Through-space shielding effects of metal-complexed phenyl rings

Several naphthalene compounds containing a methyl group in a 1,8-relationship to a metal-complexed phenyl ring bearing various substituents have been synthesized. The through-space shielding effects of the phenyl ring, as a function of substituent and complexing metal species, were monitored by observing the H-1 NMR signal of the methyl group located in the shielding zone of the ring. In all cases, the methyl signal was slightly more downfield in the complexes than in the uncomplexed analogues. A comparison of available crystal structures, however, shows that the phenyl ring is slightly closer to the naphthyl methyl group in the complexes than in their metal-free counterparts. X-ray structures and DFT calculations also reveal a slight elongation in the average length of the carbon-carbon bonds of the phenyl ring upon complexation. The effect of substituents on the signal of the naphthyl methyl group is small but discernible in the uncomplexed derivatives, and consistent with our previous report. A similar trend is absent in the corresponding metal complexes, as exemplified by the chromium series, and the effect of the metal appears to be more dominant than that of the substituents. These observations were found to be in line with NMR shift calculations.

Title	Through-space shielding effects of metal-complexed phenyl rings
Creator	Lessard, S. G.
	Miles, William H.
	Robinson, M. J.
	Thamattoor, D. M.
Publisher	Journal of Organic Chemistry
Academic Department	Chemistry
Division	Natural Sciences
Organization	Lafayette College
Date Issued	2016
Date Available	2017-10-04T01:24:23Z
Type	Article
Language	English
Bibliographic Citation	Miles, W. H., et al. (2016) "Through-space shielding effects of metal-complexed phenyl rings." Journal of Organic Chemistry 81 (22): 10791-10801.
Standard Identifier	DOI 10.1021/acs.joc.6b01858
Standard Identifier	Handle 10385/2279
Permalink	http://hdl.handle.net/10385/2279
Rights Statement	In Copyright
Rights Holders	American Chemical Society