Non-hydrothermal synthesis and structure determination of two new β-octamolybdate (VI) stabilized with dialkylammonium counterions

• Published in: Journal of molecular structure Vol. 1170; pp. 44 - 50
• Main Authors: Sarr, Bougar, Diop, Cheikh A.K., Melin, Frederic, Sidibe, Mamadou, Hellwig, Petra, Michaud, Francois, Maury, Francis, Senocq, Francois, Mbaye, Abdou, Rousselin, Yoann
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2018; Elsevier
• Subjects: Bifurcated hydrogen bonds; Chemical engineering; Chemical Sciences; Condensed Matter; Crystal structure; Hydrogen bonds; Material chemistry; Materials Science; Physics; β-octamolybdate stabilization; β-octamolybdate stabilization; Bifurcated hydrogen bonds; Hydrogen bonds; Crystal structure; B-octamolybdate stabilization
• ISSN: 0022-2860; 1872-8014; 0022-2860
• DOI: 10.1016/j.molstruc.2018.05.055

Two new organic–inorganic materials based on Mo–POM, namely (iPr2NH2)2·((CH3)2NH2)2·[Mo8O26] (1) and (Pr2NH2)4·[Mo8O26] (2), have been synthesized by a non-hydrothermal method at room temperature and characterized by single crystal X-ray diffraction, thermal gravimetric analysis (TGA) and vibrational spectroscopy. The compound (1) is a β-[Mo8O26]4- anion which crystallizes as a mixed salt of both dimethylammonium [(CH3)2NH2]+ and diisopropylammonium [iPr2NH2]+. The interaction between anions and cations leads to an inorganic-organic band structure. Similarly, in compound (2), the interconnection of β-[Mo8O26]4- anions with dipropylammonium [Pr2NH2]+ cations gives an inorganic-organic band structure. In both compounds, the cations interact with two different sites of the cluster: a fundamental site formed by four highly nucleophilic terminal oxo ligands, and a second site which is composed of Ot, μ2-O and/or μ3-O oxygen groups. A remarkable difference between the two compounds is that in compound (2) interactions between the bands involve only Van der Waals forces, whereas in compound (1) the bands interact also through hydrogen bonds. The cation-anion-cation centrosymmetric interactions favor the formation of the β-octamolybdate isomer. [Display omitted] •Polyoxometallates (such as β-octamolybdate) can be prepared at room temperature.•Stabilization of β-octamolybdate is possible with both small and large cations.•For stabilization of β-octamolybdate, all μi-O can be involved in H-bonds with the cation except μ5-O.•The polyoxometallates exhibit generally a good thermal stability.