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(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.