Darstellung, Schwingungsspektren und Normalkoordinatenanalyse der Acetatochloroditechnetate(III), cis-Tc₂(O₂CCH₃)₂Cl₄L₂ (L = axiale Donorbase) sowie Kristallstruktur von cis-Tc₂(O₂CCH₃)₂Cl₄((CH₃)₂NCOCH₃)₂ / Preparation, Vibrational Spectra and Normal Coordinate Analysis of Acetatochloroditechnetates(III), cis-Tc₂(O₂CCH₃)₂Cl₄L₂ (L = Axial Donorbase) and the Crystal Structure of cis-Tc₂(O₂CCH₃)₂Cl₄((CH₃)₂NCOCH₃)₂

Abstract

Tc 2 (O 2 CCH 3 ) 2 Cl 4 (H 2 O) 2 has been prepared by reaction of [Tc 2 Cl 8 ] 2- with acetic anhydride and fluoroboric acid. By treatment with the donor bases L = N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAA), dimethylsulfoxide (DMSO), triphenylphosphinoxide (TPO) and pyridine (Py), the green adducts Tc 2 (O 2 CCH 3 ) 2 Cl 4 L 2 are formed. The structure of Tc 2 (O 2 CCH 3 ) 2 Cl 4 (DMAA) 2 was determined by X-ray diffraction; space group C2/c with a = 29.604(4), b = 10.895(2), c = 14.404(2) Å, β = 97.87(2)°, Ζ = 8, Rw = 2.7%. The Tc-Tc distance is 2.1835(7) Å, the bridging acetate groups are in cis-positions. The IR and Raman spectra have been recorded at 80 K and assigned according to point group C 2v , supported by a normal coordinate analysis of Tc 2 (O 2 CCH 3 ) 2 Cl 4 (DMAA) 2 based on a general valence force field. The stretching interaction constant f d (TcTc) is determined to 3.38 mdyn/Å. With increasing donor strength of the axial ligands, the intense Raman vibration v(TcTc), showing up to three overtones, is lowered from 311 to 282 cm -1 . The δ-δ* transitions of all adducts are observed at 648-652 nm.