Synthesis, crystal structure and magnetic properties of the novel stackingvariant lamellar lead oxovanadium phosphate hydrate beta-Pb(VOPO4)(2)center dot 4H(2)O. Crystal chemical relationships with related intercalated M(VOPO4)(2)center dot yH(2)O compounds

The new lamellar vanadium(IV) phosphate beta-Pb(VOPO4)(2). 4H(2)O has been isolated and X-ray single crystal diffraction data gave an orthorhombic cel l [space group P2(1)2(1)2(1), Z=4; a=6.377(9), b=6.384(1), c=25.357(11) Ang strom]. The structure, solved by using direct methods and refined to the re liability factors R-1=0.027 (wR(2)=0.074), is a stacking variant of the mon oclinic derivative Pb(VOPO4)(2). 4H(2)O described previously. Magnetic meas urements in the range 3-300 K give a magnetic moment consistent with V(IV) cations with weak antiferromagnetic interactions below 6 K. Crystal chemica l relationships with related M(VOPO4)(2). yH(2)O phosphates are also discus sed.