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The two earlier posts have explored one of many oldest bonding guidelines (pre-dating quantum mechanics), which postulated that crammed valence shells in atoms forming molecules observe the magic numbers 2, 8, 18 and 32. Of the 59,025,533 molecules documented on the instantaneous I write this submit, solely one instance is claimed for the 32-electron class. Right here I counsel one other, Nobelocene (one which given the radioactive instability of nobelium, is unlikely to be ever confirmed experimentally!)
Nobelium has the digital configuration [Rn].5f14.7s2 , which implies the 6d and 7p shells are nonetheless empty. Filling these would take 10+6 electrons, or 4 extra electrons (20) if one begins from No4+, leading to an entire 32-electron crammed shell for the Nobelium. These twenty electrons could possibly be offered by two cyclo-octatetraenyl (COT) dianion ligands. Nobelium, with its nuclear cost of +102, has extremely relativistic inner-shell electrons, and so particular strategies should be used to mannequin this. Right here I’ve used a SARC all electron relativistically contracted foundation set (DOI: 10.1021/ct100736b), for use with the Douglas−Kroll−Hess scalar relativistic Hamiltonian (for particulars, see right here). The QTAIM evaluation is proven under (fairly a spider’s net):
Nobelocene. AIM evaluation. Click on for 3D.
There are 16 bond vital factors positioned alongside the strains of every No..C, with ρ(r) 0.03. It is a very low worth certainly for a covalent bond, being of the identical order as sturdy hydrogen bonds, and so must be classed as an interplay relatively than a bond. ELF basins can not usually be positioned for hydrogen bonds, and neither can they right here. Nobelocene on this regard is fairly boring, being nearly totally ionic.
ELF evaluation for Nobelocene.
Somewhat extra attention-grabbing are the molecular orbitals. Probably the most steady π-type is proven under. Most of the orbitals present the Nobelium atomic orbitals non-interacting with the ligand, most likely as a result of the relativistic contraction renders them inert to mixing, in a way which is usually used to elucidate the inert nature of e.g. the Pb 6s2 electrons in divalent lead.
Molecular orbital for nobelocene. Click on for 3D.
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