Hydrothermal synthesis and structures of the novel niobium phosphates [NbOF(PO 4)](N 2C 5H 7) and [(Nb 0.9V 1.1)O 2(PO 4) 2(H 2PO 4)](N 2C 2H 10)

Abstract

Two new niobium phosphates were synthesized and their crystal structures determined from single-crystal X-ray data. [NbOF(PO 4)](N 2C 5H 7) ( 1) (monoclinic, space group P2 1/ c, a=11.442(1), b=9.1983(7), c=9.1696(8) Å, β =109.94(1) ° ) has a layered structure and is the first example of a negatively charged NbOF(PO 4) layer analogous to the MO(H 2O)PO 4 ( M=V, Nb) layers. The layer charge is compensated by interlayer 4-aminopyridnium cations that adopt an unusual arrangement as a consequence of H-bonding and π– π interactions. The interlayer aminopyridnium cations can be exchanged with alkylammonium ions which form bilayers inclined at ∼65° to the NbOF(PO 4) layer. [(Nb 0.9V 1.1)O 2(PO 4) 2(H 2PO 4)] (N 2C 2H 10) ( 2) (orthorhombic, space group Pbca, a=15.821(2), b=9.0295(9), c=18.301(2) Å) has a disordered three-dimensional structure based on NbO(PO 4) layers cross-linked by phosphate tetrahedra, and has a similar structure to the known vanadium analog [V 2O 2(PO 4) 2(H 2PO 4)] (N 2C 2H 10).