On the Equilibrium between Alkyne and Olefin Platinum(II) Complexes of Zeise’s Salt Type: Syntheses and Characterization of [K(18C6)][PtCl<sub>3</sub>(RC≡CR′)]

König, Anja; Bette, Martin; Wagner, Christoph; Lindner, Roland; Steinborn, Dirk

doi:10.1021/om200767q

Cited by 11 publications

(8 citation statements)

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“…The differences in insertion ability between Au III and Pt II -ethylene suggest that this reaction could be involved in decomposition processes of Au III -alkene complexes, which are not observed with Pt II , as showed by the high stability of Zeise's salt and analogous [PtCl 3 (alkene)] − complexes. 7, 11 The energy trends obtained for ethylene rotation and insertion in A-E are also found for acetylene but the energies of all stationary structures are consistently shifted to lower energies relative to A. This is especially pronounced for platinum, where the insertion barrier is lowered from 41.8 to 27.2 kcal mol −1 .…”

Section: Resultsmentioning

confidence: 68%

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective

et al. 2016

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The contribution of Au(III) species to catalysis is still debated due to the limited number of characterized intermediates with this oxidation state. In particular, the coordination of alkenes and alkynes to Au(III) followed by insertion into Au(III)-X bonds has been suggested but rarely proven experimentally. Here, these reactions are explored by means of DFT and CCSD(T) calculations considering [AuX3(L)] and [AuX2(L)2](+) complexes. In these complexes, L = ethylene and acetylene have been chosen as substrates of high interest and representative of any unsaturated organic substrate, whereas X is Cl, Me or H, as found in metal salts and as model for intermediates involved in catalysis. Isoelectronic Pt(II) complexes are also considered for comparison. Ethylene coordination occurs preferentially perpendicular for all X except H, whereas for acetylene, coordination takes place in-plane for all X except Cl. These coordination isomers can represent either minima (intermediates) or saddle points (transition states) on the potential energy surface, depending on X. NBO analysis shows how this variety of structures results from the combination of electronic (M-L donation and back-donation) and steric (cis L-X repulsion) effects. With the sole exception of [AuMe2(ethylene)2](+), rotation of the unsaturated ligand and insertion into a cis Au-X bond involve low to moderate energy barriers, ΔG(‡) = 2.5 to 23.5 kcal mol(-1), and are thermodynamically feasible, ΔG = 4.3 to -47.2 kcal mol(-1). The paucity of experimental observations for such reactions should thus be caused by other factors, like the participation of the intermediates and products in competitive side reactions including the reductive elimination of XCHnCHnX (n = 1 or 2).

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Section: Resultsmentioning

confidence: 68%

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective

et al. 2016

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“…36 However, more recently Steinborn et al found for internal alkynes in experimental and theoretical studies that the Pt II −alkyne bond in Zeise's salt type complexes tends to be slightly less stable than the Pt II −alkene bond. 37 From the ratio of intermediates C and D observed during the catalytic reaction the following relative reaction rates can be estimated for the individual steps of the proposed mechanism (Scheme 8):…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes

et al. 2014

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The dicationic acetylene platinum(II) complex [ P t ( P N P ) ( C 2 H 2 ) ] ( B F 4 ) 2 (PNP = 2,6-bis-(diphenylphosphinomethyl)pyridine) was generated in situ by ligand substitution from the ethylene complex [Pt(PNP)-(C 2 H 4 )](BF 4 ) 2 and was reacted with a series of arenes at low temperature. Only electron-rich arenes added across the coordinated C−C triple bond and gave the corresponding arylalkenyl complexes (E)-[Pt(PNP)(CHCHAr)]BF 4 (Ar = C 6 Me 5 , C 6 H 2 Me 3 -2,4,6, C 6 H 3 Me 2 -2,6, C 6 H 3 Me 2 -2,4). A slow E− Z isomerization of the arylalkenyl complexes was observed. Single-crystal X-ray structure analyses were obtained for both E and Z isomers of the pentamethylbenzene derivative. The E isomers of [Pt(PNP)(CHCHAr)]BF 4 (Ar = C 6 Me 5 , C 6 H 2 Me 3 -2,4,6) reacted with excess HBF 4 •Et 2 O to give the corresponding arylalkene complexes [Pt(PNP)(CH 2 CHAr)](BF 4 ) 2 , whereas the Z isomers did not undergo immediate protonolysis. Using (E)-[Pt(PNP)(CDCDC 6 Me 5 )]BF 4 it was shown that the stereochemistry of the C−C double bond in the protonolysis product depends on the nature of the acid anion HX (X − = Cl − , BF 4 − ). The catalytic hydroarylation was studied in solution by NMR spectroscopy. The reaction studies provide a more refined view of the individual steps proposed for the Friedel−Crafts type mechanism of the Pt II -catalyzed intermolecular hydroarylation of alkynes.

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“…On the other hand, 1:1 combinations of 1 /M n + of the complexes [Pd(MeCN) 4 ](BF 4 ) 2 and [PdCl 2 (MeCN) 2 ] in a 8 % CD 3 CN/CDCl 3 mixture, and [Pt(EtCN) 4 ](CF 3 SO 3 ) 2 in pure CDCl 3 , all exhibited complex spectra with significant perturbations of the central pyridine H4′ triplet suggesting formation of multiple products as well as metal binding within the macrocycle 54…”

Section: Resultsmentioning

confidence: 99%

Synthesis of a Strained Acetylenic Macrocycle Incorporating a para‐Oligo[2]cruciform Bridge Bent over Nanoscopic Dimensions: Structural, Electronic, Spectroscopic, and Ion‐Sensing Properties

Baxter

Gisselbrecht

Karmazin-Brelot

et al. 2013

Chemistry A European J

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An Eglinton-Galbraith diethyne cyclization preferentially yielded a structurally unusual macrocycle, comprising a strained conjugated oligo[2]cruciform wire, forced into a 2.2 nm bow-shape by a terpyridine rein or tether, and stabilized towards light and heat by four insulating triisopropylsilylacetylene (TIPSA) substituents. Spectroscopic ion-binding studies revealed the macrocycle to exhibit a particularly high UV/Vis selectivity for Pd(II) in dilute solution, and one of its precursors to afford a variety of luminescence quenching and color responses to particular metals, suggestive of promising ion-sensor applications. Under more concentrated conditions, the new macrocycle is able to bind specific metals (e.g., Au(I)) within its cavity despite the steric constraints. Intriguingly, variable-temperature (VT) UV/Vis/(1)H NMR investigations showed the TIPSA substituents to undergo restricted intramolecular motions along with reversible changes in the spectroscopic bandgap of the compound with temperature. In line with the theoretical calculations, the VT UV/Vis observations are consistent with a thermal modulation of the electronic conjugation through the strained oligo[2]cruciform bridge, which is coupled with redistributions within a mixture of conformational isomers of the macrocycle with differing relative twisting between the TIPSA-substituted phenyl rings. Overall, the generation of a para-oligo[2]cruciform, bent and flexed over nanoscopic dimensions through conformational tethering within the macrocyclic ring is noteworthy, and suggests a general approach to nanosized, curved, and strained, yet heat- and light-stable, para-phenyleneethynylene oligomers with unique physicochemical properties and challenging theoretical possibilities.

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On the Equilibrium between Alkyne and Olefin Platinum(II) Complexes of Zeise’s Salt Type: Syntheses and Characterization of [K(18C6)][PtCl₃(RC≡CR′)]

Cited by 11 publications

References 45 publications

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective

Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes

Synthesis of a Strained Acetylenic Macrocycle Incorporating a para‐Oligo[2]cruciform Bridge Bent over Nanoscopic Dimensions: Structural, Electronic, Spectroscopic, and Ion‐Sensing Properties

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On the Equilibrium between Alkyne and Olefin Platinum(II) Complexes of Zeise’s Salt Type: Syntheses and Characterization of [K(18C6)][PtCl3(RC≡CR′)]

Cited by 11 publications

References 45 publications

Coordination and insertion of alkenes and alkynes in AuIIIcomplexes: nature of the intermediates from a computational perspective

Coordination and insertion of alkenes and alkynes in AuIIIcomplexes: nature of the intermediates from a computational perspective

Mechanistic Studies on Platinum(II) Catalyzed Hydroarylation of Alkynes

Synthesis of a Strained Acetylenic Macrocycle Incorporating a para‐Oligo[2]cruciform Bridge Bent over Nanoscopic Dimensions: Structural, Electronic, Spectroscopic, and Ion‐Sensing Properties

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On the Equilibrium between Alkyne and Olefin Platinum(II) Complexes of Zeise’s Salt Type: Syntheses and Characterization of [K(18C6)][PtCl₃(RC≡CR′)]

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective

Coordination and insertion of alkenes and alkynes in Au^IIIcomplexes: nature of the intermediates from a computational perspective