TY - JOUR
T1 - Kinetics and mechanisms of the axial ligand substitution reactions of platinum(III) binuclear complexes with halide ions
AU - Iwatsuki, Satoshi
AU - Ishihara, Koji
AU - Matsumoto, Kazuko
N1 - Funding Information:
We wish to express our thanks for the financial supports from 21COE “Practical Nano-Chemistry” project from MEXT, Japan and from Waseda University Grant for Special Research Projects.
PY - 2006/7
Y1 - 2006/7
N2 - The axial water ligand substitution reaction on the head-to-head (HH) and head-to-tail (HT) amidato-bridged cis-diammineplatinum(III) binuclear complexes, HH- and HT-[Pt2(NH3)4(μ-amidato)2 (OH2)2]4+ (amidato=α-pyridonato, α-pyrrolidonato, or pivalamidato), with halide ions (X-=Cl-, Br-) in acidic aqueous solution reveals a consecutive 2-step kinetics under the pseudo first-order conditions of a large excess concentration of halide ion relative to that of the complex (CX- ≫ CPt), corresponding to formation of the monohalo (step 1) and the dihalo complexes (step 2). The first substitution step of all the HH and HT diaqua dimers consists of two parallel reaction pathways: one is the simple substituion path of one of the coordinated aqua ligands with X-, and the other is the replacement in the aquahydroxo complex which is the conjugate base of the diaqua dimer. In step 2, there are three reaction pathway patterns: the direct substitution path, the path via a coordinatively unsaturated intermediate, and the unusual path of OH- replacement. Step 2 proceeds via either one or two paths of the three depending on the nature of the halide ion as well as the bridging ligand. On the other hand, the substitution reaction of the hydrogenphosphato-bridged lantern-type complex, [Pt2(μ-HPO4)4(OH2) 2]2- proceeds in 1-step at CX- ≫ CPt, in which the first aqua ligand substitution to form the monohalo species is rate-determining and the monohalo species is in rapid equilibrium with the dihalo complex. The rate-determining step consists of parallel pathways similar to step 1 in the amidato-bridged complex systems.
AB - The axial water ligand substitution reaction on the head-to-head (HH) and head-to-tail (HT) amidato-bridged cis-diammineplatinum(III) binuclear complexes, HH- and HT-[Pt2(NH3)4(μ-amidato)2 (OH2)2]4+ (amidato=α-pyridonato, α-pyrrolidonato, or pivalamidato), with halide ions (X-=Cl-, Br-) in acidic aqueous solution reveals a consecutive 2-step kinetics under the pseudo first-order conditions of a large excess concentration of halide ion relative to that of the complex (CX- ≫ CPt), corresponding to formation of the monohalo (step 1) and the dihalo complexes (step 2). The first substitution step of all the HH and HT diaqua dimers consists of two parallel reaction pathways: one is the simple substituion path of one of the coordinated aqua ligands with X-, and the other is the replacement in the aquahydroxo complex which is the conjugate base of the diaqua dimer. In step 2, there are three reaction pathway patterns: the direct substitution path, the path via a coordinatively unsaturated intermediate, and the unusual path of OH- replacement. Step 2 proceeds via either one or two paths of the three depending on the nature of the halide ion as well as the bridging ligand. On the other hand, the substitution reaction of the hydrogenphosphato-bridged lantern-type complex, [Pt2(μ-HPO4)4(OH2) 2]2- proceeds in 1-step at CX- ≫ CPt, in which the first aqua ligand substitution to form the monohalo species is rate-determining and the monohalo species is in rapid equilibrium with the dihalo complex. The rate-determining step consists of parallel pathways similar to step 1 in the amidato-bridged complex systems.
KW - Equilibrium
KW - Kinetics
KW - Ligand substitution
KW - Mechanism
KW - Platinum(III)
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U2 - 10.1016/j.stam.2006.04.005
DO - 10.1016/j.stam.2006.04.005
M3 - Review article
AN - SCOPUS:33747331639
VL - 7
SP - 411
EP - 424
JO - Science and Technology of Advanced Materials
JF - Science and Technology of Advanced Materials
SN - 1468-6996
IS - 5
ER -