F-19 NMR SPECTROSCOPIC EVIDENCE AND CALCU LATION 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 p repared for the first time. The system of the 21 innersphere mixed clu sters (Mo6IniCl8-ni)4+, n = 0-7 is formed by exchange of innersphere b ound Cl(i) against outersphere bound I(a) on tempering solid [(Mo6Cl8i )I4a] at 400-degrees-C. Prolonged tempering leads to increasing averag e n values of the mixture, which is converted into the tetrabutylammon ium salt (TBA)2[(Mo6IniCl8-ni)F6a]. Using increments of chemical shift s and integral peak intensities the 54 F-19-nmr signals of the 21 spec ies (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 deviat ion from statistical occupation, revealing the preference of isomers w ith iodine atoms occupying edges of the innersphere cube and discrimin ation of those sharing diagonals of the faces. Moreover all compounds with n = 3 and 4 are present overaverage in comparison to the others.