Chiral, Hemilabile Palladium(II) Complexes of Tridentate Oxazolidines, Including<i>C</i><sub>2</sub>-Symmetric “Pincers”

Strong, Elizabeth T. J.; Cardile, Steven A.; Brazeau, Allison L.; Jennings, Michael C.; McDonald, Robert; Jones, Nathan D.

doi:10.1021/ic8011926

Cited by 24 publications

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References 27 publications

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“…[41][42][43] With our current work, the published 15 N dipyrrinato chemical-shift ranges 23 can now be expanded to include alkali dipyrrinato complexes. As indicated in Fig.…”

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confidence: 99%

The first series of alkali dipyrrinato complexes

et al. 2010

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The first series of alkali dipyrrinato complexes is reported, encompassing lithium, sodium, and potassium salts of meso-unsubstituted and meso-aryl-substituted derivatives. By varying the substituents at the meso position, the intermolecular distance between the two nitrogen atoms and thus the k 2 -N,N-bidentate bite angle was altered, as confirmed by comparison of crystallographic structures of dipyrrin free-bases in the solid-state. The mode of bonding varies as the ionic radius of the metal ion increases: solid-state structures reveal lithium to be accommodated in the plane of the dipyrrinato unit, whilst sodium is accommodated out of plane. The reactivity of analogous lithium, sodium, and potassium dipyrrinato complexes increases as the ionic radius of the metal ion increases, in keeping with the concept that the complexes tend towards an increasingly ionic nature as the size of the alkali metal increases.Résumé : On rapporte la préparation de la première série de complexes dipyrrinato alcalins comportant les sels de lithium, de sodium et de potassium de dérivés méso non substitués et méso substitués par des groupes aryles. En faisant varier la nature des substituants en position méso, on modifie la distance intermoléculaire entre les deux atomes d'azote et, en conséquence, l'angle de morsure k 2 -N,N du bidentate, tel que confirmé par une comparaison des structures cristallographiques des bases libres dipyrrines à l'état solide. Le mode de liaison varie avec une augmentation du rayon ionique de l'ion métallique; les structures à l'état solide révèlent que le lithium s'accommode dans le plan de l'unité dipyrrinato alors que le sodium est accommodé hors du plan. La réactivité des complexes analogues du lithium, du sodium et du potassium augmente avec une augmentation du rayon ionique du métal ionique, en accord avec le concept que les complexes tendent vers une nature de plus en plus ionique avec une augmentation de la taille des métaux alcalins.

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“…[41][42][43] With our current work, the published 15 N dipyrrinato chemical-shift ranges 23 can now be expanded to include alkali dipyrrinato complexes. As indicated in Fig.…”

Section: Resultsmentioning

confidence: 99%

The first series of alkali dipyrrinato complexes

et al. 2010

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“…16) is summarized in Table 9. The Δ 15N coord obtained upon Rh(I) complexation of 1-methylpyrazole (143) and analogous imidazole (144) suggest metal coordination at position N2 (À79.3 ppm) and N3 (À64.6 ppm), respectively [103]. For the octahedral cationic Ir(III) (145) and Ru(III) (146) complexes of three coordinated pyrazoles in acetoned 6 , N2-coordination was shown by Otting and coworkers [97].…”

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confidence: 89%

“…28) showed similar 15 N NMR chemical shifts and jΔ 15N coord js with Cl À and hexafluorophosphate (PF 6 À ) counterions, revealing their comparable tridentate N-N-N geometries in dichloromethane-d 2 solution. However, the complexes having PF 6 À as counterion were significantly more stable than those having Cl À , suggesting that the Cl À complexes were involved in additional equilibrium processes [143].…”

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“…c δ 15N lig for N-(N-(2-pyridyl)methylidene)methionyl-tert-butylamine in CDCl 3 [142]. d δ 15N lig for 2,6-bis(3,4-dimethyl-5-phenyl-1,3-oxazolodin-2-yl)pyridine in CD 2 Cl 2 [143]. e δ 15N lig for 2-(2-pyridyl)-3-(2-pyridylmethyl)-4-methyl-5-phenyl-1,3-oxazolidine in CD 2 Cl 2 [143].…”

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confidence: 99%

“…d δ 15N lig for 2,6-bis(3,4-dimethyl-5-phenyl-1,3-oxazolodin-2-yl)pyridine in CD 2 Cl 2 [143]. e δ 15N lig for 2-(2-pyridyl)-3-(2-pyridylmethyl)-4-methyl-5-phenyl-1,3-oxazolidine in CD 2 Cl 2 [143]. f δ 15N lig for 5-methyl-5 0 -(4-perfluorooctyl-n-butyl)-2,2 0 -bipyridine in CD 2 Cl 2 [144].…”

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Solvent Effects on Nitrogen Chemical Shifts

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Carlsson

Nekoueishahraki

et al. 2015

Annual Reports on NMR Spectroscopy

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Thiosemicarbazone Salicylaldiminato‐Palladium(II)‐Catalyzed Mizoroki–Heck Reactions

et al. 2010

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PPh 3 ] [saltsc = salicylaldehyde thiosemicarbazone; R = H (1), 3-tert-butyl (2), 3-methoxy (3), 5-chloro (4)], have been evaluated as catalyst precursors for the Mizoroki-Heck coupling reaction between a variety of electron-rich and electron-poor aryl halides and olefins. The palladium complexes (0.1-1 mol% loading) were found to effectively catalyze these reactions with high yields being obtained when aryl iodides and aryl bromides were utilized. The effects of base, catalyst loading, reaction temperature and reaction time on the catalytic activity of the most active complex were also investigated.Keywords: aryl halides; low metal loading; methyl acrylate; Mizoroki-Heck coupling; palladium(II) complexesThe synthesis and study of thiosemicarbazones as biological agents has received copious attention over the past few decades.[1-8] These Schiff base-type compounds contain several donor atoms and research into the coordination chemistry and biological applications of their metal complexes is fast becoming an area of prominent interest. [9][10][11][12][13][14] Their palladium(II) and platinum(II) complexes have been studied as anticancer agents and show great promise as chemotherapeutic agents. [12,13] While studies into the biological application of thiosemicarbazone metal complexes is prolific there are few reports on their use in catalysis. One of the first reports of their catalytic application was published in 1998.[15] Pelagatti and co-workers described chemoselective homogeneous hydrogenation reactions using tridentate [N,N,S]thiosemicarbazone palladium(II) complexes. [15] Palladium-catalyzed reactions have become essential synthetic tools; their applications including the syntheses of polymers, [16,17] natural products, [18] agrochemicals [19,20] and pharmaceuticals. [21,22] There are several well-known reactions that utilize palladiumcontaining compounds including the Mizoroki-Heck, Stille, Suzuki and Buchwald-Hartwig cross-couplings. [23,24] As with most of these coupling reactions, the Mizoroki-Heck reaction requires a palladium(0) source as catalyst and this is usually generated in situ by reduction of a palladium(II) complex.[25] Salicylaldehyde thiosemicarbazone Pd(II) complexes were recently applied as catalyst precursors for the Heck reaction [26] and the Suzuki-Miyuara [27,28] coupling reaction and were shown to effectively catalyze carboncarbon bond formation.In our group, we are currently investigating the synthesis and application of tridentate thiosemicarbazone transition metal complexes. We have prepared a series of palladium(II) complexes containing functionalized salicylaldimine thiosemicarbazones and evaluated them for activity as anticancer and antimalarial agents.[29] These complexes have shown promising biological activity and as part of our continuing study into the versatility of thiosemicarbazone metal complexes we chose to screen these complexes as catalyst precursors for the Mizoroki-Heck coupling reaction.

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Chiral, Hemilabile Palladium(II) Complexes of Tridentate Oxazolidines, IncludingC₂-Symmetric “Pincers”

Cited by 24 publications

References 27 publications

The first series of alkali dipyrrinato complexes

The first series of alkali dipyrrinato complexes

Solvent Effects on Nitrogen Chemical Shifts

Thiosemicarbazone Salicylaldiminato‐Palladium(II)‐Catalyzed Mizoroki–Heck Reactions

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Chiral, Hemilabile Palladium(II) Complexes of Tridentate Oxazolidines, IncludingC2-Symmetric “Pincers”

Cited by 24 publications

References 27 publications

The first series of alkali dipyrrinato complexes

The first series of alkali dipyrrinato complexes

Solvent Effects on Nitrogen Chemical Shifts

Thiosemicarbazone Salicylaldiminato‐Palladium(II)‐Catalyzed Mizoroki–Heck Reactions

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Chiral, Hemilabile Palladium(II) Complexes of Tridentate Oxazolidines, IncludingC₂-Symmetric “Pincers”