Eight‐Coordinate Metal Carbonyls Containing Only Monodentate Ligands. Syntheses and Structural Characterization of [ n Pr 4 N] 2 [(Ph 3 Sn) 4 M(Co) 4 ], M = Zr, Hf

Two interpenetrating tetrahedra of carbonyl and triphenylstannyl groups form the highly symmetric dodecahedral coordination sphere of the zirconium atom in the complex dianion [(Ph 3 Sn) 4 Zr(CO) 4 ] 2⊖ (structure right with the phenyl groups of the Ph 3 Sn substituents omitted). The thermal stability of this highly reduced complex stabilized only by monodentate ligands is astounding: tetraammonium salts of this dianion decompose above 150°C!