A new class of 30-molybdo complexes: Formation, structure and electrochemical properties of bisselenitopyrophosphatotriacontamolybdate, [(SeO3)2(P2O7)Mo30O90]8−, and bispyrophosphatotriacontamolybdate, [(P2O7)2Mo30O90]8−

Abstract The tetrapropylammonium (Pr 4 N + ) salt of [(SeO 3 ) 2 (P 2 O 7 )Mo 30 O 90 ] 8− was prepared from a 75 mM Mo VI –2.8 mM P 2 O 7 4− –5.6 mM SeO 3 2− –0.95 M HCl–60% (v/v) CH 3 CN system, where [(P 2 O 7 )Mo 18 O 54 ] 4− and [H 6 (SeO 3 ) 2 Mo 15 O 48 ] 4− are first formed, then being spontaneously fused into [(SeO 3 ) 2 (P 2 O 7 )Mo 30 O 90 ] 8− . The [(SeO 3 ) 2 (P 2 O 7 )Mo 30 O 90 ] 8− anion may be isotypic with [(HPO 3 ) 2 (P 2 O 7 )Mo 30 O 90 ] 8− , in which each side of a (P 2 O 7 )Mo 12 O 42 fragment is capped by a B-type (HPO 3 )Mo 9 O 24 unit derived from [H 6 (HPO 3 ) 2 Mo 15 O 48 ] 4− . [(XO 3 ) 2 (P 2 O 7 )Mo 30 O 90 ] 8− (X = HP, Se) have the same type of 30-molybdo framework as [(P 2 O 7 ) 2 Mo 30 O 90 ] 8− , previously isolated by Koltz. These three 30-molybdo complexes with the same ionic charge of −8 constitute a new class of polyoxometallates and have common properties of undergoing a two-electron reduction in the absence of H + .