Crystal and molecular structure of 1,1,2,2-tetrakis(pentacarbonylmanganio)-1,2-dibromoditin, a transition metal substituted ditin compound

The crystal and molecular structure of 1,1,2,2-tetrakis(pentacarbonylmanganio)-1,2-dibromoditin, Br2Sn2[Mn(CO)5]4, has been determined by a single-crystal x-ray analysis using three-dimensional x-ray data collected by the ω-scan technique on an Enraf-Nonius CAD4 automated diffractometer. The compound crystallizes in the monoclinic system with four molecules in a centrosymmetric unit cell, with space group P21/c and lattice parameters a = 16.591 (5) Å, b = 12.455 (2) Å, c = 17.214 (8) Å, and β = 108.10 (3)°. The heavy-atom part of the structure was solved with a direct method. The other atoms were located by Fourier methods. A refinement by block-diagonal least-squares procedures converged to RF = 0.048 and RwF = 0.036 for 4396 independent observed reflections with I > 2.5σ(I). The crystal structure consists of discrete molecular units of Br2Sn2[Mn(CO)5]4. The two connected tin atoms are each tetrahedrally surrounded by two Mn(CO)5 groups and one bromine atom. Each manganese atom is octahedrally surrounded by five carbonyl groups and a tin atom. The four equatorial carbonyls in each Mn(CO)5 group are bent away from the axial carbonyl group by 2.7° on the average. The internal steric crowding is decreased by the deformation of some Sn-Mn-C bond angles and Sn-Mn bond distances. The molecule exhibits approximate C2 symmetry. Both the Sn-Sn bond length (2.885 (1) Å) and the Sn-Br bond lengths (2.576 (1) Å) are unusually long. The two Sn-Mn bond distances on each tin atom differ significantly by 0.040 (2) Å, with averages 2.747 (3) and 2.707 (3) Å. The average axial Mn-C distance is 1.829 (4) Å and the average equatorial Mn-C distance is 1.842 (3) Å. The mean C-O distance is 1.140 (2) Å.