STRUCTURAL REGULARITIES OF MIXED HEPTAANIONS IN STRUCTURES Na2[Pd(NH3)4]5(Mo7–xWxO24)2·nH2O AND Na[Pd(NH3)4]2(HMo3.75W3.25O24)·7H2O

• Published in: Journal of structural chemistry 2022, Vol.63 (10), p.1715-1721
• Main Authors: Sukhikh, A. S., Gromilov, S. A.
• Format: Article
• Language: English
• Subjects: Ammonia; Atomic; Atomic/Molecular Structure and Spectra; Cations; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Molecular; Optical and Plasma Physics; Physical Chemistry; Solid State Physics
• ISSN: 0022-4766; 1573-8779
• DOI: 10.1134/S0022476622100171

The main structural regularities of mixed heptapolyanions (HPAs) in structures Na 2 [Pd(NH 3 ) 4 ] 5 (Mo 7— x W x O 24 ) 2 · n H 2 O, where x  = 3.50 and 3.37, n  = 19.5 and 16, respectively, (hereinafter 1 and 2 ) and Na[Pd(NH 3 ) 4 ] 2 (HMo 3.75 W 3.25 O 24 )·7H 2 O (hereinafter 3 ) are established. The Na + cations act as bridges. Structures 1 and 2 are formed with the participation of two types of Na + cations: one type links the neighboring heptapolyanions into dimers (Na…O distances are 2.338-2.425 Å); the coordination environment of the second type of Na + cations includes two O atoms of the HPA (Na…O distances are 2.402 Å and 2.451 Å) and three O atoms of water molecules (Na…O distance is 1.963-2.499 Å). In structure 3 , all HPAs are connected into zigzag chains by bridging Na + cations (Na…O distances are 2.283-2.728 Å). Despite different HPA compositions and charges, the sites of M atoms (Mo or W) are not statistically occupied: W atoms tend to occupy the sites whose surrounding M O 6 polyhedron contains no terminal O atoms. The Mo atoms tend to occupy sites that are most distant from the bridging O atoms (~2.4 Å) connecting two M atoms. In general, the Mo/W site occupancies fall within the interval from ~0.85/0.15 to 0.12/0.88.