r/-Allyl)bromodicarbonyl(N,N'-dicyclohexylethanediimine)molybdenum(II), [MoBr(CaHs)-(CO)2(C~4H24N2)], M r = 493.30, orthorhombic, Pnam, a = 12.541 (1), b= 8.318 (1), c= 19.503 (1)A, V= 2034.5A 3, Z=4, D x= 1.611Mgm -3, 2(CuK~t)= 1.5418 A, ~= 7.322mm -1, F(000)= 1000, T= Mo Br 293K, final R=0.088 for 1267 unique observed c(1) reflections. The Mo atom shows octagonal coordination c(2) C(3) with a mirror plane passing through it, the Br atom and c(10) the central C atom of the r/-allyl group. Bonds to C(ll) Mo are Mo--Br = 2.649 (2), Mo--N = 2.221 (8), c(12) C(13) Mo-C(allyl) = 2.179 (17), and Mo-C(carbonyl) = c(14) 1.965 (14) A. C(15) C(16) O(l) N(I) Experimental. Tabular crystal, 0.13 x 0.10 x 0.05 mm, non-standard setting of space group Pnma (No. 62) used, Enraf-Nonius CAD-4 diffractometer, Ni-filtered radiation, moving-crystal/moving-counter technique, 20< 140 °, lattice parameters from measurements on 45 reflections, no absorption corrections, h=-15 to 15, k=-10 to 10, l=0 to 23, reflection 402 as intensity standard, average count 5484.5 with a (calculated from distribution of measurements) = 103.9. 4215 reflections measured and merged using SHELX76 (Sheldrick, 1976), 1651 unique reflections, merging Rin t = 0.072, 384 excluded during refinement [F o < 3a(Fo)]. Mo and Br positions from Patterson function, other non-H atoms from Fourier syntheses, based on phases defined by Mo and Br; least-squares refinement, F magnitudes; isotropic and then anisotropic temperature factors gave R = 0.088, wR = 0.0676 including H atoms at calculated positions. Weights given by w = I/[a2(F) +
