Assembling β-Octamolybdate Clusters into New Polyoxomolybdates with Unusual Architectures

Abstract

β-octamolybdate [Mo 8 O 26 ] clusters have been assembled, under hydrothermal conditions, into a variety of interesting one-dimensional structures.The compositional variations, the structural diversity coupled with the interesting properties of the inorganic oxides, are one of the important reasons for the continued focus in this area. 1,2 The assembly of transition metal oxides, especially the polyoxo ions, in the presence of organic amines is of contemporary interest. [3][4][5][6][7][8] The assembly of the polyoxo ions appears to be crucially dependent on the conditions under which they are crystallized, though a clear understanding of the organization of these hybrid materials is still elusive. The structure-directing properties of the organic components, however, have been exploited in the preparation of many metastable solids with novel architectures. The formation of new polyoxomolybdates and related solids has been investigated in great detail, in recent years, resulting in new types of structures, including the oxo-molybdenum clusters linked via organic/ inorganic tethers. 3-6 It occurred to us that it could be possible to replace the tethers by simple Mo-O linkages resulting in new types of polyoxomolybdates with novel structures, though no such compounds have been synthesized earlier. During the course of our investigations on the formation of novel zinc molybdates in the presence of organic amines, we have now isolated three new polyoxomolybdates, [NH 3 (CH 2 ) 3 NH 3 ] 2 [Mo 8 O 26 ]‚H 2 O, I, [NH 3 (CH 2 ) 2 -NH 2 (CH 2 ) 2 NH 3 ] 2 [Mo 9 O 30 ], II, and [NH 3 (CH 2 ) 2 NH 2 (CH 2 ) 3 -NH 3 ] 2 [Mo 10 O 33 ], III, synthesized in the presence of 1,3diaminopropane (DAP), diethylenetriamine (DETA), and N(2-aminoethyl)1-3-diaminopropoane (AEDAP), respectively, employing hydrothermal methods. The structures of I-III are related and have identical [Mo 8 O 26 ] β-octamolybdate clusters, while I has the Mo-O clusters connected together forming the one-dimensional chains, II and III have the [Mo 8 O 26 ] clusters linked through a MoO 6 octahedra and [Mo 2 O 7 ] units, respectively, forming new polymeric oxomolybdates. Compound II has helical columns of one-dimensional [Mo 9 O 30 ] chains, and III has zigzag chains of [Mo 10 O 33 ] separated by the amine molecules. The arrangement of the helical chains in II resemble the double helix structure of DNA. Both the structures of II and III, to our knowledge, are new and have been encountered for the first time.The compounds I-III were the products of our attempts to make novel zinc molybdates employing hydrothermal methods, resulting in novel polyoxomolydates.

Synthesis and Crystal Structure of the Coordination Polymer of Ni-Mo8-Pyrazinecarboxylic Acid

“…The [Mo 8 O 26 ] 4-cluster, which is built from eight distorted MoO 6 octahedra via sharing octahedral edges, is a typical b-octamolybdate anion. All bond lengths (Table 1) are consistent with that in ref [28]. [b-Mo 8 O 26 ] 4-unit of 1 acts as a tetradentate ligand and combines four Ni 2?…”

A Reactive Intermediate, [Ni5(C6H4N3)6(CO)4], in the Formation of Nonameric Clusters of Nickel, [Ni9(C6H4N3)12(CO)6] and [Ni9(C6H4N3)12(CO)6].2(C3H7NO)

“…Three molecular compounds Ni 5 (C 6 H 4 N 3 ) 6 (CO) 4 determined. As can be noted from the synthesis conditions, the three compounds were isolated employing the same synthesis mixture, but by a subtle variation of the reaction temperature.…”

“…The Cu centers exhibit both +1 and +2 29g and 29h Cu 5 (bta) 6 (RNC) 4 bta = 1,2,3-benzotriazole; ta = 1,2,3-triazole; Me 2 bta -5,6-dimethyl-1,2,3-benzotriazole; 5Mebta -5-methyl-1,2,3benzotriazole; DMF = N, N'-dimethyl formamide; PPh 3 = Triphenylphosphine, acac = acetylacetone; dbm -dibenzoylmethane. Me 2 CO -acetone.…”

“…Organic ligands were also employed in the stabilization of polyoxo metal clusters based on molybdenum forming interesting structures. 4 Though polyoxo metal clusters of different nuclearity have been known for a long time, 5 the discovery of single molecular magnet behaviour in the manganese compound, * For correspondence [Mn 12 O 12 (O 2 CR) 16 (H 2 O) 4 ] (R = Me, Ph), 6 renewed much interest in this class of compounds. Cronin and co-workers expanded this family of compounds to include many new heterometallic clusters.…”

“…8 Presently, we examined the formation of polyoxo metallic compounds based on nickel. During the course of this study, we have isolated three compounds, [Ni 5 (bta) 6 (CO) 4 ], I, [Ni 9 (bta) 12 (CO) 6 ], II, [Ni 9 (bta) 12 (CO) 6 ].2(C 3 H 7 NO), III (bta = benzotriazole) having five (I) and nine (II, and III) nickel species, respectively. More importantly, we have established that the five-membered compound, [Ni 5 (bta) 6 (CO) 4 ], I, could be reactive and a possible intermediate in the formation of the ninemembered compound, [Ni 9 (bta) 12 (CO) 6 ], II.…”