The salts [18-crown-6-K](4)[Sn4Se10]. 5en and [18-crown-6-K](4)[Sn4Te10]. 3en . 2THF were isolated upon addition of THF to the ethylenediamine (en) extracts of the alloys KSn0.90Se1.93 and K4Sn4Te10 that had been extracted in the presence of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane). The Sn4Te104- anion has been structurally characterized for the first time by a single-crystal X-ray diffraction study of [ 18-crown-6-K](4)[Sn4Te10]. 3en . 2THF: P2(1)/n, a = 22.420(5) Angstrom, b = 19.570(4) Angstrom, c = 24.680(5) Angstrom, beta = 96.90(3)degrees, Z = 4, and R-1 = 0.0468 at -183 degreesC. In addition to Si4Te104- and Ge4Te104-, the Sn4Te104- anion represents the only other known group 14 adamantanoid telluride. The X-ray crystal structure determination of the related [18-crown-6-K](4)[Sn4Se10]. 5en salt has also been determined: P2(1)/n, a = 22.003(2) Angstrom, b = 18.966(2) Angstrom, c = 24.393(2) Angstrom, beta = 97.548(8)degrees, Z = 4, and R-1 = 0.0843 at -123 degreesC. The anion geometries are of the adamantanoid type where the Sn-IV atoms occupy the bridgehead positions and the chalcogen atoms occupy the bridging and terminal sites. The energy minimized geometries of Sn(4)Ch(10)(4-) have also been determined using density functional theory (DFT). Mayer bond order analyses, Mayer valencies, and empirical bond valencies indicate that the terminal Sn-Ch bonds have significant multiple bond character, with the terminal Sn-Se bond having more multiple bond character than the terminal Sn-Te bond. The vibrational frequencies of the Sn4Se104- and Sn4Te104- anions have been calculated using DFT methods, allowing the Raman spectrum of Sn4Se104- to be fully assigned.