Are neutral oxocarbons stable?

Revisiting the Hitherto Elusive Cyclohexanehexone Molecule: Bulk Synthesis, Mass Spectrometry, and Theoretical Studies

The cyclohexanehexone (C₆O₆) octahydrate molecule was claimed to be synthesized as early as 1862. However, the chemical in the 1862 study and the chemicals used in most of the existing studies and sold by most chemical vendors are actually dodecahydroxycyclohexane dihydrate (C₆(OH)₁₂·2H₂O). Here we revisit our bulk synthesis method of C₆O₆ by the dehydration of the C₆(OH)₁₂·2H₂O material, and report the mass spectrum of C₆O₆ that has been highly challenging to obtain owing to its high sensitivity toward ambient conditions. A new home-built electrospray ionization mass spectrometry setup in a glovebox is utilized to detect C₆O₆ in the form of C₆O₆H^-. Tandem mass spectrometry MSⁿ (n = 2-4) presents consecutive losses of CO molecules, further confirming the structure of C₆O₆. Theoretical calculations are performed to recover the chemical bonding of C₆O₆ and to rationalize the synthetic method. This work provides a benchmark understanding of the historically elusive C₆O₆.

The unimolecular dissociation of magnesium chloride squarate (ClMgC4O4−) and reductive cyclooligomerisation of CO on magnesium

Cyclooligomerisation to squarate is initiated by the coupling of two CO units in MgCl⁻.

Theoretical insights into the CO dimerization and trimerization on Pt nanocluster

CO dimerizaiton and trimerization on icosahedral Pt₅₅ cluster.

Preparation, solid-state characterization, and computational study of a crown ether attached to a squaramide

[structure: see text] Crystals of a disecondary squaramide covalently linked to a crown ether presents a great variety of inter- and intramolecular nonbonded interactions including C-H/pi contacts, C-H...O and N-H...O hydrogen bonds, and pi-pi stacking between squaramide rings. Latter interaction, the stacking between squaramide rings, can be considered as an experimental evidence for the proposed aromaticity of squaramide when it is forming hydrogen bonds, either as acceptor or donor.

A Theoretical and Structural Investigation of Thiocarbon Anions

Density functional theory energies, geometries, and population analyses as well as nucleus-independent chemical shifts (NICS) have been used to investigate the structural and magnetic evidence for cyclic CnSn(2-) and CnSn (n = 3-6) electron delocalization. Localized molecular orbital contributions to NICS, computed by the individual gauge for localized orbitals method, dissect pi effects from the sigma single bonds and lone pair influences. CnSn(2-) (n = 3-5) structures in Dnh symmetry are minima. Their aromaticity decreases with increasing ring size. C3S3(2-) is both sigma and pi aromatic, while C4S4(2-) and C5S5(2-) are much less aromatic. NICS(0)pi, the C-C(pi) contribution to NICS(0) (i.e., at the ring center), decreases gradually with ring size. In contrast, cyclic C6S6(2-) prefers D2h symmetry due to the balance between aromaticity, strain energy, and the S-S bond energies and is as aromatic as benzene. The theoretical prediction that C6S6(6-) has D6h minima was confirmed by X-ray structure analysis. Comparisons between thiocarbons and oxocarbons based on dissected NICS analysis show that CnSn(2-) (n = 3-5) and C6S6(6-) are less aromatic in Dnh symmetry than their oxocarbon analogues.