Crystal structure of alluaudite-type Na₄Co(MoO₄)₃

Abstract

The title compound, tetrasodium cobalt(II) tris[molybdate(IV)], was prepared by solid-state reactions. The structure is isotypic with Na 3 In 2 (AsO 4 ) 3 and Na 3 In 2 (PO 4 ) 3 . The main structural feature is the presence of infinite chains of edgesharing X 2 O 10 (X = Co/Na) dimers, which are linked by MoO 4 tetrahedra, forming a three-dimensional framework enclosing two types of hexagonal tunnels in which Na + cations reside. In this alluaudite structure, Co and Na atoms are located at the same general site with occupancies of 0.503 (5) and 0.497 (6), respectively. The other three Na and one of the two Mo atoms lie on special positions (site symmetries 2, 1, 2 and 2, respectively). The structure is compared with similar structures and other members of alluaudite family.Keywords: crystal structure; X-ray diffraction; molybdate; alluaudite.

Crystal structure of (Na0.70)(Na0.70,Mn0.30)(Fe3+,Fe2+)2Fe2+(VO4)3, a sodium-, iron- and manganese-based vanadate with the alluaudite-type structure

“…Besides well-known phosphate phases, arsenates (Ðordević et al, 2015;Stock & Bein, 2003) and more recently molybdates (Nasri et al, 2014;Savina et al, 2014) and sulfates (Oyama et al, 2015;Ming et al, 2015) have been reported to crystallize with alluaudite-type structures. However, to the best of our knowledge, no vanadate adopting this type of structure has been reported so far.…”

Synthesis, crystal structure and charge-distribution validation of β-Na4Cu(MoO4)3adopting the alluadite structure-type

“…It is also possible to make substitutions with cations in different oxidation states adopting the same type of coordination number (Mo 6+ , V 5+ , P 5+ and As 5+ ). Alluaudite molybdates usually have the general formula of X(2)X(1)M(1)M(2) 2 (MoO 4 ) 3 and adopt the C2/c space group, with a ' 12, b ' 13 and c ' 7 Å , examples being the K 0.13 Na 3.87 MgMo 3 O 12 (Ennajeh et al, 2015), Na 3 Fe 2 (MoO 4 ) 3 (Muessig et al, 2003) and Na 4 Co(MoO 4 ) 3 (Nasri et al, 2014) compounds. A review of the literature also reveals the presence of other formulae, such as Na 5 Sc(MoO 4 ) 4 , Na 2 Ni(MoO 4 ) 2 (Klevtsova et al, 1991) and Na 2.2 Zn 0.9 (MoO 4 ) 2 (Efremov et al, 1975), which crystallize in the space group C2/c with cell parameters of about a ' 12, b ' 13 and c ' 7 Å .…”