Imperial College London

Henry Rzepa

The previous posts have seen how a molecule containing a hypervalent
carbon atom can be designed by making a series of logical chemical
connections. Another logical step is to investigate whether the adjacent
atoms in the periodic table may exhibit similar effects (C^2+^ ≡ B^+^ ≡
N^3+^ ≡ Be ≡ O^4+^). So here are reported some results
(B3LYP/6-311G(d,p) ) for boron, beryllium and nitrogen, for the general
tetramethyl substituted system shown below

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Pentavalency across a series
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|     |        |               |          |                 |                      |               |                                                                           |
|-----|--------|---------------|----------|-----------------|----------------------|---------------|---------------------------------------------------------------------------|
| X   | Charge | X-C length, Å | ρ(r) C-X | ELF integration | ν-Trampoline, cm^-1^ | ν X-H, cm^-1^ | Repository                                                                |
| N   | 2      | 1.616         | .172     | 1.14            | 883                  | 3417          | [10042/to-2439](http://hdl.handle.net/10042/to-2439){target="references"} |
| C   | 1      | 1.580         | .195     | 1.10            | 970                  | 3291          | [10042/to-2438](http://hdl.handle.net/10042/to-2438){target="references"} |
| B   | 0      | 1.649         | .136     | 1.06            | 949                  | 2746          | [10042/to-2440](http://hdl.handle.net/10042/to-2440){target="references"} |
| Be  | -1     | 1.817         | .064     | 0.98            | 797                  | 1887          | [10042/to-2441](http://hdl.handle.net/10042/to-2441){target="references"} |

The systems H, C and B are stable in the sense that the C~4v~-symmetric
calculated geometry has only positive calculated force constants (Be has
a small negative frequency). All show bond critical points in the  X-C
region (although these bonds are clearly  bent) and X-H region, and
significant integrations for the X-C disynaptic basins in the  ELF
analysis. The boron analogue is also of interest as being a neutral
rather than a charged molecule, and therefore may be a worthy target for
synthetic effort.

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[https://orcid.org/0000-0002-8635-8390](https://orcid.org/0000-0002-8635-8390){target="_blank"
rel="author"}
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The previous posts have seen how a molecule containing a hypervalent carbon atom can be designed by making a series of logical chemical connections.

Messaggi di Rogue Scholar

Pentavalent nitrogen and boron