Rhodium(III) Complexes with Acyclic Tetrathioether Ligands. Effects of Backbone Chain Length on the Conformation of the Rh(III) Complex

Abstract

Several Rh(III) complexes containing tetradentate thioether ligands of the general form [RhCl2(RCH2S(CH2)nS(CH2)mS(CH2)nSCH2R)]X (n, m = 2 or 3; R = COOH, C6H5; X = Cl-, PF6-, BPh4-) have been synthesized and fully characterized. The effect of the ligand backbone size on the configuration (cis or trans) has been investigated. The smaller backbone chain length favored the cis isomer while the longer chain length favored the trans isomer (n, m = 2, cis; n = 3, m = 2 or n, m = 3, trans). However, both cis and trans isomers were observed in the case where n = 2 and m = 3. Spectroscopic methods (UV−visible and NMR) were used to characterize the solution conformations of these complexes, and single-crystal X-ray diffraction analyses determined the solid state structures of the benzyl derivatives. cis-[RhCl2(PhCH2S(CH2)2S(CH2)2S(CH2)2SCH2Ph]PF6 crystallized in the monoclinic space group P21/c with a = 14.365(2) Å, b = 13.200(3) Å, c = 15.736(2) Å, β = 115.571(4)°, Z = 4, R = 0.048 and Rw = 0.057. trans-[RhCl2(PhCH2S(CH2)2S(CH2)3S(CH2)2SCH2Ph]PF6 crystallized in the monoclinic space group P21/c with a = 10.937(3) Å, b = 19.055(2) Å, c = 13.734(4) Å, β = 103.596(13)°, Z = 4, R = 0.037 and Rw = 0.046. trans-[RhCl2(PhCH2S(CH2)3S(CH2)2S(CH2)3SCH2Ph]PF6 crystallized in the triclinic space group P1̄ with a = 7.732(2) Å, b = 13.046(3) Å, c = 15.720(2) Å, α = 67.62(2)°, β = 79.63(2)°, γ = 78.60(2)°, Z = 2, R = 0.049 and Rw = 0.061. trans-[RhCl2(PhCH2S(CH2)3S(CH2)3S(CH2)3SCH2Ph]PF6 crystallized in the orthorhombic space group Pnma with a = 13.540(2) Å, b = 12.774(3) Å, c = 16.873(3) Å, Z = 4, R = 0.039 and Rw = 0.047.