Inter- vs. Intramolecular rearrangement of a (Bu3P) 2Ni moiety in its 9-alkyl and 9,10-dialkyl anthracene complexes. Limiting conditions and isomer stabilities

Journal of Organometallic Chemistry

Volumn 515, Issue 1-2, 1996, Pages 183-191

  Stanger, Amnon ^a   Weismann, Haim ^a  

^a TECHNION ISRAEL INSTITUTE OF TECHNOLOGY   (Israel)

Author keywords

9,10 dialkyl anthracene; Dynamic behavior; Fluxionality; Kinetics; Nickel; Nuclear magnetic resonance

Indexed keywords

EID: 0030607933     PISSN: 0022328X     EISSN: None     Source Type: Journal    
DOI: 10.1016/0022-328X(95)06104-5     Document Type: Article

References (28)

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13. [10] The splitting pattern is different (AA'BB' for anthracene, ABCD for 9-methyl-anthracene). However, since an AA'BB' pattern can be regarded as an averaged ABCD, the average chemical shifts can be calculated.
14. [11] We call it here "formal intramolecular process" because it may arise from an intra-as well as from an intermolecular process (see the discussion regarding 4). Thus, the data arrived from intramolecular saturation transfer, and is therefore named in this way.
15. 3Cr-naphthalene on the basis of theoretical studies. See T.A. Albright, P. Hofmann, R. Hoffmann, C.P. Lillya and A. Dobosh, J. Am. Chem. Soc., 105 (1983) 3396.
16. [13] It is well known that NMR is not a reliable method for the determination of ΔS‡. However, the similarities between the values obtained for 3a and 4a and the comparison of the free energies of activation between 3a, 3b and 4a, 4b suggest that, at least in the bulk part, the values are correct. Thus, in the analysis presented one process is considered to have large negative ΔS‡, and the other a positive value.
17. 2Ni moiety, one at the rate determining step and the other after the rate determining step.
18. -1. For a summary see P.W. Jolly and G. Wilke, The Organic Chemistry of Nickel, Vol. 1, Academic Press, New York, 1974, pp. 244-248.
19. [16] At elevated temperatures 1 is unstable and the reaction is too fast to be monitored by saturation transfer.
20. [17] NOE was measured between any two adjacent protons in the system and was found to be non-existent (within the experimental limitation). This is not surprising, since the NOE depends on the molecular mass; it is positive (up to 50%) in small molecules and negative (maximum-100%) in large molecules (see D. Neuhaus and M. Williamson, The Nuclear Overhauser Effect in Structural and Conformational Analysis, VCH, New York, 1989, pp. 30-31). It may well be that 3 is at the molecular weight range for which the NOE effect is almost unobservable. Also, the dependence of the measured effect is logarithmic with temperature (see text), whereas the NOE dependence on temperature is of a different nature (see D. Neuhaus and M. Williamson, The Nuclear Overhauser Effect in Structural and Conformational Analysis, VCH, New York, 1989, pp. 90-91, 158-160).
21. [17] NOE was measured between any two adjacent protons in the system and was found to be non-existent (within the experimental limitation). This is not surprising, since the NOE depends on the molecular mass; it is positive (up to 50%) in small molecules and negative (maximum-100%) in large molecules (see D. Neuhaus and M. Williamson, The Nuclear Overhauser Effect in Structural and Conformational Analysis, VCH, New York, 1989, pp. 30-31). It may well be that 3 is at the molecular weight range for which the NOE effect is almost unobservable. Also, the dependence of the measured effect is logarithmic with temperature (see text), whereas the NOE dependence on temperature is of a different nature (see D. Neuhaus and M. Williamson, The Nuclear Overhauser Effect in Structural and Conformational Analysis, VCH, New York, 1989, pp. 90-91, 158-160).
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24. [19] In the free ligand the chemical shifts of H(2) and H(3) are similar (see Fig. 2). Since both protons are similarly affected by the Ni in 3a and 3a′ respectively, H(2) is expected to have a similar chemical shift to H(3′) and vice versa.
25. f.
26. [21] Preliminary results for the effect of methoxy substitutions at different positions on the anthracene are found in A. Shazar, M.Sc. Thesis, Technion, Haifa, Israel, 1993.
27. 1H FT NMR Spectra, Vol. 2, Aldrich Chemical Company, 1st edn., 1993, p. 50.
28. [23] See M.L. Martin, J.J. Delpuech and G.L. Martin, Practical NMR Spectroscopy, Heyden, Chichester, UK, 1980, pp. 315-321.