چکیده انگلیسی:
Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)-tetrazole-5-stannylenes (1R), and 1,3-di(R)-tetrazole-5-stannylenes (2R), using B3LYP/6-311++G** level of theory. Nucleophilicity, multiplicity, and stability of 1R and 2R are calculated; with R = H, methyl, ethyl, i-propyl, t-butyl, Ph, OH, methoxy, NO2, CN and CF3. Asymmetric 2H appears more nucleophilic (N ̴ 4) than its corresponding symmetric 1H isomer (N ̴ 3), mostly due to the formers higher separation of charge. The N is more sensitive to electronic effects in 1R stannylenes than those in the 2R series. Electron donating R groups increase N with Hammett ρ constants of -3.3 and -2.7 for 1R and 2R, respectively. Stannylene 2H is slightly more aromatic (NICS (1) = -10.31) than 1H (NICS (1) = -10.25). Every 1R is more stable than its corresponding 2R isomer. Every 2R is generally more nucleophilic and aromatic than its corresponding 1R. In addition the former is less electrophilic with a larger band gap and narrower stannylene bond angle. Substituent effects are probed on N by devising proper isodesmic reactions. The trend for N is: 2t-buthyl> 2iso-propyl> 2ethyl> 2methyl> 2ph> 2OMeth >1t-buthyl> 2OH> 2H >1Ph> 1iso-propyl> 1OH >1ethyl >1methyl >1OMeth >1H >2CF3 >2NO2> 2CN> 1CF3> 1CN> 1NO2.
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