Coordination capacity of Keggin anions as polytopic ligands: case study of [VNb 12 O 40 ] 15

International audienceReaction of Na9H4[VNb12O40{NbO(CO3)}2] with [(C6H6)RuCl2]2 (molar ratio {VNb12}:{(C6H6)Ru} = 1:4) in aqueous solution gives a mixture of [α-{(C6H6)Ru}4VNb12O40] 7and [α-{(C6H6)Ru}3VNb12O40] 9-. Direct acetone diffusion into mother liquor leads to crystallization of Na6H[α-{(C6H6)Ru}4VNb12O40]•41.25H2O (1), characterized by single crystal x-ray diffraction (SCXRD). This anion has four organometallic fragments asymmetrically coordinated to the α-Keggin type [VNb12O40] 15backbone. Three {(C6H6)Ru} 2+ groups cap triangular faces and one group a rectangular face of [VNb12O40] 15-. Equilibrated mixture of [α-{(C6H6)Ru}4VNb12O40] 7and [α-{(C6H6)Ru}3VNb12O40] 9was studied by 1 H DOSY NMR, HPLC-ICP-AES and HPLC-ESI-MS combined techniques. Direct chromatographic separation of these complexes results in unexpected transformation of both species into [α-{(C6H6)Ru}5VNb12O40] 5-, isolated and characterized as Na5[α-{(C6H6)Ru}5VNb12O40]•16H2O (2). This anion contains five symmetrically coordinated organometallic groups occupying both triangular and rectangular faces