Preparation, structures, and EPR spectra of the rhenium(II) thionitrosyl complexes trans-[R-3(NS)Cl-3(MePh2P)(2)] and trans-[R-3(NS)Br-3(Me2PhP)(2)]

The paramagnetic rhenium(II) thionitrosyl compounds trans-[Re(NS)Cl-3(MePh2 P)(2)] and trans-[Re(NS)Br-3(Me2PhP)(2)] are characterized by structure dif fraction and EPR spectroscopy. Trans-[Re(NS)Cl-3(MePh2P)(2)] is formed duri ng the reduction of (a) [ReNCl2(MePh2P)(3)] with disulphur dichloride or (b ) of mer-[ReCl3(MePh2P)(3)] with trithiazyl chloride. Trans-[Re(NS)Br-3(MeP h2P)(3)] is the final product of the ligand exchange reaction of mer-[Re(NS )Cl-2(Me2PhP)(3)] with bromine whereby the metal occurred to be simultaneus ly oxidized. The crystal structure analyses show for trans-[Re(NS)Cl-3(MePh2P)(2)] (mono clinic, C2/c, a = 13.831(3) Angstrom, b = 13.970(1) Angstrom, c = 14.682(2) Angstrom, beta = 95.33(1), Z = 4) and trans-[Re(NS)Br-3(Me2PhP)(2)] (monoc linic, C2/c, a = 33.292(5) Angstrom, b = 8.697(1) Angstrom, c = 17.495(3) A ngstrom, beta = 115.65(1), Z = 8) linear co-ordinated NS ligands (Re-NS-ang les 180 degrees and 174.8 degrees). The metal atom is octahedrally co-ordin ated with the phosphine ligands in trans position to each other. X-band and Q-band EPR spectra of the rhenium(II) thionitrosyl complexes (5 d(5) "low-spin" configuration, S = 1/2) are detected in the temperature ran ge 295 greater than or equal to T greater than or equal to 130 K. They are characterized by well resolved Re-185,Re-187 hyperfine patterns. The hyperf ine parameters are used to get information about the spin-density distribut ion of the unpaired electron in the complexes under study.