Charge Transfers and Polarizations in Bonds to Silicon. Organosilanes and the Sₙ2(Si) Reaction of SiH₄+ Fˉ. An Ab Initio Study


The charge transfers in the bonds between silicon and common nonmetals (X = H, C, O, and F) are reported in terms of Streitwieser and Collin's integrated projection populations (IPP), Reed, Weinhold, and Weinstock's natural populations (NP), and Mulliken populations (MP). The IPP integrated populations are calibrated by several comparisons with populations integrated by the Bader method (IBP) to which they approximate. The integrated populations indicate large charge transfers (0.65-0.92 e) that result in bond moments oriented in the fashion (+)Si-X(-) and emphasize the importance of ionic contributions to common bonds involving silicon. As an example system, the reaction of SiH4 and F- to form the ion complex SiH4F- is analyzed with emphasis on an ionic model. Two trigonal bipyramid minima (apical (1) and equatorial (2) fluorine) were optimized at the 3-21+G* level. The SN2(Si) reaction to give SiH3F and H- through the intermediate ion complex, 1, is examined with IPP analysis and energy calculations up to the MP2/6-31+G**//HF/3-21+G* level. The stability of pentacoordinate silicon with respect to carbon is discussed in terms of the bond charge distributions.



International Standard Serial Number (ISSN)

0002-7863; 1520-5126

Document Type

Article - Journal

Document Version


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© 1989 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Apr 1989