Synthesis and crystal structure of Mo6-x Nb x I11 (x=1-1.5)

A solid solution Mo6 - x Nb (x) I-11 (x = 1.1-1.5) containing cluster cores {Mo5NbI8} is obtained by the high-temperature reaction of molybdenum, niobium, and iodine (550A degrees C, 70 h, quartz ampule). According to the X-ray diffraction data, heating at 800A degrees C in a molybdenum container results in the decomposition of the solution to Mo6I12 and Nb6I11. According to the X-ray structure analysis data, the compounds are isostructural to the high-spin modification Nb6I11 (space group Pccn). The presence of Nb atoms in the structure changes the structural type from the layered (Mo6I12) to framework structure, noticeably increases the metalmetal distances (2.661-2.716 , 2.695 ) Mo-6 octahedron with the retention of the distance from the metal (M) to the mu(3)-capped I atoms, and strongly elongates the M-6-I-M-6 bridges almost to the value observed in Nb6I11.