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  • Author: Z. A. Fokina x
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The 35Cl and 79Br NQR spectra of chalcogen halide complexes of aluminium, gallium, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, rhenium, iron, ruthenium, osmium, iridium, rhodium, platinum, palladium and gold are discussed.

Three structure types of these complexes have been distinguished by X-ray structure analysis: type I with AX2 ligand and [MXn„Am] coordination polyhedron; type II with AX3 ligand and [MXn+m] coordination polyhedron; type III, dimeric complexes with M-X-M bridge (where X = Cl, Br and A = S, Se, Te). The formation of secondary M-X-A or M-X-M bonds is characteristic of most structures. The spectra were interpreted by a Townes. Dailey approximation with allowance for the electronic configuration of the metal, mutual influence of ligands and structure features of complexes. Systematic investigation of a big series of chalcogen halide complexes-analogues allowed the following changes in 35CI and 79Br NQR frequencies on secondary bonding to be established for intraligand halogen atoms: A decrease in frequency for type I complexes and an increase in frequency for type II complexes; for halogen atoms in the coordination polyhedron: a decrease in frequency for p metals and transition metals with d>6, and an increase in frequency for metals with d< 6.

Abstract

The peculiarities of the 35Cl, 79Br NQR spectra of the chalcogenhalide complexes are explained in terms of intraspheric effect of ligands, formation of secondary intra-and intermolecular bonds, and electronic structure of metal atom. In the 35Cl spectra of [TeCl3 ]2[OsCl6 ] 1, [SeCl3]2[OsCl6]2 and [TeCl3]2 [ReCl6 ]3 the 7-10% increase in frequency in the low-frequency multiplet are accounted for by the disturbance of the pHal-dM π-interaction due to the formation of the peripheral coordination polyhedra [SeCl6 ] and [TeCl6 ]. The peculiarities of the 35 Cl and 79 Br spectra of [MoS2 Cl3 (SeCl2)]2 4, [MoS2 Br3 (SeCl2)]2 5, [WS2Cl3 (SeCl2)]2 6 and [WS2 Br3 (SeBr 2)] 2 7 are attributed to the disturbance of the pHal-dM π-interaction under the influence of the coordination of the SeCl2 and SeBr2 ligands and formation of secondary intramolecular bonds. For [RhCl3 (SeCl2)2]2 8, [IrCl3 (SeCl2)2]2 9 and [SCl3 ][IrCl4 (SCl2)2]10, the appearance of frequencies at 25 MHz in low-frequency triplets is attributed to the intraspheric effect of weak donors-neutral SCl2 and SeCl2 molecules; the frequencies at 18 MHz are assigned to bridging chlorine atoms. This assignment was confirmed by the dimeric structure, which was established by an X-ray structure analysis.

The 35C1 NQR spectra of the chlorochalcogenide complexes of iridium (SCl3)2 [IrCl6] 1, (TeCl3)2 [IrCl6] 2, (SeCl3) [IrCl6] 3, [IrCl3(SCl2)2]2 4, (SCl3) [IrCl4(SCl2)2] 5 and [IrCl3(SeCl2)2]2 6 have been studied. The spectra were recorded by pulse spectrometry. They consist of two mul tiplets, widely separated in frequency. The high-frequency multiplet belongs to the chlorine atoms bonded to sulfur, selenium and tellurium, respectively, in the ligand. A high-frequency shift is observed, which is typical for the coordination of the molecules ACl2(A=S, Se) and ACl4(A=S, Se, Te). The low frequencies in the multiplets of 4 and 6 are attributed to additional bonds formed between chalcogen atom and chlorine in the coordination environment of iridium.

In the spectral region 18-24 MHz lie the NQR frequencies of 35Cl bonded to iridium. For 2 the frequencies are close to those of [IrCl6]2-, which confirms the Ir oxidation state IV. The unexpectedly high frequencies for IrIII in the case of 4 and 5 are explained by the influence of ACl2 molecules, which are weaker σ-donors than the chloro ligands. This promotes electron density transfer from neighbouring chlorine atoms. The 18 MHz frequency is assigned to the bridge chlorine atoms in dimeric molecule 4. This assignment is confirmed by the positive value of d v/dT = +0,2.