Synthesis and characterization of five-co-ordinate rhenium(III) complexes with 2-(diphenylphosphino)ethanethiolate and monothiolate liqands. Crystal structure of [Re(Ph2PCH2CH2S)2(PhCH2S)]

Abstract

A new series of five-co-ordinate rhenium(III) complexes containing the mixed S,P-bidentate 2-(diphenylphosphino)ethanethiolate ligand together with a monothiol RSH [R = Ph₂PCH₂CH₂, Ph₂P(O)CH₂CH₂, PhCH₂, Ph or Prⁿ] have been synthesized and characterized. This Re^IIIP₂S₃ series was prepared by substitution reactions of [Re^IIICl₃(MeCN)(PPh₃)₂], a pre-reduced rhenium(III) precursor, by addition of 2-(diphenylphosphino)ethanethiol and the corresponding monothiol. Formation of these compounds was verified by elemental analysis and ¹H and ³¹P NMR and positive-ion fast atom bombardment mass spectroscopy. The complexes were found to be diamagnetic, neutral and stable. They exhibit a trigonal-bipyramidal geometry, where three sulfur atoms occupy the equatorial plane and two phosphorus atoms are positioned at the apices. The X-ray structural analysis of bis[2-(diphenylphoshino)ethanethiolato-κS,κP](phenylmethanethiolato-κS)rhenium(III) revealed that this compound crystallizes in the monoclinic space group P2₁/c with Z= 8, a= 21.011(9), b= 20.397(9), c= 16.289(7)Å, β= 107.13(5)°, R= 0.050, R′= 0.063, by using 5644 observed reflections. The above data further demonstrate the preference of a five-co-ordinate configuration when the P₂S₃ donor-atom set is available for co-ordinating rhenium(III).