Darstellung, Strukturen und EPR-Spektroskopie der Rhenium(II)-Thionitrosylkomplexe trans-[Re(NS)Cl3(MePh2P)2] und trans-[Re(NS)Br3(Me2PhP)2]

Abstract. The paramagnetic rhenium (II) thionitrosyl compounds trans-[Re(NS)Cl3(MePh2P)2] and trans-[Re(NS)Br3(Me2PhP)2] are characterized by crystal structure diffraction and EPR spectroscopy. Trans-[Re(NS)Cl3(MePh2P)2] is formed during the reduction of (a) [ReNCl2(MePh2P)3] with disulphur dichloride (S2Cl2) or (b) of mer-[ReCl3(MePh2P)3] with trithiazyl chloride ((NSCl)3). Trans-[Re(NS)Br3(Me2PhP)2-] is the final product of the ligand exchange reaction of mer-[Re(NS)Cl2(Me2PhP)3-] with bromine whereby the metal occurred to be simultaneusly oxidized.
The crystal structure analyses show for trans-[Re(NS)Cl3(MePh2P)2] (monoclinic, C2/c, a = 13.831 (3) C, b = 13.970 (1) C, c = 14.682 (2) C, b = 95.33 (1), Z = 4) and trans-[Re(NS)Br3(Me2PhP)2-] (monoclinic, C2/c, a = 33.292 (5) C, b = 8.697 (1) C, c = 17.495 (3) C, b = 115.65 (1), Z = 8) linear co-ordinated NS ligands (Re - N - S - angles 180° and 174.8°). The metal atom is octahedrally co-ordinated with the phosphine ligands in trans position to each other.
X-band and Q-band EPR spectra of the rhenium (II) thionitrosyl complexes (5d5 "low-spin" configuration, S = 1/2) are detected in the temperature range 295 ³ T ³ 130 K. They are characterized by well resolved 185,187Re hyperfine patterns.
The hyperfine parameters are used to get information about the spin-density distribution of the unpaired electron in the complexes under study.

Keywords: Thionitrosyl compounds, Rhenium complexes, EPR spectroscopy, X-ray structure