d-Orbital effects in silicon substituted π-electron systems. Part XII. Some spectroscopic properties of alkyl and silyl acetylenes and polyacetylenes
Abstract
Vertical ionization energies, characteristic vibrational frequencies, 1H n.m.r. signals, and electronic transitions are reported for acetylenes X·[CC]n·X (n= 1, 2, 3; X = H, CMe3, CH2·SiMe3, SiMe3). Comparison with the corresponding data of ethylene and butadiene derivatives indicates stronger electron back-donation to silicone Si â†� Cπ which is interpreted as being due to interactions with both of the perpendicular acetylene π-components. The inductive polarization +l(SiR3) > +/(CR3) can be estimated from the substituent effect of CH2·SiR3 groups.