Ring strain in bis(triethylphosphine)-3,3-dimethylplatinacyclobutane is small

Moore, S. S.; DiCosimo, Robert; Sowinski, Allan F.; Whitesides, George M.

doi:10.1021/ja00394a043

Cited by 27 publications

(3 citation statements)

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“…3 are found for the concerted one-step reductive elimination of methane from m-[Pt(H or D)Me-(PPh3)2] and in multistep reactions where reductive coupling of alkyl and hydride from platinum(IV) is rate determining. 33,37 Thus the distinction between one-step and multistep mechanisms on the basis of isotope effects in related systems is not unambiguous, although the high values of &(H)/k{D) in the protonolysis reactions do indicate that the proton must be about half-transferred in the transition state.14,15…”

Section: Resultsmentioning

confidence: 99%

Selectivity in reactions of alkyl-aryl-transition-metal complexes with electrophiles

Jawad¹,

Puddephatt²,

Stalteri³

1982

Inorg. Chem.

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Registry NO. tr~ns-[Ru(bpy)~(pyz)~](PF,),, 79733-75-8; trans-[ Ru( b p~) , ( p y )~] (ClO,),, 633 58-69-0; trans-[ Ru(bpy),-(CH3CN)(H2O)](Cl0,),, 79681-78-0; lrans-[Ru(bpy)*-(CH3CN)2](C104)2, 79732-91-5; trans-Ru(bpy),Cl,, 34795-02-3; trans-[ R~( M e~b p y ) , ( P P h , )~] (PF,),, 7968 1-80-4; trans-[ Ru-(Me2bpy)2(PPh2Me)2](PF6)2, 79681-82-6; trans-[Ru(Me,bpy),-(PPhMe,),] (PFs)2, 7968 1-84-8; tram-[Ru(bpy),(NO)(OH)] (PF6)2, 7968 1-86-0; ci~-[Ru(bpy)~(CH,CN),] (PF,),, 55 124-54-4; cis-[Ru-(Me2bpy),(PPh3)(C1)]PF6, 79681-88-2; trans-[Ru(bpy),(OH,),]-(ClO,),, 72203-26-0; Ru(bpy),CO,, 59460-48-9; cis-Ru(Me2bpy),C1,, The new methylarylmetal complexes cis-[AuMe2Ph(PPh3)], cis-[AuMe2(4-MeC6H4)(PPh,)], [PtMe(4-MeC6H,)(.CsH12)], cis-[PtMePh(PMePh,),], and ~is-[PtMe(4-Mec,H,)(PMe,Ph)~] have been prepared and characterized. In reactions with electrophilic reagents such as HC1, HgCl,, and [PtI,(PMe,Ph),], the complexes undergo selective cleavage of a methyl-metal bond (e.& cis-[PtMePh(PMePh,),]) or an aryl-metal bond (e&, cis-[AuMe,Ph(PPh,)], [PtMe(4-MeC6H4)(CEH,,)]).From the selectivity observed and from studies of relative rates of reaction, it is argued that the SE2 mechanism leads to selective aryl-metal bond cleavage and that a different mechanism, probably involving an oxidative-addition-reductiveelimination sequence, leads to selective methyl-metal bond cleavage.

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Section: Resultsmentioning

confidence: 99%

Selectivity in reactions of alkyl-aryl-transition-metal complexes with electrophiles

Jawad¹,

Puddephatt²,

Stalteri³

1982

Inorg. Chem.

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“…It is now widely accepted that the formation of such 3-coordinate 14-electron compounds offers a favourable reaction route to a number of fundamental processes as an alternative to the participation of 4- and 5-coordinate species . Among them, the uncatalyzed cis to trans isomerization of complexes of the type cis -[Pt(PEt 3 ) 2 (R)X] (R = alkyl or aryl groups; X = halide ion), β-hydride elimination from dialkyl- and monoalkyldiphosphinoplatinum(II) complexes, olefin insertion into a Pt−H bond,39a reductive elimination of hydrogen from a three-coordinate PtLH 2 (L = phosphine) fragment, some symmetrization reactions, and nucleophilic substitutions. , The fluxional motion of the phenanthroline seen in this study for the complex [Pt(Me 2 phen)(CH 3 )(Me 2 SO)] + can be safely added to the previous list. Moreover, it suggests the possibility for the flipping to occur also in other [Pt(Me 2 phen)XY] molecules and that for the [Pt(Me 2 phen)X 2 ] species it is not seen only because of the symmetry of the molecule.…”

Section: Discussionmentioning

confidence: 99%

Rates of Dimethyl Sulfoxide Exchange in Monoalkyl Cationic Platinum(II) Complexes Containing Nitrogen Bidentate Ligands. A Proton NMR Study

et al. 1996

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A series of monoalkyl square-planar complexes of the type [Pt(N-N)(CH(3))(Me(2)SO)]PF(6) (1-14), where N-N represents chelating diamines or diimines of widely different steric and electronic characteristics, was synthesized, and the complexes were fully characterized as solids and in solution. The substrates were tailored to offer only one site of exchange to a neutral molecule, i.e. Me(2)SO, in a noncoordinating solvent. No evidence for fluxionality of the N-N ligands was found, except for the case of complex 11 formed by 2,9-dimethyl-1,10-phenanthroline. In solution this complex is fluxional with the phenanthroline oscillating between nonequivalent bidentate modes by a mechanism which involves rupture of the metal-nitrogen bond and rapid interconversion of two coordinatively unsaturated T-shaped 14-electron three-coordinate molecular fragments. Rates of this fluxion were measured by NMR spectroscopy from the exchange effects on the (1)H signals of the methyl and aromatic hydrogens. The DeltaG() value for the fluxion is 49.6 +/- 4 kJ mol(-)(1). Dimethyl sulfoxide exchange with all the complexes has been studied as a function of ligand concentration by (1)H NMR line-broadening, isotopic labeling, and magnetization transfer experiments with deuterated acetone as the solvent. Second-order rate constants were obtained from linear plots of k(obs) vs [Me(2)SO] and activation parameters were obtained from exchange experiments carried out at different temperatures. Second-order kinetics and negative entropies of activation indicate an associative mechanism. The lability of dimethyl sulfoxide in the complexes depends in a rather unexpected and spectacular way upon the nature of the coordinate N-N ligands, the difference in reactivity between the first (N-N = N,N,N',N'-tetramethyl-1,2-diaminoethane, k(2)(298) = (1.15 +/- 0.1) x 10(-)(6) mol(-)(1) s(-)(1)) and the last (N-N = 2,9-dimethyl-1,10-phenanthroline, k(2)(298) = (3.81 +/- 0.005) x10(4) mol(-)(1) s(-)(1)) members of the series being greater than 10 orders of magnitude, as a result of a well-known phenomenon of steric retardation (for the first complex) and an unprecedented case of steric acceleration (for the last complex). Other factors of primary importance in controlling the reactivity are (i) the presence of an extensive pi system on the ligand N-N, (ii) the ease with which this pi system interacts with nonbonding d electrons of the metal, and (iii) the flexibility and ease of elongation of the chelate bite distance. The basicity plays a somewhat minor role, except in the restricted range of the same class of compounds such as substituted phenanthrolines.

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“…Dehydrogenation steps at hydrocarbon chain positions farther away from the surface are also possible, and in fact favored over a-H eliminations on lowvalence late transition metal complexes [67,68]. These reactions can be considered a particular example of intramolecular CAH oxidative additions, and typically lead to the formation of dicoordinated cyclic compounds.…”

Section: A-and C-hydride Eliminationsmentioning

confidence: 99%

Mechanisms of hydrocarbon conversion reactions on heterogeneous catalysts: analogies with organometallic chemistry

Zaera

2005

Top Catal

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Catalysis is central to most industrial processes for chemical manufacturing. As catalytic processes have become more complex and more demanding, selectivity has become the central issue in their design. Selectivity is defined by the relative rates of competing reaction pathways available to crucial intermediates, and can be controlled by subtle changes in the nature of the catalyst, the reactants, and/or the reaction conditions. In order to be able to do this in a systematic manner, a good understanding of the catalytic reaction mechanisms is needed. Here a connection is drawn between the key elementary steps comprising hydrocarbon conversion reactions on surfaces and those known to occur on discrete organometallic complexes. This way, the hydrogenation, dehydrogenation, hydrogenolysis, chain growth, and isomerization reactions typical in heterogeneous catalysis are redefined in terms of hydride elimination, oxidative addition, reductive elimination, migratory insertion, and . 1, 2-shift elementary steps, among others. It is suggested that the knowledge already available from organometallic chemistry can be used to further advance the understanding of the surface science involved in heterogeneous catalysis. Thanks to the commonality of the chemistry involved, a better synergy could also be established between homogeneous and heterogeneous catalytic development. These ideas are discussed in this article in a critical and personal way.

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Ring strain in bis(triethylphosphine)-3,3-dimethylplatinacyclobutane is small

Cited by 27 publications

References 1 publication

Selectivity in reactions of alkyl-aryl-transition-metal complexes with electrophiles

Selectivity in reactions of alkyl-aryl-transition-metal complexes with electrophiles

Rates of Dimethyl Sulfoxide Exchange in Monoalkyl Cationic Platinum(II) Complexes Containing Nitrogen Bidentate Ligands. A Proton NMR Study

Mechanisms of hydrocarbon conversion reactions on heterogeneous catalysts: analogies with organometallic chemistry

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