Novel N-heterocyclic Stannylenes (NHSns) Using DFT

Substitution effects are probed for novel N-heterocyclic stannylenes (NHSns), including 1,4-di(R)-tetrazole-5-stannylenes (1(R)), and 1,3-di(R)-tetrazole-5-stannylenes (2(R)), using B3LYP/6-311++G** level of theory. Nucleophilicity, multiplicity, and stability are calculated for 1(R) and 2(R); R = H, methyl, ethyl, i-propyl, t-butyl, Ph, OH, methoxy, NO2, CN and CF3. Asymmetric 2(H) appears to be more nucleophilic (N similar to 4) than its corresponding symmetric 1(H) isomer (N similar to 3), mostly due to the higher separation of charge in the former group. The N is more sensitive to electronic effects in 1(R) stannylenes than those in the 2(R) series. Electron donating R groups increase N with Hammett rho constants of -3.3 and -2.7 for 1(R) and 2(R), respectively. Stannylene 2(H) is slightly more aromatic (NICS (1) = -10.31) than 1(H) (NICS (1) = -10.25). All 1(R) isomers are more stable than the corresponding 2(R). However, all 2(R) structures are generally more nucleophilic and aromatic than the corresponding 1(R). 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: 2(t-buthyl) > 2(iso-propyl) > 2(ethyl) > 2(methyl) > 2(ph) > 2(OMeth) > 1(t-buthyl) > 2(OH) > 2(H) > 1(Ph) > 1(iso-propyl) > 1(OH) > 1(ethyl) > 1(methyl) > 1(OMeth) > 1(H) > 2(CF3) > 2(NO2) > 2(CN) > 1(CF3) > 1(CN) > 1(NO2).