Kinetic study of the reaction of tetramethylplatinum(IV) complexes with acids

Kondo, Yuichi; Ishikawa, Minako; Ishihara, Koji

doi:10.1016/0020-1693(95)04730-1

Cited by 16 publications

(9 citation statements)

References 8 publications

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“…This relationship is consistent with a mechanism that proceeds by slow electrophilic attack of HX or H + on 2 , giving H 2 and 2 equiv of [PtMe 3 (bu 2 bpy)] + , followed by a rapid coordination of X - to give the product (Scheme ). It has been shown that the electrophilic attack of HX on the tetramethylplatinum(IV) complexes [PtMe 4 (NN)] (NN = 2,2‘-bipyridine, 1,10-phenanthroline) to afford CH 4 and [PtMe 3 X(NN)] proceeds by a similar [S E 2 (open) ] mechanism. 2a, Note that electrophiles do not attack a methylplatinum group of 2 , again indicating the relatively low trans -influence of the bridging hydrido ligand. It is possible that electrophiles could attack either the Pt−H group or the MePt group trans to H in complex 3 , but since this compound has not been prepared in pure form, no studies have been made.…”

Section: Resultsmentioning

confidence: 99%

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Methyl(hydrido)platinum(IV) Complexes: X-ray Structure of the First (μ-Hydrido)diplatinum(IV) Complex

1997

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The complex fac-[PtMe3(SO3CF3)(bu2bpy)] (1) (bu2bpy = 4,4‘-di-tert-butyl-2,2‘-bipyridine) reacts with NaBH4 to give [Pt2(μ-H)Me6(bu2bpy)2]SO3CF3 (2), which is the first example of a (μ-hydrido)diplatinum(IV) complex. Complex 2 was fully characterized on the basis of microanalytical, 1H and 195Pt NMR spectroscopic, and X-ray crystallographic data. The reaction of 1 with a large excess of NaBH4 results in the formation of an equilibrium mixture of 2 and fac-[PtHMe3(bu2bpy)] (3). Complex 3 was characterized by 1H NMR spectroscopy in solution but could not be isolated in pure form due to the ease of reversion to 2. Both complexes 2 and 3, which have no ligand that can easily dissociate, are thermally stable to reductive elimination of methane (both in solution and, in the case of complex 2, in the solid state) and to isotopic exchange within Pt(D)CH3 groups, thus giving strong support to the theory that both reactions must occur from within a five-coordinate intermediate. Complex 2 reacts slowly with HX (HX = HCl, HO2CCF3, HSC6H5, NH4 +) to give either 2 equiv of fac-[PtClMe3(bu2bpy)] (4), fac- [PtMe3(O2CCF3)(bu2bpy)](5), and fac-[PtMe3(NH3)(bu2bpy)]SO3CF3 (6) or 1 equiv of [Pt2(μ-SC6H5)Me6(bu2bpy)2]SO3CF3 (7), respectively. Qualitatively, the relative rates of these reactions follow the order of acid strength, i.e. HCl ≈ HO2CCF3 ≫ HSC6H5, indicating that the rate-determining step involves electrophilic attack of H+ on 2. Complex 2 reacts very slowly with nucleophiles such as PPh3 to give 1 equiv of fac-[PtMe3(PPh3)(bu2bpy)]SO3CF3 (8) and 1 equiv of 3. The reaction of CCl4 with 2 gives fac-[PtClMe3(bu2bpy)] (4), [PtCl2Me2(bu2bpy)] (11), and mer-[PtCl3Me(bu2bpy)] (12) in a 1.0:0.8:0.2 product ratio but without formation of chloroform.

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Section: Resultsmentioning

confidence: 99%

“…Interestingly, the tetramethylplatinum(IV) complex [PtMe 4 (bu 2 bpy)] ( 8 ) reacts with HSC 6 H 5 to give not complex 7 but fac -[PtMe 3 ( S C 6 H 5 )(bu 2 bpy)] ( 9 ) (Scheme ) . No 9 was produced in the reaction of HSC 6 H 5 with 2 .…”

Section: Resultsmentioning

confidence: 99%

Methyl(hydrido)platinum(IV) Complexes: X-ray Structure of the First (μ-Hydrido)diplatinum(IV) Complex

1997

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“…[106] Kondo and coworkers found that the protonolysis of PtMe 4 (phen) (phen = 1,10-phenanthroline) by benzoic acid in methanol exhibits a KIE of 15-16 at 25 °C, and they use this value to support their conclusion that the proton attacks the metalcarbon bond. [107] Each case involves a similarly large KIE but a different mechanistic interpretation.…”

Section: Protonolysis Of Metal-alkyl and Metal-aryl Bondsmentioning

confidence: 99%

Large Isotope Effects in Organometallic Chemistry

Truong

Miller

Maria

et al. 2021

Chemistry A European J

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The kinetic isotope effect (KIE) is key to understanding reaction mechanisms in many areas of chemistry and chemical biology, including organometallic chemistry. This ratio of rate constants, k H /k D , typically falls between 1-7. However, KIEs up to 105 have been reported, and can even be so large that reactivity with deuterium is unobserved. We collect here examples of large KIEs across organometallic chemistry, in catalytic and stoichiometric reactions, along with their mechanistic interpretations. Large KIEs occur in proton transfer reactions such as protonation of organo-metallic complexes and clusters, protonolysis of metal-carbon bonds, and dihydrogen reactivity. CÀ H activation reactions with large KIEs occur with late and early transition metals, photogenerated intermediates, and abstraction by metal-oxo complexes. We categorize the mechanistic interpretations of large KIEs into the following three types: (a) proton tunneling, (b) compound effects from multiple steps, and (c) semiclassical effects on a single step. This comprehensive collection of large KIEs in organometallics provides context for future mechanistic interpretation.

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“…Measurements were carried out in a similar way to one in the previous study [4,5] Ϫ5 M, C NaOOCH ϭ (1.20 ϳ 99.0) ϫ 10 Ϫ2 M, and C NaSCN ϭ (1.13 ϳ 99.0) ϫ 10 Ϫ2 M for the [PtMe 3 (OOCH)(bipy)] ϩ NaSCN reaction. The observed reaction curves were exactly single exponential in all the systems.…”

Section: Measurementsmentioning

confidence: 99%

“…We have already studied kinetically reactions (1), (2), and (3) in this scheme [4,5]. It has been disclosed that reaction (1) proceeds with direct nucleophilic attack of dimethyl sulfide to the platinum(IV) dimer complex [3], while reaction (2) proceeds via a path with direct nucleophilic attack of NN to the bis(dimethyl sulfide)platinum(IV) complex in the case of NN ϭ 2,2Ј-bipyridine, and via both the direct path and a path with an intermediate of reduced coordination number in the case of NN ϭ 4,4Ј-dimethyl-2,2Ј-bipyridine [5].…”

Section: Introductionmentioning

confidence: 99%