Planar Tetracoordinate Carbon in Extended Systems

Abstract

A recently proposed system with a central planar tetracoordinate carbon linking two three-membered rings, C(5)(2-), lends itself to extension in one, two, and three dimensions. Our construction of potential realizations begins with an analysis of the electronic structure of C(5)(2-). Dimers such as C(10)Li(3-), C(10)Li(4), and a trimer C(15)Li(6) are then examined, and their geometries are optimized to find clues for ways the C(5)(2-) unit may polymerize in the presence of countercations. Coordination through the terminal carbons is favored in the oligomers and polymers; several electronically and structurally reasonable systems of the stoichiometry C(5)M(x) (M = Li, x = 2; M = Be, Pt, Zn, x = 1) emerge from band structure calculations and energetic considerations.

Four Decades of the Chemistry of Planar Hypercoordinate Compounds

“…[146,148] In 2004, linking the central ptC of the C 5 2À units with two three-membered rings led to extensions of ptC into one,two, and three dimensions.Derived from the monomer and dimer models,and using asimple model of the bonding capabilities of the C 5 2À units,Hoffmann and co-workers proposed avariety of extended networks,including C 5 M x (x = 1, M = Pt, Zn, Be and x = 2, M = Li) ( Figure 58). [149] In general, these novel solids have relatively large band gaps,s uggesting insulating behavior.…”

Exploring Group 14 Structures: 1D to 2D to 3D

“…A simple 908 twist results in a 0.5 eV per C energy stabilization favoring the linear polymer with tetrahedral carbon, 23. This is hardly surprising given what we know of carbon chemistry, and the absence of special factors stabilizing squareplanar carbon (a geometry close to the heart of one of us [13,14] ). Carbon is the only one of the Group 14 elements known to have metastable, kinetically persistent 1D (carbyne, nanotubes) and 2D (graphene) allotropes (and 0D, as well, counting the fullerenes).…”

“…Beyond these, the choices are somewhat arbitrary. The 2D starting geometries shown in Figure 2 include the honeycomb net or graphene (10), two-layer graph-A C H T U N G T R E N N U N G enes (11 and 12), the square-planar sheet (13), kagome net (14), wavy or corrugated square sheet (15), "cubic" planar or double square sheet (16), rhombohedral planar or trigonal prism sheet (17), and a triangular sheet (18).…”

Recent advances in planar tetracoordinate carbon chemistry

“…Using Hoffmann's strategy (also called the electronic approach), several ptC molecules have been proposed in silico 14,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] and/or experimentally detected. [38][39][40][41][42][43][44][45][46][47][48] A few realized compounds of nonclassical structures containing ptCs are shown in Figure 2.…”