Planar nitrogen compared to planar carbon in a series of compounds: the effect of replacing with nitrogen the potentially planar tetracoordinate carbon of a series of polycyclic alkanes

Previous work by Radom and Rasmussen had been extended by the author (2019, Can. J. Chem.) to identify a smaller (C17H16 cf. C23H24) polycyclic alkane with a potentially planar tetracoordinate “central” carbon. Here the series of alkanes in that latter study were computationally modified by replacing the central carbon with isoelectronic nitrogen, N+. A series of six ammonium ions was found by ab initio calculations to potentially all, with one exception, harbour a planar tetracoordinate nitrogen in a potential energy relative minimum, at the MP2/6-31G* and MP2/(large basis) levels, as indicated by the absence of an imaginary vibrational frequency. This is in contrast to the hydrocarbons, where only two such structures were indicated to be relative minima. Key words: planar tetracoordinate carbon, planar tetracoordinate nitrogen, ab initio calculations.