817. Infrared spectra and structure of some simple and bridged nitro-complexes of platinum, palladium, and cobalt

Abstract

The infrared spectra of some dinitro-complexes of platinum(II), palladium(II), and cobalt(II1) have been examined. The spectra of the transisomers have bands (some of which are split) in the regions around 1415 (v3), 1330 (VJ, and 822 cm.-l (v2). The cis-isomers have somewhat similar spectra with v1 shifted to rather lower frequency and the characteristic addition of a band a t about 1350 cm.-l; also v2, which is a single band in the spectra of the trans-isomers, is sharply split in the spectra of the cis-isomers. Two binuclear complexes having bridging nitro-groups were also examined. Their spectra have bands due to bridging nitro-groups near 1480 and 1200 cm.-l. From these we infer that the nitro-group forms bridges through the nitrogen and one oxygen atom as hitherto assumed, viz., M-N(0)-0-M.The spectra of a number of mononitro-and polynitro-complexes are also recorded. BEATTIE and TYRRELL examined some nitroammine complexes of tervalent cobalt in the infrared region between 4000 and 700 cm.-l using the potassium bromide disc technique; it was concluded that the geometrical isomers of the dinitrotetramminecobalt (111) complex may be distinguished by examination of the spectra in the 1300 and 850 cm.-l regions. Nakamoto et al., have also interpreted the splitting of the cobalt-ammonia stretching frequencies in various nitroammines in a similar manner. that the spectrum of the cis-dinitrotetramminecobalt(II1) cation, [COIII(NO,),(NH~)~]X where X = a singly charged anion, should show more bands than the trans-isomer, owing to the lower symmetry. An extra band was observed for the cis-isomer in the 1350 cm.-l region.The present work was undertaken to ascertain whether there were features in the infrared spectra which could be used to distinguish between cis-and trans-isomers of planar complexes, and if possible to assign absorption bands characteristic of bridging nitro-groups. The variation of NO, stretching frequencies with different electronic effects transmitted through the metal atom was also investigated.Results and Discussion.-The frequencies of the NO, absorption bands of the compounds examined are given in Tables 1 -4 .

Raman Spectral Studies of Cadmium–Nitrite Interactions in Aqueous Solutions and Crystals

“…nitrite ligand to a cation would produce the observed spectral results. Observed N-bonded complexes have the bound antisymmetric stretch raised to approximately 1345 to 1497 cm-', whereas in 0-bonded and bridged complexes, this band occurs at even higher frequencies (22,(24)(25)(26)(27)(28). The symmetric stretching frequency may rise or remain unshifted in N-bonded complexes but upon 0-bonded coordination this band generally shifts to much lower frequency.…”

“…Structures containing either N-bonded or 0-bonded ligands have been reported and the deformations are lower than about 850 cm-' (24)(25)(26)(27)(28)(29). On the other hand bridging or chelation gives a higher frequency, > 860 cm-' (28, 30).…”

Second sphere interaction in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of trans-dichlorobis(ethylenediamine) cobalt(III) terafluoroborate

“…The small size, unit negative charge and shape complementarity of these anions (ClO 3 À , BF 4 À , both tetrahedral) may play the similar role, thus getting sandwiched between the layers of [trans-Co(en) 2 [25] which is comparable with the N-HÁ Á ÁF bond length in the title complex salt (2.04-2.56 Å ). Cation coordination is in the form of slightly distorted octahedral (Table 4), with Co-N bonds in the range 1.940(4)-1.956(4) Å , Co-Cl bond distances of 2.2473(12) and 2.2466 (12) Å and NCo-N angles in the range 85.9(2)-94.1(2)8.…”

“…The absorption band at 887 cm À1 is assigned to CH 2 rocking region and a band at 1592 cm À1 is assigned to NH 2 asymmetric deformation [12]. There are four normal modes of vibration in a tetrahedral BF 4 À ion.…”

Second sphere coordination complexes via hydrogen bonding: synthesis, spectroscopic characterization, crystal structure and packing oftrans-[Co(en)2Cl2]2CdI4

“…The IR band at 880 cm À1 is assigned to CH 2 rocking region and a band at 1566 cm À1 to NH 2 [28]. The absorption bands for tetraiodocadmate(II) in the far-IR region could not be observed due to limitation of the instrument.…”