249a postdoctoral fellowship (A.C.A.) and the NSF for fund-Registry No. la, using the TEXSAN~~ crystallographic software package developed by Molecular Structure Corp.ing. Acknowledgment. We thank the Spanish Ministry of Education and Science and the Fulbright Comission for (22) TEXSAN: Single Crystal Structure Analysis Software, Version 5.0; Molecular Structure Corp.: The Woodlands, TX 77381, 1989. (23) DIFABS: Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39,158. DIFABS defies the average transmission factor to be near unity; therefore, the minimum and maximum transmission factors will be less than and greater than unity, respectively. (24) Least-squares function minimized &w(lFol -IFJ)', where w = ~F,~/U~(F,)~, u2(F,1) = [S2(C + R'B) + @F, ) ]/(Lp!', S = scan rate, C = total integrated peak count, R = ratio of scan time to background counting time, B = total background count, Lp = Lorentz-polarization factor, and p = p factor. (25) Standard deviation of an observation of unit weight: [xw(lFoI -vc1)2/(No -NJ]l/z, where No = number of observations and N, = number of variables. Supplementary Material Available: Tables of positional parameters and temperature factors, including the H atoms, full distances and bond angles, torsion or conformation angles, and anisotropic temperature factors (14 pages); a listing of structure factors (40 pages). Ordering information is given on any current masthead page. (4) are formed with ethylene and propylene, respectively. 4 crystallizes in the space group Pbca wth a = 13.752 (3) A, b = 14.576 (2) A, c = 15.174 (4) A, and 2 = 8; R (R,) = 0.027 (0.035) for 1837 independent reflections with I > 3a(I). Reaction of 1 with cyclic polyolefins proceeds with hydrogenation or dehy-(5) Koelle, U.; Kang, B.-S.; Raabe, G.; Kriiger, C.
