Square-planar complexes vibrational spectra

All the complexes show a strong sharp band near 3200 cm due to the N—H vibrations but no imine (C=N) absorptions. The perchlorate complexes are all diamagnetic and square planar in the solid and in solution, showing one absorption in the visible spectrum near 22.00 kK. 

The complex [Ni(2,3-Me2[14]-l,3-diene-l,4,8,lI-N4)] [ZnCU] is square planar and low-spin. The visible spectra show bands near 21.3 kK (characteristic of square planar nickel(II)), near 26.1 kK (due to the imine functions), and near 35.1 kK. The infrared spectra of all of the nickel complexes prepared show absorptions near 3195 and 1595 cm assignable to the N—H stretching vibration and to the symmetric imine vibration, respectively. A strong sharp band also occurs near 1210 cm and is characteristic of the a-diimine function. The NMR spectrum of the perchlorate complex in nitromethane shows a methyl singlet at 2.33 ppm. The ligand can be hydrogenated on nickel(II) with Raney nickel and hydrogen to produce the fully saturated macrocyclic complex [Ni(2,3-Me2[14]-ane-1,4,8,1 1-N4] ... 

This square planar nickel(II) complex was first prepared by J%er. The complex is isolated as very stable orange needles. It is insoluble in water, ethanol, and methanol but soluble in less polar solvents, such as chloroform and dichloromethane. The complex shows two very broad and intense bands in its infrared spectrum, one centered at 1650 cm , due to the C=0 stretching mode, and the other centered at 1590 cm, due to C=C and C=N stretching vibrations. 

This square planar nickel(II) complex is obtained as pink-red needles. The complex is slightly soluble in alcohols, insoluble in water, and very soluble in chloroform and dichloromethane. It is stable in air and is not hygroscopic. The compound shows a broad intense band centered at 1600 cm" in its infrared spectrum due to overlap of C=0 and C=N stretching vibrations. The complex is diam etic and the PMR in CDCI3 is fully consistent with the structure, showing four resonances at 6 7.5 (vinyl), 6 3.2 (methylene), 6 2.42 (methyl), and 5 2,26 (methyl). 

The vibrational wavenumbers of the Ni(CN)4 group vibrations of the M-Ni-bipy complexes and M-Ni-bipy-G clathrates [G=Toluene, aniline or JV,A -dimethyl-aniline] are given in Table I. The v(CN) and 6(NiCN) vibrational wave-numbers are found to be similar to those of Hofmann type clathrates [6] and the pyridine [7] complex, showing that the M-Ni(CN)4 layers have been preserved. Since we observed only one v(CN) (E ) band in the IR spectrum and the other two v(CN) (4ig and 5i ) bands in the Raman spectrum of the Cd-Ni-bipy complex, we propose a square planar environment around the tetracyanonickelate ion. 

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