Nonvalent interactions in the crystal structures of (Et4N)2[Mo3S7Br6] and (Et4N)(H9O4)[Mo3S7Cl6] clusters

Abstract

I has an anion dimer with 3Sax... During recent two decades, methods for the synthesis of duster compounds based on the [M3~3-X)(uz-X2)3] q (M3X~7) fragment, where X = O (/z3-position), S, Se; M = Mo, W (q = + 4), V (q = + 3), Re (q = + 5), have been developed. For a few dozens of these compounds, crystal structures were determined. Our previous analysis of intermolecular (interionic) contacts in these structures shows that almost all of them have clear-cut specific nonvalent interactions (SNI), giving rise to short contacts called specific nonvalent contacts (SNC) X...Y (where X is a chalcogen atom within the dichalcide group XZ, and Y is a halogen, chalcogen, N, etc. atom entering the counterion or the ion of the same charge) [1].In the M3X~7 cluster fragment, the X atoms of the X 2 groups are coordinated asymmetrically with respect to the M 3 plane and are inclined to it at angles of ~30~ three X atoms (below called equatorial and denoted as Xeq ) lie virtually in the plane, and the other three atoms (below called axial and denoted as Xax ) deviate from the plane by about 2/~ to the opposite side of the (P3-X) ligand. This difference between the atoms is also manifested by their participation in SNC: in almost all structures, the axial atoms are involved in so-called axial (3Xax...Y) contacts (the Y atom lies at the intersection of three X-X lines at equal distances from the three X atoms), whereas the equatorial atoms form several shortened contacts with donor atoms. In [1] it was shown that these interactions play a critical role in formation of crystal packing.In the salts of cluster ions M3XTHal ~-(M = Mo, W; X = S, Se; Hal = C1, Br), two types of interactions are realized: 1) the single CI-anion interacts with three axial sulfur atoms to form the Mo3S7C173-anion (S...C1 -3.0 .~); 2) two M3XTHal ~-anions form a centrosymmetric dimer in the crystal due to the contacts between the terminal Hal t Deceased.