Ongoma, Peter O. published the artcileMechanistic elucidation of linker and ancillary ligand substitution reactions in Pt(II) dinuclear complexes, SDS of cas: 6972-05-0, the publication is Dalton Transactions (2013), 42(8), 2724-2734, database is CAplus and MEDLINE.
The rate of substitution of aqua ligands by three nucleophiles, thiourea (TU), N,N-dimethylthiourea (DMTU) and N,N,N,N-tetramethylthiourea (TMTU), for [cis-{PtOH2(NH3)2}2-¦Ì-pyrazine](ClO4)2 (pzn), [cis-{PtOH2(NH3)2}2-¦Ì-2,3-dimethylpyrazine](ClO4)2 (2,3pzn), [cis-{PtOH2(NH3)2}2-¦Ì-2,5-pyrazine](ClO4)2 (2,5pzn) and [cis-{PtOH2(NH3)2}2-¦Ì-2,6-dimethylpyrazine](ClO4)2 (2,6pzn) was studied under pseudo 1st-order conditions as a function of concentration and temperature by stopped-flow and UV-Visible spectrophotometry. The reaction proceeded in three consecutive steps; each step follows 1st order kinetics with respect to each complex and nucleophile. The pseudo 1st-order rate constants, kobs(1/2/3), for sequential substitution of the aqua ligands and subsequent displacement of the linker obeyed the rate law: kobs(1/2/3) = k(1/2/3)[nucleophile]. The steric hindrance properties of the pyrazine-bridging ligand control the overall reaction pattern. The order of reactivity of the complexes is 2,3pzn ¡Ö 2,5pzn < 2,6pzn < pzn. The difference in reactivity attributed to the steric crowding at the Pt(II) center imposed by the Me groups reduces the lability of the aqua complexes. The order of reactivity of the nucleophiles decreases with the increase in steric demand TU > DMTU > TMTU. 1H and 195Pt NMR spectroscopic results confirmed the observed dissociation of the bridging ligand from the metal center of the cis-dinuclear complexes and its derivatives in the 3rd step. The dissociation process is accelerated by the introduction of the steric effect on the linker in conjunction with the increased ligand field strength imparted by addnl. thiourea ligands at each metal center. The large neg. entropy of activation ¦¤S¡Ù values in all cases support an associative substitution mechanism.
Dalton Transactions published new progress about 6972-05-0. 6972-05-0 belongs to catalysis-chemistry, auxiliary class Thiourea,Amine,Aliphatic hydrocarbon chain,Amide, name is 1,1-Dimethylthiourea, and the molecular formula is C3H8N2S, SDS of cas: 6972-05-0.
Referemce:
https://courses.lumenlearning.com/boundless-chemistry/chapter/catalysis/,
Catalysis – Wikipedia