Pentavalent nitrogen and boron

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 (C2+ ≡ B+ ≡ N3+ ≡ Be ≡ O4+). So here are reported some results (B3LYP/6-311G(d,p) ) for boron, beryllium and nitrogen, for the general tetramethyl substituted system shown below

Pentavalency across a series

Pentavalency across a series

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
C 1 1.580 .195 1.10 970 3291 10042/to-2438
B 0 1.649 .136 1.06 949 2746 10042/to-2440
Be -1 1.817 .064 0.98 797 1887 10042/to-2441

The systems H, C and B are stable in the sense that the C4v-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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