Recent advances in planar tetracoordinate carbon chemistry

Merino, Gabriel; Méndez‐Rojas, Miguel A.; Vela, Alberto; Heine, Thomas

doi:10.1002/jcc.20515

Cited by 237 publications

(173 citation statements)

References 68 publications

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“…Le Bel in 1874. However, after the proposal by Hoffmann and co-workers of tetracoordinate planar carbon in 1970, [1] extensive experimental and theoretical efforts were made to search for so-called anti-vant Hoff/ anti-Le Bel molecules (for recent reviews, see references [2][3][4]). In particular, the first experimental and theoretical realization of pentaatomic planar-coordinated carbon species in 1999 and 2000, [5][6][7][8] which confirmed earlier theoretical predictions, [9,10] has stimulated renewed interest in designing new tetracoordinate [11,12] and even hypercoordinate planar carbon molecules.…”

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confidence: 99%

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

et al. 2007

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In organic chemistry, saturated carbon is known to bond to four ligands tetrahedrally, as first recognized independently by J. H. vant Hoff and J. A. Le Bel in 1874. However, after the proposal by Hoffmann and co-workers of tetracoordinate planar carbon in 1970, [1] extensive experimental and theoretical efforts were made to search for so-called anti-vant Hoff/ anti-Le Bel molecules (for recent reviews, see references [2][3][4]). In particular, the first experimental and theoretical realization of pentaatomic planar-coordinated carbon species in 1999 and 2000, [5][6][7][8] which confirmed earlier theoretical predictions, [9,10] has stimulated renewed interest in designing new tetracoordinate [11,12] and even hypercoordinate planar carbon molecules. [13][14][15][16] Notably, a series of hypercoordinate planar carbon species with boron ligands have been proposed. [13-15, 16a,c,e] Although none of these species is the global minimum on the potentialenergy surfaces, it has been suggested that they may be viable experimentally. The two proposed hexa-and heptacoordinate carbon species are D 6h CB 6 2À [13a,b,d, 14c, 15] and D 7h CB 7 À , [13b, 14c] respectively. The CB 7 À species is isoelectronic to B 8 2À , which we have shown previously to have a global-minimum D 7h structure with a heptacoordinate boron atom. [17][18][19][20] The D 7h CB 7 À can be viewed as replacing the central B À ion in B 82À by a C atom. Herein we report serendipitous experimental observation of CB 7 À . It was investigated by photoelectron spectroscopy (PES) and ab initio calculations, which showed that the observed species is a C 2v CB 7 À ion in which the C atom replaces a B À ion at the rim of the D 7h B 8 2À molecular wheel.The experiment was performed with a laser-vaporization cluster source and a magnetic-bottle photoelectron spectrometer (see Experimental Section).[21] We recently modified our cluster source by adding a 10-cm-long and 0.3-cm-diameter stainless steel tube to enhance cluster cooling.[22] We were using boron clusters, which we have previously investigated extensively, [17][18][19][20][23][24][25][26][27][28] to test the new cluster-source conditions. A 10 B-enriched disk target containing a small amount of Au was used as the laser-vaporization target.[23] Under certain conditions, when the vaporization laser was not perfectly aligned, we noted that in addition to the pure boron clusters we were also able to produce clusters containing one or two carbon atoms, as shown in Figure 1. The carbon most likely originated from impingement of the slightly misaligned vaporization laser beam on the stainless steel tubing. The trace amount of carbon contamination was ideal to produce boron clusters doped with only one or two carbon atoms, and the beam condition was stable and reproducible.The peak of the CB 7 À cluster is particularly intense with abundance as strong as those of the nearby pure B x À clusters (Figure 1). Its photoelectron spectra at two detachment laser wavelengths are shown in Figure 2. The 193-nm spectrum rev...

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CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

et al. 2007

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“…1,2 Recent success of experimental verifications [3][4][5] of ptC 6,7 has stimulated a continuously increasing number of theoretical studies on this exciting topic. In particular, great interest has been arisen for achieving ptC(C) 4 substructure, a ptC surrounded only by carbons.…”

Section: Introductionmentioning

confidence: 99%

“…2 An alternative theoretical strategy to stabilize ptC is the ''electronic'' approach. As proposed in the first article on ptC by Hoffmann et al, 12 ptC can be stabilized by p-acceptor and r-donor substituents.…”

Section: Introductionmentioning

confidence: 99%

Perfect planar tetracoordinate carbon in neutral unsaturated hydrocarbon cages: A new strategy utilizing three‐dimensional electron delocalization

Wang

2009

J Comput Chem

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A new series of unsaturated pure and boron-substituted hydrocarbons containing a perfect planar tetracoordinate carbon (ptC) have been proposed by performing density functional computations. The ptC is effectively stabilized through three-dimensional delocalization of ptC's lone pair into pi-conjugated systems, by utilizing a new strategy opening a brand new way of designing ptC structures. Compared to previously proposed ptC-containing hydrocarbon cage compound, a neutral hydrocarbon designed here might be a more viable target for synthetic attempts.

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“…As an exception to the traditional hybridization bonding of carbon, planar tetracoordinate carbon (ptC), [4] in which a carbon atom and its four bound atoms are in the same plane, has recently received increasing attention. [5] No doubt, the tetrahedron is generally the most favorable geometric arrangement for four atoms bonded to a carbon atom. However, ptC can be achieved electronically, [4,6] mechanically, [4,7] or by a combination of both.…”

Section: Introductionmentioning

confidence: 99%

Computationally Designed Families of Flat, Tubular, and Cage Molecules Assembled with “Starbenzene” Building Blocks through Hydrogen‐Bridge Bonds

Jiang

Zhang

et al. 2010

Chemistry A European J

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Using density functional calculations, we demonstrate that the planarity of the nonclassical planar tetracoordinate carbon (ptC) arrangement can be utilized to construct new families of flat, tubular, and cage molecules which are geometrically akin to graphenes, carbon nanotubes, and fullerenes but have fundamentally different chemical bonds. These molecules are assembled with a single type of hexagonal blocks called starbenzene (D(6h) C(6)Be(6)H(6)) through hydrogen-bridge bonds that have an average bonding energy of 25.4-33.1 kcal mol(-1). Starbenzene is an aromatic molecule with six pi electrons, but its carbon atoms prefer ptC arrangements rather than the planar trigonal sp(2) arrangements like those in benzene. Various stability assessments indicate their excellent stabilities for experimental realization. For example, one starbenzene unit in an infinite two-dimensional molecular sheet lies on average 154.1 kcal mol(-1) below three isolated linear C(2)Be(2)H(2) (global minimum) monomers. This value is close to the energy lowering of 157.4 kcal mol(-1) of benzene relative to three acetylene molecules. The ptC bonding in starbenzene can be extended to give new series of starlike monocyclic aromatic molecules (D(4h) C(4)Be(4)H(4)(2-), D(5h) C(5)Be(5)H(5)(-), D(6h) C(6)Be(6)H(6), D(7h) C(7)Be(7)H(7)(+), D(8h) C(8)Be(8)H(8)(2-), and D(9h) C(9)Be(9)H(9)(-)), known as starenes. The starene isomers with classical trigonal carbon sp(2) bonding are all less stable than the corresponding starlike starenes. Similarly, lithiated C(5)Be(5)H(5) can be assembled into a C(60)-like molecule. The chemical bonding involved in the title molecules includes aromaticity, ptC arrangements, hydrogen-bridge bonds, ionic bonds, and covalent bonds, which, along with their unique geometric features, may result in new applications.

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Recent advances in planar tetracoordinate carbon chemistry

Cited by 237 publications

References 68 publications

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

Perfect planar tetracoordinate carbon in neutral unsaturated hydrocarbon cages: A new strategy utilizing three‐dimensional electron delocalization

Computationally Designed Families of Flat, Tubular, and Cage Molecules Assembled with “Starbenzene” Building Blocks through Hydrogen‐Bridge Bonds

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Recent advances in planar tetracoordinate carbon chemistry

Cited by 237 publications

References 68 publications

CB7−: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

CB7−: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

Perfect planar tetracoordinate carbon in neutral unsaturated hydrocarbon cages: A new strategy utilizing three‐dimensional electron delocalization

Computationally Designed Families of Flat, Tubular, and Cage Molecules Assembled with “Starbenzene” Building Blocks through Hydrogen‐Bridge Bonds

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CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon

CB₇⁻: Experimental and Theoretical Evidence against Hypercoordinate Planar Carbon