Article Cite This: Organometallics XXXX, XXX, XXX−XXX
Direct Access to Terminal Titanocene Hydrazides via Bis(η5:η1‑pentafulvene)titanium Complexes and 1,1Diphenylhydrazine Manfred Manßen, May-Franzis Meyer, Marc Schmidtmann, and Rüdiger Beckhaus* Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
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S Supporting Information *
ABSTRACT: The formation of the titanocene hydrazido complex 2 via double N−H bond activations at ambient temperature of 1,1-diphenylhydrazine by the use of bis(η5:η1adamantylidenepentafulvene)titanium complex 1 have been investigated. Starting from the titanium hydrazido complex 2, [2 + 2] cycloaddition and bond activation reactions are realized. In reaction with carbodiimides, the asymmetric N,N-bound ureato(2−) product 3 is observed. By use of nitriles, in addition to the [2 + 2] cycloaddition, the insertion of a second equivalent of the nitrile into the Ti−N bond is found (4). By reaction of 2 with carbon disulfide the symmetric S,S-bound thioureato(2−) complex 5 is isolated, whereas in reaction with carbon monoxide the cleavage of the N−N bond of the hydrazide unit is observed, resulting in the formation of the titanocene monocyanate 6. In contrast to the [2 + 2] cycloaddition reactions, for sterically demanding boranes such as 9-borabicyclo[3.3.1]nonane and catecholborane the hydroboration of the TiN double bond is observed, leading to the titanocene hydride complex 7 and the titanium(III) cation 8.
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2).11 The high reactivity of the bis(η5:η1-pentafulvene)titanium complexes is attributed to a strong π back-donation from the
INTRODUCTION The chemistry of titanium hydrazido complexes (LnTiNNR2)1 is strongly related to that of the corresponding titanium imido complexes (LnTiNR).2 They are known for a broad range of stoichiometric reactions with multiple-bond substrates such as alkynes,3 nitriles, isocyanides,4 isocyanates, carbon dioxide, carbon disulfide,5 etc. Furthermore, they can be used as catalysts for hydrohydrazination reactions6 and, as shown in recent studies, in activation reactions of hydride bonds of silanes7 and boranes.8 Especially the (reductive) cleavage of the Nα−Nβ bond is of interest in these kinds of reactions, which offers completely new synthetic routes in contrast to the titanium imido complexes.9 Titanium hydrazido complexes are usually synthesized by ligand exchange reactions of titanium imido complexes with the corresponding hydrazines (Scheme 1).10 In this synthetic route a wide range of further spectator ligands can be introduced via salt metathesis reactions of the chloride ligands. Some time ago we reported on a direct synthesis at ambient temperature of titanocene hydrazido complexes starting from bis(η5:η1-pentafulvene)titanium complexes and the corresponding hydrazines via double N−H bond activation without the necessity of an imido/hydrazido ligand exchange (Scheme
Scheme 2. Reactivity of Bis(η5:η1-pentafulvene)titanium Complexes and Direct Synthesis of Titanocene Hydrazido Complexes
metal to the fulvene moiety (Scheme 2).12 This coordination involves a change of the polarity (umpolung) of the exocyclic carbon atom of the fulvene ligand (Cexo). The umpolung leads to the strong nucleophilic character of the Cexo center, which is now capable of activating a broad range of E−H bonds.13 Our recent research in the field of titanocene imido synthesis via bis(η5:η1-pentafulvene)titanium complexes prompted us to transfer those results to improve the synthetic access to the corresponding titanocene hydrazido complexes.14 Here we report on an optimized synthetic route to terminal titanocene hydrazido complexes by using bis(η 5 :η 1 pentafulvene)titanium complexes and hydrazines. Furthermore, the reactivity of these complexes with multiple-bond
Scheme 1. General Synthesis of Titanium Hydrazido Complexes
Received: May 22, 2018
© XXXX American Chemical Society
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DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
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Organometallics substrates and bond activation reactions of boranes are investigated.
Scheme 4. Reactions of 2 with Carbodiimides and Nitriles
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RESULTS AND DISCUSSION Titanocene Hydrazido Complex 2. We recently optimized the reaction conditions to obtain the titanocene hydrazido complex 2 in very good yields (90%) and on a multigram scale. Upon reaction of the bis(η5:η1-adamantylidenepentafulvene)titanium complex 1 with freshly distilled 1,1diphenylhydrazine in n-hexane at ambient temperature (Scheme 3) a color change from a blue suspension to a
pentadienyl ligands are found in the 1H NMR spectrum at δ 5.89, 6.02, 6.23, and 6.58 ppm. This signal pattern is similar to that for the asymmetric [2 + 2] cycloaddition products of the imido complexes, whereas for the symmetric products only two signals are observed.14 The reaction of the titanocene hydrazido complex 2 with 2 equiv of 4-chlorobenzonitrile in n-hexane at ambient temperature (Scheme 4) results in the formation of a brown suspension of complex 4, which is isolated in good yields (74%) as a brown solid. It is best described as the product of a [2 + 2] cycloaddition and subsequent insertion of another 1 equiv of the nitrile into the Ti−N bond of the former nitrile. Similar six-membered rings were found for other nitrile reactions by us14 and the Mountford group.17 4 can be stored for months under inert conditions without any indication of decomposition. In the presence of oxygen or atmospheric moisture, however, it decomposes within 1 day. 4 has been fully characterized by NMR measurements. The 1H NMR spectrum reveals a signal pattern similar to that of 3 with four signals for the protons of cyclopentadienyl ligands at δ 5.41, 5.66, 5.81, and 6.41 ppm. In conclusion, the [2 + 2] cycloaddition reactivity of the titanocene hydrazido complex 2 is similar to that of titanocene imido complexes.14 2 in Reaction with CS2 and CO. After confirming the similarity of the [2 + 2] cycloaddition reactions of 2 in comparison to titanium imido complexes, we were interested in activation of small molecules such as carbon dioxide and carbon monoxide. Unfortunately, in the reaction with CO2 no selective formation of a single product was found, even at lower temperatures (−78 °C). Consequently, we switched to the heavier homologous compound CS2. The reaction of 2 and carbon disulfide in n-hexane at ambient temperature (Scheme 5) results in the formation of a dark green suspension of
Scheme 3. Reaction of 1 with 1,1-Diphenylhydrazine
maroon solution is observed. Immediately after the color change, pyridine is added to the solution to form a maroon suspension of 2. After removal of the solvent, the titanocene hydrazide 2 can be stored for months as solid under inert conditions without any indication of decomposition. In the presence of oxygen or atmospheric moisture, however, it decomposes within seconds. It is slightly soluble in aliphatic solvents but readily soluble in aromatic solvents, which is ideal for purification purposes and subsequent NMR experiments. Due to the optimized synthetic access, the titanocene hydrazido complex 2 has been fully characterized by NMR measurements. In the 1H NMR spectrum for the protons of the substituted cyclopentadienyl ligand four signals (two of them are superimposed) are found at δ 5.84, 5.88, and 5.96 ppm. A similar signal pattern was found for titanocene imido complexes we reported recently.14 Furthermore, the N−H bond activations are confirmed by the signal of the protonated Cexo positions of the pentafulvene ligands (1H, δ 2.67 ppm; 13 C, δ 44.7 ppm). The 15N HMBC spectrum of 2 reveals two signals, one at δ 208.6 ppm for the amine nitrogen (TiN− NPh2) and the other at δ 274.4 ppm for the pyridine nitrogen, indicating a high-field shift, in comparison to the free ligand (δ 311.6 ppm).15 Unfortunately, the signal for the TiN nitrogen atom was not observed, due to the large distances over multiple bonds to C−H groups. General Reactivity of 2 in [2 + 2] Cycloaddition Reactions. First of all, we were interested in the general reactivity of the titanocene hydrazido complex 2 in [2 + 2] cycloaddition reactions, especially in comparison to other titanocene imido complexes.14,16 In the reaction of 2 with 1 equiv of 1,3-di-p-tolylcarbodiimide (Scheme 4) in n-hexane at ambient temperature, the [2 + 2] asymmetric cycloaddition product 3 is isolated in good yields (83%) as a brown solid. In solution (n-hexane or benzene), complex 3 is stable over months and shows no indication of rearrangement of the fourmembered ring to the symmetric product, as observed for the [2 + 2] cycloaddition products of the imido complexes we reported recently.14 The stereochemistry of 3 was determined by NMR measurements. Due to the asymmetric substitution of the four-membered ring, four signals for the protons of cyclo-
Scheme 5. Proposed Mechanism of the Reaction of 2 with CS2
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DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
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Organometallics
yields (77%) as an almost black solid. The formation of the cyanate unit is best explained by a [2 + 1] cycloaddition of the CO to generate a titanaaziridinone intermediate. The threemembered ring of the titanaaziridinone rearranges by cleavage of the N−N bond to the cyanate and the amide unit. Similar cleavages of the N−N bond of hydrazides were observed in the reaction of titanium hydrazido complexes and isonitriles.4b Unfortunately, it has not yet been possible to obtain a singlecrystal X-ray structure of complex 6, but the formation of the monoamide ligand is confirmed by the chemical shift of the amide nitrogen in the 15N NMR spectrum. In comparison to the starting material the signal is shifted significantly to lower fields at δ 267.9 ppm. This value is in the range of comparable monoamide titanium complexes (Ti−N(Bz)Ph: δ 269.0 ppm).13b The formation of the cyanate ligand is confirmed by infrared spectroscopy. At ν̃ 2205 cm−1 a very strong band is observed, which is characteristic for titanium cyanate units (ν̃ (cm−1): Cp*2Ti(R)NCO,21 2215; Cp2Ti(NCO)2,22 2218, 2205). In addition to NMR and IR analyses, 6 was characterized by LIFDI mass spectrometry, where a strong signal at m/z 488 was found, which corresponds to the [(AdCp)2Ti(NCO)]+ fragment. 2 in Reaction with Boranes. Recent reactivity studies of group 4 hydrazido complexes have focused on hydridic bond activation reaction of e.g. silanes7 and boranes.8 Consequently, we decided to investigate the reactivity of the titanocene hydrazido complex 2 toward sterically demanding boranes such as 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane. By reaction of 2 with 9-BBN (in THF) at ambient temperature (Scheme 7) a color change from a maroon
complex 5, which is isolated in good yields (77%) as a green solid. This transformation to 5 is best explained by a typical cycloaddition of the CS bond to the TiN bond and subsequent retro cycloaddition to a thiocyanate unit and a titanocene sulfide intermediate (Scheme 5). This complex reacts immediately with the released thiocyanate in a [2 + 2] cycloaddition to form 5. Compound 5 is only slightly soluble in aliphatic and aromatic solvents and demonstrates fast decomposition reactions in very low concentrated solutions. Due to these two facts, it has not yet been possible to obtain suitable NMR spectra of complex 5. The structure of 5 was confirmed by single-crystal X-ray diffraction (Figure 1). Single crystals were obtained from a saturated benzene solution at 10 °C.
Figure 1. Molecular structure of 5. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): Ti1−S1 2.4745(5), Ti1−S2 2.4706(5), S1−C31 1.7513(16), S2−C31 1.7509(16), N2− C31 1.296(2), N1−N2 1.4479(18); S1−Ti1−S2 73.214(15), Ct− Ti1−Ct 133.3.
Scheme 7. Reaction of 2 with 9-BBN
The symmetry of complex 5 is demonstrated in the bonding situation of the four-membered ring with similar Ti−S (2.4745 and 2.4706 Å) and S−C (1.7513 and 1.7509 Å) bond lengths.18 The Ti−S bond lengths as well as the S−C bond lengths lie in the range of single bonds.19 The N2−C31 bond length (1.296 Å) is typical of N−Csp2 double bonds, whereas the N1−N2 bond length between both nitrogen atoms at 1.4479 Å is in the range of nitrogen−nitrogen single bonds.20 In the reaction of 2 with carbon monoxide (Scheme 6) in nhexane at ambient temperature the formation of the titanium monocyanate 6 is observed. Complex 6 is isolated in good
suspension to a brick red suspension is observed. After removal of the solvent, the titanocene hydride complex 7 is isolated in moderate yields (48%) as a red solid. The reaction is of the type of hydroboration of the TiN double bond, in which the negative hydride binds to the electropositive titanium center. Similar results are observed for the reaction of a Cp*Ti(L)NNMe2 complex with pinacolborane.8b 7 is fully characterized by NMR measurements. The hydroboration of the TiN bond is confirmed by the signal of the titanium hydride at δ 4.05 ppm in the 1H NMR spectrum, which furthermore shows no indication of any coupling in the 1H,13C HSQC spectra. In general, a broad range of chemical shifts are found for Ti−H units (δ 3.42 ppm,23 δ 5.57 ppm,8b δ 8.64 ppm24). Interestingly, in the H,H COSY spectrum the coupling of the hydride with the protons of the cyclopentadienyl ligands is observed, which is an uncommon coupling across one metal center. The structure of 7 including the position of the hydride atom is confirmed by single-crystal X-ray diffraction (see the Supporting Information), although the poor crystal quality, caused by strong and unresolved twinning, does not allow the discussion of bonding parameters in detail.
Scheme 6. Reaction of 2 with Carbon Monoxide
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DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
Organometallics In the reaction of 2 with 2 equiv of catecholborane (in THF) at ambient temperature (Scheme 8) a color change from
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CONCLUSION
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EXPERIMENTAL SECTION
In conclusion, we have presented an optimized synthesis for the titanocene hydrazido complex 2 by using the bis(η5:η1adamantylidenepentafulvene)titanium complex 1 and 1,1diphenylhydrazine via double N−H bond activations. Due to the access to complex 2 on a multigram scale, it is now possible to characterize its reactivity toward [2 + 2] cycloadditions and bond activations. In the reaction of 2 with carbodiimides, the asymmetric N,N-bound ureato(2−) complex 3 is formed without any indication of a rearrangement over time, whereas with nitriles, the [2 + 2] cycloaddition and subsequent insertion of a second equivalent of the nitrile into the Ti−N bond of the former nitrile is observed (4). Upon reaction of 2 with carbon disulfide, the S,S-bound thioureato(2−) complex 5 is generated via a titanium sulfide intermediate. In contrast to this, in the reaction of 2 with carbon monoxide, the cleavage of the N−N bond of the hydrazide unit is observed, followed by subsequent formation of the titanocene monocyanate 6. Finally, reacting 2 with the sterically demanding borane 9BBN results in the hydroboration of the TiN double bond and formation of the titanocene hydride 7, whereas reacting 2 with catecholborane results in the reduction of the metal center to the very sensitive titanium(III) borate complex 8.
Scheme 8. Reaction of 2 with Catecholborane
a maroon suspension to a brown solution is observed. From this brown suspension the azure microcrystalline product 8 precipitates immediately. After removal of the solvent, the titanium(III) cation 8 is isolated quantitatively as a blue solid. 8 is very reactive in the solid state as well as in solution and can only be stored for 1−2 days under inert conditions at −20 °C until the first signs of decompositions are observed. It has not yet been possible to isolate the primary brown intermediate observed during the reaction or the released borane- and nitrogen-containing byproducts. Due to the paramagnetic properties of 8, no NMR spectra were obtained. Instead, the structure of complex 8 is confirmed by single-crystal X-ray diffraction (Figure 2). Single crystals were collected from a saturated n-hexane/toluene solution at −30 °C.
General Considerations. All reactions were carried out under an inert atmosphere of argon or nitrogen with rigorous exclusion of oxygen and moisture using standard glovebox and Schlenk techniques. Solvents and liquid educts were dried according to standard procedures. Solvents were distilled over Na/K alloy and benzophenone under a nitrogen atmosphere. Liquid hydrazine was distilled prior use. NMR spectra were recorded on a Bruker AVANCE III 500 spectrometer (1H, 500.1 MHz; 13C, 125.8 MHz; 15N, 50.7 MHz) or a Bruker AVANCE 300 spectrometer (1H, 300.1 MHz). The NMR chemical shifts were referenced to residual protons of the solvent or the internal standard TMS. The chemical shifts of 15N are the result of 15 1 N, H HMBC NMR experiments with nitromethane as external standard (δ 378.9 vs NH3). IR spectra were recorded on a Bruker Tensor 27 spectrometer using an attenuated total reflection (ATR) method. Mass spectra were recorded on a Finnigan MAT 95 spectrometer. 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 n-hexane. Melting points were determined using a “Mel-Temp” instrument from Laboratory Devices, Cambridge, U.K. Bis(η5:η1adamantylidenepentafulvene)titanium (1) was synthesized according to a known procedure.13a Further exact details of the individually synthesized products, crystallographic data, and NMR spectra are given in the Supporting Information. Titanocene Hydrazido Complex 2. A 2.00 g (4.50 mmol) portion of 1 was suspended in 20 mL of n-hexane, and 829 mg (4.50 mmol) of 1,1-diphenylhydrazine was added. After a few minutes 0.73 mL (9.00 mmol) of pyridine was added to the solution. The reaction mixture was stirred for 120 h at 20 °C. The solid was separated, washed with n-hexane, and dried under vacuum. Yield: 2.87 g (90%). 1 H NMR (C6D6, 500 MHz): δ 1.44−2.12 (m, 28 H, Ad-H), 2.67 (m, 2 H, CexoH), 5.84, 5.88, 5.96 (m, 8 H, Cp-H), 6.39 (m, 2 H, Py-CHm) 6.77 (m, 1 H, Py-CHp), 6.87−6.90 (m, 2 H, Ar-CH), 7.17−7.20 (m, 4 H, Ar-CH), 7.26 (m, 4 H, Ar-CH), 8.54 (m, 2 H, Py-CHo) ppm. 13C NMR (C6D6, 125 MHz): δ 28.4, 28.6, 32.6, 33.0, 38.5, 39.3, 39.4 (AdCH/CH2), 44.7 (CexoH), 104.6, 110.0, 111.0, 112.2 (CHCp), 120.4 (Ar-CHm), 122.8 (Ar-CHp), 123.7 (Py-CHm), 126.8 (CipsoCp), 129.5 (Ar-CHo), 136.8 (Py-CHp), 146.9 (Ar-Ci), 154.8 (Py-CHo) ppm. 15N NMR (C6D6, 51 MHz): δ 208.6 (N−N−Ph2), 274.4 (Py) ppm. IR
Figure 2. Molecular structure of 8. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are drawn at the 50% probability level. Selected bond lengths (Å) and angles (deg): Ti1−O1 2.2350(9), Ti1−O3 2.2295(9), B1−O1 1.5166(16), B1−O2 1.4574(17), B1− O3 1.5086(16), B1−O4 1.4551(16); O1−Ti1−O3 64.17(3), Ct− Ti1−Ct 135.2.
The Ti−O bond lengths (2.2350 and 2.2295 Å) are elongated in comparison to Ti−O single bonds, which confirms the oxidation state of the titanium center.19b The boron atom B1 is tetrahedrally coordinated by the oxygen atoms O1−O4 with O−B−O bond angles ranging between approximately 103 and 116°. The four B−O bond lengths differ significantly with relatively long bond lengths for B1−O1 and B1−O3 (1.5166 and 1.5086 Å) and relatively short bond lengths for B1−O2 and B1−O4 (1.4574 and 1.4551 Å). This is attributed to the coordination of O1 and O3 to the titanium center. D
DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
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Organometallics (ATR): ν̃ 2902, 2845, 1585, 1486, 1448, 1442, 1294, 1247, 1213, 1167, 1151, 1099, 1070, 1059, 1041, 1025, 990, 842, 822, 796, 777, 768, 754, 743, 692, 663, 621 cm−1. Mp: 149 °C. Anal. Calcd for C47H53N3Ti: C, 79.75; H, 7.55; N, 5.94. Found: C, 78.52; H, 8.20; N, 6.04. Titanocene(N,N)ureate 3. A 250 mg (0.35 mmol) portion of 2 and 78 mg (0.35 mmol) of 1,3-di-p-tolylcarbodiimide were suspended in 9 mL of n-hexane. The reaction mixture was stirred for 18 h at 20 °C, forming a maroon suspension of complex 3. The solid was separated, washed with n-hexane, and dried under vacuum. Yield: 248 mg (83%). 1H NMR (C6D6, 500 MHz): δ 1.39−2.18 (m, 28 H, AdCH), 2.07 (s, 3 H, Ar-CH3), 2.09 (s, 3 H, Ar-CH3), 2.96 (s, 2 H, CexoH), 5.89, 6.02, 6.23, 6.58 (m, 8 H, Cp-H), 6.71 (m, 2 H, Ar-CH), 6.86−6.92 (m, 6 H, Ar-CH), 7.05 (m, 2 H, Ar-CH), 7.16−7.19 (m, 4 H, Ar-CH), 7.36 (m, 4 H, Ar-CH) ppm. 13C NMR (C6D6, 125 MHz): δ 20.9, 21.0 (Ar-CH3), 28.0, 32.2, 32.5, 32.5, 32.7, 37.9, 38.4, 38.7 (Ad-CH/CH2), 44.0 (CexoH), 116.5, 117.0, 118.4, 120.5 (CHCp), 120.1, 122.3, 122.5, 123.0, 128.8, 129.0 (Ar-CH), 129.6 (Ar-C), 141.7 (CipsoCp), 142.2 (N-C-N), 147.3, 147.7, 150.0 (Ar-C) ppm. IR (ATR): ν̃ 2991, 2848, 1586, 1566, 1557, 1490, 1449, 1410, 1318, 1300, 1274, 1244, 1218, 1195, 1169, 1100, 1074, 1046, 1032, 986, 886, 845, 807, 761, 742, 694 cm−1. Mp: 125 °C. Anal. Calcd for C57H62N4Ti: C, 80.45; H, 7.34; N, 6.58. Found: C, 78.53; H, 8.00; N, 6.50. Titanocenedihydrotriazine 4. A 250 mg (0.35 mmol) portion of 2 and 97 mg (0.71 mmol) of 4-chlorobenzonitrile were suspended in 10 mL of n-hexane. The reaction mixture was stirred for 18 h at 20 °C, forming a maroon suspension of complex 4. The solid was separated, washed with n-hexane and dried under vacuum. Yield: 237 mg (74%). 1H NMR (C6D6, 500 MHz): δ 1.37−2.23 (m, 28 H, AdH), 3.19 (m, 2 H, CexoH), 5.41, 5.66, 5.81, 6.41 (m, 8 H, Cp-H), 6.72 (m, 2 H, Ph-CHp), 6.87 (m, 4 H, Ph-CHo), 6.95 (m, 4 H, Ph-CHm), 7.01 (m, 2 H, Ar-CH), 7.30 (m, 2 H, Ar-CH), 7.39 (m, 2 H, Ar-CH), 8.20 (m, 2 H, Ar-CH) ppm. 13C NMR (C6D6, 125 MHz): δ 28.2, 28.2, 32.2, 32.4, 32.6, 38.0, 38.5, 39.1 (Ad-CH/CH2), 44.3 (CexoH), 108.0, 108.1, 115.6, 115.9 (CHCp), 120.8, 122.1, 127.8, 128.7, 129.1, 129.3, 130.9 (Ar-CH), 134.1 (Ar-C), 135.8 (NC−N), 136.2 (N C−N), 138.3 (CipsoCp), 141.2, 147.5, 158.9, 170.5 (Ar-C) ppm. IR (ATR): ν̃ 2905, 2848, 1662, 1579, 1539, 1487, 1448, 1415, 1391, 1324, 1310, 1294, 1266, 1217, 1163, 1085, 1062, 1053, 1030, 1013, 840, 805, 779, 746, 731, 695, 666, 638, 600 cm−1. Mp: 173 °C. Anal. Calcd for C56H56Cl2N4Ti: C, 74.42; H, 6.24; N, 6.20. Found: C, 74.14; H, 6.92; N, 6.20. Titanocene(S,S)thioureate 5. A 250 mg (0.35 mmol) portion of 2 was suspended in 10 mL of n-hexane, and 0.04 mL (0.71 mmol) of carbon disulfide was added. The reaction mixture was stirred for 18 h at 20 °C, forming a green suspension of complex 5. The solid was separated, washed with n-hexane, and dried under vacuum. Yield: 191 mg (77%). IR (ATR): ν̃ 3072, 2901, 2847, 1587, 1488, 1467, 1439, 1354, 1304, 1288, 1201, 1174, 1154, 1099, 1072, 1061, 1032, 996, 973, 952, 937, 911, 884, 843, 816, 778, 765, 744, 692, 658, 644, 612, 601 cm−1. Mp: 125 °C. Anal. Calcd for C43H48N2S2Ti: C, 73.27; H, 6.86; N, 3.97; S, 9.10. Found: C, 73.35; H, 7.72; N, 4.22; S, 8.99. Titanocene Monocyanate 6. A 250 mg (0.35 mmol) portion of 2 was suspended in 8 mL of n-hexane. The reaction mixture was stirred under carbon monoxide for 18 h at 20 °C, forming a black suspension of complex 6. The solid was separated, washed with nhexane, and dried under vacuum. Yield: 178 mg (77%). 1H NMR (C6D6, 500 MHz): δ 1.41−2.29 (m, 28 H, Ad-H), 2.98 (m, 2 H, CexoH), 5.54, 5.57, 5.79, 5.92 (m, 8 H, Cp-H), 6.81−6.84 (m, 2 H, ArCHp), 6.91 (m, 4 H, Ar-CHo), 7.06−7.12 (m, 4 H, Ar-CHm) ppm. 13C NMR (C6D6, 125 MHz): δ 28.2, 28.2, 32.0, 32.4, 32.7, 33.0, 38.0, 38.8, 39.1 (Ad-CH/CH2), 44.5 (CexoH), 106.9, 110.8, 117.7, 118.6 (CHCp), 121.2 (Ar-CHp), 127.1 (Ar-CHo), 128.4 (Ar-CHm), 140.1 (CipsoCp), 163.1 (Ar-Ci) ppm. 15N NMR (C6D6, 51 MHz): δ 267.9 (Ti-N-Ph2) ppm. IR (ATR): ν̃ = 2901, 2847, 2205, 2025, 1586, 1485, 1449, 1354, 1295, 1261, 1216, 1184, 1166, 1099, 1062, 1027, 865, 812, 778, 766, 745, 694, 642, 620, 602 cm−1. Mp: 95 °C. MS (ESI): m/z (%) 488 (100) [AdCp2Ti−NCO]+. Titanocene Hydride Complex 7. A 250 mg (0.35 mmol) portion of 2 was suspended in 10 mL of n-hexane, and 0.71 mL (0.5
M in THF, 0.35 mmol) 9-BBN was added. The reaction mixture was stirred for 18 h at 20 °C, forming a red suspension of complex 7. The solid was separated, washed with n-hexane, and dried under vacuum. Yield: 127 mg (48%). 1H NMR (C6D6, 500 MHz): δ 1.42−2.40 (m, 42 H, Ad-H, 9-BBN-H), 3.16 (m, 2 H, CexoH), 4.05 (s, 1 H, Ti-H), 4.88, 5.63, 5.82 (m, 8 H, Cp-H), 6.83 (m, 2 H, Ar-CHp), 7.06 (m, 4 H, Ar-CHm), 7.61 (m, 4 H, Ar-CHo) ppm. 13C NMR (C6D6, 125 MHz): δ 23.5, 28.4, 28.6, 32.4, 32.8, 33.7, 34.0, 34.2, 38.3, 39.5, 39.7 (Ad-CH/CH2, 9-BBN-CH/CH2), 45.5, 44.5 (CexoH), 101.0, 105.9, 108.9, 114.3 (CHCp), 123.7 (Ar-CHo), 123.9 (Ar-CHp), 127.9 (ArCHm), 151.8 (Ar-Ci) ppm. IR (ATR): ν̃ 2900, 2872, 2845, 1586, 1486, 1468, 1449, 1394, 1337, 1315, 1232, 1173, 1153, 1100, 1064, 1045, 1034, 891, 856, 808, 789, 764, 747, 715, 696 cm−1. Mp: 98 °C dec. Anal. Calcd for C50H63BN2Ti: C, 79.99; H, 8.46; N, 3.73. Found: C, 78.40; H, 9.08; N, 3.85. Titanium(III) Cation 8. A 250 mg (0.35 mmol) portion of 2 was suspended in 10 mL of n-hexane, and 0.70 mL (1 M in THF, 0.70 mmol) of catecholborane was added. The reaction mixture was stirred for 18 h at 20 °C, forming a light blue suspension of complex 8. The solid was separated, washed with n-hexane, and dried under vacuum. Yield: 234 mg (quantitative). Mp: 165 °C. IR (ATR): ν̃ 2903, 2850, 1589, 1461, 1435, 1338, 1314, 1293, 1274, 1259, 1231, 1194, 1164, 1119, 1098, 1063, 1007, 969, 954, 934, 906, 869, 833, 806, 738, 963, 658 cm−1.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.8b00343. Crystallographic parameters for compounds 5, 7, and 8 and 1H and 13C NMR spectra of all compounds (PDF) Accession Codes
CCDC 1843643−1843645 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
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AUTHOR INFORMATION
Corresponding Author
* R.B.: 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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DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
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DOI: 10.1021/acs.organomet.8b00343 Organometallics XXXX, XXX, XXX−XXX
