193 A, • but the ruthenium atom is slightly displaced to the carbon atoms in position z. .. n and W. The procedures as well as the result3 o£ the investigation of the crystal structures of 11Ni!> Cd. The density of the crystal mounted around the c-axis was measured by the flotation method. The difference may be due to small air pockets on the surface of the crystal.
The positions of the ruthenium atoms in the unit cell were readily determined from (001) and (010) Patterson projections. Accordingly, a three-dimensional Fourier synthesis was calculated, again with signs assigned to the structure factors on the basis of the ruthenium position. Estimated isotropic temperature factors for ruthenium and carbon atoms were included in the first set of calculated 9-structure factors, leading to an R factor of 0.185.
094; at this point we converted isotropic temperature factors for the carbon atoms to anisotropic and continued the refinement. The definition of the carbon atoms suggested that the hydrogen atoms could be soluble and that their contribution could be significant in the structure factor calculations. Both the temperature factors and the coordinates of the hydrogen atoms were duly changed in parallel with the carbon atoms as.
Due to the weighting function used in the last stages of processing, w oe 1/ Fo 4 • these reflections had a low weight compared to.
IIIII
In order to predict the Ru-e bond distances in the same way that Pauling considered ferrocene and ruthenocene, we must first calculate the character of the d orbitals of the ruthenium bond. The average distance between metal and carbon, however, agrees well with the average of the observed distances. We cannot find support for longer bond distances in the three-dimensional difference Fourier results (see Fig. 2C and Fig. 3 ) or in the electron density map plotted in the least-squares plane of each indenyl group ( Fig. 9 ). .
We feel that the package is adequately described in Figures 10 and 11 and that words would not enlighten the reader. iii) Accuracy of the molecular geometry. In a recent study of the crystal structure of the dimer ()£rhodium chloride I, 5-cyclooctadiene, Ibers and Snyder (22). The molecular structure of the dimer of rhodium chloride 1,5-cyclooctadiene and of bia-indenylruthenium is suitable for comparison.
0) -- that is, at the centers of symmetry of the molecule, indicating that the six-membered rings are trans. The positions of the ruthenium atom, obtained from the Patterson map, were used to assign signs to the Fo'a and an electron density.
PART II
- 6n + Z as for in P6 1 = 6n + 4
- 6n + 3 as for in P 6 l 1 c 6n + 3
We have assumed that the primitive cell is body-centered with the exception of 4 atoms at the vertex of the amall tetrahedron around 000 and an atom at. Let one of the twins be a y,y type and the other a 0, 0 type, which we defined above. This leads to the op.Posecl conformation of the rings in the latter and to the staggered conformation in ferrocene, but the analogous dicyclopentadienylruthenium and dicyclopentadienyl-:>smium ha .-e the opposite conformation in their orthorhombic crystals.
The probability that the same symmetrical derivatives of ferrocene and ruthenocene will have the same configuration will increase with increasing molecular size. I suggest that the bonding orbitals of the iron and ruthenium atoms have inherently different symmetries in these dicyclopentadienyl compounds and in their derivatives. 1 suggests that the ferrocene molecules combine in the crystalline state in such a way as to preserve the preferred symmetry of the iron ring bonds.
However, in the fairly simple sandwich compounds that have been studied so far, it appears that the nature of the metal-ring bond determines the symmetry. Hedberg, Annual Report of the Division of Chemistry and Chemical Engineering at the California Institute of Technology, Report for p. The free acid of the arsenic(V)-catechol complex was first prepared by Weinland and Heinzler (3) by adding catechol to a boiling aqueous solution of ar:enic acid.
These two problems together require a formulation of structure factor expressions that is easily amenable to computer coding; such a formulation exi sta for monoclinic space groups (Rollett and Davis, 1955) and for orthorhombic space groups {Hybl and Marsh, 1961). Programming in this way requires a common form of structure factor expressions, at least within a system. 156 space groups, the trigonometric part of each structure factor in 2.15 of the 230 Si)ace groups {all but triclinic and monoclinic) is now in the form of triple products of sines and cosines, e.g.
In developing these expressions we make use of the formulations of Trueblood (1956) and the International Tables (1952). We will again write the trigonometric part of the structure factor in the form of triple products of sine and cosine. Twelve orientations of the vibrational ellipsoid are found in the hexagonal system; the corresponding scattering factors are listed in table 6.
All the geometric structure factors for the cubic system are reduced to sums of triple products of sines and cosines. The geometric structure factors for each set of conditions on the indices for each cubic space group are presented in table 3 in terms of the sums of triple products defined in table l.
