Oxo-vanadium(IV) dihydrogen phosphate:: Preparation, magnetic study, and heterogeneous catalytic epoxidation

A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO4)(2)}(n), has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4)(2)}(n) reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H2PO4- ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 angstrom. Magnetic susceptibility of {VO(H2PO4)(2)}, has been measured in the temperature range 2-300 K on a SQUID magnetometer. The magnetic property of {VO(H2PO4)(2)}n, is explicable in the light of a two-dimensional quantum Heisenberg antiferromagnet model. Magnetic pathways are available through the dihydrogen-phosphato bridges within the layer and provide for weak antiferromagnetic interactions. Notably {VO(H2PO4)(2)}(n) catalyzes theepoxidation reaction of alkenes with tert-BuOOH in acetonitrile medium under heterogeneous condition.