26. The low-frequency infrared spectra of some complex halides of zinc, cadmium, and mercury

Abstract

Metal-chlorine and -bromine infrared stretching frequencies are reported for a variety of complex halides of zinc, cadmium, and mercury, and for several alkyl-and aryl-mercury halides, including some perfluoro-derivatives. There is no clear relation between v(M-X) and the type of ligand, but frequencies tend to be relatively high in complexes of chelating ligands. Stretching frequencies involving bridging chlorine atoms are considered to be below 200 cm.-l and were not observed. Cadmium-chlorine are lower than mercury-chlorine stretching frequencies in analogous compounds, and it is suggested that in several of the examined cadmium complexes, L,CdCl,, the metal has a distorted-octahedral rather than a tetrahedral environment. Some boronium salts are described which probably contain bridged (M,CI,) 8anions (M = Zn or Cd).INFRARED spectra, in the 2 0 0 4 0 0 cm.-l region in which absorptions due to metalchlorine and metal-bromine stretching vibrations commonly occur, have been reported for a series of tetrahedral complexes MX,2-(M = Mn, Fe, Co, Ni, Cu, or Zn) and for an extensive series of MX,, MX,, and MX, anions2 These absorptions are generally strong and the spectra are relatively simple. They should, therefore, be of considerable diagnostic value, and have, indeed, already been applied to problems in the co-ordination chemistry of tin 3 and some elements of Group VIII.4The value of spectra in this region depends on the availability of data indicating the range of metal-halogen stretching frequencies, and the extent of their dependence on the co-ordination environment of the metal. The aim of the present work is to provide such data for zinc, cadmium, and mercury complexes. Bands due to metal-halogen vibrations could easily be distinguished from those due to the other co-ordinated ligands, for example, by comparing the chloride, bromide and iodide of a given series.Zinc.-Data for thirteen complexes containing the ZnC1, group and eleven containing the ZnBr, group are given in Table 1, together with data for Cs,ZnBr, and a complex containing [ZnC13]-or [Zn2ClJ2-ions. The first point of interest is the small change in v(Zn-X) on passing from the anions ZnX42-to the neutral complexes L,ZnX,. For Cs,ZnCl,, v(Zn-Cl) is at 285 and 292 cm.-l, and is at similar frequencies for (Et4N),ZnCl4 and (Ph,MeA~),2nCl~.~ These are near the lower part of, but inside, the range 277-345 cm.-1 observed for the neutral complexes. For some tin(1v) complexesJ3 v(Sn-C1) is in much the same region for SnCla2-anions (310) as for the complexes py2SnC1, (324) and bipySnC1, (327 and 280 cm.-l). In the neutral zinc bromide complexes, v(Zn-Br) tends

Studies on complex compounds. V. Coordination compounds of mercury and biologically active amines

“…At present, the probability for the existence of a polymeric structure due to halogen bridging (7,8) cannot be ruled out. Furthermore, the low affinity of mercuric ion for oxygen as compared with its affinity for nitrogen, could account for the coordination through nitrogen preferentially over oxygen (9).…”

Synthesis and characterization of triarylphosphine complexes of zinc(II) halides

“…For the binuclear anion [Zn 2 Cl 6 ] 2− , the IR bands at 238 and 225 cm −1 have been assigned to the bridged Zn-Cl stretching frequencies. 11 The remaining two strong bands can, therefore, Table 2. Vibrational spectral data for 1 : 2 triarylphosphine complexes of zinc(II) halides be assigned to bridged Zn-X stretching frequencies ( Table 3).…”

“…Vibrational spectral data for 1 : 2 triarylphosphine complexes of zinc(II) halides be assigned to bridged Zn-X stretching frequencies ( Table 3). The ratio ν b (M-X)/ν t (M-X) for [Zn 2 Cl 6 ] 2− , Al 2 X 6 and the dimeric square planar complexes M 2 X 4 L 2 (where M = Pt or Pd; X = Cl, I; L = PR 3 ) is reported 11,16,17 to vary from 0.63 to 0.83. As shown in Table 3, the ν b (M-X)/ν t (M-X) ratios for the ZnX 2 PR 3 complexes are in the range 0.72 to 0.83.…”

Vibrational spectra of methyl mercuric chloride, bromide, iodide and cyanide

“…The observed Raman and infra-red frequencies for CH3HgX (X=Cl, Br, I) are presented in table 1, together with incomplete spectroscopic data previously published. *, 9 The structures of CH3HgCl and CH3HgBr in the vapour phase have been previously determined by microwave spectroscopy,lo and the molecules shown to possess the expected C3v symmetry.…”