Infrared and Quantum-Chemical Studies of Dimethylsilane

✍ Scribed by D.C. McKean; I. Torto

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 156 KB
• Volume: 216
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2002.8691

✦ Synopsis

Infrared spectra of (CH 3 ) 2 SiH 2 and (CH 3 ) 2 SiD 2 have been reinvestigated. Quantum-chemical calculations of geometry and force fields have been made at the HF, MP2, and B3LYP levels, followed by scaling of the force field with 14 independent parameters. Several vibration frequencies are reassigned. Bond lengths, force constants, scale factors, and electrical properties are compared with those in other methylsilanes. Both Si-H and Si-C bonds are weakened by α-methyl substitution. The C-H bonds in the methyl groups differ slightly in length and stretching frequency in ways familiar in hydrocarbons. An increase in SiH stretching intensity per bond with methylation is predicted theoretically and found by experiment. The sizes of the negative charges associated with both stretching and bending of the SiH bonds in the methylsilanes increase with the Mulliken charge with progressive methylation.