Thiolato ligand transfer from bis(thiolato)titanocenes to platinum(II) complexes

Article abstract of DOI:10.1021/om00010a019

Reactions of Cp₂Ti(SEt)² (1a) and Cp₂Ti(S-i-Pr)₂ (1b) with equimolar PtCl₂(cod)₂ give bis-(thiolato)platinum complexes, [Pt(SEt)₂]_n (2a) and [Pt(S-i-Pr)₂]_n (2b), respectively, accompanied by formation of Cp₂TiCl₂. Complexes 2a,b, which are insoluble in common organic solvents, are characterized by elemental analyses and by CP-MAS ¹³C NMR spectra in the solid state. Cp₂Ti(SC₆H₄-p-Me)₂ (1c), Cp₂Ti(SPh)₂ (1d), Cp₂Ti(S₂C₆H₄) (1e), and Cp₂Ti(S₂C₂H₄) (1f) react with equimolar PtCl₂(cod) smoothly to give mixtures of Cp₂TiCl² and (thiolato)-platinum complexes with the cod ligand, Pt(SC₆H₄-p-Me)₂(cod) (3c), Pt(SPh)₂(cod) (3d), Pt-(S₂C₆H₄)(cod) (3e), and Pt(S₂C₂H₄)(cod) (3f), respectively. Reactions of 1a with excess PtCl₂(cod) in THF and in CH₂Cl₂ cause a color change of the solution indicating initial formation of Cp₂TiCl(SEt) followed by its further reaction with Pt complexes to give Cp₂-TiCl₂. The latter step, which is much slower than the former, obeys pseudo-first-order kinetics with respect to [Cp₂TiCl(SEt)]. The observed rate constants, k_obsd, of the reaction in CH₂Cl₂ are proportional to [PtCl₂(cod)]. Temperature dependence of the rate constants in THF gives the kinetic parameters E_a = 57.4 kJ mol^-1, ΔH? = 54.8 kJ mol^-1, ΔS? = -106 J mol^-1 K^-1, and ΔG? = 86.3 kJ mol^-1 at 298 K. Reaction of 1b with excess PtCl₂(cod) also gives Cp₂TiCl₂ through Cp₂TiCl(S-i-Pr). The kinetic parameters of the reaction are E_a = 62.3 kJ mol^-1, ΔH? = 59.8 kJ mol^-1, ΔS? = -124 J mol^-1 K^-1, and ΔG? = 96.7 kJ mol^-1 at 298 K. The absorption spectrum of a reaction mixture of 1f with excess PtCl₂(cod) shows a decrease in the peak due to 1f with concomitant growth of a peak due to Cp₂TiCl₂. The reaction obeys 0.5th-order kinetics with respect to [1f]. Reactions of 1c,d with equimolar PtCl₂(cod) in toluene give the complexes formulated as [Cp₂Ti(SAr)₂PtCl₂(cod)] (4c, Ar = C₆H₄-P-Me; 4d, Ar = Ph), which are characterized by elemental analyses and ¹³C NMR spectra in the solid state. Dissolution of 4c,d in THF causes formation of a mixture of Cp₂-TiCl₂ with 3c,d, respectively.