RHODIUM(III) COMPLEXES WITH ACYCLIC TETRATHIOETHER LIGANDS - EFFECTS OF BACKBONE CHAIN-LENGTH ON THE CONFORMATION OF THE RH(III) COMPLEX

Several Rh(III) complexes containing tetradentate thioether ligands of the general form [RhCl2(RCH(2)S(CH2)(n)S(CH2)(m)S(CH2)(n)SCH(2)R)]X ( n, m = 2 or 3; R = COOH, C6H5; X = Cl-, PF6-, BPh(4)(-)) have been syn thesized and fully characterized. The effect of the Ligand backbone si ze on the configuration (cis or trans) has been investigated. The smal ler backbone chain length favored the cis isomer while the longer chai n 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 comple xes, and single-crystal X-ray diffraction analyses determined the soli d state structures of the benzyl derivatives. Cl2(PhCH(2)S(CH2)(2)S(CH 2)(2)S(CH2)(2)SCH(2)Ph]PF6 crystallized in the monoclinic space group P2(1)/c with a = 14.365(2) Angstrom, b = 13.200(3) Angstrom, c = 15.73 6(2) Angstrom, beta = 115.571(4)degrees, Z = 4, R = 0.048 and R(w) = 0 .057. Cl2(PhCH(2)S(CH2)(2)S(CH2)(3)S(CH2)(2)SCH(2)Ph]PF6 crystallized in the monoclinic space group P2(1)/c with a = 10.937(3) Angstrom, b = 19.055(2) Angstrom, c = 13.734(4) Angstrom, beta = 103.596(13)degrees , Z = 4, R = 0.037 and R(w) = 0.046. Cl2(PhCH(2)S(CH2)(3)S(CH2)(2)S(CH 2)(3)SCH(2)Ph]PF6 crystallized in the triclinic space group <P(1)over bar> with a = 7.732(2) Angstrom, b = 13.046(3) Angstrom, c = 15.720(2) Angstrom, alpha = 67.62(2)degrees, beta = 79.63(2)degrees, gamma = 78 .60(2)degrees, Z = 2, R = 0.049 and R(w) = 0.061. Cl2(PhCH(2)S(CH2)(3) S(CH2)(3)S(CH2)(3)SCH(2)Ph]PF6 crystallized in the orthorhombic space group Pnma with a = 13.540(2) Angstrom, b = 12.774(3) Angstrom, c = 16 .873(3) Angstrom, Z = 4, R = 0.039 and R(w) = 0.047.