STRUCTURAL CHARACTERIZATION OF (CO)₆Fe₂{u-SC(PH)=C(H)Se} & (CO)₆Fe₂{u-SC(H)=C(Ph)Te} . S. Narasinga Rao, Y.S. Chen, *Elizabeth J. Holt, ⁺Manuel-Soriano, ⁺⁺Shubhangi Umbarkar and Pradeep Mathur, Department of Physics, University of Central Oklahoma, Edmond, OK, ⁺Dept. of BioPhysical Science, UNAM, Mexico City Mexico, ⁺⁺Dept. of Chemistry, Indian Institute of Technology, Bombay, India, *Oklahoma State University, Stillwater, OK

When acetylene gas was bubbled through methanol solutions containing the mixed chalcogenide compounds (CO)₆Fe₂(u-EE') (E=E'; E, E': S, Se, Te), the acetylene adducts, (C0)₆Fe₂{uEC(H)=C(H) E¹} , were obtained. Crystallographic analysis of the phenyl acetylene adducts (CO)₆Fe₂{u-S(Ph)=C(H) Se} (I) and (CO)₆ Fe2{u-SCCH)=C(Ph) Te} (II) were carried out. (I) crystallized in the space group P2₁/c where a= 17.974 (2) Å, b- 6.822 (10) Å, c= 14.008 (4) Å, ,ß= 97.07 (10)deg., V= 1704.4 (4) ų, Z= 4 and refined to R= 0.053; (II) crystallized in P1 with a= 7.494 (9) Å, b= 10.5901 (18) Å, c= 12.1323 (8) Å, [[alpha]]= 105.533 (7)deg., ß= 102.25 (7)deg., [[gamma]]= 106.553 (15)deg., V= 876.6 (2) ų, Z= 2 and refined to an R of 0.054.

The structure consists of a Fe₂S Se butterfly core and the phenyl acetylene molecule is attached to the wing-tip S and Se atoms of the butterfly, such that the CH group is bonded to Se atom and the C Ph group to the S atom. Each Fe atom has three terminally bonded carbonyl groups. The three CO groups, u₃-S ligand, u₃-Se ligand and Fe-Fe bond define a distorted octahedral geometry around each Fe atom. The C-C distances indicate a reduction of acetylene triple bond to an olefinic bond. The average Se-Fe-S angle is consistent with the opening of Fe₂SSe and Fe₂Se₂ butterfly cores to accommodate the phenylacetylene molecule.