1991 Volume 64 Issue 6 Pages 1743-1749
The structure of cis-[CoF2(NH3)4]ClO4 has been determined by a single-crystal X-ray diffraction method. Crystals are tetragonal, space group P41 (or P43), a=7.2645(6), c=16.260(2) Å, V=858.1(2) Å3, Z=4,T=297(1) K, final R=0.052 for 970 observed unique reflections. The coordinated F and N atoms could be distinguished unambiguously from each other based on the thermal parameters. The bond distances Co–F and Co–N are 1.828(6)–1.870(5) and 1.924(7)–1.944(7) Å, respectively. The absorption spectra of the single crystals have been examined in the visible and infrared regions with polarized radiation by the use of microspectrophotometers. The 584 nm band (B1) was considered to borrow intensity from some A1 bands through vibronic coupling with some B1 vibrations, and the 504 nm band (A2 & B2) through some A2 and B2 vibrations. Two of the four ammine groups of this cobalt complex were found to give an NH3 rocking frequency (860 cm−1) higher by 50 cm−1 than the other two (at 810 cm−1). This fact has been attributed to two inter-molecular hydrogen bonds (NH···F=2.85–2.68 Å) in which the former two ammine groups are involved.
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