CRYSTAL-STRUCTURE OF FE-ETA(6)-C5H5BCME3)2, A PROBLEM STRUCTURE

The complex Fe(eta6-C5H5BCMe3)2 crystallizes in the centrosymmetric tr iclinic space group P1BAR(C(i)1; No. 2) with unit cell dimensions of a 8.770(1) angstrom, b 8.878(1) angstrom, c 11.991(1) angstrom, alpha 1 07.56(1)-degrees, beta 90.85(1)-degrees, gamma 90.13(1)-degrees, V 890 .0(2) angstrom3 and Z = 2. A full sphere of data was collected on a fo ur-circle diffractometer. The structure was solved and refined to R 7. 93% for all 3155 independent reflections and R 4.98% for those 2002 da ta with \F0\ > 6sigma \F0\. The molecules lie on crystallographic inve rsion centers at 0, 0, 0 and 1/2, 0, 1/2; the crystallographic asymmet ric unit therefore consists of two independent half molecules. The mol ecule centered at 0, 0, 0 (molecule ''A'') is ordered and well-defined ; that centered on 1/2, 0, 1/2 (molecule ''B'') is probably disordered , as indicated by larger ''thermal parameters'' and a greater range of apparent interatomic distances. Discussion emphasizes the geometry of molecule A, which has precise C(i). symmetry with Fe(1A)-B(1A) 2.297( 4) angstrom and Fe(1A)-C(ring) distances ranging from 2.057(6) angstro m to 2.138(4) angstrom.