Urbanization and associated landscaping has increased the abundance of year-round habitat for waterfowl, resulting in vegetation damage, loss of recreational activities, air transportation mishaps and health hazards. As part of a research program to develop socially acceptable techniques for management of pest bird populations, we are evaluating nicarbazin as a contraceptive in pest and surrogate avian species. As reproductive studies with Canada Geese (Branta canadensis) are tedious due to the difficulty of conducting controlled field studies and/or breeding geese in captivity, we evaluated the effects of oral nicarbazin administration on the production and hatchability of chicken eggs. Blood plasma and egg DNC concentrations were correlated to contraceptive efficacy. Subsequent studies are being conducted with geese to determine the diet nicarbazin concentration required to produce the desired blood and plasma DNC concentrations. This approach permits the expeditious evaluation of formulations and dosing regimes by simply monitoring blood DNC concentrations in target species.

Crystals of diferrocenyl ketone, Cell5. Fe. C5H4. CO . C5H4. Fe. C5H5, are monoclinic, a= 10.50, b= 6.18, c= 13.05/~,/~= 111°0 '. The space group is P2/c and there are two molecules in the unit cell, the molecule having a Ca axis coincident with the diad axis of the space group. The intensities of the reflexions were measured with a scintillation counter using Fe K~ radiation; the iron, oxygen and carbon atom positions were determined by Patterson and electron-density methods, the hydrogen atoms were located from an (Fo-Fc) synthesis, and all the positional and thermal parameters were refined by least-squares methods. The final R value for 664 observed reflexions is 0.063.Each iron atom is sandwiched between two five-membered rings which are planar, parallel, separated by 3.30 A, and rotated only 5 ° from an eclipsed orientation. The ferrocenyl groups are rotated 17 ° out of the carbonyl plane. The mean bond distances are Fe-C 2.05 A, C-C (cyclopentadienyl rings) 1.43 A, C-C (exocyclic) 1.45/1,, C=O 1.23 A, C-H 1"1 A, and the mean angle in the five-membered rings is 108 °. The intermolecular separations correspond to van der Waals interactions. ExperimentalCrystals of diferrocenyl ketone (Rausch, Fischer & Grubert, 1960) are red-violet plates elongated along b with (100) developed. The density was measured by flotation in aqueous silver nitrate, and the unit-cell dimensions and space group were determined from various rotation and Weissenberg photographs, and on a General Electric Spectrogoniometer. The crystals are isomorphous with those of ferrocenyl ruthenocenyl ketone.Crystaldata (2, Cu K~= 1.5418 A; 2, Fe Kc~= 1.9373 A) Diferrocenyl ketone, CzlHlsOFe2; M.W. 398.0; m.p. 204°C (decomp.). Monoclinic, a= 10.50 + 0.02, b=6.18 + 0.01, c= 13.05 + 0.03 A, fl=lll ° 0'+5'. U= 790.6 A 3.Din= 1"64, Z=2, Dz= 1"67 g.cm -3.Absorption coefficients for X-rays,/z(Cu Kc0 = 150 cm -1,/t(Fe K~)= 42 cm-1.A C 21 -5* JAMES TROTTER AND A. C. MACDONALD 361 crystals to more uniform dimensions were unsuccessful, and the use of molybdenum radiation was impractical since this would have reduced the intensities by a factor of twenty ({1.94/0.7133). It was therefore important to apply corrections for absorption errors. of reciprocal space (Buerger, 1960), and approximate corrections were applied for planes in these regions of high absorption by considering the path lengths in the crystal of beams reflected from the centre (Albrecht, 1939). The maximum correction was 40% in intensity. Because of the thinness of the crystal plate, absorption is serious only for planes in a few very narrow regionsLorentz and polarization factors were applied and the structure amplitudes were derived. Structure analysisThe irÙn atÙm pÙsitiÙn was determined from the threedimensional Patterson function and positional parameters were derived for the C=O group and for the atoms of the five-membered ring bonded to it, by assuming a structure in space group P2/c similar to that of ferrocenyl ruthenocenyl ketone (Small & Trotter, 1964). Structure factors were calcula...

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Each iron atom is sandwiched between two five-membered rings which are planar, approximately parallel, separated by 3-32 A, and oriented about midway between the fully eclipsed and fully staggered conformations. The two five-membered rings which are bonded together are coplanar, and the molecular configuration is trans. The mean bond distances are Fe-C = 2.04 A, C-C (in cyclopentadienyl rings) = 1-40 A, C-C (between rings) = 1.48 A. There are however deviations from fivefold symmetry which are possibly significant; these deviations are the same in both crystallographically independent rings, and are similar to those observed (but considered not significant) in ferrocene. All the intermolecular separations correspond to normal van der Waals interactions.

The crystal structure of anti-8.tricyclo [3,2,1,O~,4] The structure was determined by Patterson and Fourier methods, and the parameters were refined by differential syntheses and least squares. The final R value is 0"093. The configuration of the cyclopropyl methylene group is exo. The bond distances are all normal, but the valency angles in the norbornane nucleus differ from the tetrahedral value; the angles in the cyclopropyl ring are all 60 °, and the angle at the bridgehead is 96.7 °. The intermolecular distances all correspond to normal van der }Vaals interactions.