Synthesis, Solution and Solid State Structures, and Aqueous Chemistry of an Unstable Polyperoxo Polyoxometalate:  [P₂W₁₂(NbO₂)₆O₅₆]^12-

Abstract

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Transition Metal Peroxides. Synthesis and Role in Oxidation Reactions*Dedicated, on the occasion of his 80th birthday, to our ‘vitae ac studiorum magister in secunda et in adversa fortuna’ Emeritus Professor Giorgio Modena, Padova University, who showed us the way toward Chemistry.

“…The reactivity, which increased as a function of the nucleophilicity of the alkene double bond but decreased as a function of the steric crowding 186 , was related to the formation of a tungsten-peroxo intermediate activated by an adjacent manganese atom. 197,198 .…”

Trapping of NbV by {XW9O33}9– (X = As, Sb): Formation of New Sandwich‐Type POM Complexes and Their Solution Behavior

“…They were introduced and explored by Klemperer, [1] Finke, [2][3][4] Hill, [5][6][7][8][9][10] and Niu [11,12] groups, and include classical Lindqvist-type [13][14][15] Keggin-type [XW 9 Nb 3 O 40 ] n-(X = Si IV , Ge IV , n = 7; X = P V , As V , n = 6), [2,3,16,17] Dawson-type [P 2 W 12 (NbO 2 ) 6 O 56 ] 12-, [18] [P 2 W 15 Nb 3 O 62 ] 9-, [7,19] [P 2 W 17 (NbO 2 )-O 61 ] 7-, [6] as well as more complicated structures based on the condensation of simpler building blocks via Nb-O-Nb bridges. They were introduced and explored by Klemperer, [1] Finke, [2][3][4] Hill, [5][6][7][8][9][10] and Niu [11,12] groups, and include classical Lindqvist-type [13][14][15] Keggin-type [XW 9 Nb 3 O 40 ] n-(X = Si IV , Ge IV , n = 7; X = P V , As V , n = 6), [2,3,16,17] Dawson-type [P 2 W 12 (NbO 2 ) 6 O 56 ] 12-, [18] [P 2 W 15 Nb 3 O 62 ] 9-, [7,19] [P 2 W 17 (NbO 2 )-O 61 ] 7-, …”

“…They were introduced and explored by Klemperer, [1] Finke, [2][3][4] Hill, [5][6][7][8][9][10] and Niu [11,12] groups, and include classical Lindqvist-type [13][14][15] Keggin-type [XW 9 Nb 3 O 40 ] n-(X = Si IV , Ge IV , n = 7; X = P V , As V , n = 6), [2,3,16,17] Dawson-type [P 2 W 12 (NbO 2 ) 6 O 56 ] 12-, [18] [P 2 W 15 Nb 3 O 62 ] 9-, [7,19] [P 2 W 17 (NbO 2 )-O 61 ] 7-, [6] as well as more complicated structures based on the condensation of simpler building blocks via Nb-O-Nb bridges. Reactions of [NbO(C 2 O 4 ) 2 (H 2 O) 2 ]with [α-B-XW 9 O 33 ] 9-(X = As, Sb) result in formation of sandwich-type anions.…”

“…

Oxalate ligands in Nb V oxalate complexes are labile, making the latter convenient niobium source for preparation of new mixed W/Nb polyoxometalates under mild conditions. [10,11,17,20] The presence of Nb makes these POMs highly nucleophilic. For X = As, [(α-B-AsW 9 O 33 ) 2 (NbO) 3 (H 2 O)] 9and [(α-B-AsW 9 O 33 ) 2 (NbO) 2 (H 2 O)] 12-

Introduction

Mixed-addenda Nb/W polyoxometalates (POMs) merit particular attention within the polyoxoniobate family.

…”

X-Ray Structure of Keggin-type Peroxo Polyoxometalate A-α-[Si(NbO2)3W9O37]7-

“…[4][5][6] The instability of peroxoniobium POMs, in which the (Nb V O 2 ) 3+ unit has been substituted for a (W VI O) 4+ type I "octahedral" unit has rendered difficult the purification and structural characterization of such POMs in the past. 7 Given the growing importance of A-α-1, this study sought the specific goal associated with this unstable POM, i.e., to obtain a good quality single crystal X-ray diffraction study to determine the nature, and in particular, the orientation of the peroxo groups. This goal has been met as described in this note.…”