BINARY MOLYBDATES K4M2-STRUCTURE OF K4MN(MOO4)(3)((MOO4)(3) (M2+ = MG, MN, CO) AND CRYSTAL)

Binary molybdates K4M2+(MoO4)(3) (M2+ = Mg, Mn, Co) isostructural to t riclinic alpha-K4Zn(WO4)(3) were synthesized and optimal conditions fo r their spontaneous crystallization were found. It was established by XRPA and DTA that at 530 degrees C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K4Zn(Mo O4)(3). The structure of K4Mn(MoO4)(3) was determined from single crys tal diffraction data (a = 7.613: b = 9.955, c = 10.156 Angstrom alpha = 92.28, beta = 106.66, gamma = 105.58 degrees, Z = 2 space group P (1 ) over bar, R = 0.030). In this compound; Mn has a higher coordination number (CN = 5 + 1) than that of Zn in alpha-K4Zn(WO4)(3) (CN = 4 + 1 ). The main structural feature is pairs of MnO6 octahedra linked by th e bridging MoO4 tetrahedra into ribbons stretching along the a axis. T he structure is compared with related structures of binary molybdates and other members of the alluaudite family.