Cursed Carbon with 6 Bonds?! Chemistry of the Hexamethylbenzene Dication

🤔 Can carbon go beyond the octet rule? You might know the situation for CH5+, but what about the extremely cursed hexamethylbenzene dication? In this video, we explain the context, synthesis and bonding situation of this apparently hypervalent carbon.

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00:00 A rather CURSED carbon
00:34 Octet rule and some exceptions
01:14 Exotic carbons and CH5+ ("protonated methane")
02:40 Nonclassical 2-norbornyl cation
04:08 Hexamethylbenzene dication and synthesis
05:35 Magic acid craziness
07:06 Mechanism of formation
07:52 X-ray structure analysis, NBO and 13C NMR
09:10 Bonding situation and electronic structure
09:59 Closing and thank you!

Key references
Crystal Structure Determination of the Pentagonal-Pyramidal Hexamethylbenzene Dication C6(CH3)62+ | Angew. Chem. Int. Ed. 2017, 56, 368
The Pentagonal-Pyramidal Hexamethylbenzene Dication: Many Shades of Coordination Chemistry at Carbon | Chem. Eur. J. 2018, 24, 12340
On the Aromaticity and 13C-NMR Pattern of Pentagonal-Pyramidal Hexamethylbenzene Dication [C6(CH3)6]2+: A {C5(CH3)5}−–{CCH3}3+ Aggregate | Chemistry 2021, 3, 1363
Crystal Structure Determination of the Nonclassical 2-Norbornyl Cation | Science 2013, 341, 62
Structure and charge distribution of the (CH)62+ dication | Tetrahedron Letters 1973, 14, 1671
Direct observation of a remarkably stable dication of unusual structure: (CCH3)62+ | Tetrahedron Letters 1973, 14, 1665
Misconceptions on fluoronium ions and hypervalent fluorine cations | Journal of Fluorine Chemistry 2017, 204, 6

Some recommended books on organic synthesis:
Clayden, Greeves, Warren; Organic Chemistry (basic organic chemistry knowledge)
Wyatt, Warren; Organic Synthesis: The Disconnection Approach (excellent introduction to retrosynthesis)
Kurti, Czako; Strategic Applications of Named Reactions in Organic Synthesis (extensive toolkit of functional group reactions and applications thereof with common conditions)
Nicolaou; Classics in Total Synthesis 1-3 (the ultimate total synthesis trilogy)
Nicolaou; Molecules That Changed the World (the world's most important molecules and their impact on everyday life)
Carreira, Kvaerno; Classics in Stereoselective Synthesis (compilation of the groundbreaking methods of stereoselective synthesis and application to synthesis of stereochemically complex structures)