RING MOLECULES BUILT FROM GAS-UNITS

Abstract

Different synthetic routes are available for the formation of dihalogeno-(organylthio)gallanes. Some of the most important reactions leading to these compounds are reported.^1–4

Trivalent compounds of gallium are naturally Lewis acids; moreover, in organylthiogallanes a Lewis-base center exists on the sulfur atom. Therefore these molecules have the possibility of both intermolecular and intramolecular Lewis-acid-base interactions, which in the case of intermolecular interactions lead to Lewis-acid-base adducts. The thus formed adducts can be chains or rings of different sizes.

Diiodo(organylthio)gallanes are able to form monomers, dimers, and even trimers of different shapes. These differences in the structure are not only due to the group R on the sulfur atom, because investigations on these compounds in solution (molecular weight determinations, and ¹H-n.m.r. spectroscopy) and in the solid state (X-ray-structure determinations) have shown differences in the ring sizes for one and the same molecule as well.

Therefore some ¹H-n.m.r. spectroscopic investigations on I₂Ga(SR) compounds (R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, Ph) are presented and the crystal structures of both, I₂Ga(SCH₃) and I₂Ga(S i-C₃H₇) are discussed in view of some surprising differences in the structure of these two compounds.