Structural Manifestations of the Polarizability Effect in 1-Halogensilatranes According to the Dipole-Induced Dipole Mechanism

A new mechanism of the dipole-induced dipole polarizability effect by the example of 1-halogensilatranes is proposed. The mechanism involves a through-space interaction between the dipole moment μ of the core and the dipole Δμ which is induced on the halogen and, in turn, induces an extra dipole ΔΔμ on the transannular bond Si ← N to make it stronger. This effect explains for the first time the previously discovered contradiction for 1-halogensilatranes where an inverse dependence in the linear correlations between the Si ← N bond length, δ15N, δ1H(CH2N) chemical shifts, and the inductive constant σ are observed. For example, the length of the Si ← N coordination bond is shorter in 1-chlorosilatranе than in 1-fluorosilatrane due to the fact that the polarizability effect is stronger than the inductive effect in the case of the Cl atom.