Syntheses and skeletal transformations of NCNH- and NCN-bridged tetrairidium(III) cages.

The diiridium complex [Cp*IrCl2]2 (Cp* = eta5-C5Me5) reacts with 2 equiv of Na(NCNH) at room temperature to afford the 16-membered macrocyclic tetrairidium complex [Cp*IrCl(mu2-NCNH-N,N')]4 (1a). Treatment of 1a with 4 equiv of triethylamine at room temperature leads to the formation of the "C3-elongated cubane-like" tetrairidium complex [Cp*Ir(mu3-NCN-N,N,N')3(IrCp*)3(mu3-NCN-N,N,N)] (2) as the major product, which is further converted into the cubane-type complex [Cp*Ir(mu3-NCN-N,N,N)]4 (3) on refluxing in p-xylene. The molecular structures of [Cp*IrI(mu3-NCNH-N,N')]4.C7H8 (1b.C7H8), 2.0.5C7H8, and 3 have been determined by X-ray analyses.