The silicon analog of benzene–hexasilabenzene (Si6H6)

Abstract

A b initio molecular electronic structure theory has been applied to the D6h- symmetry isomer of Si6H6. Self-consistent-field (SCF) theory has been applied in conjunction with double zeta (DZ) and double zeta plus silicon 3d (DZ+d) basis sets. The DZ+d basis set may be designated Si(11s 7p 1d/6s 4p 1d), H (4s/2s). The structure of hexasilabenzene is predicted to be: re(Si–Si) =2.223 Å, re(Si–H) =1.476 Å (DZ SCF); re(Si–Si) =2.205 Å, re(Si–H) =1.463 Å (DZ+d SCF). Vibrational frequencies have been predicted at the DZ SCF level, at which the DZ SCF structure is a true minimum. However, the lowest vibrational frequency is predicted to be only 10 cm−1.

Theoretical Studies of Aluminoxane Chains, Rings, Cages, and Nanostructures

“…[7] Several isovalent electronic analogues can be considered, for instance, by moving down the periodic table (Si 6 H 6 , Ge 6 H 6 ). [8,9] Recently, the similarity between benzene and one form of methylaluminoxane, Al 3 O 3 Me 3 , [10] was discussed. In the theoretical approach described herein, the structures of aluminoxanes were explored by using the analogy between hydrocarbons and aluminoxanes.…”

“…The D 3h -symmetric (AlOH) 3 is the isovalent electronic analogue of benzene, as was discussed above. The aluminoxane analogue of cyclooctatetraene, or [8]annulene, differs somewhat from its hydrocarbon counterpart. Whereas (AlOH) 4 adopts a planar D 4h -symmetric structure, [8]annulene prefers the D 2d -symmetric tub conformation.…”

“…The aluminoxane analogue of cyclooctatetraene, or [8]annulene, differs somewhat from its hydrocarbon counterpart. Whereas (AlOH) 4 adopts a planar D 4h -symmetric structure, [8]annulene prefers the D 2d -symmetric tub conformation. [23] Wehmschulte and Power have determined the crystal structure of a planar tetrakis(m 2 -oxo)(2,4,6-tri-tert-butylphenyl)aluminum, which is an analogue of monocyclic (AlOH) 4 with bulky tert-butyl substituents.…”

“…[23] Wehmschulte and Power have determined the crystal structure of a planar tetrakis(m 2 -oxo)(2,4,6-tri-tert-butylphenyl)aluminum, which is an analogue of monocyclic (AlOH) 4 with bulky tert-butyl substituents. [24] The bicyclic isomer of (AlOH) 4 , which consists of fused Al 2 O 2 and Al 3 O 3 rings, corresponds to the C s -symmet- ric isomer of [8]annulene. The monocyclic aluminoxane is preferred by 44 kJ mol À1 over its bicyclic isomer.…”

Theoretical Investigation of Stable Structures of Ge<SUB>6</SUB> Clusters with Various Negative Charges

“…7) We found in our previous study 8) that an anionic silicon cluster (Si À ) 6 , which is isoelectronic with (SiH) 6 , forms a planar six-membered ring similar to benzene (CH) 6 , although neutral (SiH) 6 , the silicon analog of (CH) 6 , takes a nonplanar chair form. [9][10][11] The planar hexagon is aromatic with D 6h symmetry and we described it as ''silicon benzene''. 12) Since germanium is adjacent to silicon in the periodic table, Ge clusters are expected to show similar structures and properties to the corresponding Si clusters.…”