Beyond the Icosahedron: The First 13‐Vertex Carborane

Abstract

Cornering the 13th vertex: The first 13‐vertex carborane (see picture, B: brown, C: gray, H: white) has been prepared by a methodology that can in principle be applied repeatedly, leading to 14‐, 15‐, 16‐, …︁ vertex carboranes in the future. The 13‐vertex species has a henicosahedral geometry, not the docosahedral one expected, but the two forms are found to be very close in energy by DFT calculations.

Beyond the Icosahedron: A Density Functional Theory Study of 14‐Atom Germanium Clusters

“…The two lowest-lying structures 36-1 and 36-2 are not obviously recognizable and are very different from the omnicapped cube structures found for carbalanes of the type (AlX) 8 (µ 4 -CR) 6 2-with 36 apparent skeletal electrons. A triplet heptagonal prismatic structure 36-3T is found for Ge 14 8-at 20.4 kcal/mol above the lowest-energy structure 36-1.…”

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) found in the metal-free carborane [8] 1,2-µ-C 6 H 4 (CH 2 ) 2 -3-C 6 H 5 -1,2-C 2 B 11 H 10 . The remaining degree 6 vertex in the henicosahedron can also be removed by breaking a second edge to give a ditrapezoidal icosahedron with two trapezoidal faces as well as 18 of the original triangular faces.…”

“…In addition, the study of germanium clusters provide reasonable models for clusters of other group 14 elements except carbon, particularly silicon and tin. The range of charges on Ge 14 z chosen for this work spans the 36 skeletal electrons found in the carbalane clusters (AlX) 8 (µ 4 -CR) 6 2-to the 24 skeletal electrons found in the silicon-centered cluster Al 8 (µ 8 -Si)(µ 4 -AlCp*) 6 and the carbonylmetal derivative (µ 4 -C 6 H 5 P) 6 Ni 8 (CO) 8 . Isoelectronic and isolobal relationships provide analogies of our DFT results on Ge 14 z clusters to experimentally known structures.…”

“…A relatively early example of a 14-vertex omnicapped cube cluster is the carbonylnickel complex (µ 4 -C 6 H 5 P) 6 Ni 8 (CO) 8 , in which the phosphorus vertices cap the faces of an underlying Ni 8 cube. [15] The omnicapped cube is also found in a variety of 14-vertex aluminum clusters with various skeletal electron counts [16] including carbalane clusters of the general formula (AlX) 8 (µ 4 -CR) 6 2-with 36 skeletal electrons with the carbon atoms capping the faces of an Al 8 cube [17,18] as well as the silicon-centered cluster [19] Al 8 (µ 8 -Si)(µ 4 -AlCp*) 6 with 24 skeletal electrons according to the Wade-Mingos [3][4][5][6] electron-counting rules. However, if the otherwise external lone pairs of the underlying Al 8 cube in Al 8 (µ 8 -Si)(µ 4 -AlCp*) 6 are also counted, then the omnicapped cube in this cluster becomes a 24 + (8)(2) = 40-electron system, which is a favored number using the jellium model.…”

On Desilylation of 13‐Vertex Carborane 1,2‐Me2Si(CH2)2‐1,2‐C2B11H11

“…[5] A number of 13-and 14-vertex carboranes have been prepared and structurally characterized. [6][7][8][9][10][11][12][13][14] Such a breakthrough relied on the use of CAd (Carbon-Atoms-Adjacent) nido-carborane dianions or arachno-carborane tetraanions as starting materials. [15] To prepare the above CAd carborane anions, a short carbon linkage is necessary to ensure the two cage carbon atoms to remain in adjacent positions during the reduction process.…”