Therystal (Mo2FeS3O2) (Et4N)3.CH3CN belengs to space group PI of triclinic system, and α=9.98(1)A, b=13.868(3)A, c=16.796(3)A, a=74.66(2), β=85.41(1), r=72.21(1), z=2. For 3839 independent observed reflections, the block leastsquares refinement for all structural parameters gives final discrepancy factors R=0.037, R\o\=0.034. Average bond lengths are: Mo-Fe=2.722A, Mo-S-2.358A, Fe-S=2.244A and Mo-O=1.697A. The results obtained show that the titled compound is a cluster c compound having a new type of structure consisting of a tri-valent cluster anion and three monovalent tetraethyl ammonium cations combined by electrostate force and a solvent molecule CH3CN by van der Waals force.

Key words: CRYSTAL STRUCTURE DETERMINATION, CALCULATION, IRON COMPLEX, MOLYBDENUM COMPLEX, CLUSTER COMPOUND, ACETONITRILE P, MATRICES, SULFIDE COMPLEX, LEAST SQUARE METHODS