CRYSTAL-STRUCTURES OF 2 NITROPRUSSIDES - SMNA[FE(CN)(5)NO](2)CENTER-DOT-7H2O AND GDNA[FE(CN)(5)NO](2)CENTER-DOT-7H2O

Samarium sodium bis(nitrosylpentacyano-ferrate-(II)) heptahydrate/(I) crystallizes in space group Pmma: a = 25.032(3) Angstrom, b = 7.824(1) Angstrom, c = 6.277(1) Angstrom; V = 1229.4(3) Angstrom(3), Z = 2, D-x = 1.976 g cm(-3), MoKalpha = 0.71069 Angstrom, mu = 36.10 cm(-1), F(000) = 710, T = 293 K; conventional R = 0.020; R(w) = 0.033 for 1469 observed reflections. Gadolinium sodium bis(nitrosylpentacyanoferrate-(II))heptahydrate/(II) crystallizes in space group Pmma: a = 24.963(4) Angstrom, b = 7.807(6) Angstrom, c = 6.264(3) Angstrom; V = 1224.7(11) Angstrom(3), Z = 2, D-x = 2.002 gcm(-3) MoKalpha = 0.71069 Angstrom, mu = 39.39 cm(-1), F(000) = 714, T = 293 K, conventional R = 0.032; R(w) = 0.043 for 1288 observed reflections. In both isomorphous structures the iron atoms are coordinated to five cyanide ligands and one nitrosyl group, while the sodium atoms are coordinated to four cyanide groups and two water molecules. Both centres have distorted octahedral symmetries. The coordination sphere of the second cation, samarium and gadolinium? respectively, consists of four cyanide groups and five water molecules. Cyanide bridges connect the iron, sodium, and the samarium/gadolinium polyhedrons forming sinusoidal layers.