Synthesis and Structural Characterization of ... - Jacobs University

Chapter 1
Introduction
Keggin [XM 12 O 40 ] n−
Figure 1.4 The four M 3 O 13 triads and one XO 4 tetrahedron generate the Keggin-type
[XM 12 O 40 ] n− heteropolyanion. The colour code is as follows: MO 6 octahedra (red) and XO 4
tetrahedal (green).
As aforementioned, the tetrahedral heteroatom at the center of the Keggin unit can be any
of a wide array of elements. The most commonly investigated structures are those containing,
P V , As V , Si IV , Ge IV as the heteroatom but other transition metals and non-metals have been
observed playing this role. Few types of addenda atoms have been observed in Keggin
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