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Organometallics
Volumn 27, Issue 10, 2008, Pages 2152-2155
Synthesis of a benzodiazepine-derived rhodium NHC complex by C-H bond activation
Author keywords

[No Author keywords available]
Indexed keywords

ALDIMINE; C H ACTIVATION; C-H BOND ACTIVATION; CARBENE; HETERO CYCLES; METAL CO-ORDINATION; SYNTHESIS (OF CHIRAL IONIC LIQUIDS); SYNTHESIS AND CHARACTERIZATION; TRANSITION (JEL CLASSIFICATIONS:E52 ,E41 ,E31);
EID: 44649120827     PISSN: 02767333     EISSN: None     Source Type: Journal    
DOI: 10.1021/om8000839     Document Type: Article
Times cited : (42)
References (44)
  • 2
    • 0037090932 scopus 로고    scopus 로고
    • For recent reviews, see
    • For recent reviews, see: Hermann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290,
    • (2002) Angew. Chem., Int. Ed , vol.41 , pp. 1290
    • Hermann, W.A.1
  • 3
    • 44649124797 scopus 로고    scopus 로고
    • as well as issues 5 and 6 of Coord. Chem. Rev. 2007, 251, which are devoted to the topic of transition metal NHC chemistry.
    • as well as issues 5 and 6 of Coord. Chem. Rev. 2007, 251, which are devoted to the topic of transition metal NHC chemistry.
  • 5
    • 2942612461 scopus 로고    scopus 로고
    • For reviews on bond-forming reactions involving NHC ligands see: a
    • For reviews on bond-forming reactions involving NHC ligands see: (a) Cavell, K. J.; McGuiness, D. S. Coord. Chem. Rev. 2004, 248, 671.
    • (2004) Coord. Chem. Rev , vol.248 , pp. 671
    • Cavell, K.J.1    McGuiness, D.S.2
  • 6
    • 9744248685 scopus 로고    scopus 로고
    • and references therein. For a more recent example of insertion chemistry involving a cationic Ru-NHC complex
    • (b) Crudden, C. M.; Allen, D. P. Coord. Chem. Rev. 2004, 248, 2247, and references therein. For a more recent example of insertion chemistry involving a cationic Ru-NHC complex,
    • (2004) Coord. Chem. Rev , vol.248 , pp. 2247
    • Crudden, C.M.1    Allen, D.P.2
  • 7
    • 33646737012 scopus 로고    scopus 로고
    • see. (c) Becker, E.; Stingl, V.; Dazinger, G.; Puchberger, M.; Mereiter, K.; Kirchner, K. J. Am. Chem. Soc. 2006, 128, 6572.
    • see. (c) Becker, E.; Stingl, V.; Dazinger, G.; Puchberger, M.; Mereiter, K.; Kirchner, K. J. Am. Chem. Soc. 2006, 128, 6572.
  • 27
    • 0345359616 scopus 로고    scopus 로고
    • In an effort to determine whether aryl substitution at the C atom of the imine function is important to promoting the tautomerization reaction, an analogous transformation of 3,4,5,6-tetrahydropyridine generated in situ from the stable trimer β-tripiperidein was attempted. This reaction failed to provide significant conversion to either an N-bound or NHC complex by 1H NMR spectroscopy, yielding instead a lilac-colored precipitate attributed to [RhCl2(PCy3)2]2 within several minutes. Substantial equilibrium concentrations of the monomelic imine were not detected under the experimental conditions. The NHC-forming tautomerization is evidently applicable only to heterocycles capable of efficiently ligating the active RhCl(PCy3)2 fragment, and consequently only to imines that exist in solution primarily in the monomeric form. As crystallographic data for 7 imply minimal interaction between C5 and the aryl π
    • 2 fragment, and consequently only to imines that exist in solution primarily in the monomeric form. As crystallographic data for 7 imply minimal interaction between C5 and the aryl π system, it is plausible that the importance of the aryl substituent consists in stabilizing the reactive form of the heterocycle. Crude tripiperidein was prepared in a modification of De Kimpe's procedure using Rapoport's method to generate N-chloropiperidine and was purified to give β-tripiperidein according to the recyrstallization protocol described by Claxton et al. (a) Bender, D. R.; Bjeldanes, L. F.; Knapp, D. R.; Rapoport, H. J. J. Org. Chem. 1975, 40, 1264.
  • 29
    • 0000747270 scopus 로고    scopus 로고
    • De Kimpe, N.; Stevens, C. J. Org. Chem. 1993, 58, 2904. See also.
    • (c) De Kimpe, N.; Stevens, C. J. Org. Chem. 1993, 58, 2904. See also.
  • 31
    • 44649173685 scopus 로고    scopus 로고
    • Gas-phase calculations at the B3LYP/LACVP** level of theory place the model N-bound adduct 8' 4.17 kcal/mol lower in free energy than the NHC model complex 7', at variance with experimental observation of the greater stability of 7 with respect to 8 in THF solution at ambient temperature.
    • Gas-phase calculations at the B3LYP/LACVP** level of theory place the model N-bound adduct 8' 4.17 kcal/mol lower in free energy than the NHC model complex 7', at variance with experimental observation of the greater stability of 7 with respect to 8 in THF solution at ambient temperature.
  • 34
    • 44649096910 scopus 로고    scopus 로고
    • Preparation of trans-chloro(1-methyl-1,3,4,5-tetrahydro-benzo[e, 1,4] diazepin-2-one-5-ylidene)bis(tricyclohexylphosphine)rhodium(I, 7, An oven-dried 40 mL glass-walled vessel fitted with a Kontes HI-VAC valve employing a PTFE Kontes plug (8 mm bore diameter, no O-ring) opening to a glass sidearm terminating in a 14-20 female ground-glass joint was taken inside a nitrogen glovebox. This vessel was charged with a solution of 6 (90.0 mg, 517 μmol, RhCl(coe)2]2 (185 mg, 258 μmol, and tricyclohexylphosphine (374 mg, 1.33 mmol) in THF 18 mL, The valve was stoppered with the Teflon plug, and the reaction mixture was subjected to four freeze-pump-thaw cycles on a dual manifold. The reaction mixture was blanketed with an atmosphere of argon, and the reaction vessel was resealed. The resulting reaction mixture was stored at room temperature in the dark for 45 days, at which time crystallization of the NHC complex was apparently complete. The crystals were col
    • 2Rh: C, 63.73; H, 9.11; N, 2.75. Found: C, 63.64; H, 9.50; N, 2.80.
  • 35
    • 0001812460 scopus 로고    scopus 로고
    • NMR scale experiments may be conducted simply by sealing the tube under high vacuum while the reaction mixture is frozen, followed by warming the tube to the reaction temperature. However, preparative-scale experiments must be performed under an atmosphere of argon using denitrogenated solvent in order to prevent competitive formation of the dinitrogen adduct RhCl(PCy 3)2N2, a reaction first reported in: Van Gaal, H. L. M, Moers, F. G, Steggerda, J. J. J. Organomet. Chem. 1974, 65, C43. The dinitrogen complex otherwise crystallizes simultaneously with 7
    • 2), a reaction first reported in: Van Gaal, H. L. M.; Moers, F. G.; Steggerda, J. J. J. Organomet. Chem. 1974, 65, C43. The dinitrogen complex otherwise crystallizes simultaneously with 7.
  • 36
    • 44649101913 scopus 로고    scopus 로고
    • Representative procedure for monitoring the formation of trans chloro(1 -methyl-1,3,4,5-tetrahydrobenzo[e, 1,4]diazepin-2-one-5-ylidene) bis(tricyclohexylphosphine)rhodium(I, 7) by NMR: inside a nitrogen glovebox, a solution of [RhCl(coe)2]2 (6.2 mg, 8.5 μmol) and tricyclohexylphosphine (12.5 mg, 45 μmol) in THF-d8 (600 μL) was used to transfer 6 (3.0 mg, 17 μmol) and 2,6-dimethoxytoluene (2.6 mg, 17 μmol) to an oven-dried medium-walled Wilmad NMR tube. The NMR tube was inserted into a Cajon adapter and flame-sealed under vacuum while the reaction mixture was frozen in liquid nitrogen. Upon thawing, the reaction mixture was monitored by 1H NMR (400 MHz) and 31P NMR (162 MHz) spectroscopy, allowing the reaction mixture to stand at ambient temperature for the duration of the experiment. The reaction mixture took on a dark greenish brown color shortly after preparation and gradually became reddish-brown. After
    • 6-H proton resonance of 7 to the integral of the resonance arising from the two protons meta to the methyl group of the internal standard (2,6-dimethoxytoluene). Yields of 35% are typical for the above procedure; higher NMR yields can be observed (up to 50%) by increasing the volume of solvent to 900 μL and by increasing the number of equivalents of 6 with respect to rhodium to 1.3.
  • 40
    • 44649168793 scopus 로고    scopus 로고
    • The numbering scheme used in this figure deviates from that used in the crystallographic structural solution in order to be compatible with the numbering scheme (Figure 1) conventionally used for benzodiazepine heterocycles
    • The numbering scheme used in this figure deviates from that used in the crystallographic structural solution in order to be compatible with the numbering scheme (Figure 1) conventionally used for benzodiazepine heterocycles.

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