A theoretical study on C2HXSi silylenes (X = H, CN, NH2, and OMe)

✍ Scribed by M. Z. Kassaee; S. M. Musavi; M. Ghambarian

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 334 KB
• Volume: 18
• Category: Article
• ISSN: 1042-7163
• DOI: 10.1002/hc.20297

✦ Synopsis

Abstract

Relative stabilities and structural characters of 30 silylenic C~2~HXSi species (X = H, NH~2~, CN, and OMe), with singlet (s) and/or triplet (t) states, are calculated at six levels of theory: HF/6‐311++G**, MP3/6‐31G*, B1LYP/6‐311++G**, B3LYP/6‐311++G**, MP2/6‐311++G**, and MP4(SDTQ)/6‐311++G**. The four possible isomers considered for C~2~SiHX are (i) 3‐X‐1‐silacyclopropenylidene (1~s‐X~ and 1~t‐X~), (ii) X‐vinilydensilylene (2~s‐X~ and 2~t‐X~), (iii) ethynyl‐X‐silylene (3~s‐X~ and 3~t‐X~), and (iv) (X‐ethynyl)silylene (4~s‐X~ and 4~t‐X~). The GIAO–NICS calculations show that singlet cyclic structures, 1~s‐X~, are considerably more aromatic than benzene. Conversely, triplet cyclic C~2~HCNSi breaks down through optimization, and transforms into a novel high‐spin acyclic carbenosilylene minimum (1~t‐CN~). Singlet 3 and triplet 3 cross at a divalent angle (|XSiC) of 152°. This angle narrows to 137° for crossing of singlet 3~s‐CN~ and triplet, 3~t‐CN~. The smallest |XSiC occurs at 132° for crossing of 3~s‐H~ and 3~t‐H~. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:283–293, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20297