Planar 1,3λ4δ2,2,4-Benzodithiadiazine and Its Nonplanar 5,6,7,8-Tetrafluoro Derivative: Gas-Phase Structures Studied by Electron Diffraction and Ab Initio Calculations

✍ Scribed by Frank Blockhuys; Sarah L. Hinchley; Alexander Yu. Marakov; Yuri V. Gatilov; Andrey V. Zibarev; J. Derek Woollins; David W. H. Rankin

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 159 KB
• Volume: 7
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/1521-3765(20010817)7:16<3592::aid-chem3592>3.0.co;2-8

✦ Synopsis

The gas-phase molecular structures of 1,3l 4 d 2 ,2,4-benzodithiadiazine and 5,6,7,8-tetrafluoro-1,3l 4 d 2 ,2,4benzodithiadiazine have been investigated by ab initio calculations and electron diffraction using the SARA-CEN method of structural analysis. Important structural parameters (r h1 structure) for the parent compound were found to be: r(SN) b 1.546(3), r(SÀN) 1.697(5), r(CÀS) 1.784(5), and r(CÀN) 1.393(6) . For the tetrafluoro derivative, these are (r h1 structure): r(SN) b 1.552(3), r(SÀN) 1.723(8), r(CÀS)

1.812( ), and r(CÀN) 1.396(7) . Furthermore, the GED ex-periment (Gas Electron Diffraction) quite convincingly demonstrates the nonplanarity of the former and the planarity of the latter in agreement with DFT calculations; but the results contradict calculations at the MP2 level. The effect of the fluorine atoms on the conformations of the molecules is discussed.