Hydrothermal synthesis and structures of the novel niobium phosphates [NbOF(PO4)](N2C5H7) and [(Nb0.9V1.1)O2(PO4)2(H2PO4)](N2C2H10)

Two new niobium phosphates were synthesized and their crystal structures determined from single-crystal X-ray data. [NbOF(PO4)](N2C5H7) (1) (monoclinic, space group P21/c, a=11.442(1), b=9.1983(7), c=9.1696(8) A, β=109.94(1) deg. ) has a layered structure and is the first example of a negatively charged NbOF(PO4) layer analogous to the MO(H2O)PO4 (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 deg. to the NbOF(PO4) layer. [(Nb0.9V1.1)O2(PO4)2(H2PO4)] (N2C2H10) (2) (orthorhombic, space group Pbca, a=15.821(2),b=9.0295(9),c=18.301(2) A) has a disordered three-dimensional structure based on NbO(PO4) layers cross-linked by phosphate tetrahedra, and has a similar structure to the known vanadium analog [V2O2(PO4)2(H2PO4)] (N2C2H10)