| Phys. Chem. Chem. Phys., 2011 | |
Additions and corrections Planarity takes over in the CxHxP6-x (x = 0–6) series at x = 4 |
Timur R. Galeev and Alexander I. Boldyrev
Phys. Chem. Chem. Phys., 2011, DOI: 10.1039/C1CP21959F. Amendment published 27th September 2011
The correct Table 1 and the subsequent text until the end of the section should be:
Table 1 NICSzz values (ppm) calculated at B3LYP/6-311++G**| Distance/Å | P6 | CHP5 | C2H2P4 | C3H3P3 | C4H4P2 | C5H5P | C6H6 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| I.11 | II.16 | III.5 | III.10 | III.13 | IV.2 | IV.4 | IV.5 | V.I | V.2 | V.3 | VI.1 | VII.1 | |
| 0.0 | -23.7 | -12.1 | -9.0 | -9.1 | -9.0 | -9.2 | -9.2 | -8.9 | -10.4 | -10.4 | -10.2 | -12.5 | -14.5 |
| 0.2 | -24.2 | -12.9 | -10.0 | -10.1 | -10.0 | -10.4 | -10.3 | -10.1 | -11.7 | -11.7 | -11.5 | -14.1 | -16.3 |
| 0.4 | -25.5 | -15.1 | -12.7 | -12.8 | -12.5 | -13.5 | -13.4 | -13.2 | -15.1 | -15.2 | -14.9 | -17.9 | -20.6 |
| 0.6 | -27.2 | -18.0 | -16.0 | -16.2 | -15.8 | -17.2 | -17.2 | -16.9 | -19.1 | -19.2 | -19.0 | -22.3 | -25.2 |
| 0.8 | -28.7 | -20.7 | -19.2 | -19.3 | -18.9 | -20.6 | -20.5 | -20.2 | -22.5 | -22.6 | -22.4 | -25.5 | -28.3 |
| 1.0 | -29.6 | -22.7 | -21.4 | -21.5 | -21.1 | -22.8 | -22.6 | -22.3 | -24.4 | -24.4 | -24.2 | -27.0 | -29.2 |
| 1.2 | -29.7 | -23.6 | -22.5 | -22.4 | -22.1 | -23.6 | -23.3 | -23.0 | -24.7 | -24.7 | -24.5 | -26.6 | -28.2 |
| 1.4 | -29.0 | -23.6 | -22.4 | -22.3 | -22.0 | -23.2 | -22.8 | -22.6 | -23.8 | -23.7 | -23.6 | -25.0 | -26.0 |
| 1.6 | -27.7 | -22.7 | -21.5 | -21.3 | -21.0 | -21.9 | -21.5 | -21.3 | -22.1 | -21.9 | -21.8 | -22.7 | -23.2 |
| 1.8 | -25.9 | -21.3 | -20.0 | -19.8 | -19.6 | -20.1 | -19.7 | -19.4 | -20.0 | -19.8 | -19.7 | -20.2 | -20.2 |
| 2.0 | -23.8 | -19.6 | -18.3 | -18.1 | -17.9 | -18.1 | -17.7 | -17.5 | -17.8 | -17.6 | -17.4 | -17.6 | -17.4 |
In order to probe aromaticity in all planar ring-type structures of the CxHxP6-x (x = 0–6) series we used both the NICS (Table S2, ESI†) and NICSzz (Table 1, Table S1, ESI†) indices, two of the most popular methods for evaluating aromaticity in planar species. For the NICS and NICSzz calculations we used only planar benzene-type structures, even though some of them are actually saddle points.
According to our calculations, the NICS indices (B3LYP/ 6-311++G**) of all the benzene-like structures in the CxHxP6-x (x = 0–6) series (Table S2, ESI) have their highest (negative) values at 0.8-1.1 Å. The maximum NICS value (-11.5 ppm, Z = 1.0 Å) for P6 is almost the same as the highest index (-10.6 ppm, Z = 0.8 Å) of benzene. The maximum NICS values of all other benzene-like structures in the CxHxP6-x (x = 1-5) series are all very high and vary from -8.4 (III.13) to -10.3 (VI.1) ppm. Thus, according to the NICS indices, all benzene-like structures are almost as aromatic as hexaphosphabenzene and benzene. Schleyer et al.77 calculated NICS(π) = -14.7 (-15.9) ppm, NICS(σ) = +1.2 (+3.0) ppm and NICS(tot) = -15.8 (-15.2) ppm (NICS calculated at 0.5 Å with values at Z = 0 Å in parentheses) for planar P6, which are comparable to those of benzene (NICS(π) = -16.8 (-20.7) ppm, NICS(σ) = +8.8 (+13.8) ppm and NICS(tot) = -10.7 (-8.9) ppm) at the same level of theory. Hofmann et al.53 calculated NICS at the center of the benzene-like structures using the GIAO-SCF/6-31+G* method at the MP2(full)/6-31G* optimized geometries. They got the following values: -8.4 ppm (VI.1), -7.9 ppm (V.1), -7.1 ppm (V.2), -7.3 ppm (V.3), -7.3 ppm (IV.2), -6.4 ppm (IV.4), and -5.8 ppm (IV.5). Our NICS values calculated for the same species in the same positions are somewhat different from the reported numbers, but the overall picture is consistent with the other studies.53,57
The calculated maximum values of the NICSzz indices (Table 1) are significantly higher than the NICS indices and vary from -22.1 (III.13) ppm to -29.7 ppm (I.11). However these results lead to a similar conclusion on aromaticity in these planar structures: all benzene-like structures are almost as aromatic as hexaphosphabenzene and benzene. Thus, the relative stabilities of the benzene-like structures do not depend on aromaticity. Additional studies are required to make a reliable assessment of the aromaticity of benzene-like structures in the series.
The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
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