All crystallographic calculations were performed with the Siemens
SHELXTL-PC program package [13]. An initial set of non-hydrogen
atom positions were determined from Direct Methods and the
remainder of the non-hydrogen atoms were located using difference
Fourier maps. All hydrogen atoms were placed in calculated
positions with the appropriate molecular geometry and a d(C–
H) = 0.96 Å. The isotropic thermal parameter associated with each
hydrogen atom was fixed equal to 1.2 times the Ueq of the atom to
which it was bound. Full matrix refinement of the positional and
anisotropic thermal parameters for all non-hydrogen atoms versus
F2 resulted in convergence in all of the structures.