Kinetic Results and Reaction pathways of Intermolecular Thiolato Ligand Migration between Titanocene Complexes and from Cp_2TiX(SAr) (X=Cl,SAr) to PtCl(Me)(cod) (cod=#eta#~2,#eta#~2-1,5-Cyclooctadiene)

摘要

Cp_2TiCl(SPh) (1a),prepared from an equimolar reaction of Cp_2TiCl_2 with NaSPh,undergoes partial and reversible disproportionaltion in THF into Cp_2TiCl_2 and Cp_2Ti(SPh)_2 (2a).The thermodynamic parameters of the reaction are determined to be #DELTA#Hdeg=13.0(0.6)kJ mol~(-1) and #DELTA#S deg=14(2)JK~(-1) mol~(-1) at 298 K.An equimolar reaction of Cp_2Ti(SAr)_2( 2a: Ar=C_6H_5,2b: Ar=C_6H_RMe-p,2d: Ar=C_6H_4Cl-p,2e:Ar=C_(10)H_7) with PtCl(Me)(cod) in THF leads to an intermolecular exchange of the thiolato and chloro ligands to afford Pt(Me)(SAr) (cod) (3a: Ar=C_6H_5,3b: Ar-C_YH_4M_(e-p),3c: Ar=C_6H_4Cl-p 3e: Ar=C_(10)H_7) .Ti complexes :CP_2TiCl_,Cp_2TiCl(SAr),CP_2Ti9SAr)_2, and a minor amount of (Cp_2TiCl)_2o,are also present in the products.Absorption spectra of solution of 2a and excess PtCl(Me)(cod) exhibit distinct changes due to the thiolato ligand transfer,and indicate initial formation of 1a and its subsequent reaction with the Pt complex to form Cp-2TiCl_w.The reaction of 1a with excess PtCl(Me)(cod)obeys second-order kinetics to [1a] .The observed rate constants,K_(obsd),increase with an increase in the concentration of PtCl(Me((cod).Linear plots of the reciprocal of K_(obsd0 versus [1a]_0/[PtCl(LMe)(cod)]_0 are consistent with the reaction pathway involving the disproportionation of 1a into an equimolar mixture of Cp_2TiCl_2 and 2a, the latter of which readily reacts with PtCl(Me)(cod) to regenerate 1a.