| Popis: |
The photochemical reaction of bis-(trimethylsily) butediyne, Me3SiC4SiMe3, with Fe(CO)5 in benzene yields a product of formula [Me3C4SiMe3]2Fe2(CO)7, II. The formula and molecular structure were determined by single crystal x-ray analysis. The results correct a structure (I) previously proposed based on spectroscopic evidence. The red crystals are monoclinic, space group I2/a with a = 21.647(6), b = 8.924(2), c = 19.544(8) A, β = 96.09(3]° and Z = 4. Anisotropic refinement of 21 independent atoms with 872 observed reflections converged at R = 0.062 and Rw = 0.064. The molecule II is made up of two diacetylene ligands, an inserted CO group and an (CO)3Fe-Fe(CO)3 group. The diacetylene ligands line up in a “head-to-head” arrangement and combine with the CO and iron carbonyl through reaction off one of the triple bonds. The two reactive carbon atoms from one ligand π-bond to one iron atom, while one of these carbon atoms σ-bonds to the second iron atom. The reverse occurs for the second ligand. A molecule of CO inserts and bridges between carbon atoms of each ligand substituted with SiMe3. The other carbon atoms which σ-bond to the iron atoms are substituted with CCSime3. Three isomers are possible for this reaction, but II is the only one observed. |
