F-19 NMR SPECTROSCOPIC EVIDENCE AND CALCULATION OF THE STATISTICAL FORMATION OF MIXED CLUSTER ANIONS [(MO6IN(I)CL8-N(I))F6(A)]2-, N = 0-7, AND PREPARATION OF (TBA)2[(MO6I8(I))F6(A)]

The octa-mu3-iodo-hexafluoro-hexamolybdate(2-)ion [(Mo6I8i)F6a]2- is prepared for the first time. The system of the 21 innersphere mixed clusters (Mo6IniCl8-ni)4+, n = 0-7 is formed by exchange of innersphere bound Cl(i) against outersphere bound I(a) on tempering solid [(Mo6Cl8i)I4a] at 400-degrees-C. Prolonged tempering leads to increasing average n values of the mixture, which is converted into the tetrabutylammonium salt (TBA)2[(Mo6IniCl8-ni)F6a]. Using increments of chemical shifts and integral peak intensities the 54 F-19-nmr signals of the 21 species (compound n = 8 is absent) are assigned and confirmed by the 2D-F-19/F-19-COSY spectrum. From the measured intensities the distribution of the different compounds is determined and proves significant deviation from statistical occupation, revealing the preference of isomers with iodine atoms occupying edges of the innersphere cube and discrimination of those sharing diagonals of the faces. Moreover all compounds with n = 3 and 4 are present overaverage in comparison to the others.