Regularities in the Crystal Structures of Heterocationic Octacyanometallates(IV) Molybdenum and Tungsten

Abstract

A review of the crystal structures of octacyanomolybdates(IV) and octacyanotungstates(IV) of {[K(H 2 O)][Ln(H 2 O) 4 ][M(CN) 8 ]·2H 2 O} n ( M 4+ = Mo and Ln 3 + = Y, La, Sm, Gd, Yb, M 4+ = W and Ln 3+ = Tb, Dy, Ho, Er, Lu) composition has been done. These compounds have 3D-structures and contain infinite chains -C≡N-M-N≡C-Ln-, which extend in three dimensions, unlike CeH 3 O[W(CN) 8 ]·6H 2 O, which has 2D-structure. The coordination polyhedra [ M (CN) 8 ] 4-(M 4+ = Mo, W) is different (dodecahedron, square antiprism, bicapped trigonal prism), depending on the nature of the rare-earth elements. The composition and form of the coordination polyhedra of the atoms of rareearth elements (square antiprism, monocapped tetragonal antiprism, tricapped trigonal prism) are also different. All complexes are polymeric compounds and differ in structure from octacyanometallates(IV) d-elements and octacyanometallates(V) f-elements.

Dimethyl Derivatives of 2,2′-Bipyridine as Ligands in [W(CN)6(bpy)]2−-Type Complexes

“…In both structures, the bond lengths in the coordination sphere of the tungsten atom had values close to each other and were consistent with the literature data [27,28]; however, the average length of the W-C and W-N bpy bonds was longer for the dimethyl derivatives (1 and 3) than for complexes with an unsubstituted ligand 2,2 ′ -bpy. This indicates that the presence of methyl substituents in the pyridine ring contributed to the weakening (lengthening) of the tungsten-ligand bond, and this weakening was slightly greater in the case of the 5,5 ′ -Mebpy ligand (3). The volumes of the unit cells of all the compounds tested differed significantly from each other, and the structure of compound 3 had the largest volume of up to 11,915.93(5) Å 3 .…”

“…This indicates that the presence of methyl substituents in the pyridine ring contributed to the weakening (lengthening) of the tungsten-ligand bond, and this weakening was slightly greater in the case of the 5,5 ′ -Mebpy ligand (3). The volumes of the unit cells of all the compounds tested differed significantly from each other, and the structure of compound 3 had the largest volume of up to 11,915.93(5) Å 3 . In structures 1 and 3, whose bidentate ligand bpy contained methyl substituents, a decrease in crystal density was observed; the density for compound 1 had the lowest value of 1.409 Mg/m 3 .…”

“…Tungsten (IV) coordination compounds are an area of ongoing research, starting from the octacyanometallates to the currently described ion-based compounds [W(CN) 6 (bpy)] 2−/− [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Molybdenum, niobium, and tungsten octacyanometallates are interesting types of coordination compounds because systems can be built on their base multicores with cyanide bridges [ 13 , 14 , 15 , 16 , 17 ].…”