Between Elemental Match and Mismatch: From K 12 Ge 3.5 Sb 6 to Salts of (Ge 2 Sb 2 ) 2- , (Ge 4 Sb 12 ) 4- , and (Ge 4 Sb 14 ) 4 .

The solid mixture "K 2 GeSb" was shown to comprise single-crystalline K 12 Ge 3.5 Sb 6 (1), a double salt of K 5 [GeSb 3 ] with carbonate-like [GeSb 3 ] 5- anions, and the metallic Zintl phase K 2 Ge 1.5 . Extraction of 1 with ethane-1,2-diamine in the presence of crypt-222 afforded [K(crypt-222)] + salts of several novel binary Zintl anions: (Ge 2 Sb 2 ) 2- (in 2), (Ge 4 Sb 12 ) 4- (in 3), and in the presence of [AuMePPh 3 ] also (Ge 4 Sb 14 ) 4- (in 4). The anion in 2 represents a predicted, yet heretofore missing pseudo-tetrahedral anion. 4 comprises a cluster analogous to (Ge 4 Bi 14 ) 4- and (Ga 2 Bi 16 ) 4- , and thus one of the most Sb-rich binary p-block anions. The unprecedented cluster topology in 3 can be viewed as a defect-version of the one in 4 upon following a "dead end" of cluster growth. The findings indicate that Ge and Sb atoms are at the border of a well-matching and a mismatch elemental combination. We discuss the syntheses, the geometric structures, and the electronic structures of the new compounds.