S2N2[Mo2Cl8(NO)2](2Mo)
In S2N2[Mo(NO)Cl4]22¯ (2Mo ), S2N2 molecule act as a η2-bridging ligand between two Mo(NO)Cl4¯ fragments. The crystal structure of this compound is reported by Dehnicke and co-workers in the year 1987.[74] It is expected that the bonding andanti -bonding combination of twoa1 -orbitals (Scheme 3) from two metal fragments can accept the lone pairs from two N-atoms and bonding combination of the two π-type perpendicular e -orbitals would be engaged in a multi-centre π-back donation to the S‒N π*-MO (LUMO +1, π4 in Figure 2). Figure 1 shows the optimized geometry of S2N2[Mo(NO)Cl4]22¯ . The geometrical parameters of the optimized structure of 2Moare close to the experimentally reported geometrical parameters (Table S4).[74] Here, S2N2 ring is planar with a rectangular shape, where N1‒S2 and N2‒S1 bonds are slightly longer (1.676 Å) than N1‒S1 and N2‒S2 bonds (1.663 Å), which is close to S‒N bond length in S2N2. Analogous to 1Mo , an increase in bond angles at N-atom is observed in 2Mo (93.9°) to facilitate metal coordination at N-atoms. The S1···Cl3 and S2···Cl5 distance are relatively shorter (3.050 Å) than S1···Cl7 and S2···Cl1 distance (3.475 Å) indicating possible non-covalent interactions between chloride and sulphur atoms in the complex, as noted by Dehnicke and coworkers.[23] This interaction can be correlated to the σ-hole present at S-atom. The HOMO-26 shows N→Mo σ-donation and HOMO-1 shows Mo→N back donation (Figure 7). In addition, the S···Cl interaction can be observed in HOMO-3.