Tubular polyoxoanion [(SeMoO)(CO)] and its transformations

Self-assembly reactions in the Na 2 MoO 4 /SeO 2 /H 2 C 2 O 4 system lead to the formation of a tubular [(SeMo 6 O 21 ) 2 (C 2 O 4 ) 3 ] 10− hybrid polyanion, isolated and characterized by single crystal X-ray diffraction (SCXRD) as Na 9 H[(SeMo 6 O 21 ) 2 (C 2 O 4 ) 3 ]·NaNO 3 ·20.6H 2 O ( SeMo6-1 ). Dehydration of this compound leads to the formation of Na 10 [(SeMo 6 O 21 ) 2 (C 2 O 4 ) 3 ]·0.5NaNO 3 ·8H 2 O ( SeMo6-2 ). The electrochemical behavior of SeMo6-2 as a component of the paste electrode was studied by CV in CH 3 CN solution. A concentrated aqueous solution of SeMo6-2 was studied using 77 Se and 95 Mo NMR techniques, which show extensive degradation of the complex. Addition of TBABr to the concentrated solution leads to a precipitate consisting of TBA salts of [Mo 6 O 19 ] 2− and [β-Mo 8 O 26 Na 2 (NO 3 ) 2 ] 2− anions. The latter was characterized by SCXRD as (TBA) 3 [β-Mo 8 O 26 Na 2 (NO 3 )]·CH 3 CN ( Mo8-Na ). This transformation shows the presence of [β-Mo 8 O 26 ] 4− and [Mo 6 O 19 ] 2− in the aqueous solution of SeMo6-2 . The study of (NBu 4 ) 4 [β-Mo 8 O 26 ] and (NBu 4 ) 2 [Mo 6 O 19 ] solutions in CH 3 CN by HPLC shows equilibration between [β-Mo 8 O 26 ] 4− and [Mo 6 O 19 ] 2− . Tubular [(SeMo 6 O 21 ) 2 (C 2 O 4 ) 3 ] 10− polyoxoanion can be assembled from Na 2 MoO 4 /SeO 2 /H 2 C 2 O 4 system. TBABr precipitates complexes of [Mo 6 O 19 ] 2− and [β-Mo 8 O 26 Na 2 (NO 3 )] 3− from its aqueous solution. Speciation of [β-Mo 8 O 26 ] 4− and [Mo 6 O 19 ] 2− has been studied.