Sulfur chelates 36. Structural characterization of the Trans isomers of the O-ethylphenyldithiophosphonates of Pd(II) and Pt(II), M[S2P(OC2H5)C6H5]2. Cis-Trans isomerization of the planar Pd(II) complex

Abstract Ni(II), Pd(II) and Pt(II) complexes of O -ethylphenyldithiophosphate, [S 2 P(OEt)C 6 H 5 ] − , crystalize as trans products although the MS 4 coordination about the metal is square planar. Isomerization occurs in organic solvents to produce essentially (by NMR) equal amounts of cis and trans isomers. The rate of isomerization decreases Ni ⪢ Pd > Pt. The isomerization of trans -Pd[S 2 P(OEt)C 6 H 5 ] 2 has been studied quantitatively in various solvents. In benzene E a ≅ 18 kcal/mole with ΔH DG ≅ 18 kcal/mole and ΔS ‡ ≅ −17 e.u. The rearrangement appears to be solvent assisted. CS 2 increases the isomerization rate by a factor of five. The X-ray crystal structures of the Pd(II) and Pt(II) complexes are described in detail. The MS distances are approximately 2.34 A in both complexes, although the space groups are different.