The use of a novel mixed-valence pentavanadate phosphate cluster as a building block has made possible the low-temperature hydrothermal self-assembly of the new three-dimensional square pyramidal−tetrahedral framework vanadium phosphates [HN(CH2CH2)3NH]K1.35[V5O9(PO4)2]·xH2O (1) and Cs3[V5O9(PO4)2]·xH2O (2), from structurally simple starting materials. These materials possess some of the lowest framework densities and the largest cavities thus far observed in open-framework solid-state materials. The degree of curvature, size, shape, and charge of the mixed valence {V5O9(PO4)2} V(4+/5+) pentameric building block, which resembles a portion of an arc of a circle, favors the formation of very large cavities. Phosphate 1 crystallizes in space group I4̄3m with a = 26.247(3) Å and has very large cubic-shaped cavities that display 4̄3m point symmetry, each of which enclose nearly 50 positive charges. These charges are distributed among 12 HN(CH2CH2)3NH2+, 32 K+ cations, and several waters of crystallization. Each cavity, which could contain a sphere of approximately 13.0 Å diameter and which displays an enormous 32-ring at its maximum diameter, communicates via six 16-ring windows to other similar supercages via intervening smaller cavities. Phosphate 2 is built up from the same pentamers as those in 1 but arranged in a different manner in space group Fd3̄m with a = 32.306(4) Å such that one pentamer lies on each of the six faces of a cube. The three-dimensional structure of 2 consists of two types of cavity, larger ones with all six pentamers curved in an outward fashion, with a free diameter along the diagonal of the cubic-shaped cavity of approximately 20 Å and exhibiting a 24-ring diameter, and smaller ones with all six curved to the inside with cavity diagonals of 7.5 Å. The large cavities are interconnected to one another in a manner that is topologically identical to the arrangement of the carbon atoms in diamond. The ion exchange and sorption properties of these two phosphates are also to be presented.

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The hydrothermal reactions of vanadium oxide and molybdenum oxide starting materials with divalent first-row transition metal cations in the presence of nitrogen donor chelating ligands yield the heterometallic hexanuclear clusters [{Zn(bipy)(2)}(2)V(4)O(12)] (2), [{Zn(phen)(2)}(2)V(4)O(12)].H(2)O (3.H(2)O), and [{Ni(bipy)(2)}(2)Mo(4)O(14)] (4). A similar reaction in the presence of excess 2,2'-bipyridine yields [Zn(bipy)(3)](2)[V(4)O(12)].11H(2)O (1.11H(2)O), a species with an isolated {V(4)O(12)}(4)(-) cluster. The structure of 2 consists of a {V(4)O(12)}(4)(-) ring covalently attached to each of two {Zn(bipy)(2)}(2+) moieties through the terminal oxo groups of alternate vanadium sites. In contrast, the structure of 3 exhibits a {V(4)O(12)}(4)(-) ring linked through oxo groups of adjacent vanadium sites to two {Zn(phen)(2)}(2+) moieties. The structure of 4 is constructed from two {Mo(2)O(7)}(2)(-) units linked through two {Ni(bipy)(2)}(2+) groups to form a cyclic 12-membered {Mo(4)Ni(2)O(6)} core. Crystal data: [Zn(bipy)(3)](2)[V(4)O(12)].11H(2)O (1.11H(2)O), a = 21.910(4) Å, b = 14.044(2) Å, c = 23.815(4) Å, beta = 106.15(1) degrees, monoclinic, C2/c, Z = 4; [{Zn(bipy)(2)}(2)V(4)O(12)] (2), a = 12.017(2) Å, c = 15.120(2) Å, tetragonal P4(2)/n, Z = 2. [{Zn(o-phen)(2)}(2)V(4)O(12)].H(2)O (3.H(2)O), a = 18.182(2) Å, b = 11.3668(9) Å, c = 23.455(2) Å, beta = 97.815(7) degrees, monoclinic P2(1)/c, Z = 4; [{Ni(bipy)(2){(2)Mo(4)O(14)] (4), a = 12.323(2) Å, c = 14.897(4) Å, tetragonal P4(2)2(1)2, Z = 2.

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