Synthesis and structures of an unusual germanium(II) calix[4]arene complex and the first germanium(II) calix[8]arene complex and their reactivity with diiron nonacarbonyl

The protonolysis reaction of the germanium(II) amide GeN(SiMe3)2]2 with calix4]arene and calix8]arene furnishes the two germanium(II) calixarene complexes {calix4]}Ge2 and {calix8]}Ge4, respectively, which have been crystallographically characterized. The calix4]arene complex contains a Ge2O2 rhombus at the center of the molecule and is one of the only four germanium(II) calix4]arenes that have been structurally characterized. The calix8]arene species is the first reported germanium calix8]arene complex, and it exhibits an overall bowl-shaped structure which contains two Ge2O2 fragments. The latter complex reacts with Fe2(CO)9 to yield an octairon compound, which has also been structurally characterized and contains four GeFe2 triangles arranged around the macrocyclic ring. The germanium(II) centers are oxidized to germanium(IV) in this process, with concomitant reduction of the neutral diiron species to Fe2(CO)(8)2- anions.