Pentacoordinate Carbon Atoms in a Ferrocene Dication Derivative—[Fe(Si2-η5-C5H2)2]2+

Abstract

Pentacoordinate carbon atoms are theoretically predicted here in a ferrocene dication derivative in the eclipsed-(1; C2v), gauche-(2; C2) and staggered-[Fe(Si2-η5-C5H2)2]2+(3; C2h) forms for the first time. Energetically, the relative energy gaps for 2 and 3 range from −3.06 to 16.74 and −2.78 to 40.34 kJ mol−1, respectively, when compared to the singlet electronic state of 1 at different levels. The planar tetracoordinate carbon (ptC) atom in the ligand Si2C5H2 becomes a pentacoordinate carbon upon complexation. The ligand with a ptC atom was predicted to be both a thermodynamically and kinetically stable molecule by some of us in our earlier theoretical works. Natural bond orbital and adaptive natural density partitioning analyses confirm the pentacoordinate nature of carbon in these three complexes (1–3). Although they are hypothetical at the moment, they support the idea of “hypercoordinate metallocenes” within organometallic chemistry. Moreover, ab initio molecular dynamics simulations carried out at 298 K temperature for 2000 fs suggest that these molecules are kinetically stable.

Five Bonds to Carbon through Tri-Coordination in Al3C3−/0

“…Chemistry 2023, 5, FOR PEER REVIEW 2 coworkers [47]. While a gradual amount of progress has been made in these classes of molecules to date, to a larger extent in the literature, the concept of making hyper-coordinate carbon molecules was predominantly focused on making single bonds to the central carbon atom irrespective of whether they are planar or non-planar [48]. However, in this article, the intent is to make five bonds to a carbon atom through tri-coordination instead of penta-coordination, as is normally carried out.…”