Novel Synthesis of Macrocyclic Amine-Thiophenolate Ligands: X-ray Crystal Structure of a Ni4 Complex of an N8S4 Ligand

A series of mixed tetraaminodiborane(4) compounds bearing pyrrolyl, indolyl, and carbazolyl substituents besides dimethylamino groups has been prepared and subjected to reduction with elemental Li in the presence of diethyl ether. Tetraaminodiborates(2-) are formed, which feature a boron-boron double bond. The diborate anion acts as a double bidentate ligand coordinating pairwise through two of its nitrogen atoms to an Li center, which is tricoordinated by one O and the two N atoms. The new diborates are isoelectronic with tetraaminoethylenes and are expected to be electron-transfer reagents.