR (125 MHz, C6D6, 305 K): δ = 12.8 (C5Me5), 21.0 (pTol CH3), 21.1 (pTol CH3), 51.6 (CHexo), 103.0 (C5H4), 105.7 (d, 1JPC = 33.1 Hz, CHylide), 109.7 (C5H4), 110.8 (C5H4), 111.9 (C5H4), 118.3 (C5Me5), 129.0 (pTol CH), 129.2 (pTol CH), 129.6 (pTol CH), 130.4 (pTol CH), 130.7 (d, J = 2.7 Hz, PPh3), 133.4 (d, J = 9.1 Hz, PPh3), 134.8 (Cipso Cp), 134.8 (pTol C), 135.1 (d, 1JPC= 81 Hz, PPh3), 135.5 (pTol C), 142.6 (pTol C), 144.4 (pTol C) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 16.5 (1JPC = 81 Hz) ppm. IR (ATR, 16 scans): ṽ = 3074, 2962, 2899, 2860, 1510, 1481, 1437, 1377, 1262, 1186, 1102, 1069, 1040, 1024, 999, 950, 951, 804, 785, 762, 750, 705, 694, 577 cm−1. Anal. Calcd for C49H50ClPZr: C 73.88, H 6.33; found C 72.86, H 6.62. Synthesis of Zr2a-benzo. Zr1a-benzo (0.250 g, 0.44 mmol) and Y2 (0.121 g, 0.44 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The former red solution turns into a yellow suspension and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (3 × 5 mL). Drying in vacuo afforded 0.273 g (0.34 mmol, 69%) of Zr2bbenzo as a yellow solid, mp 99 °C (dec.). Single crystals suitable for X-ray diffraction were obtained from a saturated solution of Zr2abenzo in n-hexane at room temperature. Due to the poor solubility of Zr2a-benzo in common deuterated NMR solvents, NMR experiments could not be performed. IR (ATR, 16 scans): ṽ = 3052, 3018, 2954, 2907, 2859, 1588, 1509, 1483, 1437, 1376, 1346, 1262, 1184, 1099, 1022, 999, 962, 938, 857, 806, 776, 757, 745, 710, 693, 639, 595, 575 cm−1. Anal. Calcd for C48H70ClPZr: C 71.64, H 8.77; found C 63.76, H 8.04. Synthesis of Zr2b-benzo. Zr1b-benzo (0.250 g, 0.44 mmol) and Y1 (0.121 g, 0.44 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The former red solution turns into a yellow suspension and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (3 × 5 mL). Drying in vacuo afforded 0.305 g (0.36 mmol, 82%) of Zr2bbenzo as a yellow solid, mp 115 °C (dec.). Single crystals suitable for X-ray diffraction were obtained from a saturated solution of Zr2bbenzo in n-hexane at 5 °C. 1H NMR (500 MHz, C6D6, 305 K): δ = 1.74 (s, 15 H, C5Me5), 2.01 (s, 3 H, CH3), 2.16 (s, 3 H, CH3), 2.72 (d, 2JPH = 22.1 Hz, 1 H, CHylide), 5.86 (d, J = 2.8 Hz, 1 H, C5H2), 5.92 (d, 1 H, J = 2.8 Hz, C5H2), 6.25 (m, 1 H, C6H4), 6.42 (m, 1 H, C6H4), 6.57 (s, 1 H, CHexo), 6.83 (m, 2 H, pTol CH), 7.08 (m, 11 H, PPh3 + pTol CH), 7.18 (m, 2 H, pTol CH), 7.28 (m, 1 H, C6H4), 7.38 (m, 1 H, C6H4), 7.60 (m, 6 H, PPh3), 7.77 (m, 2 H, pTol CH) ppm. 13C NMR (126 MHz, C6D6, 305 K): δ = 12.6 (C5Me5), 21.0 (CH3), 21.1 (CH3), 51.3 (CHexo), 91.3 (C5H2), 103.9 (d, 2JPC = 40.2 Hz, CHylide), 114.4 (C5H2), 119.0 (C5Me5), 123.0 (C6H4), 124.8 (C6H4), 124.9 (C6H4), 125.0 (C6H4), 126.3 (C6H4), 128.1 (d, JPC = 11.3 Hz, CHylide), 129.1 (pTol CH), 129.27 (pTol CH), 129.31 (pTol CH), 130.6 (d, J = 2.7 Hz, PPh3), 131.0 (pTol CH), 132.7 (Cp Cipso), 133.0 (C6H4), 133.6 (d, J = 9.3 Hz, PPh3), 135.0 (pTol C), 135.2 (d, 1JPC = 82.1 Hz, PPh3), 135.4 (pTol C), 141.8 (pTol C), 143.6 (pTol C) ppm. 31P NMR (202 MHz, C6D6, 305 K): δ = 5.92 (1JPC = 82.0 Hz) ppm. IR (ATR, 16 scans): ṽ = 3058, 3025, 2959, 2903, 2858, 1587, 1492, 1482, 1451, 1435, 1377, 1296, 1262, 1153, 1098, 1075, 1028, 999, 951, 880, 801, 772, 750, 740, 695, 624, 601 cm−1. Anal. Calcd for C53H52ClPZr: C 75.19, H 6.19; found C 73.70, H 6.62. Synthesis of Zr2c. Zr1b (0.250 g, 0.48 mmol) and Y2 (0.142 g, 0.48 mmol) were placed in a Schlenk tube and 7 mL of n-hexane was added. The former red solution turns into a yellow suspension and was stirred at room temperature overnight. The mother liquor was decanted and the solid washed with n-hexane (2 × 3 mL). Drying in vacuo afforded 0.282 g (0.35 mmol, 72%) of Zr2c as a yellow solid,

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00831. Crystallographic parameters for compounds Zr2a, Zr2b, Zr2b-benzo, Ti2b, Ti4a, Ti5, Ti6, Ti7a, Ti8, Ti9, and Ti10; NMR spectra of all compounds (PDF) Accession Codes

CCDC 1878078−1878088 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Web: https:// www.uni-oldenburg.de/ac-beckhaus/. ORCID

Rüdiger Beckhaus: 0000-0003-3697-0378 Notes

The authors declare no competing financial interest.

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REFERENCES

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