Electronic and molecular structure of 2,2′-bipyrimidine-bridged bis(organoplatinum) complexes in various oxidation states. Radical-bridged diplatinum species and the absence of a Pt(III)/Pt(II) mixed-valent intermediate

Klein, Axel; Kaim, Wolfgang; Hornung, Fridmann M.; Fiedler, Jan; Záliš, Stanislav

doi:10.1016/s0020-1693(97)05704-6

Cited by 37 publications

(25 citation statements)

References 85 publications

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“…The average Pt−C(sp 3 ) distance [2.13 Å] is significantly longer than that observed when the opposite ligand is the chloride ion (mean value 2.05 Å) . The actual value is in accord with what was recently found for mutually trans methyl groups in the platinum(IV) compounds [PtMe 4 (CyNCH−CHNCy)] [2.14 Å, av] and [Pt 2 Me 8 (bpym)] [2.13 Å, av] . The bond distances for the equatorial ligands Pt−N av 2.15, Pt−C(olefin) av 2.05, and CC 1.45(1) Å are normal and in accord with the values just discussed for 1a .…”

Section: Resultssupporting

confidence: 70%

First Coordinatively Saturated Carbene Complexes of Platinum(II): Synthesis, Structure, and Reactivity

Cucciolito¹,

Panunzi²,

Ruffo³

et al. 1999

Organometallics

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Coordinatively saturated carbene complexes of platinum(II) have been obtained by oxidative addition of [ClCHNMe2]Cl to Pt(0) precursors. The cationic products of general formula [PtCl(CHNMe2)(N,N-chelate)(olefin)]Cl have been characterized through NMR spectroscopy and for [PtCl(CHNMe2)(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]Cl by X-ray diffractometry. The latter species reacts with nucleophiles affording dimethylformamide and the corresponding Pt(0) precursor [Pt(2,9-Me2-1,10-phen)(Z-MeO2CCHCHCO2Me)]. Attempts to obtain related complexes containing carbene groups PtCHY without a heteroatom in α-position (Y = CO2Et, CO2NMe2, CN) have led to the isolation of complexes of formula [PtR(dmphen){η1,η2-CH(Y)O2CCHCHCO2Me}] (R = Me, Ph), formally derived from an intramolecular nucleophilic addition to a carbene intermediate. The X-ray structure of a representative product, [PtMe(dmphen){η1,η2-CH(CO2Et)O2CCHCHCO2Me}], is reported.

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Section: Resultssupporting

confidence: 70%

First Coordinatively Saturated Carbene Complexes of Platinum(II): Synthesis, Structure, and Reactivity

Cucciolito¹,

Panunzi²,

Ruffo³

et al. 1999

Organometallics

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“…However, in contrast to the reactivity observed for (L 2 )Pt(CH 3 ) 2 , [(bpy)Pt III (CH 3 ) 2 (NCCH 3 )] •+ is stable enough on an electrochemical time scale to be reduced and regenerate the (bpy)Pt II (CH 3 ) 2 . This contrasts to prior reports identifying ligand sterics as the primary driver of Pt III stability; substitution of the both methyl ligands with bulkier mesityl groups has been shown to inhibit axial ligation of the initially generated Pt III species by a donor ligand, along with subsequent oxidative disproportionation, dimerization, and other bimolecular reactivity. ,− We attribute the enhanced stability of [(bpy)Pt III (CH 3 ) 2 ] •+ to the formation of a Pt III –Pt III dimer [{(bpy)Pt III (CH 3 ) 2 (L)} 2 ] 2+ , which is in equilibrium with the monomeric radical [(bpy)Pt III (CH 3 ) 2 (L)] •+ . These findings reveal the key role that axial ligation plays in tuning the reactivity and stability of Pt III radical cations and opens avenues for navigating access to electrochemically generated Pt IV species capable of methane functionalization.…”

Section: Discussioncontrasting

confidence: 73%

Role of Axial Ligation in Gating the Reactivity of Dimethylplatinum(III) Diimine Radical Cations

et al. 2021

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Electrochemical methods are coupled with chemical oxidant-based analytical strategies to evaluate the oxidative reactivity of the platinum(II) diimine complex (bpy)Pt II (CH 3 ) 2 (bpy = 2,2′bipyridine) in coordinating and noncoordinating media. Through this mechanistic analysis, we show that the one-electron oxidation of (bpy)Pt II (CH 3 ) 2 generates a highly reactive, 15-electron Pt III radical cation and identify three reaction pathways that can follow this oxidation: radical−substrate dimerization, radical−radical dimerization, and oxidative disproportionation. Axial ligation of the initially generated [(bpy)Pt III (CH 3 ) 2 ] •+ species is a critical driver of this reactivity, gating the available mechanistic pathways and tuning the competition between radical−radical dimerization and oxidative disproportionation.

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“…An intense bipyrimidyl ligand π–π* transition is observed in the near-UV region for all complexes (not shown, λ max ∼300 nm). There are two diagnostic absorptions that have been assigned as MLCT transitions for similar platinum–bpym complexes . The higher of the two in energy is not observed for the parent complex 1 (likely due to overlap with the intense π–π* transition), but occurs between 400 and 425 nm for adducts 2 – 4 .…”

Section: Results and Discussionmentioning

confidence: 98%

Biaryl Reductive Elimination Is Dramatically Accelerated by Remote Lewis Acid Binding to a 2,2′-Bipyrimidyl–Platinum Complex: Evidence for a Bidentate Ligand Dissociation Mechanism

et al. 2016

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The silicon and zinc Lewis acids Si(cat)2 (cat = catecholato), Si(catF)2 (catF = tetrafluorocatecholato), and Zn(C6F5)2 bind to the remote ligand site of a 2,2′-bipyrimidyl–platinum diaryl complex. This platinum complex provides a platform to systematically evaluate electronic and reactivity differences triggered by Lewis acid binding. The electron density of the bipyrimidine ligand is substantially depleted upon Lewis acid binding, as evidenced by UV–vis spectroscopy and cyclic voltammetry. Biaryl reductive elimination studies allowed quantification of the effect of Lewis acid binding on reactivity, and Lewis acid binding accelerated reductive elimination rates by up to 8 orders of magnitude. Kinetics experiments in combination with DFT studies support an unusual mechanism featuring complete dissociation of the Lewis acid-coordinated bidentate bipyrimidine ligand prior to reductive elimination.

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Electronic and molecular structure of 2,2′-bipyrimidine-bridged bis(organoplatinum) complexes in various oxidation states. Radical-bridged diplatinum species and the absence of a Pt(III)/Pt(II) mixed-valent intermediate

Cited by 37 publications

References 85 publications

First Coordinatively Saturated Carbene Complexes of Platinum(II): Synthesis, Structure, and Reactivity

First Coordinatively Saturated Carbene Complexes of Platinum(II): Synthesis, Structure, and Reactivity

Role of Axial Ligation in Gating the Reactivity of Dimethylplatinum(III) Diimine Radical Cations

Biaryl Reductive Elimination Is Dramatically Accelerated by Remote Lewis Acid Binding to a 2,2′-Bipyrimidyl–Platinum Complex: Evidence for a Bidentate Ligand Dissociation Mechanism

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