MICROWAVE INVESTIGATIONS OF $C_{5}H_{5}N-SO_{3}$ AND $HCCCN-SO_{3}$: THE PRINCIPLE OF HARD AND SOFT ACIDS AND BASES APPLIED TO PARTIALLY BONDED SYSTEMS
Loading...
Date
2000
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The Lewis acid-base adducts $C_{5}H_{5}N-SO_{3}$ and $HCCCN-SO_{3}$ have been studied by Fourier transform microwave spectroscopy. The spectrum of $C_{5}H-5N-SO_{3}$ indicates a short N-S bond length of $1.91540(66)$ \AA and free rotation of the $SO_{3}$ unit. In contrast, $HCCCN-SO_{3}$ is more weakly bound with an N-S distance of $2.5676(76)$ \AA, only slightly less than the expected van der Waals interaction distance. The NSO angles are $98.9212(45)^{\circ}$ and $91.89(36)^{\circ}$ for $C_{5}H_{5}N-SO_{3}$ and $HCCCN-SO_{3}$ respectively. A Townes and Dailey analysis of the $^{14} N$ quadrupole coupling constant of $C_{5}H_{5}N-SO_{3}$ indicates a transfer of 0.54 electrons upon formation of the dative bond. This is physical measurement of the ``soft'' portion of the chemical interaction and comparisons are made with other adducts of $SO_{3}$. Bonding is considered in light of Pearson's concept of Hard and Soft Acids and $Bases,^{a}$ nothing the correlation of adduct properties, such as electron transfer and bond length, with the energy gap between the donor and acceptor orbital.
Description
$^{a}$R.G. Pearson J. Am. Chem. Soc. 85, 3533 (1963).
Author Institution: Department of Chemistry, University of Minnesota
Author Institution: Department of Chemistry, University of Minnesota