Intensity data were measured at 21±1 š C by using w/2q scans (2qmax = 48š ) on a Nicolet R3mV diffractometer with graphite-monochromated Mo Ka radiation (l = 0.71073 Å). The data were corrected for Lorentz and polarization effects; the intensities of three reflections, remeasured periodically throughout data collection varied by less than 2%, indicating no need for a decay correction. An absorption correction, based on azimuthal scans of several intense reflections, was applied to the data. The structures were solved by direct methods and refined by using full-matrix least-squares techniques. All non-hydrogen atoms were refined anisotropically and all hydrogen atoms were refined with isotropic thermal parameters. Structure solution, refinement and the calculation of derived results were perforemd with the SHELXTL[1] package of computer programs. Neutral atom scattering factors and the real and imaginary anomalous dispersion corrections were taken from International Tables for X-ray Crystallography, Vol. IV [2]. Relevant crystallographic data are given in Table 1.
Footnotes:
1. Sheldrick, G.M. SHELXTL, Crystallographic Computing System; Nicolet Instruments Division: Madison, WI, 1986.
2. International Tables for X-ray Crystallography, Vol. IV, The Kynoch Press, Birmingham England, 1974.