Versatile Behavior of Conjugated Diynes with Zirconocene Reactive

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Organometallics 2009, 28, 181–187

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Versatile Behavior of Conjugated Diynes with Zirconocene Reactive Species Ste´phane Bredeau,†,‡ Esteban Ortega,† Genevie`ve Delmas,† Philippe Richard,† Roland Fro¨hlich,‡ Bruno Donnadieu,§ Gerald Kehr,‡ Nadine Pirio,*,† Gerhard Erker,‡ and Philippe Meunier*,† Institut de Chimie Mole´culaire de l’UniVersite´ de Bourgogne (ICMUB)-UMR CNRS 5260, 9, aVenue Alain SaVary, BP 47870, 21078 Dijon Cedex, France, Organisch-Chemisches Institut der UniVersita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany, and Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse cedex 4, France ReceiVed June 4, 2008

Thermal decomposition of Cp2ZrPh2 in the presence of the buta-1,3-diynes RCtCCtCR (R ) Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused sevenmembered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiCtCCtCSiMe3 a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This R monoinsertion complex is an intermediate in the exchange of the metalated moiety with a main-group atom (e.g., antimony) in a zirconacyclocumulene, explaining the formation of a 2-alkynyl-substituted stibaindene. In the thermal decomposition of Cp2Zr(Me)SCH2R4 (R4 ) Ph, p-MeOC6H4) in the presence of PhCtCCtCPh, only the R monoinsertion of one triple bond of the diacetylenic reagent in the transient zirconathiirane is observed. The 2-alkynyl-substituted fivemembered zirconathiolane is isolated as a bis-sulfonium zirconocene-ate dimer. X-ray diffraction studies corroborate the molecular structure of all these zirconacyclic complexes and stibacycle. Introduction The search for new pathways permitting carbon-carbon and carbon-heteroatom bond formation remains among the most important goals of modern chemistry. The use of group 4 transition metal assisted methodology is one efficient tool to reach this objective.1 Some zirconocene-based reactions were developed by our group concerning the access to main-group heterocycles not easily available by other procedures.2 Our investigations were focused on the reaction of the transient zirconocene benzyne 1 with unsaturated heteroatom-containing derivatives, acetylenic substrates for the most part. We reported the preparation of 2-phosphino-1-zirconaindenes 23 as well as benzo-zirconacyclohexadiene-phosphacyclobutenes 34,5 or * To whom correspondence should be addressed. N.P.: e-mail, [email protected]; tel, +33(0)3-8039-6106; fax, +33(0)3-80393682. P.M.: e-mail, [email protected]; tel, +33(0)3-80396105; fax, +33(0)3-8039-3682. † Institut de Chimie Mole´culaire de l’Universite´ de Bourgogne (ICMUB)UMR CNRS 5260. ‡ Organisch-Chemisches Institut der Universita¨t Mu¨nster. § Laboratoire de Chimie de Coordination du CNRS. (1) Reviews and book contributions: (a) Titanium and Zirconium in Organic Chemistry; Marek, I., Ed.; Wiley-VCH: Weinheim, Germany, 2002. ´ lvarez-Rodrigo, L.; Fan˜ana´s, F. J. Chem. (b) Barluenga, J.; Rodrı´guez, F.; A Soc. ReV. 2005, 34, 76. (c) Meunier, P.; Pirio, N. In Encyclopedia of Inorganic Chemistry; King, R. B., Ed.; Wiley: Chichester, U.K., 2005, 4488. (d) Marek, I.; Chinkov, N.; Levin, A. Synlett 2006, 4, 501. (e) Rosenthal, U.; Burlakov, V. V.; Bach, M. A.; Beweries, T. Chem. Soc. ReV. 2007, 36, 719. (2) Majoral, J.-P.; Meunier, P.; Igau, A.; Pirio, N.; Zablocka, M.; Skowronska, A.; Bredeau, S Coord. Chem. ReV. 1998, 145, 178–180. (3) Miquel, Y.; Igau, A.; Donnadieu, B.; Majoral, J.-P.; Dupuis, L.; Pirio, N.; Meunier, P. Chem. Commun. 1997, 729. (4) Dupuis, L.; Pirio, N.; Meunier, P.; Igau, A.; Donnadieu, B.; Majoral, J.-P. Angew. Chem., Int. Ed. Engl. 1997, 9, 987.

-silacyclobutenes 45 by the coupling reaction of the benzyne complex 1 with alkynylphosphanes and bis(alkynyl)phosphanes or -silanes, respectively (Scheme 1). In the case of P-tethered diynes, 3-(alkynylphosphino)zirconaindenes 55 were also formed as minor products. Recently, we reported the reaction of zirconocene thioaldehydes 6 with (diphenylphosphino)acetylene, leading to the sulfur-bridged binuclear R-phosphinozirconathiolanes 7 (Scheme 2).6 These zirconacyclic complexes were converted on one hand into a variety of mono- (A-C), di- (D, E), or tricyclic (F, G) derivatives incorporating one or two group 14 or 15 elements when treated with HCl or dihalogenated main-group-element reagent (Chart 1).3,5,7 In the course of discovering new zirconocene-mediated methodologies of synthetic use, it was demonstrated that the zirconocene fragment [Cp2Zr:] promoted the coupling of diynes with formation of zirconacyclic cumulenes.8 We have established in a previous contribution that reaction of 1,4-diphenylbuta-1,3-diyne with zirconocene benzyne 1 yielded quantitatively the stable seven-membered zirconacyclocumulene 8a (Scheme 3).9 In contrast, the synthesis of a metallaindene complex with an alkynyl substituent in the β-position was (5) Pirio, N.; Bredeau, S.; Dupuis, L.; Schu¨tz, P.; Meunier, P.; Donnadieu, B.; Igau, A.; Majoral, J.-P. Tetrahedron 2004, 1317. (6) (a) Ortega, E.; Pirio, N.; Meunier, P.; Donnadieu, B. Chem. Commun. 2004, 678. (b) Ortega, E.; Pirio, N.; Meunier, P.; Richard, P. Acta Crystallogr., Sect. E 2004, E60 (2), m201. (7) Ortega, E. Ph.D. Thesis, University of Burgundy, Burgundy, France, 2003. (8) (a) Rosenthal, U.; Pellny, P. M.; Kirchbauer, F. G.; Burlakov, V. V. Acc. Chem. Res. 2000, 33, 119. (b) Rosenthal, U.; Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A. Organometallics 2005, 24, 456.

10.1021/om800512u CCC: $40.75  2009 American Chemical Society Publication on Web 12/11/2008

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Scheme 1. Reaction of Zirconocene Benzyne with Alkynylphosphanes and Bis(alkynyl)phosphanes or -silanes

Scheme 2. Reaction between Zirconocene Thioaldehydes and Alkynylphosphane

described starting from the benzyne tantalum carborane complex (Et2C2B4H4)CpTa(η2-C6H4) and PhCtCCtCPh.10 The present report aims at describing the extension of this latter reaction to another diyne (e.g., 1,4-bis(trimethylsilyl)buta-1,3-diyne) as well as to another low-valent zirconocene species (e.g., zirconocene thioaldehydes 6a,b in Scheme 2).

Results and Discussion The above-mentioned reaction of 1 with 1,4-diphenylbuta1,3-diyne provides the starting point for the current investigation. Thermolysis of Cp2ZrPh2 in the presence of PhCtCCtCPh has been shown to produce only the seven-membered zirconacyclocumulene 8a (no formation of the 3-alkynylzirconaindene 9a) probably arising from the 2-fold insertion of the two carbon-carbon triple bonds of the diyne into the zirconium-carbon bond of the in situ generated complex 1 via the formation of the 2-alkynylzirconaindene intermediate 8′a (Scheme 3). Such a two-step mechanism was already evidenced in the formation of the benzo-zirconacyclohexadiene-phosphacyclobutenes 3a-c resulting from reaction of P-tethered diynes and diphenylzirconocene.5 Nevertheless, the postulated intermediate 8′a was never observed in the reaction mixture. Therefore, a variable-temperature NMR study was realized. At ambient temperature only one bis(cyclopentadienyl)zirconium complex is formed quantitatively (δ1H(Cp) 5.62 ppm) corresponding to complex 8a. In a CDFCl2/CDF2Cl/CD2Cl2 solvent mixture11 at lower temperature (213 K) no chemical shift corresponding to the intermediate 8′a is detected in the expected range for a Cp ring. The 8a a 8′a equilibration is probably too fast on the NMR time scale, indicating that in our case the 2-alkynylzirconaindene 8′a represents a high-lying intermediate. This feature is probably due to the remarkable stability of complex 8a as evidenced by DFT calculations reported elsewhere9 resulting directly from the interaction between the dxy metal atomic orbital with one terminal σ orbital and with the in-plane π orbital of the cumulene.

In order to gain a deeper understanding of the coupling reaction of buta-1,3-diynes with zirconocene benzyne 1, the analogous reaction was performed with the more hindered 1,4bis(trimethylsilyl)-1,3-butadiyne. A toluene solution of Me3SiCtCCtCSiMe3 and Cp2ZrPh2 heated up at 80 °C over 15 h led to the formation of two complexes as shown by the usual spectroscopic and analytical methods (Scheme 3). The 1H NMR spectrum of the crude product exhibits two cyclopentadienyl signals at 5.83 (minor) and 5.23 (major) ppm as well as two pairs of trimethylsilyl signals at 0.40, 0.33 (major) and 0.23, 0.19 (minor) ppm, allowing us to conclude that two bis(cyclopentadienyl)zirconium complexes are formed in a 10: 5.2 ratio. The 29Si NMR spectrum is in agreement with the formation of two zirconium complexes, as two pairs of chemical shifts at -24.1, -20.0 (minor) and -15.1, -12.3 (major) ppm are detected. The 13C NMR data are also consistent with a reaction yielding a pair of products. The mass spectrum (EI 70 eV) shows only one molecular ion peak [M]+ at m/z 490, indicative of two mononuclear complexes with the same molecular formula. IR data are also instructive, as two characteristic absorption bands appeared at 1874 and 2126 cm-1 which can be assigned to a >CdCdCdC< and -CtC- units, respectively. All these data are in agreement with a sevenmembered zirconacyclocumulene as well as with a fivemembered zirconacycle containing a pendant triple carbon-carbon bond. One might suppose that these two complexes are the expected zirconacyclocumulene 8b and the intermediary species 2-alkynylzirconaindene 8′b, arising respectively from the double and single insertion of the acetylenic function of the starting buta-1,3-diyne in the zirconium-carbon bond of the zirconocene benzyne 1 (Scheme 4). In order to displace this 8b a 8′b equilibration, some 1H and 13C NMR experiments were carried out at higher temperature in toluene-d8 (T ) 368 K). However, the cyclopentadienyl resonances are not modified in terms of chemical shifts and ratios. Moreover, the respective proportions of the two complexes remain the same after 21 days of heating at 90 °C and 8 days more at 110 °C. Consequently, identification based only on spectroscopic data was uncertain. In order to complete the characterization of these zirconacycles, suitable crystals for X-ray diffraction study were obtained by recrystallization from pentane. Figures 1 and 2 show the ORTEP views of the two different complexes contained surprisingly in the same cell unit: the seven-membered zirconacyclocumulene 8b and the five-membered zirconaindene 9b. Important bond lengths and angles are also summarized. On one hand the solidstate structure shows that the compound 8b has the expected

Chart 1. Diversity of Heterocycles Coming from Zirconacycles 3-7

BehaVior of Conjugated Diynes with Zirconocenes

Organometallics, Vol. 28, No. 1, 2009 183

Scheme 3. Reactivity of Zirconocene Benzyne with Conjugated Diynes

conjugated arrangement and is very similar to that of the previously described complex 8a.9 Structural features for similar highly strained cyclic zirconacyclocumulenes already reported in the literature12 closely resemble those in 8b. The molecular structure reveals a characteristic bent-metallocene arrangement of the ligands around zirconium. The angle between the geometrical centers of both Cp rings and the zirconium is 131.8°.

Figure 1. ORTEP view of 8b. Selected bond lengths (Å) and angles (deg): Zr-C1 ) 2.393(3), Zr-C10 ) 2.454(3), Zr-C9 ) 2.435(3), Zr-C8 ) 2.430(3), C10-C9 ) 1.275(5), C9-C8 ) 1.327(5), C8-C7 ) 1.338(5), C7-C6 ) 1.477(4); Cp1-Zr-Cp2 ) 131.8, C1-Zr-C10 ) 127.43(11), C10-C9-C8 ) 149.7(3), C9-C8-C7 ) 160.8(3).

Figure 2. ORTEP view of 9b. Selected bond lengths (Å) and angles (deg): Zr-C1 ) 2.270(3), Zr-C10 ) 2.276(3), C10-C7 ) 1.369(4), C7-C6 ) 1.488(5), C8-C9 ) 1.199(5), C10-Si ) 1.874(4), C9-Si ) 1.839(4); Cp1-Zr-Cp2 ) 137.4, C1-Zr-C10 ) 79.03(12), C7-C8-C9 ) 177.9(4), C8-C9-Si ) 173.0(4), C10-C7-C8 ) 121.4(3), C10-C7-C6 ) 122.3(3), C6-C7-C8 ) 116.3(3).

The four Zr-C(sp2) bond lengths are 2.454(3), 2.435(3), 2.430(3), and 2.393(3) Å for Zr-C10, Zr-C9, Zr-C8, and Zr-C1, respectively. The C1-Zr-C10 angle is relatively open at 127.43(11)°, pointing out that the zirconacycle is practically planar. The bond lengths for C10-C9, C9-C8, C8-C7, and C7-C6 are about 1.30 Å, indicating the same bond order. The angle values for C10-C9-C8 and C9-C8-C7 (149.7(3) and 160.8(3)°, respectively) are quite far from the theoretical value of 180°, but they agree with a deformed cumulene fragment in order to decrease the cyclic strain. These data corroborate the ones already described for 8a. Indeed, the molecular structures of 8a and 8b closely resemble each other, differences coming only from the substituent of the starting 1,3-diyne (Ph versus SiMe3). On the other hand, the molecular structure of the unforeseen 3-alkynyl-substituted zirconaindene 9b is clearly evidenced. Similar to the structural features mentioned above for 8b, the two zirconium-carbon(sp2) distances Zr-C10 and Zr-C1 and the angle values C10-Zr-C1 and Cp1-Zr-Cp2 clearly confirmed the bent character of 9b. Moreover, the C8-C9 distance (1.199(5) Å) is representative of a triple carbon-carbonbond.TheC7-C8-C9(177.9(4)°)andC8-C9-Si (173.0(4)°) angles are in good agreement with a linear CtCSiMe3 unit. The molecular structure is comparable to that observed for the 3-(alkynylphosphino)stibaindene E (Chart 1) previously structurally characterized starting from 5a by an exchange reaction with PhSbCl2.5 Therefore, these results clearly demonstrated that, depending on the nature of the substituent of the acetylenic reagent, two types of zirconacycles are formed. On the basis of NMR experiments and X-ray diffraction studies, we can propose the mechanism outlined in Scheme 3 for the preparation of five- and seven-membered zirconacycles (9a,b, 8a,b): (i) formation of the R-regioisomeric zirconacycles 8′a,b arising from the insertion reaction of one of the CtC triple bonds of the buta-1,3-diyne into a Zr-C bond of the transient zirconocene benzyne 1 and (ii) rapid intramolecular insertion reaction of the second alkynyl group into a Zr-C bond of the intermediates 8′a,b providing the highly stabilized sevenmembered zirconacyclocumulenes 8a,b. Nevertheless, due to the probably strong steric interaction between the trimethylsilyl group and zirconium (this interaction being lower in the case of the phenyl substituent), the β-regioisomeric zirconacycle 9b is also formed. It is noteworthy that it is not possible to further transform this latter complex because of its regiochemistry. A (9) Bredeau, S.; Delmas, G.; Pirio, N.; Richard, P.; Donnadieu, B.; Meunier, P. Organometallics 2000, 19, 4463. (10) Boring, E.; Sabat, M.; Finn, M. G.; Grimes, R. N. Organometallics. 1998, 17, 3865. (11) Siegel, J. S.; Anet, F. A. L. J. Org. Chem. 1988, 53, 2629.

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Scheme 4. Formation of Dimeric 2-Alkynylzirconathiolanes rac-/meso-11a,b

Chart 2. Predictable Products from Reaction of Conjugated Diynes and Cp2Zr(η2-RCHS)

similar behavior was already reported in the case of intramolecular coupling of P-tethered diynes promoted by the zirconocene benzyne.5 On the basis of the promising results we obtained with Ph2PCtCH and zirconocene thioaldehydes 6a-c,6 we focused our efforts on the preparation of functionalized chalcogenated heterocycles using buta-1,3-diynes. Indeed, considering the structural diversity of complexes obtained by the coupling reaction of various conjugated diynes with zirconocene benzyne 1, it was of interest to explore this chemistry with related reactive species such as 6a,b. In that case, insertion reactions of buta1,3-diynes in the Zr-C bond(s) could lead to the formation of various complexes: a thiazirconacyclocumulene (H) and/or fivemembered alkynylthiazirconacycles (I and/or J) and/or sulfurbridged binuclear alkynylzirconathiolanes (K and/or L) (Chart 2). A toluene solution of 1,4-diphenylbuta-1,3-diyne and the zirconocene thioaldehyde precursor Cp2Zr(Me)SCH2R,4 prepared from dimethylzirconocene and 1 equiv of the corresponding thiol (PhCH2SH for 6a and p-MeOC6H4CH2SH for 6b), led to the precipitation of a mixture of two complexes after 24 h of stirring at 90 °C (Scheme 4). After washing with pentane, the major complexes rac/meso-11a,b were isolated in quite good yield (around 70%). NMR studies of these new zirconacycles were regarded as hard to manage, due to their poor solubility in any common solvent. Only 1H NMR spectra could be measured. For the unindentified product in the reaction mixture, two Cp resonances representative of a monomeric complex were found in the spectra (5.48, 5.30 ppm (a) and 5.61, 5.54 ppm (b)). For the major complexes 1H NMR spectra revealed the presence of four singlet resonances for the cyclopentadienyl ligands characteristic of a formation of a pair of dimers in a 1:1 ratio: e.g., 6.33, 6.24, 5.68, and 5.59 ppm for rac-/meso11a and 6.36, 6.26, 5.85, and 5.73 ppm for rac-/meso-11b. Moreover, elementary analysis was consistent with a stoichiometric reaction between the corresponding transient zirconocene thioaldehydes 6a,b and the diyne. The real structure of rac-/ meso-11a,b was not yet clear even though we could obtain good crystals suitable for X-ray analysis, since two sulfur-bridged binuclear alkynylzirconathiolanes (K or L) were expected.

Finally the slow diffusion of pentane in a highly diluted dichloromethane solution of rac-/meso-11b afforded single crystals, and X-ray crystal structure analysis provided unequivocal evidence for the regio- and also stereochemical assignment. The molecular structure reveals two zirconathiolane units with an alkynyl group in an R position linked with each other by two Zr-S bonds. The Ortep view and a summary of pertinent bond lengths and angles are depicted in Figure 3. The molecule is centrosymmetric, with the center of symmetry at the center of the four-membered Zr-S-Zr-S ring. The two p-methoxyphenyl groups are in trans positions. The structural features of this meso diastereoisomeric complex are comparable to those of related sulfur-bridged zirconocene dimers.6 The complex meso-11b appears as a bis-sulfonium 2-alkynyl-substituted zirconocene-ate dimer: the two zirconium-sulfur distances Zr-S and Zr-S# (2.568(4) and 2.716(4) Å, respectively) and the large angle value C1-Zr-S# (131.21(8)°) are typical for five-coordinated Cp2ZrIV complexes.13 In comparison to the intermediate complex 8′, the major R-regioisomer 10 did not give a ring-enlarged seven-membered zirconacycle and evolved to a dimeric product that prevented the zirconacyclopentene from reacting with the second acetylenic function. It is well established that five-membered zirconacycles are good building blocks for preparing heterocyclic molecules through the exchange reaction of a zirconium atom with transfer of the organic part to an electrophilic reagent. Therefore, interesting tricyclic derivatives incorporating two group 14 and/ or 15 elements, F and G (Chart 1), were generated by a zirconium dihalogenated main group element exchange reaction starting from 3a and 4a,5 and we felt that zirconacyclocumulenes 8a,b would provide a ready entry for the synthesis of new maingroup heterocycles. Treatment of a toluene solution of 8a with 1 equiv of phenylantimony dichloride gave the metalloid heterocycle 12 (eq 1). After extraction in pentane, the only byproduct of the reaction (Cp2ZrCl2) is removed by flash chromatography on silica. The stibacycle 12 was isolated in quite good yield after workup and characterized by usual spectroscopic and analytical methods. Although no relevant information could be retained from the 1H NMR data, the 13C NMR clearly shows two singlets at 100.4 and 91.8 ppm in the expected range for a CtC unit (classical acetylenic carbon resonances are in the 70-110 ppm range). Moreover, in the IR spectrum (KBr), (12) (a) Hsu, D. P.; Davis, W. M.; Buchwald, S. L. J. Am. Chem. Soc. 1993, 115, 10394. (b) Rosenthal, U.; Ohff, A.; Baumann, W.; Kempe, R.; Tillack, A; Burlakov, V. V. Angew. Chem., Int. Ed. Engl. 1994, 33, 1605. (c) Kempe, R.; Ohff, A.; Rosenthal, U. Z. Kristallogr. 1995, 210, 707. (d) Ashe, A. J., III; Al-Ahmad, S.; Kampf, J. Organometallics 1999, 18, 4234. (e) Pellny, P.-M.; Kirchbauer, F. G.; Burlakov, V. V.; Baumann, W.; Spannenberg, A.; Rosenthal, U. J. Am. Chem. Soc. 1999, 121, 8313. (f) Burlakov, V. V.; Ohff, A.; Lefeber, C.; Tillack, A.; Baumann, W.; Kempe, R.; Rosenthal, U. Chem. Ber. 1995, 128, 967. (13) Majoral, J.-P.; Zablocka, M. New J. Chem. 2005, 29, 13.

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Organometallics, Vol. 28, No. 1, 2009 185

good agreement with those of other structurally characterized stibole derivatives.5,15 The solid-state structure of 12 confirms that the formation of 8 involves a consecutive insertion of the two carbon-carbon triple bonds of RCtCCtCR into the zirconium bond of the transient zirconocene benzyne 1 via the 2-alkynylzirconaindene 8′.

Conclusion

Figure 3. ORTEP view of meso-11b. Selected bond lengths (Å) and angles (deg): Zr-C1 ) 2.348(13), Zr-S ) 2.568(4), Zr-S# ) 2.716(4), C4-C5 ) 1.203(17); Cp(1)-Zr-Cp(2) ) 128.86, C1-Zr-S ) 70.1(3), S-Zr-S# ) 61.12(6), C1-Zr-S# ) 131.21(8).

Figure 4. ORTEP view of 12. Selected bond distances (Å) and angles (deg) for both independent molecules of 12: Sb-C1 ) 2.140(4) and 2.154(4), Sb-C8 ) 2.164(4) and 2.154(4), Sb-C11 ) 2.160(4) and 2.152(4); C8-Sb-C11 ) 95.27(15) and 94.47(16), C1-Sb-C11 ) 95.63(15) and 95.41(15), C1-Sb-C8 ) 79.92(15) and 79.88(16).

one absorption is observed at 2174 cm-1 in the area characteristic of the stretching vibrations for free carbon-carbon triple bonds (2050-2200 cm-1). Such informations are in favor of the existence of a five-membered ring with a CtC unit and the loss of the original seven-membered metallacyclocumulene arrangement. Recrystallization of 12 from diethyl ether/ pentane generates suitable single crystals for its X-ray crystal structure analysis. Elucidation of 12 as a 2-alkynyl-substituted stibaindene was achieved by X-ray diffraction studies. The ORTEP view and the relevant bond lengths and angles are shown in Figure 4. In the five-membered stibacyclic ring, the three Sb-C(sp2) distances are identical in length with those found in known tertiary stibines:14 e.g., 2.155 Å for Ph3Sb and 2.129 Å for (C4H3S)3Sb. The stibaindene ring is planar and is orthogonal to the plane of the phenyl ring. More generally, the highly pyramidalized geometry around the antimony atom and the bond distances and angles within the ring system are all in

Zirconocene benzyne and thioaldehydes react with 1,4diphenyl- and 1,4-bis(trimethylsilyl)buta-1,3-diynes to yield seven-membered and 2- or 3-alkynyl-substituted five-membered zirconacycles, demonstrating how the combination of the substituent on the diyne and the nature of the three-membered zirconacyclic species can lead to three reaction patterns. A twostep mechanism involving a double insertion of the two carbon-carbon triple bonds of the conjugated diynes into the zirconium-carbon bond of the transient zirconocene benzyne explains the formation of the 18-electron zirconacyclocumulenes (stabilization by interaction between the metal and the middle double bond). With a more hindered substituent, a further minor 3-alkynylzirconaindene arising from the simple β insertion of one of the triple bonds is provided. With zirconocene thioaldehydes, the simple R insertion of one of the acetylenic bonds leads to a 2-alkynylzircothiolane which is preferentially stabilized by the formation of a coordination dimer. These results point out that the zirconacycles with an alkynyl group in a position R to the metal show ring expansion to seven-membered zirconacycles or bridged association to dimeric zirconacycles, whereas those with an alkynyl group in a β position are stable. This work also furnishes a novel path for the preparation of a functionalized stibaindene. Investigations are underway in our laboratory to further explore the use of zirconacyclic intermediates as vehicles for the preparation of new and attractive maingroup compounds.

Experimental Section General Remarks. All reactions were carried out under argon using Schlenk-type glassware or in a glovebox. Solvents, including deuterated solvents used for NMR spectroscopy, were dried and distilled prior to use. Mass spectra were determined by using a Kratos Concept IS spectrometer, while NMR spectra were measured using a Bruker DRX500 or Varian Unity Plus 600 NMR spectrometer. Most assignments were based on a series of 2D NMR experiments (chemical shifts are given in ppm relative to TMS for 1 H, 13C, and 29Si nuclei). IR spectra were measured using a Nicolet 5 DXC FT IR spectrometer. Melting points were determined by differential scanning calorimetry (2010 DSC, DuPont/STA Instruments). Combustion analyses were performed by the analytical service of the ICMUB of the Universite´ de Bourgogne or by the Organisch-Chemisches Institut der Universita¨t Mu¨nster. Reagents (14) (a) Adams, E. A.; Kolis, J. W.; Pennington, W. T. Acta Crystallogr. Sect. C 1990, 46, 917. (b) Vela, J.; Sharma, P.; Cabrera, A.; Alverez, C.; Rosas, N.; Hernandez, S.; Toscano, A. J. Organomet. Chem. 2001, 634, 5. (15) (a) Buchwald, S. L.; Fischer, R. A.; Foxman, B. M. Angew. Chem., Int. Ed. Engl. 1990, 29, 771. (b) Hsu, D. P.; Warner, B. P.; Fisher, R. A.; Davis, W. M.; Buchwald, S. L. Organometallics 1994, 13, 5160. (c) Yasuike, S.; Iida, T.; Yamaguchi, K.; Seki, I.; Kurita, J. Tetrahedron Lett. 2001, 42, 441.

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Table 1. Crystallographic Data and Data Collection and Structure Refinement Details for 8b, 9b, meso-11b, and 12 8b, 9b rormula Mr T, K cryst syst Sspace group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z F(000) Dcalcd, g/cm3 λ, Å µ, mm-1 cryst size, mm3 (sin θ)/λmax, Å-1 index ranges no. of rflns collected (RC) no. of indep RC (IRC) no. of IRC with I > 2σ(I) (IRCGT) refinement method no. of data/restraints/params R for IRCGT R for IRC goodness of fitc largest diff peak and hole, e Å-3 a

C52H64Si4Zr2 983.83 198(2) triclinic P1j 10.071(1) 16.353(1) 16.588(1) 107.83(1) 98.08(1) 95.16(1) 2549.1(3) 2 1024 1.282 0.710 73 0.535 0.35 × 0.30 × 0.15 0.67 -13 e h e 13 -21 e k e 21 -22 e l e 21 27 654 12 465 (R(int) ) 0.055) 7723 full-matrix least squares on F2 12 465/0/535 R1a ) 0.0526, wR2b ) 0.1127 R1a ) 0.1052, wR2b ) 0.1312 1.026 0.580 and -0.468

meso-11b C68H56O2S2Zr2 1151.68 180(2) monoclinic P21/c 12.748(2) 8.0431(15) 30.174(6) 90 98.960(16) 90 3056.1(10) 4 1184 1.252 0.710 73 0.451 0.67 -14 e h e 14 -8 e k e 5 -33 e l e 33 16 419 4369 (R(int) ) 0.1520) 2067 full-matrix least squares on F2 4369/10/336 R1a ) 0.1005, wR2b ) 0.2485 R1a ) 0.1728, wR2b ) 0.2791 0.985 0.872 and -0.831

12 C28H19Sb 477.18 110(2) triclinic P1j 10.4651(2) 10.8893(3) 18.5233(5) 85.015(1) 83.552(1) 81.445(1) 2068.88(9) 4 952 1.532 0.710 73 1.344 0.17 × 0.04 × 0.04 0.672 -13 e h e 13 -14 e k e 13 -24 e l e 23 15 609 9372 (R(int) ) 0.0505) 5762 full-matrix least squares on F2 9372/156/614 R1a ) 0.045, wR2b ) 0.072 R1a ) 0.104, wR2b ) 0.087 0.98 0.737 and -0.997

R1 ) ∑(||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2/∑[w(Fo2)2]1/2. c Goodness of fit ) [∑w(Fo2 - Fc2)2/(No - Nv)]1/2.

were purchased from commercial suppliers and used without further purification, except for the thiols which were distilled and stored under an argon atmosphere. Cp2ZrPh2,16 Cp2ZrMe2,16 and PhSbCl217 were prepared according to the literature procedures. X-ray Crystal Structure Analysis. 8b and 9b. The data sets were collected at 198 K with a Nonius KappaCCD diffractometer (λ ) 0.710 73 Å), equipped with a Nonius FR591 rotating anode generator. The structure was solved with direct methods and refined with full-matrix least-squares methods based on F2 (SHELX97).18 An absorption correction was applied (SORTAV).19 meso-11b. Data were collected at 180 K on a Stoe Imaging Plate Diffraction System (IPDS) (λ ) 0.710 73 Å), equipped with an Oxford Cryosystems Cryostream Cooler device. The final unit cell parameters were obtained by least-squares refinement of a set of 5000 reflections, and crystal decay was monitored by measuring 200 reflections by image. Any fluctuations of the intensity were observed over the course of the data collection. Numerical absorption corrections20 were applied to the data. The structure was solved by direct methods using SIR9221 and refined by least-squares procedures on F2 with the aid of SHELX97.18 All hydrogen atoms were located on a difference Fourier map and refined with a riding model, and all non-hydrogen atoms were anisotropically refined. (16) Samuel, E.; Rausch, M. D. J. Am. Chem. Soc. 1973, 95, 6263. (17) Wieber, M.; Wirth, D.; Fetzer, I. Z. Anorg. Allg. Chem. 1983, 505, 134. (18) Sheldrick, G. M. SHELX97 (includes SHELXS97 and SHELXL97), Release 97-2, Programs For Crystal Structure Analysis; University of Go¨ttingen, Go¨ttingen, Germany, 1998. (19) (a) Blessing, R. H. Acta Crystallogr. 1995, A51, 33. (b) Blessing, R. H. J. Appl. Crystallogr. 1997, 30, 421. (20) X-SHAPE (revision 1.01): A Crystal Optimisation for Numerical Correction; STOE and Cie, July 1996 (X SHAPE is based on the program HABITUS by Dr. Wolfgang Herrendorf, Institut fu¨r Anorganische Chemie, Universita¨t Giessen). (21) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagiardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. SIR92 Program for Automatic Solution of Crystal Structures by Direct Methods. J. Appl. Crystallogr. 1994, 27, 435.

12. Single crystals were mounted in inert oil and transferred to the cold nitrogen stream (110 K) of a Nonius Kappa CCD diffractometer (λ ) 0.710 73 Å). The structure was solved via a Patterson search program and refined with full-matrix least-squares methods based on F2 (SHELX97)18 with the aid of the WINGX program.22 The phenylacetylene groups of both independent molecules present in the asymmetric unit are disordered over two positions. The occupancies converged to 0.5 (due to steric reasons, the same value is observed in both molecules). Hydrogen atoms were included using a riding model. Although all non-hydrogen atoms were anisotropically refined, restraints (ISOR) were applied to the Uij values of the atoms of the disordered groups to approximate an isotropic behavior in order to prevent some atoms from becoming “nonpositive-definite”. Crystallographic data and data collection and structure refinement details for 8b, 9b, meso-11b, and 12 are given in Table 1. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC-635422 (8b, 9b), CCDC-635391 (meso-11b), and CCDC634729 (12). Copies of the data can be obtained, free of charge, on application to The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax +44-1223-336033; e-mail [email protected], or web http://www.ccdc.cam.ac.uk). Temperature-Dependent 1H and 13C NMR Spectra for Zirconacyclocumulene 8a. 1H NMR (dichloromethane-d2, 600 MHz, 213 K): δ 7.89 (d, JHH ) 7.6 Hz, 1H, 9-H), 7.73 (m, 2H, o-Ph2), 7.70 (m, 2H, o-Ph5), 7.49 (m, 2H, m-Ph2), 7.47 (m, 2H, (22) International Tables for X-ray Crystallography; Kynoch Press: Birmingham, U.K., 1994; Vol. IV. (23) Burnett, M. N.; Johnson, C. K. ORTEP-III: Oak Ridge Thermal Ellipsoid Plot Program for Crystal Structure Illustrations;Oak Ridge National Laboratory Report ORNL-6895; Oak Ridge National Laboratory, Oak Ridge, TN, 1996. Windows implementation: Farrugia, L. J J. Appl. Crystallogr. 1997, 30, 565. (24) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.

BehaVior of Conjugated Diynes with Zirconocenes m-Ph5), 7.38 (m, 1H, p-Ph5), 7.36 (m, 1H, p-Ph2), 7.34 (d, JHH ) 7.6 Hz, 1H, 6-H), 7.04 (t, JHH ) 7.6 Hz, 1H, 7-H), 6.99 (t, JHH ) 7.6 Hz, 1H, 8-H), 5.58 (s, 10H, Cp) ppm. 1H NMR (dichloromethane-d2, 600 MHz, 298 K): δ 7.92 (m, 1H, 9-H), 7.76 (m, 2H, o-Ph2), 7.71 (m, 2H, o-Ph5), 7.51 (m, 2H, m-Ph2), 7.49 (m, 2H, m-Ph5), 7.40 (m, 1H, p-Ph5), 7.37 (m, 1H, p-Ph2), 7.35 (m, 1H, 6-H), 7.07 (m, 1H, 7-H), 7.04 (m, 1H, 8-H), 5.62 (s, 10H, Cp) ppm. 13C NMR (dichloromethane-d2, 151 MHz, 213 K): δ 183.5 (9a), 163.3 (5a), 160.7 (2), 144.3 (1JCH ) 152 Hz, 9), 140.6 (5), 138.8 (i-Ph5), 134.3 (i-Ph2), 132.4 (1JCH ) 164 Hz, o-Ph2), 128.7 (1JCH ) 162 Hz, m-Ph2), 128.5 (1JCH ) 163 Hz, o-Ph5), 128.3 (1JCH ) 162 Hz, p-Ph2), 128.2 (1JCH ) 162 Hz, m-Ph5), 127.6 (1JCH ) 162 Hz, p-Ph5), 124.0 (1JCH ) 156 Hz, 6), 123.0 (1JCH ) 158 Hz, 8), 122.5 (1JCH ) 159 Hz, 7), 105.7 (Cp), n.o (3, 4) ppm [signals at 170.7, 111.6, and 86.1 from unidentified product]. 13C NMR (dichloromethane-d2, 151 MHz, 298 K): δ 184.4 (9a), 164.2 (5a), 161.6 (2, from ghmbc), 144.7 (9), 141.8 (5), 140.0 (i-Ph5), 135.3 (i-Ph2), 132.9 (o-Ph2), 129.3 (m-Ph2), 129.1 (o-Ph5), 128.73 (pPh2), 128.71 (m-Ph5), 128.1 (p-Ph5), 125.0 (6), 123.9 (8), 123.3 (7), 106.6 (Cp), not obsd (3, 4) ppm (signals at 112.3 and 87.7 from unidentified product). Preparation of Zirconacyclocumulene 8b and 3-Alkynylzirconaindene 9b. A solution of Cp2ZrPh2 (0.375 g, 1.0 mmol) and Me3SiCtCCtCSiMe3 (0.194 g, 1.0 mmol) in 35 mL of toluene was heated at 80 °C for 15 h. After removal of the solvent in vacuo, the solid obtained was stirred with pentane to afford a yellow powder (0.40 g, 0.81 mmol, 81%), which was recrystallized from pentane to yield 0.35 g (0.71 mmol, 71%) of the seven- and fivemembered zirconacycles 8b and 9b as yellow crystals. Mp 151.7 °C. Anal. Calcd for C26H32Si2Zr: C, 63.48; H, 6.56. Found: C, 63.58; H, 6.56. IR (KBr): 2937, 2126, 1874, 1623, 1427, 1238, 1099, 1015, 840, 812 cm-1. MS (70 eV): m/z (%): 490 (22) [M]+. 8b. 1H NMR (toluene-d8, 500 MHz, 298 K): δ 7.78 (m, 1H, 9-H), 7.61 (m, 1H, 6-H), 7.18 (m, 1H, 7-H), 7.08 (m, 1H, 8-H), 5.23 (s, 10H, Cp), 0.40 (JSiH ) 6.7 Hz, 9H, Me3Si5), 0.33 (JSiH ) 6.6 Hz, 9H, Me3Si2) ppm. 13C NMR (toluene-d8, 126 MHz, 298 K): δ 190.9 (9a), 170.0 (5a), 163.8 (2), 156.0 (5), 144.1 (9), 126.3 (6), 123.6 (7), 123.4 (8), 106.0 (Cp), 1.38 (Me3Si5), -0.40 (Me3Si2), not obsd (3, 4) ppm. 22Si{1H} NMR (benzene-d6, 39.8 MHz, 300 K): δ -15.1, -12.3 ppm. 9b. 1H NMR (toluene-d8, 500 MHz, 298 K): δ 7.98 (m, 1H, 7-H), 7.43 (m, 1H, 4-H), 7.18 (m, 1H, 5-H), 7.08 (m, 1H, 6-H), 5.83 (s, 10H, Cp), 0.23 (JSiH ) 6.9 Hz, 9H, Me3SiCt), 0.19 (JSiH ) 6.3 Hz, 9H, Me3Si2) ppm. 13C NMR (toluene-d8, 126 MHz, 298 K): δ 221.9 (2), 186.0 (7a), 138.9 (4), 127.2, 125.7 (5,6), 125.4 (7), 112.3 (Cp), 102.8 (-Ct), 93.9 (SiCt), 0.70 (Me3Si2), 0.10 (Me3SiCt), not obsd (3, 3a) ppm. 22Si{1H} NMR (benzene-d6, 39.8 MHz, 300 K): δ -24.1, -20.0 ppm. Preparation of Dimeric 2-Alkynylzirconathiolanes rac-/ meso-11a,b. To a solution of dimethylzirconocene (1.20 g; 4.8 mmol) in toluene (15 mL) was added 1,4-diphenylbutadiyne (0.97 g; 4.8 mmol) followed by a stoichiometric amount of phenylmethanethiol (for 11a: 0.56 mL, 4.8 mmol) or (4-methoxyphenyl) methanethiol (for 11b: 0.67 mL, 4.8 mmol). The resulting solution

Organometallics, Vol. 28, No. 1, 2009 187 was stirred for 2 h at room temperature, and then it was heated to 90 °C for 24 h. A beige solid precipitated during the reaction. The mixture was cooled to room temperature and then concentrated in vacuo, and then pentane (20 mL) was added. The resulting solid product was washed with 5 × 10 mL of pentane and vacuum-dried to yield 1.86 g of rac-/meso-11a (1.70 mmol, 71%) as a beige powder and 1.91 g of rac-/meso-11b (1.66 mmol, 69%) as a beige powder. rac-/meso-11a. Mp 145 °C dec. Anal. Calcd for C66H52S2Zr2: C, 72.61; H, 4.80; S, 5.87. Found: C, 72.54; H, 4.91; S, 5.83. MS (70 eV): m/z (%) 544 (65) [1/2M]+ (monomeric form). 1H NMR (toluene-d8, 500 MHz, 300 K): δ 7.42-7.32 (m, Harom), 7.19-7.00 (m, Harom), 6.96-6.89 (m, Harom), 6.33, 6.24, 5.68, 5.59 (s, 40H, Cp), 5.34 (broad s, 4H, CHPh) ppm. rac-/meso-11b. Mp 150 °C dec. Anal. Calcd for C68H56O2S2Zr2: C, 70.91; H, 4.90; S, 5.57. Found: C, 70.88; H, 4.99; S, 5.49. MS (70 eV): m/z (%) 574 (67) [1/2M]+ (monomeric form). 1H NMR (toluene-d8, 500 MHz, 300 K): δ 7.46-7.09 (m, Harom), 7.01-6.94 (m, Harom), 6.36, 6.26, 5.85, 5.73 (s, 40H, Cp), 5.37 (broad s, 4H, CHPh), 3.22, 3.18 (s, 12H, OMe) ppm. Preparation of Stibacycle 12. A solution of PhSbCl2 (0.14 g, 0.34 mmol) in toluene was added dropwise to a solution of complex 8a (0.17 g, 0.34 mmol) in toluene cooled to -30 °C. The reaction mixture was warmed slowly to room temperature and stirred for 15 h. After removal of the solvent in vacuo, the residue was extracted with pentane (2 × 10 mL) and purified by column chromatography (SiO2, diethyl ether) to afford the expected compound as a yellow oil (0.14 g, 0.29 mmol, 87%), which was recrystallized from 10 mL of pentane to yield 0.09 g (0.19 mmol, 56%) of 2-phenylalkynylstibaindole 12 as yellow crystals. Anal. Calcd for C28H19Sb: C, 70.44; H, 3.98. Found: C, 70.36; H, 4.25. IR (KBr): 2174 cm-1. MS (70 eV): m/z (%) 476 (27) [M]+. 1H NMR (chloroform-d, 500 MHz, 298 K): δ 6.84-7.03 (m, Harom), 7.16-7.27 (m, Harom), 7.48-7.51 (m, Harom), 7.59-7.64 (m, Harom) ppm. 13C{1H} NMR (chloroform-d, 125 MHz, 298 K): δ 163.5, 152.5, 146.8, 139.0, 138.4 (s, Cquat), 135.7, 134.9, 131.8, 129.62, 129.55, 129.51, 129.3, 129.0, 128.7, 128.60, 128.58, 128.4, 128.3 (s, CHarom and Ph), 124.6 (s, Cquat), 100.4 (s, tC-Ph), 91.8 (s, CtCPh) ppm.

Acknowledgment. Financial support from the Ministe`re de l’Education Nationale, de la Recherche et la Technologie (France), the CNRS (France), Conseil Re´gional de Bourgogne (France), Fonds der Chemischen Industrie, and the Deutsche Forschungsgemeinschaft (Germany) is gratefully acknowledged. We thank S. Royer for her helpful technical assistance. Supporting Information Available: CIF files giving crystal data for 8b, 9b, meso-11b, and 12. This material is available free of charge via the Internet at http://pubs.acs.org. OM800512U