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Silaacetylene: A possible target for experimental studies
Author(s) -
Stegmann Ralf,
Frenking Gernot
Publication year - 1996
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/(sici)1096-987x(199605)17:7<781::aid-jcc3>3.0.co;2-o
Subject(s) - natural bond orbital , chemistry , bond length , single bond , triple bond , bond order , basis set , sextuple bond , bent bond , computational chemistry , molecular geometry , bond energy , singlet state , ionic bonding , bent molecular geometry , crystallography , atomic physics , molecule , double bond , density functional theory , ion , physics , excited state , crystal structure , polymer chemistry , alkyl , organic chemistry
The equilibrium geometries and transition states for interconversion of the CSiH 2 isomers in the singlet electronic ground state are optimized at the MP2 and CCSD(T) levels of theory using a TZ2P basis set. The heats of formation, vibrational frequencies, infrared intensities, and rotational constants are also predicted. There are three energy minima on the CSiH 2 potential energy surface. Energy calculations at CCSD(T)/TZ2P(fd) + ZPE predict that the global energy minimum is silavinylidene (1), which is 34.1 kcal mol −1 lower in energy than trans‐bent silaacetylene (2) and 84.1 kcal mol −1 more stable than the vinylidene isomer (3). The barrier for rearrangement 2→1 is calculated at the same level of theory to be 5.1 kcal mol −1 , while for the rearrangement 3→2 a barrier of 2.7 kcal mol −1 is predicted. The natural bond orbital (NBO) population scheme indicates a clear polarization of the C(SINGLE BOND)Si bonds toward the carbon end. A significant ionic contribution to the C(SINGLE BOND)Si bonds of 1 and 2 is suggested by the NBO analysis. The C(SINGLE BOND)Si bond length of trans‐bent silaacetylene (2) is longer than previously calculated [1.665 Å at CCSD(T)/TZ2P)]. The calculated carbon‐silicon bond length of 2 is in the middle between the C(SINGLE BOND)Si double bond length of 1 (1.721 Å) and the C(SINGLE BOND)Si triple bond of the linear form HCSiH (4), which is 1.604 Å. Structure 4 is a higher‐order saddle point on the potential energy surface. © 1996 by John Wiley & Sons, Inc.