Bis(Î·5:Î·1-pentafulvene)titanium Complexes: Catalysts for

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Organometallics 2010, 29, 1806–1817 DOI: 10.1021/om100056q

Bis(η5:η1-pentafulvene)titanium Complexes: Catalysts for Intramolecular Alkene Hydroamination and Reagents for Selective Reactions with N-H Acidic Substrates† Thomas Janssen, Rene Severin, Mira Diekmann, Marion Friedemann, Detlev Haase, Wolfgang Saak, Sven Doye,* and R€ udiger Beckhaus* Institute of Pure and Applied Chemistry, Carl von Ossietzky University Oldenburg, D-26111 Oldenburg, Germany Received January 22, 2010

Intramolecular catalytic hydroamination reactions of geminally disubstituted amino alkenes employing the bulky substituted bis(η5:η1-pentafulvene)titanium complexes 1a and 1b and the corresponding benzannelated derivative 2 as catalysts are presented. While all three complexes are competent hydroamination catalysts, best results are achieved with the bis(benzofulvene) derivative 2. In addition, a series of Ti-N-containing compounds became available by stoichiometric reactions of 1 with N-H acidic substrates. In such a way, using aniline derivates (H2N-Ar, Ar: p-tolyl, 1naphthyl) the bisamides (η5-C5H4-CHR2)2Ti(NHAr)2 (CHR2: adamantyl, Ar: p-tolyl 5a; R: p-tolyl, Ar: p-tolyl 5b; R: p-tolyl, Ar: 1-naphthyl 5c; CHR2: adamantyl, Ar: 1-naphthyl 5d) are prepared in high yields under mild conditions. In contrast to this, the employment of the catalytically relevant amine H2NCH2C(Ph)2CH2CHdCH2 (3a) in a reaction with (η5:η1-C5H4dCR2)2Ti (CR2: adamantylidene, 1a) leads to the titanium monoamide (η5:η1-C5H4dCR2)(η5-C5H4-CHR2)Ti(NHCH2C(Ph)2CH2CHdCH2) (6), characterized by X-ray diffraction. In reaction of 1a and 1b with benzophenone imine the titanocene bis(enamides) (η5-C5H4-CHR2)2Ti(NdCPh2)2 7a and 7b are formed. Titanium nitrogen double bonds are formed by treatment of 1a with 1,1-diphenylhydrazine. In that manner the hydrazido titanocene (η5-C5H4-CHR2)2TidN-N(Ph)2 (CHR2: adamantyl) was structurally characterized as the pyridine adduct 9. Three different Ti-N bonds are formed in one step by reaction of (η5:η1-C5H4dCR2)2Ti (R: p-tolyl, 1b) with 1,1-diphenylhydrazine and pyridine (py), leading to (η5-C5H4-CHR2)Ti(dN-NPh2)(-N-NPh2)py 10b (dative Ti-N bond: Ti-py 2.211(2) A˚ , single Ti-N bond: Ti-NNPh2- 1.968(2) A˚ , double Ti-N bond: Ti-NNPh22- 1.738(1) A˚ ). The formation of 10b is accompanied by the liberation of one C5H5CHR2 ligand. Generally, the bis(η5:η1-pentafulvene)titanium complexes 1 and 2 are valuable catalysts in hydroamination reactions and reagents in order to prepare Ti-N-containing metallocene-type derivatives.

Introduction Metallocene derivatives of the early transition metals of the type Cp2M(CR3)2 (A, M: Ti, Zr, Hf) are well-known complexes for a large number of catalytic as well as stoichiometric transformations of many substrates.1,2 By formal combination of the Cp anion with the σ-bonded carbon ligand, bis(pentafulvene)metal complexes B become available (Scheme 1). These complexes can be synthesized in the † Dedicated to Prof. Dr. Uwe Rosenthal on the occasion of his 60th birthday. *Corresponding authors. (S.D.) Phone: þ49 441 798 3888. E-mail: [email protected]. (R.B.) Phone: þ49 441 798 3656. Fax: þ49 441 798 3851. E-mail: [email protected]. (1) Jutzi, P.; Edelmann, F.; Bercaw, J. E.; Beckhaus, R.; Negishi, E.; Royo, P.; Okuda, J.; Halterman, R. L.; Janiak, C.; Hoveyda, A. H.; Togni, A.; Manners, I., Metallocenes; Wiley-VCH: Weinheim, 1998. (2) Rosenthal, U.; Burlakov, V. V. In Titanium and Zirconium in Organic Synthesis; Marek, I., Ed.; Wiley-VCH: Weinheim, 2002; pp 355-390. (3) Diekmann, M.; Bockstiegel, G.; L€ utzen, A.; Friedemann, M.; Haase, D.; Saak, W.; Beckhaus, R. Organometallics 2006, 25, 339–348.

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case of early transition metals by reaction of TiCl3 3 3thf with Mg in the presence of bulky substituted pentafulvenes (Fv).3 In such a way the bulky substituted bis(pentafulvene)- 1, and bis(benzofulvene)titanium complexes 2 can be obtained in high yields (Scheme 2).3 The bonding situation of the bis(fulvene)titanium complexes 1 is best described as a π-η5:σ-η1 coordination mode.4 Due to the general strong nucleophilic character of the exocyclic carbon in the pentafulvene complexes (Cexo) of early transition metals, subsequent reactions with electrophiles are found under comparably mild conditions. While Cp2Ti(CH3)2 itself is stable against electrophiles (e.g., water) at room temperature,5,6 fulvene complexes 1 and 2 show significantly higher reactivity, even at -78 °C. Such reaction patterns are observed for fulvene titanium derivatives in (4) Koch, R.; B€ olter, E.; Stroot, J.; Beckhaus, R. J. Organomet. Chem. 2006, 691, 4539–4544. (5) Clauss, K.; Bestian, H. Liebigs Ann. Chem. 1962, 654, 8–19. (6) Siebeneicher, H.; Doye, S. J. Prakt. Chem. 2000, 342, 102–106. r 2010 American Chemical Society

Article Scheme 1. Bentmetallocenes vs Bis(pentafulvene)metal Complexes

Scheme 2. Bis(pentafulvene)- and Bis(benzofulvene)titanium Complexes

Scheme 3. Expected Formation of Imido Complexes during Reactions with Primary Amines

reactions with ketones,7,8 nitriles,9 isonitriles,10 water,11 and hydrogen chloride,3,12 or other electrophiles.13-15 In this manner, the formation of titanium imido derivates C were initially expected to occur during reactions of 1 or 2 with primary amines (Scheme 3). Generally, imido titanium complexes can be generated by a lot of different synthetic strategies.16,17 Most of these strategies contain R-H-abstraction reactions to eliminate alkanes (mostly CH4) or amines at higher temperatures. Additionally several of these protocols contain salt metathesis reactions, leading to separation difficulties. Imido ligand complexes are of great interest because they are discussed as intermediates in different catalytic cycles, for example in (7) Stroot, J.; Beckhaus, R.; Saak, W.; Haase, D.; L€ utzen, A. Eur. J. Inorg. Chem. 2002, 1729–1737. (8) Beckhaus, R.; L€ utzen, A.; Haase, D.; Saak, W.; Stroot, J.; Becke, S.; Heinrichs, J. Angew. Chem. 2001, 113, 2112–2115. Angew. Chem., Int. Ed. 2001, 40, 2056-2058. (9) Stroot, J.; Saak, W.; Haase, D.; Beckhaus, R. Z. Anorg. Allg. Chem. 2002, 628, 755–761. (10) Fandos, R.; Meetsma, A.; Teuben, J. H. Organometallics 1991, 10, 2665–2671. (11) Stroot, J.; Haase, D.; Saak, W.; Beckhaus, R. Z. Kristallogr.New Cryst. Struct. 2002, 217, 47–48. (12) Stroot, J.; Haase, D.; Saak, W.; Beckhaus, R. Z. Kristallogr.New Cryst. Struct. 2002, 217, 49–50. (13) Scherer, A.; F€ urmeier, S.; Haase, D.; Saak, W.; Beckhaus, R.; Meetsma, A.; Bouwkamp, M. W. Organometallics 2009, 28, 6969–6974. (14) Varga, V.; Sindelar, P.; Cisarova, I.; Horacek, M.; Kubista, J.; Mach, K. Inorg. Chem. Commun. 2005, 8, 222–226. (15) Pinkas, J. C., I.; Gyepes, R.; Horacek, M.; Kubista, J.; Cejka, J.; Gomez-Ruiz, S.; Hey-Hawkins, E.; Mach, K. Organometallics 2008, 27, 5532–5547. (16) Hazari, N.; Mountford, P. Acc. Chem. Res. 2005, 38, 839–849. (17) Fout, A. R.; Kilgore, U. J.; Mindiola, D. J. Chem.;Eur. J. 2007, 13, 9428–9440.

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the biological and synthetic activation and transformation of molecular nitrogen, as shown by the Schrock NH3 cycle containing hydrazido, imido, and amido intermediates.18,19 In addition, group IV metal imido complexes are often discussed as intermediates in hydroamination reactions of alkynes or alkenes performed in the presence of neutral Ti or Zr catalysts.20-28 While corresponding reactions of alkynes can be achieved inter-29-51 and intramolecularly,52-58 the hydroamination of alkenes is (18) Yandulov, D. V.; Schrock, R. R. Science 2003, 301, 76–78. (19) Schrock, R. R. Chem. Commun. 2003, 2389–2391. (20) M€ uller, T. E.; Beller, M. Chem. Rev. 1998, 98, 675–703. (21) Pohlki, F.; Doye, S. Chem. Soc. Rev. 2003, 32, 104–114. (22) Bytschkov, I.; Doye, S. Eur. J. Org. Chem. 2003, 935–946. (23) Doye, S. Synlett 2004, 1653–1672. (24) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2004, 104, 3079–3160. (25) Odom, A. L. Dalton Trans. 2005, 225–233. (26) Severin, R.; Doye, S. Chem. Soc. Rev. 2007, 36, 1407–1420. (27) Lee, A. V.; Schafer, L. L. Eur. J. Inorg. Chem. 2007, 2007, 2245– 2255. (28) M€ uller, T. E.; Hultzsch, K. C.; Yus, M.; Foubelo, F.; Tada, M. Chem. Rev. 2008, 108, 3795–3892. (29) Walsh, P. J.; Baranger, A. M.; Bergman, R. G. J. Am. Chem. Soc. 1992, 114, 1708–1719. (30) Baranger, A. M.; Walsh, P. J.; Bergman, R. G. J. Am. Chem. Soc. 1993, 115, 2753–2763. (31) Haak, E.; Bytschkov, I.; Doye, S. Angew. Chem. 1999, 111, 3584– 3586. Angew. Chem., Int. Ed. 1999, 38, 3389-3391. (32) Haak, E.; Siebeneicher, H.; Doye, S. Org. Lett. 2000, 2, 1935– 1937. (33) Shi, Y.; Ciszewski, J. T.; Odom, A. L. Organometallics 2001, 20, 3967–3969. (34) Cao, C.; Ciszewski, J. T.; Odom, A. L. Organometallics 2001, 20, 5011–5013. (35) Cao, C.; Shi, Y.; Odom, A. L. Org. Lett. 2002, 4, 2853–2856. (36) Tillack, A.; Castro, I. G.; Hartung, C. G.; Beller, M. Angew. Chem. 2002, 114, 2646–2648. Angew. Chem., Int. Ed. 2002, 41, 2541-2543. (37) Khedkar, V.; Tillack, A.; Beller, M. Org. Lett. 2003, 5, 4767– 4770. (38) Zhang, Z.; Schafer, L. L. Org. Lett. 2003, 5, 4733–4736. (39) Heutling, A.; Pohlki, F.; Doye, S. Chem.;Eur. J. 2004, 10, 3059– 3071. (40) Khedkar, V.; Tillack, A.; Michalik, M.; Beller, M. Tetrahedron Lett. 2004, 45, 3123–3126. (41) Tillack, A.; Jiao, H.; Castro, I. C.; Hartung, C. G.; Beller, M. Chem.;Eur. J. 2004, 10, 2409–2420. (42) Tillack, A.; Khedkar, V.; Beller, M. Tetrahedron Lett. 2004, 45, 8875–8878. (43) Tillack, A.; Khedkar, V.; Jiao, H.; Beller, M. Eur. J. Org. Chem. 2005, 2005, 5001–5012. (44) Heutling, A.; Pohlki, F.; Bytschkov, I.; Doye, S. Angew. Chem. 2005, 117, 3011–3013. Angew. Chem., Int. Ed. 2005, 44, 2951-2954. (45) Marcsekova, K.; Wegener, B.; Doye, S. Eur. J. Org. Chem. 2005, 2005, 4843–4851. (46) Esteruelas, M. A.; Lopez, A. M.; Mateo, A. C.; Onate, E. Organometallics 2005, 24, 5084–5094. (47) Swartz, D. L., II; Odom, A. L. Organometallics 2006, 25, 6125– 6133. (48) Buil, M. L.; Esteruelas, M. A.; L opez, A. M.; Mateo, A. C. Organometallics 2006, 25, 4079–4089. (49) Lee, A. V.; Schafer, L. L. Synlett 2006, 2973–2976. (50) Buil, M. L.; Esteruelas, M. A.; Lopez, A. M.; Mateo, A. C.; Onate, E. Organometallics 2007, 26, 554–565. (51) Zhang, Z.; Leitch, D. C.; Lu, M.; Patrick, B. O.; Schafer, L. L. Chem.;Eur. J. 2007, 13, 2012–2022. (52) Bytschkov, I.; Doye, S. Tetrahedron Lett. 2002, 43, 3715–3718. (53) Ackermann, L.; Bergman, R. G. Org. Lett. 2002, 4, 1475–1478. (54) Ackermann, L.; Bergman, R. G.; Loy, R. N. J. Am. Chem. Soc. 2003, 125, 11956–11963. (55) Li, C.; Thomson, R. K.; Gillon, B.; Patrick, B. O.; Schafer, L. L. Chem. Commun. 2003, 2462–2463. (56) Mujahidin, D.; Doye, S. Eur. J. Org. Chem. 2005, 2689–2693. (57) Severin, R.; Mujahidin, D.; Reimer, J.; Doye, S. Heterocycles 2007, 74, 683–700. (58) Weitershaus, K.; Ward, B. D.; Kubiak, R.; M€ uller, C.; Wadepohl, H.; Doye, S.; Gade, L. H. Dalton. Trans. 2009, 4586–4602.

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Scheme 4. Originally Proposed Catalytic Cycle of Ti-Catalyzed Intramolecular Hydroamination Reactions of Alkenes60

limited to the cyclization of aminoalkenes.59-73 In the case of titanium-catalyzed reactions of alkynes, imido intermediates are generally accepted to be the catalytically active species.74 These react with an alkyne in a [2þ2]-cycloaddition via a precoordinated species41 to give an azatitanacyclobutene. The azatitanacyclobutene then reacts with additional amine to a bisamide, which finally liberates the hydroamination product and regenerates the catalytically active imido species. On the basis of this knowledge, it was initially proposed that the intramolecular hydroamination of alkenes performed with neutral titanium catalysts takes place by a corresponding [2þ2]-cycloaddition mechanism (Scheme 4) that involves the imido intermediate II as the catalytically active species.60

Janssen et al.

However, on the basis of experimental findings75 as well as computational studies,76 alternative mechanisms for the group IV metal-catalyzed intramolecular hydroamination of alkenes have recently been proposed. For example, Stubbert and Marks have suggested that the rate-limiting step of the catalytic cycle of the group IV metal-catalyzed cyclization of aminoalkenes is an insertion of the alkene moiety into a group IV metal amido bond of a simple amido complex.75 Although a similar mechanism is operative in rare-earthmetal-catalyzed hydroamination reactions,77-80 it is also possible that metal imido amido complexes are the catalytically active species.76 However, the formation of such species from common catalyst precursors such as Cp2TiMe2 or Ind2TiMe2 (Ind: η5-indenyl) must involve a possible loss of one of the Cp (or Ind) ligands.81 With regard to the ongoing discussion of the mechanistic details of Ti-catalyzed alkene hydroamination the isolation of intermediates of the catalytic cycle seems to be inevitable. However, most mechanistic investigations and especially studies dealing with the isolation or the synthesis of possible intermediates of a catalytic cycle are performed under conditions and with starting materials or catalyst precursors that are different from those applied during the original reaction. Interestingly, our bis(fulvene)titanium complexes 1 and 2 (Scheme 2) are very reactive even at room temperature, which is in sharp contrast to most of the extensively used hydroamination precatalysts (e.g., Cp2TiMe2, Ind2TiMe2), which need high temperatures to react with amines.31,39,53 On the basis of this fact, we decided to use the bis(fulvene)titanium complexes 1 and 2 as tools for studying some mechanistic details of the Ti-catalyzed intramolecular hydroamination of alkenes. Herein, we present the catalytic application of 1 and 2 in hydroamination reactions of aminoalkenes as well as stoichiometric reactions of 1 with amines, imines, and hydrazines. In addition, some hints are discussed concerning the alternative insertion mechanism75 as well as the possible loss of one Cp ligand during the catalytic reaction.81

Results and Discussion (59) Kim, H.; Lee, P. H.; Livinghouse, T. Chem. Commun. 2005, 5205–5207. (60) Bexrud, J. A.; Beard, J. D.; Leitch, D. C.; Schafer, L. L. Org. Lett. 2005, 7, 1959–1962. (61) Thomson, R. K.; Bexrud, J. A.; Schafer, L. L. Organometallics 2006, 25, 4096–4071. (62) Lee, A. V.; Schafer, L. L. Organometallics 2006, 25, 5249–5254. (63) Kim, H.; Kim, Y. K.; Shim, J. H.; Kim, M.; Han, M.; Livinghouse, T.; Lee, P. H. Adv. Synth. Catal. 2006, 348, 2609–2618. (64) Watson, D. A.; Chiu, M.; Bergman, R. G. Organometallics 2006, 25, 4731–4733. (65) M€ uller, C.; Loos, C.; Schulenberg, N.; Doye, S. Eur. J. Org. Chem. 2006, 2499–2503. (66) Wood, M. C.; Leitch, D. C.; Yeung, C. S.; Kozak, J. A.; Schafer, L. L. Angew. Chem. 2007, 119, 358–362. (67) Bexrud, J. A.; Li, C.; Schafer, L. L. Organometallics 2007, 26, 6366–6372. (68) M€ uller, C.; Saak, W.; Doye, S. Eur. J. Org. Chem. 2008, 2008, 2731–2739. (69) Majumder, S.; Odom, A. L. Organometallics 2008, 27, 1174– 1177. (70) Gott, A. L.; Clarke, A. J.; Clarkson, G. J.; Scott, P. Chem. Commun. 2008, 1422–1424. (71) Leitch, D. C.; Payne, P. R.; Dunbar, C. R.; Schafer, L. L. J. Am. Chem. Soc. 2009, 131, 18246–18247. (72) Zi, G.; Liu, X.; Xiang, L.; Song, H. Organometallics 2009, 28, 1127–1137. (73) Bexrud, J. A.; Schafer, L. L. Dalton. Trans. 2010, 39, 361–363. (74) Pohlki, F.; Doye, S. Angew. Chem. 2001, 113, 2361–2364. Angew. Chem., Int. Ed. 2001, 40, 2305-2308. (75) Stubbert, B. D.; Marks, T. J. J. Am. Chem. Soc. 2007, 129, 6149– 6167.

Catalytic activities in hydroamination reactions were examined using the bisfulvene complexes 1a, 1b, and 2. In the stoichiometric reaction part the bisfulvene complexes 1 are preferred, due to the higher crystallization tendency. Hydroamination Reactions. Initial hydroamination experiments were carried out with 1-amino-2,2-diphenyl-4-pentene (3a, Table 1, entries 1-3) in toluene at 105 °C in the presence of 5 mol % of either 1a, 1b, or 2. First of all, it must be mentioned that successful cyclization reactions took place with all three catalysts and 100% conversion was always reached after a reaction time of 24 h. Correspondingly, in all cases, the desired pyrrolidine 4a could be isolated in good yield (73-88%) after purification of the crude reaction mixture by column chromatography. However, a slightly different result was obtained with aminoalkene 3b (Table 1, entries 4-6), which bears sterically less demanding benzyl (76) M€ uller, C.; Koch, R.; Doye, S. Chemistry 2008, 14, 10430–10436. (77) Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 580–591. (78) Motta, A.; Lanza, G.; Fragala, I. L.; Marks, T. J. Organometallics 2004, 23, 4097–4104. (79) Hultzsch, K. C. Org. Biomol. Chem. 2005, 3, 1819–1824. (80) Aillaud, I.; Collin, J.; Hannedouche, J.; Schulz, E. Dalton Trans. 2007, 5105–5118. (81) Johnson, J. S.; Bergman, R. G. J. Am. Chem. Soc. 2001, 123, 2923–2924.

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Table 1. Synthesis of Pyrrolidines by Intramolecular Hydroamination

a Reaction conditions: (1) amino alkene (2.40 mmol), catalyst (0.12 mmol, 5 mol %), toluene (2.0 mL), 105 °C, 24 h; (2) BzCl (2.64 mmol), NEt3 (7.2 mmol), CH2Cl2 (10 mL), 25 °C, 12 h. Yields refer to the isolated pure compounds.

substituents at the alkyl tether. While the reaction of this less Thorpe-Ingold-activated substrate still went to completion within 24 h at 105 °C in the presence of the bis(benzofulvene)titanium complex 2, the use of the bis(pentafulvene)titanium complexes 1a and 1b led to only 68% and 70% conversion, respectively. Correspondingly, the pyrrolidine product 4b was obtained in good yield (93%) from the reaction performed in the presence of 2, while only modest yields (58% and 61%) were reached with the catalysts 1a and 1b. These results as well as the fact that the simple bis(indenyl)titanium complex Ind2TiMe2 is a catalytically more active hydroamination catalyst than the corresponding bis(cyclopentadienyl)titanium complex Cp2TiMe239 suggest that the bis(benzofulvene)titanium complex 2 represents a more active hydroamination catalyst than the bis(pentafulvene)titanium complexes 1a and 1b. This hypothesis is strongly supported by the fact that the less Thorpe-Ingold-activated substrates 3c and 3d (Table 1, entries 7-11) do not undergo any cyclization at 105 °C in the presence of 1a or 1b, while under identical reaction conditions, 2 is still able to convert these substrates to the desired pyrrolidines. Due to the low boiling points of the hydroamination products initially formed from 3c and 3d, benzoyl chloride and NEt3 were added to the crude reaction mixtures prior to isolation. Subsequently,

the nonvolatile benzamides 4c and 4d could be isolated in 70% and 18% yield, respectively. Reactions with Amines. As shown, the bis(pentafulvene)- 1 and bis(benzofulvene)titanium 2 complexes are active hydroamination catalysts. We decided to use 1 in subsequent reactions with N-H acidic compounds due to the better crystallization tendency of the reaction products. Reacting 1 with aniline derivatives at room temperature, a fast color change from green to red occurs. The crystalline titanocene amides 5 are obtained in yields from 41% (5a) to 61% (5b). They are easily soluble in benzene, toluene, and thf and moderately soluble in n-hexane. Solid 5 reacts very slowly if exposed to air, although solutions degrade faster. The primary expected imido derivates C (Scheme 3) are never observed, not even using different stoichiometries or pyridine as trapping agent.82 However, as expected, the nucleophilic Cexo fulvene atoms are protonated first by the amine to form the corresponding substituted CpR derivates 5, as shown in Scheme 5. The 1H NMR spectra of 5a-d show characteristic signals of the NH unit between 7.39 (5a) and 8.72 ppm (5c) as a broadened (82) Dunn, S. C.; Mountford, P.; Robson, D. A. J. Chem. Soc., Dalton Trans. 1997, 293–304.

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Scheme 5. Reactions of 1 with Primary Anilines

Table 2. Selected 1H NMR Data [δ, ppm] (C6D6, 500.13 MHz, 300 K) of 5a-d

CHR2 Ar C5H4 NH

5a

5b

5c

5d

adamantyl p-tolyl 5.64 6.06 7.39

R = p-tolyl p-tolyl 5.13 5.88 7.84

R = p-tolyl 1-naphthyl 5.61 6.06 8.72

adamantyl 1-naphthyl 5.70 6.10 8.30

singlets (Table 2). Of high diagnostic value in the formation of 5 are the two signals for the C5H4 fragment in the expected range (Table 2), in contrast to the four singlets for the C5H4dCR2 ligands in 1. Additionally, characteristic singlets are found at 5.30 (5b) and 5.42 ppm (5c) for the CexoH proton if bistolylfulvene is used. The corresponding signals for the adamantyl derivates are found in the expected range. The complexes 5a-d do not give an Mþ signal in the mass spectrum (neither CI nor EI mode). Dark red crystals of 5 suitable for X-ray structure determination can be obtained at room temperature from a saturated n-hexane solution. Due to the similarities of the molecular structures of 5a-d, only 5a is given in Figure 1.83 Selected bond distances and angles of 5a-d are summarized in Table 3. The titanocene amides 5a crystallize in the monoclinic space group P21/n, 5b and 5c in P21/c, and 5d in the orthorhombic space group Pbcn. The Ti(IV) atom has the typical pseudotetrahedral coordination features when the Ct-Ti-Ct (128°) and the N-Ti-N (95-98°) angles are compared with other titanocene derivatives.84 The observed Ti-N bond lengths, 2.01 to 2.04 A˚, are in the expected range for Ti-N single bonds without pπ-dπ interactions.85 If pπ-dπ interactions become possible, depending on the rotameric orientation of the Ti-NR2 unit, shorter Ti-N distances are found (CpTiCl2(NHt-Bu) 1.879(3) A˚;86 CpTiCl2(Ni-Pr2) 1.865(2) A˚87). If the nitrogen lone pair is orientated perpendicular to the mirror plane of the metallocene fragement,88,89 longer Ti-N distances are found (Cp2TiCl(C5H3N4) 2.131(5) A˚;90 Cp*2TiN(Me)Ph 2.054(2) A˚88). (83) Structural data of 5b, 5c, 5d, and 7b are given in the Supporting Information. (84) Cozak, D.; Melnik, M. Coord. Chem. Rev. 1986, 74, 53–99. (85) Herrmann, W. A.; Denk, M.; Albach, R. W.; Behm, J.; Herdtweck, E. Chem. Ber. 1991, 124, 683–689. (86) Giolando, D. M.; Kirschbaum, K.; Graves, L. J.; Bolle, U. Inorg. Chem. 1992, 21, 3887–3890. (87) Pupi, R. M.; Coalter, J. N.; Petersen, J. L. J. Organomet. Chem. 1995, 497, 17–25. (88) Feldman, J.; Calabrese, J. C. J. Chem. Soc., Chem. Commun. 1991, 1042–1044. (89) Lukens, W. W., Jr.; Smith, M. R., III; Andersen, R. A. J. Am. Chem. Soc. 1996, 118, 1719–1728. (90) Beauchamp, A. L.; Cozak, D.; Mardhy, A. Inorg. Chim. Acta 1984, 92, 191–197.

Figure 1. ORTEP plot of the solid-state molecular structure of 5a (50% probability ellipsoids). Selected bond lengths (A˚) and angles (deg): Ti1-N1 2.0127(13), Ti1-N2 2.0101(13), Ti1-Ct1 2.122, Ti1-Ct2 2.127, N1-C1 1.392(2), N2-C8 1.399(2), C15C20 1.534(2), C30-C35 1.5206(18), Ti1-C15 2.4835(15), Ti1C16 2.4650(15), Ti1-C17 2.4240(16), Ti1-C18 2.3801(16), Ti1-C19 2.4442(16), Ti1-C30 2.5218(13), Ti1-C31 2.4474(15), Ti1-C32 2.3701(16), Ti1-C33 2.4028(16), Ti1-C34 2.4699(15), C15-C19 1.415(2), C15-C16 1.434(2), C16-C17 1.402(2), C17-C18 1.413(2), C18-C19 1.417(2), C30-C31 1.411(2), C30-C34 1.426(2), C31-C32 1.414(2), C32-C33 1.406(2), C33-C34 1.404(2), C1-N1-Ti1 133.27(10), C8-N2-Ti1 135.19(10), N2-Ti1-N1 95.33(6), Ct-Ti1-Ct 128.2; Ct1 = centroid of C15-C19; Ct2 = centroid of C30-C34. Hydrogen atoms are omitted for clarity. Table 3. Selected Bond Lengths [A˚] and Angles [deg] of 5a-d 5a

5b

5c

5da

CHR2

adamantyl

R = p-tolyl

R = p-tolyl

adamantyl

Ar

p-tolyl

p-tolyl

1-naphthyl

1-naphthyl

2.021(4) 2.027(3) 1.403(5) 1.398(5) 2.116 2.113

2.041(2)

127.6 136.5(3) 134.6(3) 94.5(2)

128.6 133.7(2)

Bond Lengths Ti-N N-C Ti-Ctb

2.010(1) 2.013(1) 1.392(2) 1.399(2) 2.122 2.127

2.008(3) 2.015(3) 1.399(5) 1.415(5) 2.122 2.125

1.384(3) 2.102

Bond Angles Ct-Ti-Ct Ti-N-C N-Ti-N a

128.2 133.3(1) 135.2(1) 95.3(1)

128.5 132.8(3) 133.8(3) 96.5(1)

98.2(1)

b

Molecule on the dyadic axis. Ct = centroid of Cp rings.

In contrast to the reaction course of aniline derivates and 1, which leads to the bisamides 5, the reaction of bis(adamantylidenefulvene)titanium 1a with catalytically relevant alkylamine 3a leads to the monoamide 6. Independent from the stoichiometric conditions, 5 is formed in a selective way, even if an excess of 3a is used. This reaction proceeds at room temperature leading to the orange-red crystalline 6. Surprisingly, only one fulvene ligand of 1a is protonated, to give the mixed CpR-fulvene complex 6 (Scheme 6). The formation of the monoamide 6, in contrast to the bisamides 5a-d, becomes understandable by the lower acidities of

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Figure 3. Detail of the molecular structure of 6 (olefinic C-C double bond green). Scheme 7. Reaction of 1 with Benzophenone Imine

Figure 2. ORTEP plot of the solid-state molecular structure of 6 (50% probability ellipsoids). Selected bond lengths (A˚) and angles (deg): Ti1-N1 1.9386(15), Ti1-Ct1 2.019, Ti1-Ct2 2.058, Ti1-C18 2.1724(19), Ti1-C19 2.3324(18), Ti1-C20 2.472(2), Ti1-C21 2.464(2), Ti1-C22 2.3085(19), Ti1-C23 2.4034(19), Ti1-C33 2.4010(18), Ti1-C34 2.3824(18), Ti1C35 2.3682(19), Ti1-C36 2.376(2), Ti1-C37 2.3869(19), N1C1 1.460(2), C4-C5 1.314(4), C18-C19 1.438(3), C18-C22 1.453(3), C18-C23 1.434(3), C19-C20 1.410(3), C20-C21 1.406(3), C21-C22 1.391(3), C33-C34 1.417(3), C33-C37 1.423(3), C33-C38 1.514(3), C34-C35 1.418(3), C35-C36 1.403(3), C36-C37 1.403(3), C1-N1-Ti1 141.32(12), Ct1Ti1-Ct2 136.4; Ct1 = centroid of C18-C22; Ct2 = centroid of C33-C37. Hydrogen atoms are omitted for clarity.

alkylamines compared with anilines.91 Isolated crystalline 6 is very sensitive to air and moisture, particularly in contrast to the bisamides 5a-d. The monoamide 6 is easily soluble in thf, benzene, toluene, and even n-hexane. The 1H NMR spectrum shows four singlets for the protonated fulvene ligand C5H4-Cp (5.05, 5.08, 5.72, 5.86 ppm), whereas for the unchanged fulvene C5H4-Fv four singlets (4.13, 5.24, 5.29, 5.99 ppm) are found. The NH singlet (6.15 ppm) is characteristically broadened. The complex 6 does give an Mþ signal in the mass spectrum (CI mode, m/z (%): 681 (8)). The EI mode spectrum shows that in a primary step the liberation of the amine 3a leads to an [M - C17H18N]þ fragment (m/z: 445). Crystals of 6, suitable for X-ray structure determination, can be directly obtained from the reaction mixture (benzene/n-hexane) after a few days at room temperature. 6 crystallizes in the triclinic space group P1. The molecular structure of 6 is given in Figure 2. The adamantyle CpR fragment and the adamantylidenefulvene ligand can easily be distinguished (Figure 2) comparing the C18-C23 fulvene bond (1.434(3) A˚) and the elongated C33-C38 distance (1.514(3) A˚). The exocyclic C-C double

bond of the fulvene ligand in 6 is bent out of the fivemembered ring plane by 34.5°, as expected for titanium fulvene complexes.3 The Ti-N-C angle (141.32(12)°) is typical for an amidotitanium complex and comparable to 5 (av 133-135°), although the Ti-N bond (1.9386(15) A˚) is slightly shortened compared to the bisamides 5 (av 2.012.04 A˚). The C-C double bond of the amido alkenyl side chaine in 6 is orientated in a suprafacial manner in the direction of the titanium-nitrogen center (Figure 3). This orientation can be explained on one hand by the Thorpe-Ingold effect of the phenyl groups on the amine 3a.92 On the other hand, the ligand geometry of 6 is in accordance with the intermediate I in the catalytic hydroamination cycle (Scheme 4). A second R-H-shift from the N atom in 6 to the Cexo atom of the intact fulvene ligand would lead to the active imido species (II or III). However, under experimental conditions this rearrangement was not observable upon heating to 60 °C for 5 h. Reactions with Imines. The effect of the shortened Ti-N bond can also be observed in the reaction products of 1 with benzophenone imine in n-hexane at room temperature. Again a fast reaction of 1 to 7 can be observed by the change of color from green to dark red. Dark red crystals of 7 are isolated in 74% (7a, mp 179 °C dec) and 54% (7b, mp 154 °C dec) yield. Solid 7 can be handled without inert conditions in the short-term, but solutions degrade faster, which is visible by a change in color from red to yellow. The Cexo atoms are protonated to give the CpR derivate and two N ligands are bound, comparable to the bisamides 5 as shown in Scheme 7. In the 1H NMR spectra two characteristic triplets (J = 2.6 Hz) of the CpR ligands at 5.47, 5.89 (7a) and 5.22, 5.76 ppm (7b) are found. These values are in agreement with 5 (5.64, 6.06 (5a); 5.13, 5.88 (5b); 5.61, 6.06 (5c), and 5.70, 6.10 (5d)). Again the typical new CexoH singlet for p-tolyl derivative 7b is found at 5.56 ppm. Crystals suitable for X-ray structure determination can be obtained directly from the reaction solution after a few days at room temperature. The complexes 7a,b do not give an Mþ signal in the mass spectrum (neither CI nor EI mode). The molecular structure of 7a is given in Figure 4 as an example, and selected bond distances

(91) Habibi-Yangjeh, A.; Pourbasheer, E.; Danandeh-Jenagharad, M. Monatsh. Chem. 2009, 140, 15–27.

(92) Beesley, R. M.; Ingold, C. K.; Thorpe, J. F. J. Chem. Soc., Trans. 1915, 107, 1080–1106.

Scheme 6. Reaction of 1a with the Aminoalkene 3a

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7b

893

1.945(1) 2.015(1) 1.272(2) 1.274(2)

1.901(2)

164.8(1) 151.8(1) 101.2(1) 135.3

179.1(2)

Bond Lengths Ti-N N-C

1.957(2) 1.960(2) 1.260(3) 1.266(3)

1.259(3)

Bond Angles Ti-N-C N-Ti-N/C Ct-Ti-Ct

168.6(2) 168.4(2) 101.9(1) 135.1

96.41(8) 138.9

Scheme 8. Reaction of 1a with 1,1-Diphenylhydrazine

Figure 4. ORTEP plot of the solid-state molecular structure of 7a (50% probability ellipsoids). Selected bond lengths (A˚) and angles (deg): Ti1-N1 1.9573(18), Ti1-N2 1.9595(18), Ti1-Ct1 2.092, Ti1-Ct2 2.093, N1-C1 1.260(3), N2-C14 1.266(3), Ti1-C27 2.453(2), Ti1-C28 2.423(2), Ti1-C29 2.376(2), Ti1C30 2.395(2), Ti1-C31 2.425(2), Ti1-C42 2.444(2), Ti1-C43 2.417(3), Ti1-C44 2.396(2), Ti1-C45 2.386(2), Ti1-C46 2.432(2), C27-C28 1.418(3), C27-C31 1.434(3), C27-C32 1.520(3), C28-C29 1.409(3), C29-C30 1.420(3), C30-C31 1.405(3), C42-C46 1.413(3), C42-C43 1.429(3), C42-47 1.530(3), C43-C44 1.407(3), C44-C45 1.417(4), C45-C46 1.416(3), C1-N1-Ti1 168.61(16), C14-N2-Ti1 168.36(16), N1-Ti1-N2 101.89(7), N1-Ti1-C29 132.44(9), Ct1-Ti1Ct2 135.1; Ct1 = centroid of C27-C31; Ct2 = centroid of C42-C46. Hydrogen atoms are omitted for clarity.

are summarized in Table 4. 7a crystallizes in the monoclinic space group P21/c and 7b in the triclinic space group P1. The titanium center has the typical pseudotetrahedral coordination features with a Ct-Ti-Ct angle of 135° (7a 135.1°, 7b 135.2°) and a N-Ti-N angle of 102° (7a 101.9(1)°, 7b 101.2(1)°). A comparable reaction pattern was observed by trapping a titanaallene intermediate, Cp*2TidCdCH2, with benzophenone imine and formation of Cp*2Ti(CHdCH2)(N=CPh2) (8). Generally, two different ligand motives of the imine ligand are discussed, leading to azavinylidene (TidNdCR2) or enamide (Ti-NdCR2) forms.93 To distinguish between both forms, the Ti-N-C angle is the essential criterion. In the case of the azavinylidene form a perfect Ti-N-C angle of 180° is observed, e.g., in 8. In contrast, for 7 (7a 168.6° and 168.4°, 7b 164.8° and 151.8°) smaller angles are found. Additionally, the Ti-N bond length in 8 (1.90 A˚) is shorter than in 7a (1.96 A˚) or in 7b (1.95/2.02 A˚). The N-C bonds (1.26-1.27 A˚) are in the range of typical NdC double bonds. A similar bonding situation can be found for Cp2Ti(NCPh2)2.94 However, this complex is formed in a quite different reaction, by a N-N bond cleavage of benzophenone azine. (93) Beckhaus, R.; Wagner, M.; Burlakov, V. V.; Baumann, W.; Peulecke, N.; Spannenberg, A.; Kempe, R.; Rosenthal, U. Z. Anorg. Allg. Chem. 1998, 624, 129–134. (94) Zippel, T.; Arndt, P.; Ohff, A.; Spannenberg, A.; Kempe, R.; Rosenthal, U. Organometallics 1998, 17, 4429–4437.

Reactions with Hydrazine. Whereas the desired TidN double-bond-containing complexes are not available by reaction of 1 with primary amines, the reaction of bis(adamantylidenefulvene)titanium 1a with 1,1-diphenylhydrazine is successful. Reacting 1a with 1,1-diphenylhydrazine and pyridine at room temperature in a benzene/ n-hexane mixture (1:2) as solvent, the titanium hydrazide can be obtained as the pyridine adduct 9 (Scheme 8). The reaction mixture turns instantly from green to red with the 1,1-diphenylhydrazine and does not change when the pyridine is added. It is important to add the pyridine after the hydrazine, because otherwise the pyridine reacts directly with the bis(fulvene)complex 1, forming unknown products. Again the Cexo atoms are both protonated, as shown in Scheme 8, to give the CpR derivative, and the pyridine saturates the coordination of the titanium center. After a few days at 6 °C the product 9 crystallizes directly from the reaction mixture in the form of brown-red crystals suitable for X-ray structure determination. The molecular structure is given in Figure 5. The titanium hydrazide 9 degrades instantly with air or moisture even as a solid and is easily soluble in benzene, toluene, and thf and moderately soluble in n-hexane. However, in solution rearrangement processes are observed, leading to the mono-Cp derivative 10 by a liberation of one CpR ligand (vide infra). Therefore it was not possible to obtain a representative 1H NMR spectra of 9. The complex 9 does not give an Mþ signal in the mass spectrum (neither CI nor EI mode). 9 crystallizes in the monoclinic space group P21/n. The molecular structure of 9 (Figure 5) reveals a typical titanium pseudotetrahedral coordination mode with a Ct-Ti-Ct angle of 126.2° and a N-Ti-N angle of 92.42(6)°. The molecular structure of 9 is clearly indicative for an end-on bonded NNPh22- ligand. This structure motive is in contrast to side-on hydrazido(1-) moieties95-97 as well as bridging coordination (95) Hughes, D. L.; Leigh, G. J.; Walker, D. G. J. Chem. Soc., Dalton Trans. 1989, 1413–1416. (96) Latham, I. A.; Leigh, G. J.; Huttner, G.; Jibril, I. J. Chem. Soc., Dalton Trans. 1986, 385–392. (97) Goetze, B.; Knizek, J.; N€ oth, H.; Schnick, W. Eur. J. Inorg. Chem. 2000, 1849–1854.

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Scheme 9. Reaction of 1b with Two Equivalents of 1,1-Diphenylhydrazine

Figure 5. ORTEP plot of the solid-state molecular structure of 9 (50% probability ellipsoids). Selected bond lengths (A˚) and angles (deg): Ti1-Ct1 2.199, Ti1-Ct2 2.192, Ti1-N1 1.7567(13), Ti1-N3 2.2430(14), N1-N2 1.3534(18), N2-C1 1.401(2), N2-C7 1.438(2), Ti1-C18 2.6123(16), Ti1-C19 2.5239(17), Ti1-C20 2.3936(17), Ti1-C21 2.4582(17), Ti1C22 2.5399(16), Ti1-C33 2.4484(16), Ti1-C34 2.4480(17), Ti1C35 2.5419(17), Ti1-C36 2.5813(18), Ti1-C37 2.4734(17), C18-C19 1.406(2), C18-C22 1.435(2), C18-C23 1.511(2), C19-C20 1.416(3), C20-C21 1.413(3), C21-C22 1.401(2), C33-C34 1.412(2), C33-C37 1.417(2), C33-C38 1.514(2), C34-C35 1.416(3), C35-C36 1.392(3), C36-C37 1.416(2), N1-Ti1-N3 92.42(6), N2-N1-Ti1 171.05(11), N1-N2-C1 121.99(13), N1-N2-C7 116.78(12), Ct1-Ti1-Ct2 126.2; Ct1 = centroid of C18-C22; Ct2 = centroid of C33-C37. Hydrogen atoms are omitted for clarity.

modes (e.g., μ1:μ2-[CpTiCl(NNPh2)]2,98 [Ti2(μ-η2,η1-NNMe2)2Cl4(HNMe2)2]99). The TidN bond lengths to the hydrazido(2-) ligand (1.7567(13) A˚) is in the range of typical TidN double bonds, and the almost linear TidN-N angle (171.05(11)°) indicates an sp-hybridized N atom, as found also in comparable compounds ([Ti(NNPh2)Cl2(HC(Me2Pz)3)]:99 TidN 1.718(2) A˚, Ti-N-N 176.03(16)°; [Ti(NNMe2)(t-Bu-bpy)(dpma)]:100 TidN 1.708(3) A˚, Ti-N-N 177.3(2)°; [Ti{MeN(CH2CH2NSiMe3)2}(NNPh2)(py)]:101 TidN 1.733(5) A˚, Ti-N-N 177.7(4)°; [Ti(NNPh2)(Me2Calix)]102 TidN 1.717(2) A˚, Ti-N-N 177.3(2)°; [Ti[NN(H)Ph](t-Bu-bpy)(dpma)]:103 TidN 1.712(4) A˚; [Cp*Ti(NXylN)(NNPh2)]:104 TidN 1.736(2) A˚, Ti-N-N 168.2(2)°). A structural analogue to 9 is found in the case of a zirconocene derivative in the form of (98) Hughes, D. L.; Latham, I. A.; Leigh, G. J. J. Chem. Soc., Dalton Trans. 1986, 393–398. (99) Parsons, T. B.; Hazari, N.; Cowley, A. R.; Green, J. C.; Mountford, P. Inorg. Chem. 2005, 44, 8442–8458. (100) Li, Y.; Shi, Y.; Odom, A. L. J. Am. Chem. Soc. 2004, 126, 1794– 1803. (101) Selby, J. D.; Manley, C. D.; Feliz, M.; Schwarz, A. D.; Clot, E.; Mountford, P. Chem. Commun. 2007, 4937–4939. (102) Clulow, A. J.; Selby, J. D.; Cushion, M. G.; Schwarz, A. D.; Mountford, P. Inorg. Chem. 2008, 47, 12049–12062. (103) Patel, S.; Li, Y.; Odom, A. L. Inorg. Chem. 2007, 46, 6373–6381. (104) Weitershaus, K.; Wadepohl, H.; Gade, L. H. Organometallics 2009, 28, 3381–3389. (105) Walsh, P. J.; Carney, M. J.; Bergman, R. G. J. Am. Chem. Soc. 1991, 113, 6343–6345.

(DMAP = dimethylami[Cp2ZrdNNPh2(DMAP)] nopyridine).105 The N-N distance of 1.364(10) A˚ versus 1.3534(18) A˚ (9) is indicative of an N-N single bond (NtN: 1.0975(2) A˚,106 PhNdNPh: 1.255 A˚,107 Ph(H)N-N(H)Ph: 1.394(7) A˚108). However, the N-N distance in the Ph2NN2complexes is characterized by a weak shortening of the N-N bond compared to free hydrazines (H2N-NH2: 1.46 A˚,109 Ph2N-NPh2: 1.406(4) A˚,110 Py(H)N-N(H)Py: 1.3934(14) A˚111). In the presence of two equivalents of Ph2NNH2 the expected liberation of one CpRH ligand is observed, leading to a monocyclopentadiene derivative 10 as shown in Scheme 9. When the solution of 1,1-diphenylhydrazine in n-hexane is added to the solution of 1b in benzene, the reaction can instantly be observed by the rapid change in color from green to red. Again the pyridine has to be added after the hydrazine. After stirring for 70 h orange-red 10b can be isolated in 59% yield (mp 111 °C) by filtration. 10b degrades very fast with air and moisture, visible in a color change from orangered to green (less dark than 1b) to light yellow, and is easily soluble in benzene, toluene, and thf and moderately soluble in n-hexane. 10a was obtained from a solution of 9 after heating for a few minutes to 60 °C. The liberation of one equivalent of the corresponding CpRH derivate was proven by GC-MS. Instead of this ligand, a second hydrazido ligand (Ph2N-(H)N-) is bound and pyridine saturates the coordination sphere of the titanium center. Product 10b is isolated independently from the start stoichiometry. 10a was characterized via NMR spectroscopy, and the corresponding signals are very similar to 10b. The characteristic NMR signals are four singlets of a CpR ligand at 5.62, 5.78, 6.22, 6.31 (10a) compared to 5.60, 5.87, 6.10, 6.19 (10b) ppm and a broadened singlet at 8.33 (10a) compared to 8.29 (10b) ppm for the NH unit. The CexoH singlet of 10b at 5.72 ppm is in the same range as the corresponding signals for 5b (5.30 ppm), 5c (5.42 ppm), and 7b (5.56 ppm). The complexes 10a,b do not give an Mþ signal in the mass spectrum (neither CI nor EI mode). Crystals suitable for X-ray structure determination were obtained from a saturated benzene solution after a few days at room temperature. The piano stool titanium complex 10b crystallizes in the triclinic space group P1. The molecular structure of 9 is given in Figure 6, and selected bond distances compared to 9 are summarized in Table 5. (106) Wilkinson, P. G.; Hounk, N. B. J. Chem. Phys. 1956, 24, 528– 534. (107) Allen, F. H.; Kennrad, O.; Watson, D. G.; Brammer, L.; Orpen, A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1–S19. (108) Pestana, D. C.; Power, P. P. Inorg. Chem. 1991, 30, 528–535. (109) Sutton, L. E. Tables of Interatomic Distances and Configurations in Molecules and Ions; Chemical Socienty: London, 1958; Vol. 11. (110) Hoekstra, A.; Vos, A.; Braun, P. B.; Hornstra, J. Acta Cryst., Sect. B 1975, B31, 1708–1715. (111) Theilmann, O.; Saak, W.; Haase, D.; Beckhaus, R. Organometallics 2009, 28, 2799–2807.

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titanium hydrazido(1-) complexes are unknown up to now. The Ti-N-N angles of the (NNPh2)2- ligand are found nearly linear (av 170°) in 9 and 10b compared to 131.53(14)° for the (N(H)NPh2)- ligand in 10b. The N-Cphenyl bond lengths (1.40-1.44 A˚) are in the expected range. The liberation of one Cp ligand during attempts of the preparation of [Cp*2TidNNPh2(py)] is observed by Mountford et al., leading to [Cp*Ti(dNNPh2)(NHNPh2)(py)],101 comparable to 10. However, the X-ray structural characterization of these Cp* derivatives failed. The mixed hydrazido(2-)/(1-) adduct 10 itself is comparable to Bergman’s amide/imide complex CpTi(NAr)(NHAr)(py), which is used as a model for the active species in the Cp2TiMe2-catalyzed hydroamination of alkynes and allenes.81

Conclusion Figure 6. ORTEP plot of the solid-state molecular structure of 10b (50% probability ellipsoids). Selected bond lengths (A˚) and angles (deg): Ti1-Ct1 2.076, Ti1-N3 1.7338(17), Ti1-N1 1.9575(18), Ti1-N5 2.2053(17), N1-N2 1.410(2), N2-C7 1.402(3), N2-C1 1.420(3), N3-N4 1.370(2), N4-C13 1.414(3), N4-C19 1.422(3), Ti1-C30 2.386(2), Ti1-C31 2.382(2), Ti1C32 2.423(2), Ti1-C33 2.412(2), Ti1-C34 2.375(2), C30-C31 1.421(3), C30-C34 1.410(3), C30-C35 1.523(3), C31-C32 1.410(3), C32-C33 1.402(3), C33-C34 1.420(3), N3-Ti1-N1 101.55(8), N3-Ti1-N5 96.71(7), N1-Ti1-N5 98.83(7), N2-N1Ti1 131.53(14), C7-N2-N1 117.79(16), N1-N2-C1 116.78(17), N4-N3-Ti1 170.20(14), N3-N4-C13 116.54(17), N3-N4C19 118.59(17), Ct1-Ti1-N1 115.8, Ct1-Ti1-N3 122.8, Ct1-Ti1-N5 116.9; Ct1 = centroid of C30-C34. Hydrogen atoms are omitted for clarity. Table 5. Selected Bond Lengths [A˚] and Angles [deg] of 9 and 10b 9

10b

Bond Lengths 2-

Ti-N (NNPh2) Ti-N (N(H)NPh2)Ti-N (pyridine) N-N (NNPh2)2N-N (N(H)NPh2)N-C (NNPh2)2N-C (N(H)NPh2)1-

1.757(1) 2.243(1) 1.353(2) 1.401(2) 1.438(2)

1.7338(17) 1.9575(18) 2.2053(17) 1.370(2) 1.410(2) 1.414(3) 1.422(3) 1.402(3) 1.420(3)

Bond Angles Ti-N-N (NNPh2)2Ti-N-N (N(H)NPh2)-

171.1(1)

170.20(14) 131.53(14)

In the molecular structure of 10b the (NNPh2)2- and the (N(H)NPh2)- ligand can easily be distinguished by the TidN double bond length of 1.7338(17) A˚ as a typical double bond (comparable to 1.757(1) A˚ in 9, vide supra) in contrast to the Ti-N single bond length of 1.9575(18) A˚ for a slightly shortened single bond (comparable to 1.96 A˚ in 7a). Both hydrazido ligands are bonded in a end-on coordination mode, in contrast to side-on hydrazido(2-)98-100 and hydrazido(1-)95-97,100,112,113 ligands. To the best of our knowledge, structurally characterized end-on coordinated (112) Hemmer, R.; Thewalt, U.; Hughes, D. L.; Leigh, G. J.; Walker, D. G. J. Organomet. Chem. 1987, 323, C29–C32. (113) Hughes, D. L.; Jimenez-Tenorio, M.; Leigh, G. J.; Walker, D. G. J. Chem. Soc., Dalton Trans. 1989, 2389–2395.

Bis(pentafulvene)titanium complexes are thermally stable, storable, and efficient alternative substrates in applications of titanocene(IV) derivatives. In such a way, the bis(pentafulvene)titanium complexes have been found to be competent catalysts for intramolecular hydroamination reactions of geminally disubstituted amino alkenes. Among the catalysts investigated, best activities are found for the benzofulvene derivative 2. Generally, the bis(pentafulvene)titanium complexes are valuable reagents for the preparation of Ti-N-containing products under comparably mild conditions. In stoichiometric reactions of 1 with aniline derivates and keto imines CpR2Ti(NHAr)2 and CpR2Ti(NdCPh2)2 complexes become available in high yields. The expected formation of imido derivatives CpR2TidNR in reactions of primary aryl amines with 1 is not observed. Employing the catalytically relevant amine H2NCH2C(Ph)2CH2CHdCH2 (3a) in reaction with 1, a selective formation of a structurally characterized titanium monoamide (6) occurs. In reactions of diphenylhydrazine and 1, hydrazido complexes are formed. Further detailed mechanistic investigations are in progress.

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 glovebox and Schlenk techniques. Solvents were dried according to standard procedures. Solvents were distilled over Na/K alloy and benzophenone under a nitrogen atmosphere. 1H and 13C NMR spectra were recorded on a Bruker AVANCE III 500 spectrometer (1H 500.1 MHz; 13C 125.8 MHz) or a Bruker AVANCE 300 spectrometer (1H 300.1 MHz). The NMR chemical shifts were referenced to residual protons of the solvent (benzene-d6 or CDCl3) or the internal standard TMS. Electron impact (EI) mass spectra were taken on a Finnigan-MAT 95 spectrometer. IR spectra were recorded on a Bio-Rad FTS-7 spectrometer using KBr pellets or on a Bruker Tensor 27 spectrometer using an attenuated total reflection (ATR) method. Elemental analyses were carried out on a EuroEA 3000 elemental analyzer. Melting points were determined using a Mel-Temp by Laboratory Devices, Cambridge. The bis(fulvene)titanium complexes 1 and 2 were prepared according to literature procedures.3 The 1,1-diphenylhydrazine was generated from the hydrochloride by the literature method.114 All hydroamination reactions were performed under an inert atmosphere of nitrogen in oven-dried (114) Blake, A. J.; McInnes, J. M.; Mountford, P.; Nikonov, G. I.; Swallow, D.; Watkin, D. J. J. Chem. Soc., Dalton Trans. 1999, 379–391.

Article Schlenk tubes (Duran glassware, 100 mL, i 30 mm) equipped with Teflon stopcocks and magnetic stirring bars (15 4.5 mm). For flash chromatography, silica gel 60 from Fluka (230400 mesh, particle size 0.040-0.063 mm) was used. PE: light petroleum ether, bp 40-60 °C. MTBE: tert-butyl methyl ether. Hydroamination of Nonvolatile Aminoalkenes. General Procedure A. An oven-dried Schlenk tube equipped with a Teflon stopcock and a magnetic stirring bar was transferred into a nitrogen-filled glovebox and charged with the catalyst (0.12 mmol, 5 mol %), toluene (1.0 mL), the aminoalkene (2.40 mmol), and toluene (1.0 mL). Then the tube was sealed and the resulting mixture was heated to 105 °C for 24 h. After the mixture had been cooled to room temperature, the solution was diluted with CH2Cl2 (30 mL) and washed with saturated aqueous NH4Cl solution. The aqueous layer was extracted with CH2Cl2 (3 50 mL), and the combined organic layers were dried with MgSO4. After concentration under vacuum in the presence of Celite, the product was isolated by flash chromatography. Hydroamination of Volatile Aminoalkenes and Subsequent Formation of Benzoylamides. General Procedure B. An ovendried Schlenk tube equipped with a Teflon stopcock and a magnetic stirring bar was transferred into a nitrogen-filled glovebox and charged with the catalyst (0.12 mmol, 5 mol %), toluene (1.0 mL), the aminoalkene (2.40 mmol), and toluene (1.0 mL). Then the tube was sealed, and the resulting mixture was heated to 105 °C for 24 h. After the mixture had been cooled to room temperature, CH2Cl2 (10 mL) and NEt3 (1.0 mL, 7.2 mmol) were added. Then benzoyl chloride (0.3 mL, 2.64 mmol) was added dropwise at 25 °C, and the resulting mixture was stirred for 12 h. Then the solution was diluted with CH2Cl2 (30 mL) and washed with a saturated aqueous NH4Cl solution. The aqueous layer was extracted with CH2Cl2 (3 50 mL), and the combined organic layers were dried with MgSO4. After concentration under vacuum in the presence of Celite, the product was isolated by flash chromatography. 2-Methyl-4,4-diphenylpyrrolidine (4a). General procedure A was used to synthesize 4a from 1-amino-2,2-diphenyl-4-pentene (3a, 570 mg, 2.40 mmol). After chromatography (SiO2, MTBE/7 N NH3 in MeOH, 95:5, Rf = 0.35), 4a (502 mg, 2.12 mmol, 88%, catalyst: 2) was obtained as a colorless oil. IR (neat): 1/λ 2960 (w), 2869 (w), 1599 (w), 1494 (m), 1447 (m), 1374 (w), 1099 (w), 1034 (w), 774 (m), 756 (m), 698 (s) cm-1. 1H NMR (CDCl3, 500 MHz): δ 1.20 (d, J = 6.7 Hz, 3 H, CH3), 2.03 (dd, J = 12.5, 8.9 Hz, 1 H, CH3-CH-CH2), 2.10 (br s, 1 H, NH), 2.74 (dd, J = 12.5, 6.4 Hz, 1 H, CH3-CH-CH2), 3.32-3.41 (m, 1 H, CH3-CH), 3.47 (d, J = 11.0 Hz, 1 H, NH-CH2), 3.67 (d, J = 11.6 Hz, 1 H, NHCH2), 7.14-7.18 (m, 2 H, aryl-H), 7.20-7.31 (m, 8 H, aryl-H) ppm. 13C NMR (CDCl3, 126 MHz, DEPT): δ 22.3 (CH3), 47.0 (CH2), 53.0 (CH), 57.2 (C), 57.9 (CH2), 125.9 (CH), 125.9 (CH), 126.9 (CH), 127.0 (CH), 128.2 (CH), 128.3 (CH), 147.0 (C), 147.8 (C) ppm. MS (EI, 70 eV): m/z (%) 237 (12) [M]þ, 178 (5), 165 (6), 115 (5), 91 (4), 57 (100), 56 (6). HRMS: calcd (C17H19N) 237.1517; found 237.1520. 4,4-Dibenzyl-2-methylpyrrolidine (4b). General procedure A was used to synthesize 4b from 1-amino-2,2-dibenzyl-4-pentene (3b, 637 mg, 2.40 mmol). After chromatography (SiO2, MTBE/7 N NH3 in MeOH, 90:10, Rf = 0.32), 4b (593 mg, 2.23 mmol, 93%, catalyst: 2) was obtained as a colorless oil. IR (neat): 1/λ 3026 (w), 2955 (w), 2921 (w), 2885 (w), 1602 (w), 1494 (m), 1453 (m), 1373 (w), 1083 (w), 1030 (w), 750 (s), 738 (s), 700 (vs) cm-1. 1 H NMR (CDCl3, 500 MHz): δ 0.97 (d, J = 6.7 Hz, 3 H, CH3), 1.30 (dd, J = 12.8, 9.2 Hz, 1 H, CH3-CH-CH2), 1.44 (br s, 1 H, NH), 1.90 (dd, J = 12.8, 7.3 Hz, 1 H, CH3-CH-CH2), 2.73 (d, J = 6.1 Hz, 4 H, CH2-aryl), 2.82 (d, J = 11.6 Hz, 1 H, NH-CH2), 2.94 (d, J = 11.6 Hz, 1 H, NH-CH2), 2.95-3.02 (m, 1 H, CH3CH), 7.14-7.25 (m, 6 H, aryl-H), 7.26-7.31 (m, 4 H, aryl-H) ppm. 13C NMR (CDCl3, 126 MHz, DEPT): δ 21.4 (CH3), 43.9 (CH2), 45.0 (CH2), 45.3 (CH2), 48.7 (C), 54.1 (CH), 56.2 (CH2), 126.1 (CH), 126.1 (CH), 128.0 (CH), 130.4 (CH), 130.5 (CH), 139.0 (C), 139.1 (C) ppm. MS (EI, 70 eV): m/z (%) 265 (6) [M]þ,


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264 (14), 250 (12), 187 (14), 174 (51), 173 (53), 115 (12), 96 (37), 91 (92), 65 (13), 57 (100). HRMS: calcd (C19H23N) 265.1830; found 265.1827. (3-Methyl-2-azaspiro[4.5]decan-2-yl)(phenyl)methanone (4c). General procedure B was used to synthesize 4c from (1-allylcyclohexyl)methanamine (3c, 368 mg, 2.40 mmol). After chromatography (SiO2, PE/EtOAc, 80:20, Rf = 0.57), 4c (433 mg, 1.68 mmol, 70%, catalyst: 2) was obtained as a colorless oil. IR (neat): 1/λ 2992 (m), 2853 (m), 1626 (vs), 1577 (m), 1447 (s), 1403 (vs), 1354 (w), 1304 (w), 1221 (w), 1179 (w), 1142 (w), 1106 (w), 792 (m), 716 (s), 698 (s), 661 (s) cm-1. 1H NMR (CDCl3, 500 MHz, 50 °C): δ 1.22-1.49 (m, 14 H), 2.12 (dd, J = 12.6, 7.5 Hz, 1 H, CH3-CHCH2), 3.16 (d, J = 11.0 Hz, 1 H, NH-CH2), 3.29 (br s, 1 H, NHCH2), 4.30 (br s, 1 H, CH3-CH), 7.33-7.41 (m, 3 H), 7.43-7.55 (m, 2 H) ppm. 13C NMR (CDCl3, 126 MHz, DEPT, 50 °C): δ 20.3 (CH3), 22.6 (CH2), 23.7 (CH2), 26.1 (CH2), 33.7 (CH2), 36.3 (CH2), 42.2 (C), 44.8 (CH2), 52.0 (CH), 60.2 (CH2), 127.2 (CH), 128.1 (CH), 129.6 (CH), 137.5 (C), 170.1 (C) ppm. MS (EI, 70 eV): m/z (%) 257 (10) [M]þ, 242 (6), 161 (5), 160 (12), 106 (6), 105 (100), 77 (25), 56 (7), 41 (4). HRMS: calcd (C17H24NO) 258.1858; found 258.1864. Phenyl(2,4,4-trimethylpyrrolidin-1-yl)methanone (4d). General procedure B was used to synthesize 4d from 1-amino-2,2dimethyl-4-pentene (3d, 272 mg, 2.40 mmol). After chromatography (SiO2, PE/EtOAc, 80:20, Rf = 0.27) 4d (91 mg, 0.42 mmol, 18%, catalyst: 2) was obtained as a colorless oil. IR (neat): 1/λ 2957 (m), 2868 (m), 1716 (w), 1626 (vs), 1577 (m), 1447 (m), 1403 (vs), 1372 (m), 1352 (m), 1290 (m), 1213 (m), 1136 (m), 1074 (w), 851 (w), 792 (m), 716 (s), 698 (s), 661 (m) cm-1. 1H NMR (CDCl3, 500 MHz): δ 0.91 (s, 3 H, CH3), 1.05 (s, 3 H, CH3), 1.37-1.45 (m, 4 H), 1.95 (dd, J = 12.8, 7.3 Hz, 1 H, CH3-CH-CH2), 3.10 (d, J = 10.4 Hz, 1 H, NH-CH2), 3.29 (d, J = 10.4 Hz, 1 H, NH-CH2), 4.31-4.40 (m, 1 H, CH3-CH), 7.36-7.55 (m, 5 H, aryl-H) ppm. 13 C NMR (CDCl3, 126 MHz, DEPT): δ 20.2 (CH3), 25.4 (CH3), 25.7 (CH3), 38.2 (C), 47.5 (CH2), 52.9 (CH), 62.6 (CH2), 127.5 (CH), 128.1 (CH), 129.9 (CH), 137.1 (C), 170.1 (C) ppm. MS (EI, 70 eV): m/z (%) 217 (14) [M]þ, 174 (26), 105 (100), 77 (82), 56 (64), 55 (27), 51 (51), 50 (11), 42 (14), 41 (47). HRMS: calcd (C14H19NO) 217.1467; found 217.1464. X-ray Diffraction. Single-crystal experiments were performed on a Stoe IPDS or Bruker ApexII diffractometer with graphitemonochromated Mo KR radiation (λ = 0.71073 A˚). The structures were solved by direct phase determination and refined by full-matrix least-squares techniques against F2 with the SHELXL97 program system.115 X-ray data of compounds 5a, 6, 7a, 9, and 10b are given in Table 6 (for 5b, 5c, 5d, and 7b see ref 83). CpAd2Ti(NHp-tolyl)2, 5a. 1a (200 mg, 0.45 mmol) and 96 mg (0.9 mmol) of p-methylaniline were placed in a Schlenk tube, and 20 mL of n-hexane was added. The color of the reaction mixture changed instantly from green to red. Storing the solution for a few days at room temperature and filtration led to a fine crystalline product. X-ray-quality crystals were obtained from a saturated n-hexane solution of X at room temperature. The solid product can be handled without inert atmosphere for short periods. Yield: 112 mg (38%). Mp: 162 °C. IR (KBr): 1/λ 3364 (s), 3087 (w), 2999 (s), 2896 (vs), 2848 (s), 1601 (s), 1565 (w), 1496 (vs), 1447 (s), 1351 (w), 1294 (w), 1260 (vs), 1170 (s), 1098 (s), 1060 (w), 972 (w), 951 (w), 884 (w), 854 (s), 897 (vs), 764 (s), 649 (w), 571 (w), 529 (w), 511 (s) cm-1. 1H NMR (C6D6, 500 MHz): δ 1.37-2.77 (m, 28 H, adamantyl), 2.18 (s, 6 H, CH3), 5.64 (s, 4 H, C5H4), 6.06 (s, 4 H, C5H4), 6.85 (d, J = 7.8 Hz, 4 H, C6H4CH3), 6.97 (d, J = 7.9 Hz, 4 H, C6H4CH3), 7.39 (s, 2 H, NH) ppm. 13C NMR (C6D6, 125 MHz): δ 20.8 (CH3), 28.0, 28.1, 32.2, 32.7, 38.1, 39.0, 44.5 (adamantyl), 110.7, 112.2, 118.5 (C5H4), 127.1, 128.3, 129.0, 129.4 (tolyl) ppm. MS (EI, 70 eV): m/z (%) 106.1 (59) [NH-p-tolyl]þ, 200.1 (100) [CpHAd]þ, 335.0 (6) [CpAdTi(NH-p-tolyl)]þ. (115) Sheldrick, G. M. SHELXL-97. A Program for Refining Crystal Structures; University of G€ottingen: Germany, 1997.

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Table 6. Crystal Structure Data for Compounds 5a, 6, 7a, 9, and 10b

empirical formula fw color, habit cryst dimens, mm cryst syst space group a, A˚ b, A˚ c, A˚ R, deg β, deg γ, deg V, A˚3 Z Dcalc, g cm-3 μ, mm-1 T, K θ range, deg no. of reflns colld no. of indep reflns no. of reflns with I > 2σ(I) abs corr max., min. transmn final R indices (I > 2σ(I)) R indices (all data)

5a

6

7a

9

10b

C44H54N2Ti 658.79 dark red prisms 0.45 0.31 0.17 monoclinic P21/n 11.7970(6) 13.6327(5) 22.8239(12) 90 97.930(6) 90 3635.6(3) 4 1.204 0.268 153(2) 2.34 to 26.13 38 728 7181 [R(int) = 0.0548] 4561

C47H55NTi 681.82 orange red crystals 0.35 0.21 0.05 triclinic P1 10.3527(5) 12.7086(6) 15.6582(7) 73.898(3) 82.947(3) 66.625(3) 1816.67(15) 2 1.246 0.270 153(2) 3.32 to 30.11 40 975 10 585 [R(int) = 0.0411] 7340

C59H65N2Ti 850.03 dark red needles 1.10 0.34 0.13 monoclinic P21/c 12.2434(8) 34.6448(14) 11.6890(6) 90 105.166(7) 90 4785.4(4) 4 1.180 0.219 153(2) 2.09 to 26.09 40 335 8895 [R(int) = 0.0629] 5282

C47H53N3Ti 707.82 red crystals 0.78 0.56 0.37 monoclinic P21/n 12.2755(4) 13.1717(5) 23.3612(8) 90 99.800(2) 90° 3722.1(2) 4 1.263 0.268 153(2) 3.07 to 29.21 40 459 9952 [R(int) = 0.0320] 7599

C58H58N5Ti 872.99 red brown prisms 0.27 0.21 0.14 triclinic P1 12.8053(4) 12.8506(4) 15.4208(5) 93.880(2) 104.058(2) 102.959(2) 2378.78(13) 2 1.219 0.224 153(2) 2.59 to 28.00 35 642 11 313 [R(int) = 0.0436] 7031

numerical 0.9558 and 0.8888 R1 = 0.0305, wR2 = 0.0630 R1 = 0.0584, wR2 = 0.0670


none 0.9721 and 0.7948 R1 = 0.0420, wR2 = 0.1038 R1 = 0.0748, wR2 = 0.1128


none 0.9694 and 0.9425 R1 = 0.0508, wR2 = 0.1096 R1 = 0.1020, wR2 = 0.1289

CpTol2Ti(NHp-tolyl)2, 5b. 5b was prepared in the same manner with 200 mg (0.35 mmol) of 1b and 76 mg (0.7 mmol) of pmethylaniline. Yield: 175 mg (64%). Mp: 155 °C. IR (KBr): 1/λ 3365 (w), 3001 (s), 2914 (s), 2853 (s), 1602 (s), 1498 (vs), 1445 (w), 1374 (w), 1292 (w), 1257 (vs), 1172 (w), 1105 (s), 1019 (s), 944 (w), 919 (w), 891 (w), 853 (w), 804 (vs), 759 (s), 574 (s), 535 (w), 508 (s), 483 (s) cm-1. 1H NMR (C6D6, 300 MHz): δ 2.08 (s, 12 H, CH3), 2.22 (s, 6 H, CH3-aniline), 5.13 (s, 4 H, C5H4), 5.30 (s, 2 H, C5H4-CH), 5.88 (s, 4 H, C5H4), 6.89-6.99 (m, 16 H, C6H4CH3), 7.09 (d, J = 8.0 Hz, 8 H, aniline), 7.84 (s, 2 H, NH) ppm. MS (EI, 70 eV): m/z (%) 106 [p-tolyl-NH]þ, 258 [p-tolyl2Fv]þ, 260 [CpRH]þ, 516.3 [M - CpR - 3H]þ. CpTol2Ti(NH-naphthyl)2, 5c. 5c was prepared in the same manner with 200 mg (0.35 mmol) of 1b and 102 mg (0.7 mmol) of 1-naphthylamine. Yield: 132 mg (44%). Mp: 162 °C. IR (KBr): 1/λ 3042 (w), 3015 (w), 2914 (w), 1563 (s), 1506 (s), 1438 (s), 1391 (vs), 1284 (s), 1221 (s), 1089 (s), 1018 (s), 918 (w), 882 (s), 815 (s), 784 (s), 764 (vs), 721 (s), 643 (w), 617 (s), 571 (s), 542 (w), 507 (s), 482 (s) cm-1. 1H NMR (C6D6, 500 MHz,): δ 2.03 (s, 12 H, CH3), 5.42 (s, 2 H, C5H4-CH), 5.61 (t, 3J = 2.7 Hz, 4 H, C5H4), 6.06 (t, 3J = 2.6 Hz, 4 H, C5H4), 6.82 (d, 3J = 7.9 Hz, 8 H, tolyl), 7.03 (d, J = 8.0 Hz, 8 H, tolyl), 7.15 (t, 3J = 7.8 Hz, 2 H, naphthyl), 7.21 (d, 3J = 8 Hz, 2 H, naphthyl), 7.35 (t, 3J = 7.6 Hz, 4 H, naphthyl), 7.44, (td, J = 7.0 Hz, 2 H, naphthyl), 7.73 (d, J = 7.5 Hz, 2 H, naphthyl), 8.08 (d, J = 8.5 Hz, 2 H, naphthyl), 8.72 (s, 2 H, NH) ppm. 13C NMR (C6D6, 125 MHz,): δ 20.9 (CH3), 31.9 (CH3), 52.2 (C5H4-CHR2), 110.6 (C5H4), 115.0 (C5H4), 115.8 (C5H4), 118.9 (C5H4), 121.9, 124.3, 124.4, 125.3, 127.8, 128.0, 128.2, 128.3, 129.1, 129.2, 129.4, 131.1, 135.0, 136.1, 142.0, 153.9 (NH-C) ppm. MS (EI, 70 eV): m/z (%) 143 [Naph - NH2]þ, 258 [Fv]þ, 260 [Fv þ2H)]þ. CpAd2Ti(NH-naphthyl)2, 5d. 5d was prepared in the same manner with 178 mg (0.4 mmol) of 1a and 115 mg (0.8 mmol) of 1-naphthylamine. Yield: 170 mg (61%). Mp: 159 °C. IR (KBr): 1/λ 2997 (s), 2847 (s), 1565 (s), 1504 (m), 1447 (m), 1397 (s), 1286 (s), 1225 (s), 1113 (m), 1090 (m), 1048 (m), 1019 (m), 885 (m), 818 (s), 783 (m), 768 (s), 723 (m), 572 (m), 515 (m), 391 (m) cm-1. 1H NMR (C6D6, 500 MHz): δ 1.58-1.82 (m, 24 H, adamantyl), 1.99 (s, 4 H, adamantyl), 2.96 (s, 2 H, adamantyl), 5.70 (s, 4 H, C5H4), 6.10 (s, 4 H, C5H4), 7.24 (d, J = 7.8 Hz, 2 H,

naphthyl), 7.27 (t, J = 7.7 Hz, 2 H, naphthyl), 7.33 (t, J = 7.5 Hz, 2 H, naphthyl), 7.42 (t, J = 7.6 Hz, 2 H, naphthyl), 7.55 (d, J = 7.2 Hz, 2 H, naphthyl), 7.72 (d, J = 8.1 Hz, 2 H, naphthyl), 7.89 (d, J = 8.4 Hz, 2 H, naphthyl), 8.30 (s, 2 H, NH) ppm. 13C NMR (C6D6, 125 MHz): δ 28.0, 28.1, 32.2, 32.5, 38.0, 38.6, 44.0 (adamantly), 111.0, 112.2, 116.0, 118.9, 121.6, 124.2, 124.7, 125.3, 129.2, 131.1, 135.0, 154.3 (C-N) ppm. MS (EI, 70 eV): m/z (%) 143 (100) [naphthyl-NH2]þ, 200 (43) [CpRH]þ, 267 (22) [CpCHTiNH-naphthyl]þ, 446 (2) [CpR2Ti]þ, 465 (10) [CpRCpCHTiNH-naphthyl]þ, 587 (11) [CpR2TiNH-naphthyl]þ. Anal. Calcd for C50H54N2Ti: C 80.53; H 7.45, N 3.83. Found: C 80.59, H 7.76, N 3.75. CpAd2TiNHCH2CPh2CH2CHdCH2, 6. 1a (178 mg, 0.4 mmol) was placed in a Schlenk tube, and 5 mL of benzene was added. Then 95 mg (0.4 mmol) of 3a was dissolved in 10 mL of nhexane and added to the reaction solution. The color of the reaction mixture changed instantly from green to red. Crystals of X-ray-quality were obtained from the solution after a few days at 6 °C. Yield: 42 mg (15.5%). Mp: 108 °C. IR (KBr): 1/λ 3350 (s), 3055 (w), 2900 (vs), 2846 (s), 2360 (w), 2342 (w), 1634 (vw), 1597 (vw), 1494 (s), 1447 (s), 1384 (w), 1260 (s), 1098 (vs), 914 (s), 870 (s), 793 (s), 756 (s), 723 (w), 699 (s), 665 (w), 564 (w) cm-1. 1H NMR (C6D6, 500 MHz): δ 1.42-2.90 (m, 29 H, adamantyl), 2.77 (m, 2 H, -CH2-CHd), 4.0 (d, J = 6.4 Hz, 2 H, -NH-CH2-), 4.13, 5.24, 5.29, 5.99 (s, 4 H, C5H4-Fv), 4.9, 5.0 (m, 2 H, dCH2), 5.05, 5.08, 5.72, 5.86 (s, 4 H, C5H4--Cp), 5.5 (m, 1 H, -CHd), 6.15 (s, 1 H, NH), 7.03-7.14 (m, 10 H, C6H5) ppm. 13C NMR (C6D6, 125 MHz): δ 28.3-64.3 (adamantyl/ adamantylidene), 42.3 (-CH2-CHd), 64.3 (NH-CH2-), 100.8, 107.7, 108.1, 113.2 (C5H4), 107.7, 111.5, 113.2 (C5H4-Fv),109.8 (-CHd), 117.3 (dCH2), 125.1-128.7 (Ph) ppm. MS (EI, 70 eV): m/z (%) 200 (100) [CpRH]þ, 445 (33) [CpRFvTi]þ. MS (CI, isobutane): m/z (%) 200 (42) [CpRH]þ, 236 (100) [amine-H]þ, 443 (14) [CpR2Ti]þ, 681 (8) [M]þ. Anal. Calcd for C53H69NTi: C 81.33; H 9.06, N 1.82. Found: C 81.64, H 8.95, N 1.62. CpAd2Ti(NdCPh2)2, 7a. 1a (200 mg 0.45 mmol) was placed in a Schlenk tube, and 40 mL of n-hexane was added. Then 163 mg (0.9 mmol) of benzophenone imine was added, and the color of the reaction mixture changed instantly from green to red. Storing the solution for a few days at room temperature and

Article filtration led to a fine crystalline product. X-ray-quality crystals were obtained from a saturated n-hexane solution at room temperature. In the solid state, 7a can be handled without inert atmosphere for short periods. Yield: 238 mg (74%). Mp: 179 °C (dec.). IR (KBr): 1/λ 3054 (w), 2897 (s), 2847 (m), 1616 (s), 1442 (m), 1232 (m), 1025 (m), 887 (m), 777 (s), 694 (s), 621 (m), 475 (m), 409 (m), 343 (w) cm-1. 1H NMR (C6D6, 500 MHz): δ 1.36-1.99 (m, 28 H, adamantyl), 3.26 (s, 2 H, adamantyl), 5.47 (t, J = 2.6 Hz, 4 H, C5H4), 5.89 (t, J = 2.6 Hz, 4 H, C5H4), 7.19 (t, J = 7.2 Hz, 4 H, para-C6H5), 7.27 (t, J = 7.5 Hz, 8 H, orthoC6H5), 7.56 (d, J = 7.2 Hz, 8 H, meta-C6H5) ppm. 13C NMR (C6D6, 125 MHz): δ 23.0, 28.1, 28.2, 32.1, 32.3, 38.1, 38.4, 42.7 (adamantly), 101.8, 114.9 (C5H4), 128.3, 128.4, 128.5, 128.5, 131.3, 141.5 (C6, 165.9 (-NdC) ppm. MS (EI, 70 eV): m/z (%) 180 (29) [Ph2CN]þ, 198 (10) [AdFv]þ, 444 (11) [AdFv2Ti - 2H], 446 (8) [CpR2Ti]þ, 625 (100) [CpR2TiNdCPh2]þ. Anal. Calcd for C66H58N2Ti: C 81.86, H 7.24, N 3.47. Found: C 81.60, H 7.59, N 3.46. CpTol2Ti(NdCPh2)2, 7b. This was prepared in the same manner with 200 mg (0.35 mmol) of 1b and 99 mg (0.7 mmol) of benzophenone imine. Yield: 178 mg (54%). Mp: 154 °C (dec). IR (KBr): 1/λ 3015 (m), 2918 (m), 1609 (s), 1509 (s), 1486 (m), 1441 (m), 1233 (s), 1071 (m), 1056 (m), 1022 (m), 890 (s), 838 (m), 798 (m), 780 (s), 763 (s), 697 (s), 624 (m), 574 (m), 507 (m), 479 (m) cm-1. 1H NMR (C6D6, 500 MHz): δ 2.01 (s, 12 H, CH3), 5.22 (t, J = 2.6 Hz, 4 H, C5H4), 5.56 (s, 2 H, C5H4-CH), 5.76 (t, J = 2.6 Hz, 4 H, C5H4), 6.79 (d, J = 7.8 Hz, 8 H, C6H4CH3), 7.00 (d, J = 8.0 Hz, 8 H, C6H4CH3), 7.16-7.19 (m, 4 H, paraC6H5), 7.20-7.24 (m, 8 H, ortho-C6H5), 7.44 (d, 3J = 7 Hz, 8 H, meta-C6H5) ppm. 13C NMR (C6D6, 125 MHz): δ 20.9 (CH3), 50.8 (Cp-CHR2), 104.2 (C5H4), 115.6 (C5H4), 128.1, 128.3, 128.7, 129.1, 129.5, 131.4, 135.3, 142.5, 142.8, 167.3 (-NdC) ppm. MS (EI, 70 eV): m/z (%) 180 (29) [Ph2CN]þ, 258 (26) [Fv]þ, 306 (70) [CpCHTiNdCPh2]þ, 384 (35) [CpRTiNdCPh2 - tolyl]þ, 487 (100) [CpRTiNdCPh2]þ, 565 (18) [FvR2Ti]þ, 667 (1) [CpRTi(NdCPh2)2]þ, 745 (36) [CpR2TiNdCPh2]þ. Anal. Calcd for C66H58N2Ti: C 84.22, H 6.31, N 3.02. Found: C 84.42, H 6.59, N 3.10. CpAd2Ti(dN-NPh2)py, 9. 1a (178 mg, 0.4 mmol) was placed in a Schlenk-tube and 2 mL benzene were added. 74 mg (0.4 mmol) N,N-diphenylhydrazin were dissolved in 10 mL n-hexane and added. The color of the reaction mixture changed instantly from green to red. Then 0.1 mL (1.2 mmol) pyridine were given to the reaction mixture. After storing the solution for a few days at 6 °C crystals with X-ray-quality were obtained. Yield: 53 mg (12%). Mp: 108 °C (dec.). Due to the high reractivity and spontanous subsequent reactions of 9, forming 10b and further uncharacterized products, no further analytical data of 9 are available. CpAdTidN-NPh2(-NH-NPh2)py, 10a. 1a (178 mg, 0.4 mmol) was placed in a Schlenk tube, and 2 mL of benzene was added. Then 148 mg (0.8 mmol) of N,N-diphenylhydrazine was dissolved in 10 mL of n-hexane, and this was added to the reaction solution. The color of the reaction mixture changed instantly from green to red. Then 0.1 mL (1.2 mmol) of pyridine was added and the reaction mixture refluxed for a minute. The product was isolated from the solution by filtration as a pale brown-yellow solid after a few days at room temperature.


1817

Crystals of X-ray quality were not obtained. Yield: 46 mg (16%). Mp: 108 °C. 1H NMR (C6D6, 300 MHz): δ 1.44-2.34 (m, 14 H, adamantyl), 3.15 (s, 1 H, adamantyl), 5.62 (s, 1 H, C5H4), 5.78 (s, 1 H, C5H4), 6.22 (t, J = 6.9 Hz, 2H, metaC5H5N), 6.31 (s, 1 H, C5H4), 6.32 (s, 1 H, C5H4), 6.66 (t, J = 7.6 Hz, 1 H, para-C5H5N), 6.80 (t, J = 7.2 Hz, 2 H, para-C6H5), 6.86 (t, J = 7.3 and 7.5 Hz, 2 H, para-C6H5), 7.08 (t, J = 7.7 Hz, 4 H, meta-C6H5), 7.18 (t, J = 7.7 Hz, 4 H, meta-C6H5), 7.26 (d, J = 8.0 Hz, 4 H, ortho-C6H5), 7.65 (d, J = 7.7 Hz, 4 H, orthoC6H5), 8.20 (d, J = 4.8 Hz, 2 H, ortho-C5H5N), 8.33 (s, 1 H,NH) ppm. CpTolTidN-NPh2(-NH-NPh2)py, 10b. 1b (565 mg , 1 mmol) was placed in a Schlenk tube, and 10 mL of benzene was added. Then 370 mg (2 mmol) of N,N-diphenylhydrazine was dissolved in 20 mL of n-hexane, and this was added to the reaction solution. The color of the reaction mixture changed instantly from green to red. Then 0.2 mL (2.4 mmol) of pyridine was added and the reaction mixture stirred for 70 h. After filtration from the solvent the light yellow-brown product was dried in vacuo. X-ray-quality crystals were obtained from a saturated benzene solution. Yield: 449 mg (49%). Mp: 111 °C. (KBr): 1/λ 3255 (w), 3015 (w), 2913 (w), 1582 (vs), 1486 (vs), 1441 (s), 1364 (w), 1273 (s), 1260 (w), 1152 (w), 1068 (w), 1020 (w), 937 (w), 804 (vs), 743 (vs), 694 (vs), 574 (w), 503 (s) cm-1. 1H NMR (C6D6, 500 MHz): δ 2.03 (s, 3 H, CH3), 2.18 (s, 3 H, CH3), 5.60 (s, 1 H, C5H4), 5.87 (s, 1 H, C5H4), 6.10 (s, 1 H, C5H4), 6.19 (s, 1 H, C5H4), 5.72 (s, 1 H, C5H4-CHR2), 6.14 (t, 2 H, J = 7.2 and 6.6 Hz, meta-NC5H5), 6.61 (t, 1 H, J = 7.6 Hz, para-NC5H5), 6.77 (t, 2 H, 3J = 7.2 Hz, para-C6H5), 6.85 (m, 2 H, meta-C6H4CH3), 6.88 (t, 2 H, J = 8.2 Hz, para-C6H5), 7.00 (m, 2 H, metaC6H4CH3), 7.01-7.18 (m, 12 H, C6H5), 7.11 (m, 2 H, orthoC6H4CH3), 7.31 (m, 2 H, 3J = 7.9 Hz, ortho-C6H4CH3), 7.68 (d, 4H, 3J = 8.0 Hz, ortho-C6H6), 8,03 (d, 2 H, 3J = 4.9 Hz, orthoNC5H5), 8.29 (s, 1 H, NH) ppm. 13C NMR (C6D6, 125 MHz): δ 20.9 (CH3), 21.1 (CH3), 51.8 (Cp-CHR2), 106.2 (C5H4), 109.6 (C5H4), 112.4 (C5H4), 112.5 (C5H4), 119.2 (para-C6H5), 119.7 (para-C6H5), 119.8 (para-C6H5), 120.2 (para-C6H5), 122.1 (meta-C6H4CH3), 123.5 (meta-C5H5N), 128.3 (meta-C6H4CH3), 128.5, 128.9 (meta-C6H4CH3), 129.0 (ortho-C6H4CH3), 129.2 (ortho-C6H4CH3), 129.3, 129.4, 129.5, 129.8, 135.1, 135.3, 137.2 (para-C5H5N), 142.5, 144.0, 146.9, 149.7, 153.1 (ortho-C5H5N) ppm. Anal. Calcd for C52H52N5Ti: C 78.57; H 6.59, N 8.81. Found: C 78.14, H 6.72, N 8.74.

Acknowledgment. This investigation was financially supported by the Deutsche Forschungsgemeinschaft. Supporting Information Available: Additional crystallographic data for structures 5-10 have been deposited with the Cambridge Data Centre as supplementary publications nos. CCDC 75899 (5d), 75900 (5a), 759001 (7a), 759002 (7b), 759003 (9), 759004 (10b), 759005 (6), 759006 (5c), and 761178 (5b). Copies of the data can be obtained free of charges on application to CCDC, 12 Union Road, Cambridge CB21EZ, U.K. (fax (þ44)1223-336-033; e-mail [email protected]), or free of charge via the Internet at http://pubs.acs.org.

Bis(Î·5:Î·1-pentafulvene)titanium Complexes: Catalysts for

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