2,6-Bis(azaindole)pyridine: reactivity with iron(III) and copper(II) salts

Collins, Sibrina N.; Taylor, Stephen A.; Krause, Jeanette A.; Connick, William B.

doi:10.1107/s0108270107039686

Cited by 5 publications

(8 citation statements)

References 23 publications

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“…Compared to [Pt(CH 3 )( 1 )](SbF 6 ) and [Pt(CH 3 )( 2 )](SbF 6 ), the ligands in [Pt(CH 3 )( 7 )](SbF 6 ) and [Pt(CH 3 )( 8 )](SbF 6 ) are significantly twisted (see Supporting Information for more details). This was also seen in the related complexes [Ru( 7 ) 2 ](PF 6 ) 2 , [Ru( 7 )(MeCN) 3 ](PF 6 ) 2 and [Cu( 8 )(NO 3 ) 2 ], − although a different coordination mode was recently observed in [Zn( 8 )(OTf) 2 ] . The larger bite angle of the 6-membered N , N ′ chelate rings in [Pt(CH 3 )( 7 )](SbF 6 ) and [Pt(CH 3 )( 8 )](SbF 6 ) allows the trans N–Pt–N angles to approach 180°, being 177.7(4)-178.4(5), and 177.29(13)° in [PtCH 3 ( 7 )](SbF 6 ) ( A – D ) and [PtCH 3 ( 8 )](SbF 6 ), respectively, cf.…”

Section: Resultsmentioning

confidence: 57%

Oxygen Insertion into Metal Carbon Bonds: Formation of Methylperoxo Pd(II) and Pt(II) Complexes via Photogenerated Dinuclear Intermediates

et al. 2014

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Platinum(II) and palladium(II) complexes [M(CH3)(L)]SbF6 with substituted terpyridine ligands L undergo light-driven oxygen insertion reactions into metal methyl bonds resulting in methylperoxo complexes [M(OOCH3)(L)]SbF6. The oxygen insertion reactions occur readily for complexes with methyl ligands that are activated due to steric interaction with substituents (NH2, NHMe or CH3) at the 6,6″-positions on the terpyridine ligand. All complexes exhibit attractive intermolecular π···π or M···M interactions in the solid state and in solution, which lead to excited triplet dinuclear M-M complexes upon irradiation. A mechanism is proposed whereby a dinuclear intermediate is generated upon irradiation that has a weakened M-C bond in the excited state, resulting in the observed oxygen insertion reactions.

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Section: Resultsmentioning

confidence: 57%

Oxygen Insertion into Metal Carbon Bonds: Formation of Methylperoxo Pd(II) and Pt(II) Complexes via Photogenerated Dinuclear Intermediates

et al. 2014

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“…In line with the lack of measurable inter-ring H···H nuclear Overhauser enhancement (NOE) effects for the unprotonated ligands in solution, the molecular structures of L1 (Figure S4a, top, in the SI), L2 (Figure a, top), and L3 (Figure a, top) in the solid state systematically show the terdentate ligand strand to adopt the trans–trans conformation, which minimizes both steric constraints and intramolecular electric multipolar interactions. , Whereas the closest inter-ring interatomic contact distances in L1 [N(distal)···H(central) = 2.94 Å; Figure S4b, top, in the SI] and in L2 [N(distal)···H(central) = 2.26 Å; Figure b, top] are compatible with an approximate coplanar arrangement of the three aromatic rings, L3 displays a significant twist (interplanar pyridine–quinoline angles = 46.4–47.0°; Figure b top) for restoring an acceptable contact distance N(distal)···H(central) = 2.65 Å . Protonations of L2 and L3 with CF 3 SO 3 H in CH 2 Cl 2 /CH 3 CN (1:1), followed by the slow evaporation or diffusion of diethyl ether yield X-ray-quality prisms for [H L2 ](CF 3 SO 3 ) ( 1 ), [H 2 L2 ](CF 3 SO 3 ) 2 ( 2 ), [H L3 ](CF 3 SO 3 ) ( 3 ), and [H 2 L3 ](CF 3 SO 3 ) 2 ( 4 ).…”

Section: Resultsmentioning

confidence: 85%

“…In this context, neutral N-heterocyclic donor atoms in bidentate 2,2′-bipyridine and terdentate 2,2′;6′,2″-terpyridine ( L1 ; Scheme ) also provide reasonably stable five-membered chelate complexes with Ln III . , Surprisingly, the extended analogous six-membered chelates 2,6-bis(azaindolyl)pyridine ( L2 ) and 2,6-bis(8-quinolinyl)pyridine ( L3 ) have not been considered for the coordination of Ln III , while some complexes with d-block cations of variable sizes such as Mn II (67 pm), Cu II (73 pm), Ru II (>82 pm), and Pt II (94 pm) have been isolated and characterized in the solid state.…”

Section: Introductionmentioning

confidence: 99%

Protonation and Complexation Properties of Polyaromatic Terdentate Six-Membered Chelate Ligands

et al. 2012

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The successive protonation steps occurring in 2,2′;6′,2″-terpyridine (L1) are characterized by a strong affinity for the first entering proton (ΔG(connect)(H,L1) = −17 kJ/mol) followed by allosteric anticooperativity (ΔE(interaction)(H,H,L1) = 6 kJ/mol), a behavior mirrored by 2,6-bis(azaindolyl)pyridine (L2) despite the extension of the chelate ring size from five members (L1) to six members (L2; ΔG(connect)(H,L2) = −28 kJ/mol and ΔE(interaction)(H,H,L2) = 7 kJ/mol). On the contrary, 2,6-bis(8-quinolinyl)pyridine (L3) is less eager for the initial protonation (ΔG(connect)(H,L3) = −10 kJ/mol), but the fixation of a second proton in [H2L3]2+ is driven to completion by positive cooperativity (ΔE(interaction)(H,H,L3) = −5 kJ/mol). Because of its unusual ability to adopt a cis–cis conformation with a large affinity for the entering protons, L2 has been selected for exploring the reactivity of a terdentate fused six-membered chelate with labile metallic cations possessing increasing electrostatic factors along the series Mz+ = Li+ < Mg2+ ≈ Zn2+ < Y3+. Spectroscopic, thermodynamic, and structural studies demonstrate that covalency is crucial for stabilizing the complexes [Zn(L2)n]2+. With the highly charged Y3+ cation, hydrolysis drastically competes with ligand complexation, but anhydrous conditions restore sufficient selectivity for the successful coordination of neutral fused six-membered polyaromatic terdentate chelates with large 4f-block cations.

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“…These constants decrease by 3 orders of magnitude in going from Ln = Gd(III) to Lu(III), because of the steric constraints produced by the helical wrapping of the three strands in the final complexes. 5t,9d With this in mind, we suspect that the large distortion of the polyaromatic backbone detected upon meridional ter-coordination of L6 (fused 6,6-membered chelate) to Zn(II) 10 or Cu(II), 11 compared with the coplanar arrangement found for L1 (fused 5,5-membered chelate) in [Zn(L1)Br 2 ], 12 could produce unusual thermodynamic effects. Along this line of reasoning, we note that L6 indeed reacts with YI 3 under anhydrous conditions to give [Y(L6) n ] 3+ (n = 1, 2), despite its claimed reluctance for large cations; however, the extreme sensitivity of these complexes to moisture and their low solubility prevent further investigations.…”

Section: ■ Introductionmentioning

confidence: 99%

A Polyaromatic Terdentate Binding Unit with Fused 5,6-Membered Chelates for Complexing s-, p-, d-, and f-Block Cations

et al. 2013

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The polyaromatic terdentate ligand 6-(azaindol-1-yl)-2,2′-bipyridine (L7) combines one 5-membered chelate ring with a fused 6-membered chelate ring. It is designed to provide complexation properties intermediate between 2,2′;6′,2″-terpyridine (L1) (two fused 5-membered chelate rings) and 2,6-bis(azaindol-1-yl)pyridine (L6) (two fused 6-membered chelate rings). In polar organic solvents, L7 displays remarkable affinities for the successive fixation of two small univalent cations M = H+ or Li+, leading to stable [M(m)(L7)]m+ (m = 1–2) complexes. Upon reaction with M = Mg2+ or Zn2+ cations, the large positive charge densities borne by the metals result in the successive cooperative complexation of two ligands to give [M(L7)n]n+ (n = 1–2). For small Sc3+, unavoidable traces of water favor the formation of the protonated ligand at millimolar concentrations in acetonitrile, but the use of larger Y3+ cations leads to [Y(L7)n]n+ (n = 1, 2), for which stability constants of log(β(1,1)(Y,L7)) = 2.9(5) and log(β(1,2)(Y,L7)) = 5.3(4) are estimated. The complexation behaviors are supported by speciations in solution, thermodynamic analyses, and solution and solid-state structures.

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2,6-Bis(azaindole)pyridine: reactivity with iron(III) and copper(II) salts

Cited by 5 publications

References 23 publications

Oxygen Insertion into Metal Carbon Bonds: Formation of Methylperoxo Pd(II) and Pt(II) Complexes via Photogenerated Dinuclear Intermediates

Oxygen Insertion into Metal Carbon Bonds: Formation of Methylperoxo Pd(II) and Pt(II) Complexes via Photogenerated Dinuclear Intermediates

Protonation and Complexation Properties of Polyaromatic Terdentate Six-Membered Chelate Ligands

A Polyaromatic Terdentate Binding Unit with Fused 5,6-Membered Chelates for Complexing s-, p-, d-, and f-Block Cations

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