Stable homopolyatomic anions. Synthesis and crystal structures of salts containing the pentaplumbide(2-) and pentastannide(2-) anions

Abstract

The synthesis and crystal structure are reported for two salts in which the pentaplumbide(2--) (I) and pentastannide(2--) (II) anions have been stabilized as a result of complexation of the sodium cations by 4, 7, 13, 16, 21, 24-hexaoxa-1, 10-diazobicyclo(8.8.8)hexacosane (2,2,2-crypt). The phases are prepared by the reaction of solutions of crypt in ethylenediamine with the intermetallic compositions NaPb/sub 1.7-2/ and NaSn/sub 1--1.7/. The compounds are trigonal and isostructural; for I a = 11.615 (3) A and c = 22.120 (12) A while for II a = 11.620 (1) A and c = 22.160 (7) A, the data applying at temperatures of approximately 5 and approximately 30/sup 0/C, respectively. The compounds contain the trigonal-bipyramidal homopolyatomic anions Pb/sub 5//sup 2-/(I) and Sn/sub 5//sup 2--/ (II) with substantially D/sub 3h/ symmetry. In Pb/sub 5//sup 2--/ the equatorial-equatorial and axial-equatorial bond distances are 3.238 (4) and 3.002 (3) A, respectively, while in Sn/sub 5//sup 2--/ the corresponding distances are 3.095 (10) and 2.887 (7) plus 2.854 (6) A. crypt complexation of sodium or potassium cations is evidently not sufficient to allow isolation of these derivatives of the Pb/sub 9//sup 4--/ anion from ethylenediamine or ammonia solvents.