Atomic interactions in the hydrides and alkyls of C,Si, Ge,and Sn

The spectra of these group IV (M=C, Si, Ge, and Sn) compounds show that induction from M increases in a sequence that qualitatively agrees with the Pauli-Gordy-Mulliken scale; the induction constant o* for (CH₃)₃M is –0.3, –0.72, –0.76, and –0.9 in the four cases. M also acts as an electron acceptor, the effect increasing from Si via Ge to Sn; this and the induction determine the electron-density distribution in adjacent bonds. These concepts explain the anomalous behavior of the optical parameters and chemical shifts in the methyl derivatives of M. The analogy with the magnetic parameters indicates that the Olred-Rakhov electronegativity scale (X _C=2.6; X _Sl=1.9; X _Ge=2.0; X _Sn=1.93) does not reflect the induction effects of M in pure form but provides a good measure of the sum of the electronic effects. The present results do not confirm the view that silicon transmits induction less readily than carbon.