Rates and Mechanisms of Substitution in Inorganic Complexes in Solution.

Taube, Henry

doi:10.1021/cr60155a003

Cited by 408 publications

(222 citation statements)

References 138 publications

(214 reference statements)

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“…Therefore, the first axial water ligand substitution (k 1 path) for both lantern-type and amidato-bridged Pt(III) binuclear complexes would proceed as a dissociative interchange (I d ) mechanism, which is due to the filled dp orbital of the d 7 Pt(III) centers [46,52].…”

Section: Consecutive Formation Constants Of the Monohalo And Dihalo Cmentioning

confidence: 99%

Kinetics and mechanisms of the axial ligand substitution reactions of platinum(III) binuclear complexes with halide ions

Iwatsuki

Ishihara

Matsumoto

2006

Science and Technology of Advanced Materials

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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-[Pt 2 (NH 3 ) 4 (m-amidato) 2 (OH 2 ) 2 ] 4+ (amidato ¼ a-pyridonato, a-pyrrolidonato, or pivalamidato), with halide ions (X À ¼ Cl À , Br À ) 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 ðC X À bC Pt Þ, 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 À , 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 À 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, [Pt 2 (m-HPO 4 ) 4 (OH 2 ) 2 ] 2À proceeds in 1-step at C X À bC Pt , 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. r

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Section: Consecutive Formation Constants Of the Monohalo And Dihalo Cmentioning

confidence: 99%

Kinetics and mechanisms of the axial ligand substitution reactions of platinum(III) binuclear complexes with halide ions

Iwatsuki

Ishihara

Matsumoto

2006

Science and Technology of Advanced Materials

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“…Moreover, photoinduced structural rearrangements of metal complexes also raise a lot of interest. 17 Depending on ligand exchange reaction rates, metal complexes are classified into two categories: 18 inert complexes, where ligand exchange is slow (rate constants, <10 proposed classifying the mechanisms of ligand exchange reactions into associative, dissociative, and interchange mechanisms. The associative mechanism (A) involves the reaction intermediate species with the coordination number larger than that of the initial complex due to association with the incoming ligand.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Formation of Copper(II) Chloro Complexes Revealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations

et al. 2015

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Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 10 6 −10 9 M −1 s −1 . As a result, it is often difficult to identify the actual formation mechanism of these complexes. In this work, using UV−vis transient absorption when probing in a broad time range (20 ps to 8 μs) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl 4 2− chloro complexes from copper(II) CuCl 3 − trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl 4 2− upon 420 nm excitation into the ligand-to-metal-charge-transfer electronic state, are found to recombine into parent complexes with bimolecular rate constants of (9.0 ± 0.1) × 10 7 and (5.3 ± 0.4) × 10 8 M −1 s −1 in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where [CuCl 3 ]− reacts with the solvent to form a [CuCl 3 CH 3 CN] − complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a [CuCl 4 CH 3 CN] 2− intermediate. In both solvents, the recombination reaction is potential energy controlled.

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“…2,3 It is noteworthy that coordinative bonds with transition metals such as ruthenium can reach kinetic stabilities that are comparable with those of covalent bonds. 4 With this in mind, a ruthenium center may be considered as a virtual "hypervalent carbon" with unique structural opportunities.We recently introduced a strategy for developing ruthenium complexes that target the ATP-binding site of protein kinases by copying structural features of small organic molecule inhibitors. 5 The adenine base of ATP is lined with a cleft-forming set of conserved hydrophobic residues and forms two hydrogen bonds to the backbone of the hinge between the N-terminal and C-terminal domain.…”

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confidence: 99%

An Organometallic Inhibitor for Glycogen Synthase Kinase 3

et al. 2004

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The vast majority of specific enzyme inhibitors are small organic molecules that gain their specificity by a combination of weak interactions, including hydrogen bonding, electrostatic contacts, and hydrophobic interactions. In contrast, inorganic compounds find applications in medicinal chemistry predominately for their reactivity and imaging properties. 1 We started a research program that aims in exploring the versatility of organometallic and inorganic compounds as structural scaffolds for the design of specific enzyme inhibitors. 2,3 It is noteworthy that coordinative bonds with transition metals such as ruthenium can reach kinetic stabilities that are comparable with those of covalent bonds. 4 With this in mind, a ruthenium center may be considered as a virtual "hypervalent carbon" with unique structural opportunities.We recently introduced a strategy for developing ruthenium complexes that target the ATP-binding site of protein kinases by copying structural features of small organic molecule inhibitors. 5 The adenine base of ATP is lined with a cleft-forming set of conserved hydrophobic residues and forms two hydrogen bonds to the backbone of the hinge between the N-terminal and C-terminal domain. 6 Small-molecule inhibitors usually copy this binding mode. 7 For example, the protein kinase inhibitor staurosporine 1 contains the planar hydrophobic indolo[2,3-a]carbazole aglycon 2a in which the lactam moiety mimics the hydrogen bonding pattern of the adenine base (Figure 1). 8 We envisioned that replacing the indolocarbazole alkaloid scaffold with metal complexes in which the structural features of the indolocarbazole aglycon 2a or the related arcyriaflavin A 2b are retained in one of the ligands would allow metal complexes to be targeted to the ATP-binding site of protein kinases. Potent and specific inhibitors for a particular kinase could then be obtained by assembling elaborate structures around the metal center. As a demonstration of this concept, we here report the organometallic ruthenium compound 3 as an extremely potent inhibitor for the glycogen synthase kinase 3 (GSK-3).The key component of our design is the novel pyridocarbazole ligand 4, derived from arcyriaflavin A 2b by just replacing one indole moiety with a pyridine (shown in red in Figure 1). An X-ray structure of the N-benzylated derivative of 3 proves that ligand 4 can in fact serve as a bidentate ligand for ruthenium, having one classical coordinative bond with the pyridine (Ru1-N19 ) 2.13 Å) in addition to one covalent σ-bond with the indole nitrogen (Ru1-N2 ) 2.11 Å) (indicated in green in Figure 1). 9 The coordination sphere is further filled up by a cyclopentadienyl and CO group. This neutral half-sandwich ruthenium complex 3 is stable under air and in water and can even withstand the presence of millimolar concentrations of thiols as determined by 1 H NMR spectroscopy.Screening a small library of ruthenium complexes against a panel of protein kinases identified 3 as an extremely potent inhibitor for GSK-3. The concentration at ...

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Rates and Mechanisms of Substitution in Inorganic Complexes in Solution.

Cited by 408 publications

References 138 publications

Kinetics and mechanisms of the axial ligand substitution reactions of platinum(III) binuclear complexes with halide ions

Kinetics and mechanisms of the axial ligand substitution reactions of platinum(III) binuclear complexes with halide ions

Mechanism of Formation of Copper(II) Chloro Complexes Revealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations

An Organometallic Inhibitor for Glycogen Synthase Kinase 3

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