ARTICLE pubs.acs.org/Organometallics
1,2-C-H Activation of Benzene Promoted by (Arylimido)vanadium(V)-Alkylidene Complexes: Isolation of the Alkylidene, Benzyne Complexes Shu Zhang,† Matthias Tamm,*,‡ and Kotohiro Nomura*,† † ‡
Department of Chemistry, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan Institut f€ur Anorganische und Analytische Chemie, Technische Universit€at Carolo-Wilhelmina zu Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
bS Supporting Information ABSTRACT: Reactions of the (arylimido)vanadium(V) dialkyl complex containing an imidazolin-2-iminato ligand, V(NAr)(CH2SiMe3)2(L) [2, Ar = 2,6-Me2C6H3; L = ImDIPPN = 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato], with C6D6 or C6H6 took place affording the phenyl complex V(NAr)(CH2 SiMe 3 )(C 6 H 5 )(L) (3) or V(NAr)[CH(D)SiMe 3 ](C6D5)(L) (3-d6) by 1,2-C-H or C-D activation of benzene via a vanadium(V)-alkylidene intermediate. The reaction of 2 in n-hexane in the presence of PMe3 afforded the vanadium(V)alkylidene complex V(CHSiMe3)(NAr)(ImDIPPN)(PMe3) (4), and the structure of 4 has been determined by X-ray crystallography. The reaction of 3 or 3-d6 with C6D6 or C6H6 took place to afford the diphenyl complex V(NAr)(C6H5)2(L) (5) or V(NAr)(C6D5)2(L) (5-d10). The same reaction in the presence of PMe3 afforded the proposed intermediate, the PMe3-trapped benzyne complex V(NAr)(η2-C6D4)(L)(PMe3) (6), and the structure of 6 has been determined by X-ray diffraction analysis.
’ INTRODUCTION Transition metal-alkyl complexes are important reagents or intermediates in stoichiometric/catalytic organic reactions, as well as in olefin coordination/insertion polymerization.1,2 It has been known that high-oxidation-state early transition metal alkyl complexes play essential roles in efficient olefin polymerization/ oligomerization. High-oxidation-state early transition metal alkylidene complexes have also attracted considerable attention3-5 since they play essential roles as catalysts in olefin metathesis and Wittig-type or group transfer reactions,3-6 as demonstrated especially by molybdenum.3,4a,4b,4e We focused on the synthesis and reaction chemistry of (imido)vanadium(V)-alkyl and -alkylidene complexes,5,7 because these complexes exhibited remarkable catalytic activities for ethylene (co)polymerization2e,5,8 and unique reactivity in the ring-opening metathesis polymerization of norbornene.2e,5 Recently, we demonstrated that these complexes can be tuned as efficient catalyst precursors for ethylene dimerization by modification of the imido ligand.9 In particular, we reported four “olefin metathesis active” (imido)vanadium(V)-alkylidene complexes (A-D), as shown in Chart 1, and these complexes were prepared by R-hydrogen elimination in C6D6 in the presence of PMe3 or NHC [NHC = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene].2e,5,7a,7d-f Since no examples of “olefin metathesis active” vanadium(V)alkylidene had been reported until recently, their syntheses and reaction chemistry are thus of fundamental importance for basic r 2011 American Chemical Society
understanding in organometallic chemistry and might also lead to promising applications in catalysis. The approach to promote R-H abstraction reactions from metal alkyl complexes lacking β-hydrogens has been known as the most common method to prepare high-oxidation-state metal alkylidenes.4,5 However, we sometimes faced difficulties in isolating the desired vanadium(V)-alkylidene. More recently,10 we realized that 1,2-C-H (or C-D) activation takes place in certain reaction mixtures during thermolysis of the dialkyl precursor, as exemplified be the reaction of V(NAr)(CH2SiMe3)2(L) [Ar = 2,6-Me2C6H3; L = ImDIPPN = 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato] in C6D6 in the presence of PMe3.10,11 Therefore, we explored this reaction in more detail and to identify possible intermediate. In this paper, we thus present that exclusive formation of the phenyl analogues V(NAr)[CH(D)SiMe3](C6D5)(L) and V(NAr)(CH2SiMe3)(C6H5)(L), by 1,2-C-H or C-D bond activation of C6D6 or C6H6 with the dialkyl analogue V(NAr)(CH2SiMe3)2(L) takes place via a vanadium(V)-alkylidene intermediate, and subsequent thermolysis in C6D6 or C6H6 afforded the analogous diphenyl complexes V(NAr)(C6H5)2(L) and V(NAr)(C6D5)2(L).12-14 The corresponding vanadium(V)-alkylidene complex [proposed as a key intermediate in the reaction of the dialkyl analogue in C6D6 or Received: January 30, 2011 Published: February 22, 2011 2712
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Chart 1. Olefin Metathesis Active Vanadium(V)-Alkylidenes.7a,d-f
Scheme 1
C6H6] and vanadium(V)-benzyne complex [assumed as an intermediate in the latter reaction affording the diphenyl complexes] could be isolated from the reaction mixture by trapping with PMe3, and their structures have been determined by X-ray diffraction analysis.
’ RESULTS AND DISCUSSION We chose the imidazolin-2-iminato ligand, ImDIPPN [L = 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato, N-1,3-(20 ,60 i Pr2C6H3)N2C3H2],15c as a promising anionic ancillary donor ligand, since ligands of this type have been widely used for the preparation of early transition metal complexes because of their ability to act as a strong 2σ,4π-electon donor toward early transition metals and/or metal in a higher oxidation state.15 The (arylimido)vanadium(V) dichloride analogue, V(NAr)Cl2(L) [1, Ar = 2,6-Me2C6H3; L = ImDIPPN], could be prepared in good yield (92%) by reacting V(NAr)Cl3 with L-SiMe3 in toluene (Scheme 1). The procedure is somewhat similar to that for the preparation of CpTiCl2(L).15c Complex 1 was identified by 1H, 13C, and 51V NMR spectra and elemental analysis, and the structure was determined by X-ray diffraction analysis.16 As expected from the ketimide analogue, V(NAr)Cl2(NdCtBu2),7a 1 displays a distorted tetrahedral geometry around the vanadium atom. The V-Cl bond distances [2.2314(4), 2.2251(6) Å] and the V-N distance to the ImDIPPN ligand [V(1)-N(2) 1.7308(11) Å] are shorter than those in V(NAr)Cl2(NdCtBu2) [2.2710(5), 2.2338(5); 1.787(1) Å, respectively],7a whereas the V-N bond distance to the arylimido ligand [V(1)-N(1) 1.6684(13) Å] is similar to that in V(NAr)Cl2(NdCtBu2) [1.660(2) Å]. The Cl(1)-V-Cl(2) bond angle in 1 [111.45(2)°] is smaller than that in the ketimide analogue [118.87(2)°], whereas the N(1)V(1)-N(2) bond angle [112.87(5)°] is larger [98.42(6)°];7a these may be explained by the presence of the sterically demanding ImDIPPN (L) ligand. Treatment of 1 with 2.0 equiv of LiCH2SiMe in toluene afforded V(NAr)(CH2SiMe3)2(L) (2)
in high yield (82%, Scheme 1), and the complex was identified by H, 13C, and 51V NMR spectra and elemental analysis. We previously reported that both V(CHSiMe3)(NAr)(NdCtBu2)(PMe3)7a and V(CHSiMe3)(NAr)(O-2,6-iPr2C6H3)(PMe3)7d were formed by R-hydrogen elimination from the corresponding dialkyl precursors in C6D6 in the presence of PMe3 (excess, 7 equiv) at 80 °C. Therefore, C6D6 was used as the solvent to prepare the corresponding vanadium(V)-alkylidene from the dialkyl complex (2). However, a characteristic resonance that could be assigned to the proton in the alkylidene (VdCH-SiMe3) was not observed in the 1H NMR spectrum when the mixture of complex 2 and PMe3 in C6D6 was heated at 60 °C for 4 days. In contrast, a new resonance at 294 ppm was observed in the 51V NMR spectrum with disappearance of the resonance at 402 ppm ascribed to 2.16 The new product could be isolated as brown microcrystals from n-hexane solution at -30 °C in 58% isolated yield. The product was identified as V(NAr)(CHDSiMe3)(C6D5)(L) (3-d6) by means of NMR spectroscopy, elemental analysis, and X-ray diffraction analysis (Scheme 2, Figure 1). Heating a solution of complex 2 in C6D6 at 60 or 70 °C in the absence of PMe3 afforded complex 3-d6 in quantitative yield (as estimated by the 1H NMR spectrum, isolated yield: 82%). Kinetic studies (conversion of 2 to 3-d6) at 70 °C revealed first-order kinetics with a rate constant of 2.97 10-5 s-1 (Figure 2), suggesting that the reaction took place without the formation of a bimetallic intermediate. The two mechanisms shown in Scheme 2, (i) 1,2-C-D activation via the initially generated alkylidene intermediate or (ii) σ-bond metathesis between 2 and C6D6, can be considered for explaining the product formation upon C-D bond activation. The proton in CHDSiMe3 was not clearly confirmed in the 1 H NMR spectroscopy, since its resonance is probably covered up by the isopropyl methyl resonances of the ImDIPPN ligand.16 However, the D atom in CHDSiMe3 (by incorporation of a deuterium atom from C6D6 to afford 3-d6) was confirmed by a 1
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Scheme 2
2
H NMR spectrum (δ = 2.10 ppm, d, JDH = 40 Hz).16 No resonances ascribable to D atoms in CD2SiMe3 in the 2H NMR spectrum nor protons in CH2SiMe3 in the 1H NMR spectrum were observed. These results thus strongly suggest that the reaction proceeds via 1,2-C-D bond activation of C6D6 via a vanadium(V)-alkylidene intermediate, as previously postulated for the reaction of (PNP)V(CH2tBu)2 with C6D6, affording (PNP)V(C6D5)2 [PNP = N{2-PiPr2-4-Me-C6H3}2-] via a vanadium(III)-alkylidene intermediate.11 X-ray diffraction analysis of 3-d6 reveals a 16-electron complex with a distorted tetrahedral geometry around the vanadium atom.16 The V-C bond distance in V-CHDSiMe3 [V(1)C(106) 2.0680(16) Å] is longer than that in V-C6D5 [V(1)C(100) 2.0448(14) Å], and the V-N distances in both the ImDIPPN and the arylmido ligand [V(1)-N(2) 1.7655(12), V(1)-N(1) 1.6810(12) Å] are slightly longer than those in the dichloride 1 [1.7308(11), 1.6684(13) Å]. Similarly, formation of the phenyl analogue, V(NAr)(CH2SiMe3)(C6H5)(L) (3), was confirmed by both 1H and 51 V NMR spectroscopy when the reaction of complex 2 was carried out in C6H6 at 60 °C for 5 days in the absence of PMe3 (Scheme 2). However, isolation of pure 3 seemed very difficult, as indicated by the observation of unidentified byproducts. In contrast, 3 could be successfully isolated in satisfactory yield (62%) when the same reaction was conducted in the presence of PMe3 (7 equiv), which significantly decreased the amount of byproducts in the reaction mixture. Complex 3 was also fully characterized by NMR spectroscopy and elemental analysis. It is important to note that heating a solution of the dialkyl complex 2 in n-hexane (in place of C6D6) at 60 °C in the presence of PMe3 (7.0 equiv) afforded V(CHSiMe3)(NAr)(L)(PMe3) (4)
as the PMe3 adduct of the proposed vanadium(V)-alkylidene intermediate. Crystallization from n-hexane solution at -30 °C afforded pure 4 in moderate isolated yield (42%). The resultant vanadium(V)-alkylidene complex was identified by 1H, 13C, and 51 V NMR spectroscopy and elemental analysis, and the structure of 4 was determined by X-ray crystallography (Scheme 3, Figure 3). One broad resonance that can be ascribed to the proton in VdCHSiMe3 (δ = 15.6 ppm) was observed in the 1H NMR spectrum in addition to a single resonance each in the 51V and the 31P NMR spectra; this may suggest the absence of syn/ anti isomers in solution. The crystallographic results indicate that 4 displays a distorted tetrahedral geometry around the vanadium atom and could be regarded as an 18-electron species.16 The VCHSiMe3 bond distance [V(1)-C(100) 1.866(5) Å] is close to that in the ketimide analogue, V(CHSiMe3)(NAr)(NdCtBu2)(PMe3) [1.860(2) Å],7a whereas the V-P bond distance in 4 [V(1)-P(1) 2.4202(14) Å] is somewhat shorter than that in the ketimide analogue [2.4331(7) Å].7a The V-N distance to the ImDIPPN ligand [V(1)-N(2) 1.810(3) Å] is also shorter than that in the ketimide analogue [1.847(2) Å].7a The V(1)C(100)-Si(1) bond angle in 4 [137.7(3)°] is somewhat larger than that in V(CHSiMe3)(NAr)(NdCtBu2)(PMe3) [121.4(1)°],7a probably due to the steric bulk of the 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato ligand (L) in 4; an apparent agnostic interaction of the R-hydrogen with the vanadium was not observed. Complex 4 was stable in C6D6 at 80 °C for more than 5 days, and this high thermal stability can be ascribed to the strong coordination of the PMe3 ligand. Heating the vanadium alkyl-phenyl complexes V(NAr)(CHDSiMe3)(C6D5)(L) (3-d6) and V(NAr)(CH2SiMe3)(C6H5)(L) (3) in C6D6 or C6H6 at higher temperature 2714
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Figure 1. ORTEP drawing for V(N-2,6-Me2C6H3)(CHDSiMe3)(C6D5)(L) [3-d6, L = ImDIPPN, 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato]. Thermal ellipsoids are drawn at the 50% probability level, and H atoms are omitted for clarity.16 Selected bond distances (Å): V(1)-N(1) 1.6810(12), V(1)-N(2) 1.7655(12), V(1)-C(100) 2.0448(14), V(1)-C(106) 2.0680(16), N(1)-C(16) 1.3813(18), N(2)-C(1) 1.3078(17). Selected bond angles (deg): N(1)-V(1)N(2) 116.55(5), N(1)-V(1)-C(100) 104.07(6), N(1)-V(1)C(106) 105.89(6), N(2)-V(1)-C(100) 107.01(5), N(2)-V(1)C(106) 113.01(6), C(100)-V(1)-C(106) 109.88(6), V(1)-N(1)C(16) 165.72(10), V(1)-N(2)-C(1) 156.06(10).
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Figure 3. ORTEP drawing for V(CHSiMe3)(N-2,6-Me2C6H3)(L)(PMe3) [4, L = ImDIPPN, 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2iminato]. Thermal ellipsoids are drawn at the 50% probability level, and H atoms are omitted for clarity.16 Selected bond distances (Å): V(1)-P(1) 2.4202(14), V(1)-N(1) 1.698(4), V(1)-N(2) 1.810(3), V(1)-C(100) 1.866(5), Si(1)-C(100) 1.827(4), N(1)-C(16) 1.388(6), N(2)-C(1) 1.290(5). Selected bond angles (deg): P(1)V(1)-N(1) 103.30(12), P(1)-V(1)-N(2) 109.76(11), P(1)-V(1)C(100) 89.88(14), N(1)-V(1)-N(2) 124.45(17), N(1)-V(1)C(100) 108.5(2), N(2)-V(1)-C(100) 114.71(19), V(1)-N(1)C(16) 173.8(3), V(1)-N(2)-C(1) 170.1(3), V(1)-C(100)-Si(1) 137.7(3).
Scheme 3
Figure 2. First-order kinetic plots of the conversion of V(N-2,6Me2C6H3)(CH2SiMe3)2(L) (2, L = ImDIPPN) to V(N-2,6-Me2C6H3)(CHDSiMe3)(C6D5)(L) (3-d6) in C6D6 at 70 °C. Detailed conditions are shown in the Experimental Section, and the spectra are shown in the Supporting Information.16
(80 °C, 4-5 days) afforded the corresponding diphenyl complexes V(NAr)(C6D5)2(L) (5-d10) and V(NAr)(C6H5)2(L) (5), in low yields (36, 37%, respectively, Scheme 4). The same diphenyl complex (5) could also be obtained from the dichloride analogue, V(NAr)Cl2(L) (1), by treatment with phenyllithium (yield 62%, Scheme 4). The resulting diphenyl complex 5 decomposed at higher temperature (70 °C, 2 days) or upon addition of PMe3 (even at 25 °C), which would explain the low yield in the
preparation of 5 from 3. Two mechanisms can be considered that proceed either (i) via a vanadium-benzyne intermediate or (ii) by σ-bond metathesis (Scheme 4), and the former mechanism via a vanadium(III)-benzyne was assumed for the reaction of (PNP)V(CH2tBu)2 [PNP = N{2-PiPr2-4-Me-C6H3}2-] with C6D6, affording (PNP)V(C6D5)2.11 We thus explored the possibility of isolating a benzyne complex by thermolysis of 3 in benzene in the presence of an excess of PMe3 (7 equiv). After heating the reaction mixture at 70 °C for 7 days, red microcrystals could be isolated by extraction and recrystallization from n-hexane solution at -30 °C, and the 1H NMR clearly suggested the formation of the benzyne complex V(NAr)(η2-C6H4)(L)(PMe3) (6),16 whereas both the 51V NMR 2715
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Scheme 4
and the 31P NMR spectra showed two resonances due to the presence of different isomers in solution.17 X-ray diffraction analysis, however, affords a sole structure even after several trials. The molecular structure of 6 reveals that the vanadium atom is pentacoordinated and displays a distorted tetrahedral geometry with regard to the two nitrogen donor ligands, PMe3 and the benzyne ligand [bond angles (deg): N(1)-V(1)-N(2) 119.69(4), N(1)-V(1)-C(100) 112.89(5), N(1)-V(1)-C(101) 106.04(5), P(1)-V(1)-N(2) 105.46(3)]. The V-C bond distances to the benzyne ligand are 1.9978(12) and 2.0660(13) Å, with a C(100)-V(1)-C(101) bond angle of 38.65(5)°, suggesting the formation of a metallacyclopropenyl ring, with a C-C bond length of 1.3465(18) Å. The bond angles in N(1)-V(1)-C(100) [112.89(5)°] and N(2)-V(1)-C(100) [125.14(4)°] are larger than those in N(1)-V(1)-C(101) [106.04(5)°] and N(2)-V(1)-C(101) [108.71(4)°], whereas the C(100)-C(105) bond distance [1.4019(19) Å] is longer than the C(101)-C(102) distance [1.3959(18)°]. The other C-C bond distances in the benzyne ligand ranged between 1.3840(19) and 1.3899(2) Å. Unfortunately, similar to the alkylidene complex 4, the reaction of the PMe3-trapped benzyne complex 6 with C6H6 did not take place upon heating [70 °C, 24 h], which can also be ascribed to the strong binding of the
PMe3 ligand atom, as indicated by an ever shorter V-P bond of 2.3962(4) Å in comparison with that in the vanadium(V)alkylidene (4) [2.4202(14) Å].
’ CONCLUDING REMARKS The experimental results observed in this study are summarized in Scheme 5. We have isolated the (arylimido)vanadium(V)alkylidene complex (4) containing the ImDIPPN ligand (L) [ImDIPPN = 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2-iminato] from the dialkyl analogue 2 in n-hexane in the presence of PMe3. The reaction of the same dialkyl complex in C6D6 or C6H6 afforded the corresponding phenyl complexes V(NAr)(CH2SiMe3)(C6H5)(L) (3) and V(NAr)[CH(D)SiMe3](C6D5)(L) (3-d6), via 1,2-C-H or C-D activation of benzene via a vanadium(V)alkylidene intermediate. The reaction of 3 or 3-d6 in C6D6 or C6H6 afforded the diphenyl complexes V(NAr)(C6H5)2(L) (5) and V(NAr)(C6D5)2(L) (5-d10), and the same reaction in the presence of PMe3 afforded the proposed intermediate, the PMe3trapped benzyne complex V(NAr)(η2-C6H4)(L)(PMe3) (6). We confirmed that the first C-H (C-D) activation proceeded via a vanadium(V)-alkylidene; however, the resultant benzyne complex (6) did not afford the diphenyl complex in C6H6 upon 2716
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proceed via the benzyne intermediate; however, we cannot not fully exclude other possibilities (like σ-bond metathesis) at present. Since we succeeded in isolating both the vanadium(V)-alkylidene (4) and the vanadium(V)-benzyne (6) complexes, we are currently further exploring their reactivity and catalytic applicability (e.g., in olefin metathesis), and the results of these collaborative efforts will be published in due course.
’ EXPERIMENTAL SECTION
Figure 4. ORTEP drawing for V(N-2,6-Me2C6H3)(η2-C6H4)(L)(PMe3) [6, L = ImDIPPN, 1,3-(20 ,60 -diisopropylphenyl)imidazolin-2iminato]. Thermal ellipsoids are drawn at the 50% probability level, and H atoms are omitted for clarity.16 Selected bond distances (Å): V(1)P(1) 2.3962(4), V(1)-N(1) 1.6914(10), V(1)-N(2) 1.7985(9), V(1)-C(100) 2.0660(13), V(1)-C(101) 1.9978(12), N(1)-C(16) 1.3760(16), N(2)-C(1) 1.2853(14), C(100)-C(101) 1.3465(18), C(100)-C(105) 1.4019(19), C(101)-C(102) 1.3959(18), C(102)C(103) 1.387(2). Selected bond angles (deg): P(1)-V(1)-N(1) 96.01(3), P(1)-V(1)-N(2) 105.46(3), P(1)-V(1)-C(100) 82.76(3), P(1)-V(1)-C(101) 121.41(3), N(1)-V(1)-N(2) 119.69(4), N(1)-V(1)-C(100) 112.89(5), N(1)-V(1)-C(101) 106.04(5), N(2)-V(1)-C(100) 125.14(4), N(2)-V(1)-C(101) 108.71(4), C(100)-V(1)-C(101) 38.65(5), V(1)-N(1)-C(16) 175.90(9), V(1)-N(2)-C(1) 167.47(9), V(1)-C(100)-C(101) 67.93(7), V(1)-C(101)-C(100) 73.41(7), V(1)-C(100)-C(105) 171.00(10), V(1)-C(101)-C(102) 163.33(10).
General Procedures. All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox. Anhydrous grade toluene, benzene, n-hexane, and dichloromethane (Kanto Kagaku Co., Ltd.) were transferred into a bottle containing molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13X 1/16) in the drybox under N2 and were passed through an alumina short column under N2 stream before use. Elemental analyses were performed by using a PE2400II Series (Perkin-Elmer Co.). All 1H, 2H, 13C, 31P, and 51V NMR spectra were recorded on a JEOL JNM-LA400 spectrometer (399.65 MHz for 1H, 61.4 MHz for 2H, 100.40 MHz for 13C, 161.70 MHz for 31P, and 105.31 MHz for 51V) or a Bruker AV500 spectrometer (500.13 MHz for 1H, 125.77 MHz for 13C, and 131.55 MHz for 51V). All spectra were obtained in the solvent indicated at 25 °C unless otherwise noted. Chemical shifts are given in ppm and are referenced to SiMe4 (δ 0.00, 1 H, 13C), H3PO4 (δ 0.00, 31P), and VOCl3 (δ 0.00, 51V). Coupling constants and half-width values, Δν1/2, are given in Hz. V(N-2,6Me2C6H3)Cl3 was prepared according to the previous report,18 and ImDIPPNSiMe3 was also prepared according to the reported procedure.15c Synthesis of V(N-2,6-Me2C6H3)Cl2(ImDIPPN) (1). Into a toluene solution containing V(N-2,6-Me2C6H3)Cl3 (420 mg, 1.5 mmol)17 ImDIPPNSiMe3 (720 mg, 1.5 mmol)15c was added at -30 °C. The reaction mixture was warmed slowly to room temperature, and the mixture was then stirred for 6 h. The resultant solution was filtrated through a Celite pad, and the filter cake was washed with hot toluene. The combined solution (filtrate and the wash) was then concentrated in vacuo and was placed in the freezer (-30 °C). The green microcrystals were collected from the chilled solution. Yield: 890 mg (1.38 mmol, 92%). 1H NMR (CDCl3): δ 7.47 (t, 2H, J = 7.60, Ar-H), 7.26-7.24 (m, 4H, Ar-H), 6.71 (s, 2H, CHd), 6.67-6.60 (m, 3H, NAr-H), 2.78 (m, 4H, CH(CH3)2), 1.92 (s, 6H, ArCH3), 1.21 (d, 12H, J = 6.80, CH(CH3)2), 1.17 (d, 12H, J = 7.20, CH(CH3)2). 13C NMR (CDCl3): δ 145.9, 134.0, 130.9, 130.7, 126.3, 124.3, 124.2, 117.0, 29.0, 24.1, 22.9,
Scheme 5
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Organometallics 18.4. 51V NMR (CDCl3): δ -147 (Δν1/2 = 1244 Hz). Anal. Calcd for C35H45Cl2N4V: C, 65.32; H, 7.05; N, 8.71. Found: C, 64.98; H, 6.86; N, 8.49. Synthesis of V(N-2,6-Me2C6H3)(CH2SiMe3)2(ImDIPPN) (2). Into a toluene solution containing V(N-2,6-Me2C6H3)Cl2(ImDIPPN) (1, 430 mg, 0.67 mmol) was added LiCH2SiMe3 (126 mg, 1.34 mmol) at -30 °C. The reaction mixture was warmed slowly to room temperature and was stirred for 6 h. The solvent was then removed in vacuo, and the resulting residue was extracted with n-hexane. After removing the n-hexane in vacuo, a small amount of n-hexane was added to solve the product. The solution was cooled to -30 °C, and the red microcrystals (408 mg, 0.55 mmol) were obtained in a yield of 82%. 1H NMR (C6D6): δ 7.19-7.15 (m, 2H, Ar-H), 7.05 (d, 4H, J = 7.60, Ar-H), 7.01 (d, 2H, J = 7.60, Ar-H), 6.80 (t, 1H, J = 7.60, Ar-H), 5.90 (s, 2H, CHd), 3.14 (m, 4H, CH(CH3)2), 2.61 (s, 6H, ArCH3), 1.82 (d, 2H, J = 11.20, CH2SiMe3), 1.35 (d, 12H, J = 6.80, CH(CH3)2), 1.08 (d, 12H, J = 6.80, CH(CH3)2), 0.72 (d, 2H, J = 10.80, CH2SiMe3), 0.08 (s, 18H, CH2SiMe3). 13C NMR (C6D6): δ 147.1, 133.7, 133.6, 130.3, 127.5, 124.4, 122.5, 115.8, 29.1, 25.1, 23.3, 20.6, 2.4. 51V NMR (C6D6): δ 402 (Δν1/2 = 1053 Hz). Anal. Calcd for C43H67N4Si2V: C, 69.13; H, 9.04; N, 7.50. Found: C, 68.92; H, 9.16; N, 7.71.
Synthesis of V(N-2,6-Me2C6H3)(CHDSiMe3)(C6D5)(ImDIPPN) (3-d6). A C6D6 solution (ca. 2 mL) containing the dialkyl complex 2
(80 mg, 0.107 mmol) was heated at 60 °C in a sealed tube under a nitrogen atmosphere. After 4 days, the solvent was then removed in vacuo and the resulting residue was extracted with n-hexane. The solution was then placed in vacuo, and the resultant tan residue was dissolved in the minimum amount of n-hexane (about 0.3 mL). The chilled solution (-30 °C) gave red microcrystals (66 mg, 0.088 mmol, yield of 82%). 1H NMR (C6D6): δ 7.26 (t, 2H, J = 7.60, Ar-H), 7.07 (t, 4H, J = 7.60, Ar-H), 6.97 (d, 2H, J = 7.60, Ar-H), 6.80 (t, 1H, J = 7.60, Ar-H), 5.82 (s, 2H, CH=), 3.05 (m, 2H, CH(CH3)2), 2.93 (m, 2H, CH(CH3)2), 2.37 (s, 6H, ArCH3), 1.23 (d, 6H, J = 6.80, CH(CH3)2), 1.17 (d, 6H, J = 7.20, CH(CH3)2), 1.09 (d, 6H, J = 7.20, CH(CH3)2), 1.05 (d, 6H, J = 7.20, CH(CH3)2), -0.02 (s, 9H, CH2SiMe3). 13C NMR (C6D6): δ 147.0, 146.9, 133.5, 130.3, 128.3, 127.3, 124.5, 124.4, 122.4, 115.5, 29.2, 29.1, 24.4, 24.0, 23.5, 23.0, 20.3, 2.3. 51V NMR (C6D6): δ 294 (Δν1/2 = 756 Hz). Anal. Calcd for C45H55D6N4SiV: C, 72.74; H, 8.29; N, 7.54. Found: C, 72.63; H, 8.29; N, 7.47.
Synthesis of V(N-2,6-Me2C6H3)(CH2SiMe3)(C6H5)(ImDIPPN) (3). A C6H6 solution (ca. 2 mL) containing the dialkyl complex 2
(90 mg, 0.12 mmol) and PMe3 (64 mg, 0.84 mmol) was heated at 60 °C in a sealed tube under a nitrogen atmosphere. After 5 days, the solvent was removed in vacuo, and the result residue was then extracted with n-hexane. After removal of n-hexane in vacuo, the resultant solid was dissolved with a small amount of n-hexane (ca. 0.3 mL). The chilled solution (-30 °C) gave red microcrystals (55 mg, 0.075 mmol, yield 62%). 1H NMR (C6D6): δ 7.70 (d, 2H, J = 6.80, V-Ph-H), 7.26 (t, 2H, J = 7.60, Ar-H), 7.09-7.05 (m, 5H, Ar-H), 6.98-6.92 (m, 4H, Ar-H), 6.80 (t, 1H, J = 7.60, Ar-H), 5.82 (s, 2H, CHd), 3.06 (m, 2H, CH(CH3)2), 2.93 (m, 2H, CH(CH3)2), 2.46 (d, 1H, J = 11.20, CH2SiMe3), 2.38 (s, 6H, ArCH3), 1.78 (d, 1H, J = 10.00, CH2SiMe3), 1.23 (d, 6H, J = 6.80, CH(CH3)2), 1.17 (d, 6H, J = 6.80, CH(CH3)2), 1.09 (d, 6H, J = 7.20, CH(CH3)2), 1.05 (d, 6H, J = 7.20, CH(CH3)2), 0.01 (s, 9H, CH2SiMe3). 13C NMR (C6D6): δ 146.9, 146.8, 136.2, 133.5, 133.4, 130.3, 127.3, 126.0, 124.4, 124.3, 122.3, 115.5, 29.2, 29.1, 24.4, 24.0, 23.4, 23.0, 20.3, 2.2. 51V NMR (C6D6): δ 294 (Δν1/2 = 733 Hz). Anal. Calcd for C45H61N4SiV: C, 73.33; H, 8.34; N, 7.60. Found: C, 72.65; H, 8.60; N, 7.47.
Time Course for Conversion of V(N-2,6-Me2C6H3)(CH2SiMe3)2(L) (2) to V(N-2,6-Me2C6H3)(CHDSiMe3)(C6D5)(L) (3-d6) in C6D6 at 70 °C. A C6D6 solution (ca. 0.5 mL) containing the
dialkyl complex V(N-2,6-Me2C6H3)(CH2SiMe3)2(ImDIPPN) (2, 10 mg) was heated in a sealed NMR tube at 70 °C. The mixture was monitored by 1H NMR to estimate the ratio between the starting material and
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product by the integration ratio of the resonances ascribed to N-PhMe. Detailed spectra are shown in the Supporting Information.
Synthesis of V(CHSiMe3)(N-2,6-Me2C6H3)(ImDIPPN)(PMe3) (4). An n-hexane solution (ca. 0.5 mL) containing the dialkyl complex V(N-2,6-Me2C6H3)(CH2SiMe3)2(ImDIPPN) (2, 50 mg, 0.067 mmol) and PMe3 (35 mg, 0.46 mmol) was heated in a sealed NMR tube at 60 °C for 3 days. The solution was then filtrated through a Celite pad, and the filter cake was washed with n-hexane. The combined solution (filtrate and wash) was concentrated to ca. 0.3 mL, and the chilled solution (-30 °C) gave brown microcrystals (21 mg, 0.028 mmol, yield 42%). 1H NMR (C6D6): δ 15.64 (s, 1H, dCHSiMe3), 7.22-7.16 (m, 3H, Ar-H), 7.13-7.05 (m, 5H, Ar-H), 6.81 (t, 1H, J = 7.80, Ar-H), 5.85 (s. 2H, CH=), 3.21-3.12 (m, 4H, CH(CH3)2), 2.23 (s, 6H, ArCH3), 1.39 (d, 6H, J = 7.60, CH(CH3)2), 1.31 (d, 6H, J = 6.80, CH(CH3)2), 1.16 (d, 6H, J = 7.20, CH(CH3)2), 1.14 (d, 6H, J = 6.40, CH(CH3)2), 0.82 (s, 4.5H, PMe3), 0.80 (s, 4.5H, PMe3), 0.31 (s, 9H, dCHSiMe3). 13 C NMR (C6D6): δ 312 (broad), 147.7, 147.6, 134.4, 129.5, 129.4, 128.6, 127.2, 124.3, 124.1, 123.9, 118.6, 114.1, 31.9, 29.1, 29.0, 24.1, 24.0, 23.9, 23.4, 23.0, 20.6, 19.4, 19.1, 14.3, 2.4, 2.3. 51V NMR (C6D6): δ 0 (Δν1/2 = 1571 Hz). 31P NMR (C6D6): δ 21.9. Anal. Calcd for C42H64N4PSiV: C, 68.63; H, 8.78; N, 7.62. Found: C, 68.49; H, 9.10; N, 7.32.
Synthesis of V(N-2,6-Me2C6H3)(C6H5)2(ImDIPPN) (5). Method 1 (from 4):. A C6H6 solution (ca. 2 mL) containing complex 4
(60 mg, 0.081 mmol) was heated at 80 °C in a sealed tube under a nitrogen atmosphere. After 4 days, the solvent was then removed in vacuo, and the resultant residue was washed with cold n-hexane. The red solid (21 mg, 0.029 mmol) was obtained in a yield of 36%. Method 2 (from 1): Into a toluene solution containing the dichloride 1 (310 mg, 0.48 mmol), PhLi (0.5 mL, 1.9 M in n-hexane, 0.95 mmol) was added at -30 °C. The reaction mixture was warmed slowly to room temperature and was stirred for 6 h. The mixture was then filtered through a Celite pad, and the filter cake was washed with toluene. The combined solution (filtrate and the wash) was then removed in vacuo, and the resultant residue was washed with cold n-hexane. The red solid (230 mg, 0.316 mmol) was obtained in a yield of 66%. 1H NMR (C6D6): δ 7.70 (d, 4H, J = 7.84, V-Ph-H), 7.28 (t, 2H, J = 7.80, Ar-H), 7.09 (d, 4H, J = 7.80, Ar-H), 6.99 (d, 2H, J = 7.08, Ar-H), 6.94 (t, 6H, J = 7.82, V-Ph-H), 6.78 (t, 1H, J = 7.58, Ar-H), 5.85 (s, 2H, CHd), 3.03 (m, 4H, CH(CH3)2), 2.37 (s, 6H, ArCH3), 1.08 (d, 12H, J = 7.08, CH(CH3)2), 1.06 (d, 12H, J = 6.84, CH(CH3)2). 13C NMR (C6D6): δ 147.0, 135.3, 133.9, 133.5, 130.4, 129.0, 128.6, 128.3, 127.8, 127.5, 127.3, 126.3, 124.5, 122.6, 116.0, 29.4, 24.7, 23.3, 20.8. 51V NMR (C6D6): δ 155 (Δν1/2 = 985 Hz). Anal. Calcd. for C47H55N4V: C, 77.66; H, 7.63; N, 7.71. Found: C, 75.39; H, 7.43; N, 7.55. Synthesis of V(N-2,6-Me2C6H3)(C6D5)2(ImDIPPN) (5-d10). A C6D6 solution (ca. 2 mL) containing complex 3-d6 (112 mg, 0.151 mmol) was heated at 80 °C in a sealed tube under a nitrogen atmosphere. After 5 days, the solvent was then removed in vacuo, and the resultant residue was washed with cold n-hexane. The red solid (41 mg, 0.056 mmol) was obtained in a yield of 37%. 1H NMR (C6D6): δ 7.28 (t, 2H, J = 7.80, Ar-H), 7.09 (d, 4H, J = 7.60, Ar-H), 6.93(d, 2H, J = 7.60, ArH), 6.78 (t, 1H, J = 7.60, Ar-H), 5.85 (s, 2H, CHd), 3.03 (m, 4H, CH(CH3)2), 2.36 (s, 6H, ArCH3), 1.08 (d, 12H, J = 7.20, CH(CH3)2), 1.06 (d, 12H, J = 7.20, CH(CH3)2). 13C NMR (C6D6): δ 147.1, 133.9, 133.5, 130.4, 128.6, 127.3, 124.5, 122.6, 116.0, 29.2, 24.4, 23.1, 20.5. 51 V NMR (C6D6): δ 154 (Δν1/2 = 1038 Hz). Anal. Calcd for C47H45D10N4V: C, 76.60; H, 7.54; N, 7.60. Found: C, 74.91; H, 7.51; N, 7.95.
Synthesis of V(N-2,6-Me2C6H3)(η2-C6H4)(ImDIPPN)(PMe3) (6). A C6H6 solution (ca. 30 mL) containing complex 3 (293 mg,
0.40 mmol) and PMe3 (210 mg, 2.76 mmol) was heated at 70 °C in a sealed tube under a nitrogen atmosphere. After 7 days, the solvent was then removed in vacuo, and the resultant residue was solved with toluene. 2718
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Organometallics The solution was filtrated through a Celite pad, and the filtrate was then removed in vacuo. The resultant residue was washed with cold n-hexane, and the red solid (157 mg, 0.216 mmol) was obtained in a yield of 54%. 1 H NMR (C6D6):17 δ 0.99 and 1.01 (s, 9H, PMe3), 1.08 (d, 3H, J = 6.9 Hz, -CHC(CH3)2), 1.12 (d, 3H, J = 6.8 Hz, -CHC(CH3)2), 1.13 (d, 3H, J = 7.0 Hz, -CHC(CH3)2), 1.15 (d, 3H, J = 7.0 Hz, CHC(CH3)2), 3.00 (m, 2H, -CHCMe2), 3.16 (m, 2H, -CHCMe2), 5.90 (s, 2H, -CHdNAr), 6.67 (t, 1H, J = 7.4 Hz, Ar), 6.90 (d, 2H, J = 4 Hz, Ar-H), 7.11 (dd, 2H, J = 7.6 Hz, Ar-H), 7.19 (dd, 2H, J = 7.8 Hz, ArH), 7.28 (t, 2H, J = 7.7 Hz, Ar-H), 7.44-7.50 (m, 3H, benzyne), 7.73 (d, 1H, J = 6.5 Hz, benzyne). 13C NMR (C6D6): δ 147.9, 147.4, 134.4, 132.8, 131.8, 129.5, 129.3, 128.5, 127.1, 125.6, 124.1, 120.8, 114.8, 29.1, 29.0, 24.6, 24.3, 23.7, 23.0, 20.3, 18.3, 18.1. 51V NMR (C6D6): δ -502, -500. 31P NMR (C6D6): δ 13, 26. Several attempts for the elemental analysis failed probably because the sample would decompose even in the analysis run. Crystallographic Analysis. All measurements were made on a Rigaku RAXIS-RAPID imaging plate diffractometer with graphite0monochromated Mo KR radiation. The crystal data and collection parameters of 1, 3-d6, 4, and 6, CIF files, and crystal structure reports for complexes 1, 3-d6, 4, and 6 are placed in the Supporting Information.16 All structures were solved by direct methods19 and expanded using Fourier techniques,20 and the non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included but not refined. All calculations were performed using the Crystal Structure21,22 crystallographic software package. Detailed analysis data including the collection parameters, CIF files, and the structure reports are shown in the Supporting Information.16
’ ASSOCIATED CONTENT
bS
Supporting Information. (1) Crystal data and collection parameters of 1, 3-d6, 4, and 6, (2) 1H NMR and 51V NMR spectra (in C6D6 at 25 °C) for monitoring the formation of V(N2,6-Me2C6H3)(CHDSiMe3)(C6 D5)(ImDIPPN) (3-d6) from V(N-2,6-Me2C6H3)(CH2DSiMe3)2(ImDIPPN) (2) in C6D6 at 60 °C, (3) 2H NMR spectra (in C6H6 at 25 °C) of V(N-2,6Me2C6H3)(CHDSiMe3)(C6D5)(ImDIPPN) (3-d6), (4) 1H NMR spectra (expanded, in C6D6 at 25 °C) for kinetic plots of the conversion from 2 to 3-d6 in C6D6 at 70 °C, (5) 1H NMR spectra (expanded, in C6D6 at 25 °C) of complexes 3 and 3-d6, (6) 1H and 51V NMR spectra (in C6D6 at 25 °C) for monitoring the formation of V(CHSiMe3)(N-2,6-Me2C6H3)(ImDIPPN)(PMe3) (4) in n-hexane at 60 °C, (7) 51V NMR spectra (in C6D6 at 25 °C) for monitoring the formation of V(N-2,6-Me2C6H3)(C6D5)2(ImDIPPN) (5-d10) in C6D6 at 80 °C, (8) ORTEP drawing for V(N-2,6-Me2C6H3)Cl2(ImDIPPN) (1), (9) CIF files and crystal structure reports for complexes 1, 3-d6, 4, and 6. These materials are available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*Tel: þ81-42-677-2547. Fax: þ81-42-677-2547. E-mail: ktnomura@ tmu.ac.jp (K.N.);
[email protected] (M.T.).
’ ACKNOWLEDGMENT K.N. and S.Z. express their heartfelt thanks to Mr. Shohei Katao (Nara Institute Science and Technology, Japan) for his strong support in the crystallographic analyses. The research was partly supported by a Grant-in-Aid for Scientific Research on
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Priority Areas (No. 19028047, “Chemistry of Concerto Catalysis”) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and The Ube Foundation. S.Z. expresses his sincere thanks to the Japan Society for the Promotion of Science (JSPS) for a postdoctoral fellowship (P08361).
’ REFERENCES (1) (a) In The Organometallic Chemistry of the Transition Metals, 5th ed.; Crabtree, R. H., Ed.; John Wiley & Sons, Inc.: Hoboken, NJ, USA; 2009; p 58. (b) In Comprehensive Organometallic Chemistry III; Crabtree, R. H.; Mingos, D. M. P., Eds.; Elsevier Science/Pergamon US: USA, 2006. (c) In Synthesis of Organometallic Compounds: A Practical Guide; Komiya, S., Ed.; John Wiley & Sons, Inc.: West Sussex, England, 1997. (d) In Organometallics in Synthesis A Manual, 2nd ed.; Schlosser, M., Ed.; John Wiley & Sons Ltd.: West Sussex, England, 2002. (e) In Organometallic Chemistry and Catalysis; Astruc, D., Ed.; Springer-Verlag: Berlin, Germany, 2007. (2) Related reviews for olefin polymerization catalysts including vanadium complexes: (a) Gambarotta, S. Coord. Chem. Rev. 2003, 237, 229. (b) Hagen, H.; Boersma, J.; van Koten, G. Chem. Soc. Rev. 2002, 31, 357. (c) Bolton, P. D.; Mountford, P. Adv. Synth. Catal. 2005, 347, 355. (d) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev. 2003, 103, 283. (e) Nomura, K. In New Developments in Catalysis Research; Bevy, L. P., Ed.; Nova Science Publishers, Inc.: New York, 2005; p 199. (f) Nomura, K. Zhang, S. Chem. Rev., in press (DOI: 10.1021/ cr100207h). (3) For examples, see: (a) Schrock, R. R. Acc. Chem. Res. 1990, 23, 158. (b) Schrock, R. R. In Alkene Metathesis in Organic Synthesis; F€urstner, A., Ed.; Springer: Berlin, Germany, 1998; p 1. (c) Schrock, R. R. In Handbook of Metathesis; Grubbs, R. H., Ed.; Wiley-VCH: Weinheim, Germany, 2003; Vol. 1, p 8. (4) For examples, see: (a) Schrock, R. R. Acc. Chem. Res. 1979, 12, 98. (b) Schrock, R. R. Chem. Rev. 2002, 102, 145. (c) Mindiola, D. Acc. Chem. Res. 2006, 39, 813. (d) Mindiola, D.; Bailey, B.; Basuli, F. Eur. J. Inorg. Chem. 2006, 16, 3135. (e) Schrock, R. R. Chem. Rev. 2009, 109, 3211. (5) Nomura, K.; Zhang, W. Chem. Sci. 2010, 1, 161. (6) (a) Buchmeiser, M. R. Chem. Rev. 2000, 100, 1565. (b) Grubbs, R. H., Ed. Handbook of Metathesis; Wiley-VCH: Weinheim, Germany, 2003; Vols. 1-3. (c) Khosravi, E.; Szymanska-Buzar, T., Eds. RingOpening Metathesis Polymerisation and Related Chemistry; Kluwer: Dordrecht, The Netherlands, 2002. (d) Imamoglu, Y., Dragutan, V., Eds. Metathesis Chemistry; Springer: Dordrecht, The Netherlands, 2007. (7) (a) Yamada, J.; Nomura, K. Organometallics 2005, 24, 2248. (b) Yamada, J.; Fujiki, M.; Nomura, K. Organometallics 2005, 24, 3621. (c) Yamada, J.; Fujiki, M.; Nomura, K. Organometallics 2007, 26, 2579. (d) Nomura, K.; Onishi, Y.; Fujiki, M.; Yamada, J. Organometallics 2008, 27, 3818. (e) Zhang, W.; Yamada, J.; Nomura, K. Organometallics 2008, 27, 5353. (f) Zhang, W.; Nomura, K. Organometallics 2008, 27, 6400. (g) Zhang, W.; Katao, S.; Sun, W.-H.; Nomura, K. Organometallics 2009, 28, 1558. (8) For example, see: (a) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002, 35, 1583. (b) Wang, W.; Nomura, K. Macromolecules 2005, 38, 5905. (c) Wang, W.; Nomura, K. Adv. Synth. Catal. 2006, 348, 743. (d) Onishi, Y.; Katao, S.; Fujiki, M.; Nomura, K. Organometallics 2008, 27, 2590. (e) Zhang, S.; Nomura, K. Organometallics 2009, 28, 5925. (9) Zhang, S.; Nomura, K. J. Am. Chem. Soc. 2010, 132, 4960. (10) We previously described in ref 5 that one probable reason for this difficulty for clean isolation of the alkylidene could be due to the formed vanadium(V)-alkylidene species being highly reactive even in C6D6 and affording another species [such as V[CH(D)SiMe3](C6D5) confirmed by the crystallographic analysis] by C-H activation. The present article describes a detailed study concerning these observations. (11) Related chemistry recently published for reaction of (PNP)V(CH2tBu)2 with C6D6 affording (PNP)V(C6D5)2 [PNP = N{2-PiPr2-4-Me-C6H3}2-] via intermolecular C-H bond activation 2719
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Organometallics of benzene. Andino, J. G.; Kilgore, U. J.; Pink, M.; Ozarowski, A.; Krzystek, J.; Telser, J.; Baik, M.-H.; Mindiola, D. Chem. Sci. 2010, 1, 351. They postulated that the double 1,2-C-H bond activation proceeds via vanadium(III)-alkylidene and the vanadium(III)-benzyne intermediate including isolation of (oxo)vanadium(V)-alkylidene, (PNP)V(O)(CHtBu). (12) For example (1,2-C-H bond activation of benzene using Mo, W), see: (a) Pamplin, C. B.; Legzdins, P. Acc. Chem. Res. 2003, 36, 223. (b) Wada, K.; Pamplin, C. B.; Legzdins, P. J. Am. Chem. Soc. 2002, 124, 9680. (c) Wada, K.; Pamplin, C. B.; Legzdins, P.; Patrick, B. O.; Tsyba, I.; Bau, R. J. Am. Chem. Soc. 2003, 125, 7035. (d) van der Heijden, H.; Hessen, B. Chem. Commun. 1995, 145. (e) Tran, E.; Legzdins, P. J. Am. Chem. Soc. 1997, 119, 5071. (f) Adams, C. S.; Legzdins, P.; McNeil, W. S. Organometallics 2001, 20, 4939. (g) Adams, C. S.; Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612. (h) Adams, C. S.; Legzdins, P.; Tran, E. Organometallics 2002, 21, 1474. (i) Tsang, J. Y. K.; Buschhaus, M. S. A.; Legzdins, P.; Patrick, B. O. Organometallics 2006, 25, 4215. (13) For example (1,2-C-H bond activation of benzene using Ti), see: (a) McDade, C.; Green, J. C.; Bercaw, J. E. Organometallics 1982, 1, 1629. (b) van der Heijden, H.; Hessen, B. Chem. Commun. 1995, 145. (c) Cheon, J.; Rogers, D. M.; Girolami, G. S. J. Am. Chem. Soc. 1997, 119, 6804. (d) Bailey, B. C.; Fan, H.; Baum, E. W.; Huffman, J. C.; Baik, M.-H.; Mindiola, D. J. J. Am. Chem. Soc. 2005, 127, 16016. (e) Bailey, B. C.; Huffman, J. C.; Mindiola, D. J. J. Am. Chem. Soc. 2007, 129, 5302. (f) Bailey, B. C.; Fan, H.; Huffman, J. C.; Baik, M.-H.; Mindiola, D. J. J. Am. Chem. Soc. 2007, 129, 8781. (g) Fout, A. R.; Scott, J.; Miller, D. L.; Bailey, B. C.; Pink, M.; Mindiola, D. J. Organometallics 2009, 28, 331. (14) For example (1,2-C-H bond activation of benzene using Ta), see: (a) Chamberlain, L. R.; Rothwell, I. P.; Huffman, J. C. J. Am. Chem. Soc. 1986, 108, 1502. (b) Abbott, J. K. C.; Li, L.; Xue, Z. L. J. Am. Chem. Soc. 2009, 131, 8246. (15) (a) Tamm, M.; Randoll, S.; Bannenberg, T.; Herdtweck, E. Chem. Commun. 2004, 876; (b) Tamm, M.; Beer, S.; Herdtweck, E. Z. Naturforsch. 2004, 59b, 1497; (c) Tamm, M.; Randoll, S.; Herdtweck, E.; Kleigrewe, N.; Kehr, G.; Erker, G.; Rieger, B. Dalton Trans. 2006, 459; (d) Beer, S.; Hrib, C. G.; Jones, P. G.; Brandhorst, K.; Grunenberg, J.; Tamm, M. Angew. Chem. 2007, 119, 9047; Angew. Chem., Int. Ed. 2007, 46, 8890. (e) Panda, T. K.; Randoll, S.; Hrib, C. G.; Jones, P. G.; Bannenberg, T.; Tamm, M. Chem. Commun. 2007, 5007. (f) Beer, S.; Brandhorst, K.; Grunenberg, J.; Hrib, C. G.; Jones, P. G.; Tamm, M. Org. Lett. 2008, 10, 981. (g) Stelzig, S. H.; Tamm, M.; Waymouth, R. M. J. Polym. Sci. Part A., Polym. Chem. 2008, 46, 6064. (h) Panda, T. K.; Trambitas, A. G.; Bannenberg, T.; Hrib, C. G.; Randoll, S.; Jones, P. G.; Tamm, M. Inorg. Chem. 2009, 48, 5462. (i) Beer, S.; Brandhorst, K.; Hrib, C. G.; Wu, X.; Haberlag, B.; Grunenberg, J.; Jones, P. G.; Tamm, M. Organometallics 2009, 28, 1534. (j) Sharma, M.; Botoshanskii, M.; Bannenberg, T.; Tamm, M.; Eisen, M. S. C. R. Chim. 2010, 13, 767. (k) Trambitas, A. G.; Panda, T. K.; Bannenberg, T.; Hrib, C. G.; Daniliuc, C. G.; Jones, P. G.; Jenter, J.; Roesky, P. W.; Tamm, M. Inorg. Chem. 2010, 49, 2435. (l) Haberlag, B.; Wu, X.; Brandhorst, K.; Grunenberg, J.; Daniliuc, C. G.; Jones, P. G.; Tamm, M. Chem.—Eur. J. 2010, 16, 8868. (m) Panda, T. K.; Hrib, C. G.; Jones, P. G.; Tamm, M. J. Organomet. Chem. 2010, 695, 2768. (n) Trambitas, A. G.; Panda, T. K.; Tamm, M. Z. Anorg. Allg. Chem. 2010, 636, 2171. (16) Detailed NMR spectra and structural analysis data including CIF files for complexes (1, 3-d6, 4, 6) are shown in the Supporting Information. (17) Two resonances were observed in both the 31P and 51V NMR spectra for the benzyne complex 6, and two resonances ascribed to the protons in PMe3 were observed in the 1H NMR spectrum. Since the crystallographic analysis result for 6 reveals that 6 has a rather distorted tetrahedral geometry around vanadium and because the bond angles of N(1)-V(1)-C(100) [112.89(5)°] and N(2)-V(1)-C(100) [125.14(4)°] are larger than those of N(1)-V(1)-C(101) [106.04(5)°] and N(2)-V(1)-C(101) [108.71(4)°], it seems likely that there are two isomers in the solution. (18) Buijink, J.-K. F.; Teubin, J. H.; Kooijman, H.; Spek, A. L. Organometallics 1994, 13, 2922.
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(19) SIR92: Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla, M.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435. (20) DIRDIF99: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-99 program system, Technical Report of the Crystallography Laboratory; University of Nijmegen: The Netherlands, 1999. (21) CrystalStructure 3.8, Crystal Structure Analysis Package; Rigaku and Rigaku Americas: The Woodlands, TX, USA, 2000-2007. (22) Sheldrick, G. M. SHELX97; University of G€ottingen: Germany, 1997.
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