Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

Poitras, Jacques; Beauchamp, André L.

doi:10.1139/v94-211

Cited by 15 publications

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“… Coordination of the π face of the pyrrole moiety in an η 5 -fashion has also been reported for a purported titanocene dichloride analogue, although no solid-state structure exists for this compound . Of the transition metal complexes of 7-azaindole reported to date, the majority incorporate multiple metal centers in bridging or direct M–M bonding motifs. − For those complexes that contain only a single transition metal ion, coordination of the 7-azaindole primarily occurs through the pyridine N7 atom. − In very few instances have transition metal complexes featuring exclusive κ 1 -N1 coordination been reported, − although this coordination mode is better established for main group metals such as aluminum. − In addition to binding to metals in its neutral and deprotonated forms, the 7-azaindole moiety has also been incorporated into a variety of chelating ligands. − In such complexes, coordination is again primarily observed through the N7 atom. − …”

Section: Introductionmentioning

confidence: 99%

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

et al. 2015

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Homoleptic complexes of the anion of 7-azaindole (AzaIn) have been synthesized and characterized for a series of 3d transition metals. For Mn(II), Fe(II), and Co(II), complexes of formula Na2[M(AzaIn)4]·2L (L = THF, 2-MeTHF, toluene, or benzene) have been isolated by treatment of the corresponding metal chloride salts with 7-azaindole in the presence of sodium hexamethyldisilazide. The complexes adopt tetrahedral geometries with exclusive coordination to the transition metal ion through the pyrrolic N1 nitrogen atoms of the AzaIn ligands. Solid-state structures of the complexes demonstrate that the sodium cations remain tightly associated to the coordination entities through interaction with both the pyrrolic and pyridine nitrogen atoms of the azaindolide ligands. For Fe(II), replacement of the sodium cations by other alkali metal ions (Li or K) generates new complexes that demonstrate similar coordination geometries to the sodium salts. As a means of comparison, the Fe(II) complex of 4-azaindolide was also investigated. Na2[Fe(4-AzaIn)4]·2L adopts a similar solution structure to the 7-azaindolide complexes as judged by NMR spectroscopy and cyclic voltammetry. DFT calculations have been performed to investigate the bonding in the 7-azaindolide complexes. Results demonstrate that 7-azaindolide-κ1-N1 is a nearly pure sigma donor ligand that features a high degree of ionic character in its bonding to mid 3d transition metal ions.

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Section: Introductionmentioning

confidence: 99%

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

et al. 2015

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“…NbCl, and excess Haza in refluxing benzene have been shown t o give a red-brown insoluble mixture in which NbCl,(Haza), NbCl,(Haza),, and (H,aza)+ could be identified (1). When the mixture was washed with acetonitrile, two compounds eventually crystallized from this solvent and they were shown by X-ray diffraction to contain the (H2aza-aza)' cation, thereby identifying this species as an oxidation product.…”

Section: Nbclfazaindole Reactionmentioning

confidence: 99%

Preparation and characterization of azaindolyl-azaindole and structure of its halogen-free dicationic cluster containing the µ₄-oxotetracopper(II) core

Poitras¹,

Beauchamp²

1994

Can. J. Chem.

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JACQUES POITRAS and AND& L. BEAUCHAMP. Can. J. Chem. 72,2339Chem. 72, (1994.Refluxing NbCl, and excess 7-azaindole (Haza) in benzene yielded a solid mixture containing NbCI,(Haza), NbCl,(Haza),, the azaindolium ion (H,aza)+, and the azaindolyl-azaindolium ion (H2aza-aza)+. The neutral (Haza-aza) molecule was obtained from the hydrolysed mixture and shown by X-ray diffraction (monoclinic, P2,lc, a = 10.025, b = 13.758, c = 8.416 A, P = 102.89", Z = 4, R = 0.035) to result from the coupling of two azaindole units via N7-C6'. This compound was the only oxidation product detected, but concurrent formation of other niobium-and (or) azaindole-containing products keeps the yield of Haza-aza low. Dark green crystals of [Cu,O(aza-aza),]CI2.6.5Hfl were obtained from (Haza-aza) and CuCl, in wet methanol. The crystal structure (monoclinic, C2/c, a = 17.704, b = 25.240, c = 14.457 A, P = 116.14', Z = 4, R = 0.051) shows the presence of a tetranuclear dicationic cluster consisting of a p,-oxide ion surrounded by a tetrahedron of Cu(I1) atoms. A distorted square-planar coordination is achieved about each copper atom by (aza-aza)-ligands each bridging two copper atoms and providing a third nitrogen donor to one of them. For each such cation, the unit cell also includes two chloride ions and 6.5 disordered lattice water molecules. The 'H NMR and infrared spectroscopy data are discussed. Chem. 72,2339Chem. 72, (1994.Le reflux de NbCI, et de 7-azaindole (Haza) en excts dans le benztne a conduit un milange solide contenant NbCIS(Haza), NbCl,(Haza),, l'ion azaindolium (H,aza)+ et l'ion azaindolyl-azaindolium (H,aza-aza)'. Le composC neutre (Haza-aza) a Ct C obtenu a partir du melange hydrolysC et la diffraction des rayons X (monoclinique, P2,lc, a = 10,025, b = 13,758, c = 8,416 A,

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“…Compound (II) is a congener of complexes (I) and (H 2 azaaza)[O NbCl 4 (Haza)]Á0.5CH 2 Cl 2 (Haza is 7-azaindole; Poitras & Beauchamp, 1994). We have also optimized the geometry of the C 2v symmetrical [O NbCl 4 (py)] À anion at the pbe1pbe/SDD level of theory using GAUSSIAN03 (Frisch et al, 2004) and will refer to it as (III-DFT) (DFT is density functional theory).…”

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A long Nb=O double bond in bis(pyridinium) tetrachlorooxo(pyridine-κN)niobate(V) chloride

Guzei

Saulys

2006

Acta Crystallogr C

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The asymmetric unit of the title compound, (C 5 H 6 N) 2 -[NbCl 4 O(C 5 H 5 N)]Cl or (pyH) 2 [O NbCl 4 (py)]Cl (py is pyridine), contains a discrete anionic niobium(V) complex, [O NbCl 4 (py)] À , and two protonated pyridine molecules, which form medium±strong hydrogen bonds with the Cl À counter-ion. The Nb O distance of 1.7643 (17) A Ê is the longest among those in congener niobium complexes reported to date. Extensive density functional theory studies of conformations of [O NbCl 4 (py)] À and structural data mining raise doubts regarding the reliability of the length of this Nb O double bond. CommentRecently, we reported a niobium(V) complex, viz. (pyH)[O NbCl 4 (py)]Ápy (py is pyridine), (I) (see scheme) (Guzei et al., 2002), which posed an interesting crystallographic problem. The assignment of the space group was problematic due to pseudosymmetry, and a careful differentiation between space groups Pnc2 and Pmna was necessary. We have since isolated the title compound, (pyH) 2 -[O NbCl 4 (py)]Cl, (II), which presents a different issue, in that the Nb O double bond is considerably longer than that in (I), and we report here a discussion of this fact based on the results of crystallographic data mining and theoretical computations.The asymmetric unit of (II) contains four discrete ions: the niobium(V) anion [O NbCl 4 (py)] À , (III), two pyridinium cations and a Cl À anion (Fig. 1). The pyridinium cations form two unequal hydrogen-bonding interactions with the Cl À counter-ion. The N2ÐH2NÁ Á ÁCl5 interaction is somewhat weaker than the N3ÐH3NÁ Á ÁCl5 bond, as revealed by the donor±acceptor distances and NÐHÁ Á ÁCl angles ( Table 2). The charge-assisted hydrogen bonds are medium±strong and agree well with the average NÁ Á ÁCl separation [3.05 (5) A Ê ] calculated for 18 hydrogen-bonding contacts between pyridinium and Cl À in 13 relevant structures reported to the Cambridge Structural Database (CSD, Version 5.27, update of May 2006; Allen, 2002). The NÐHÁ Á ÁCl angle in these complexes averaged 164 (8) .

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Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

Cited by 15 publications

References 28 publications

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

Preparation and characterization of azaindolyl-azaindole and structure of its halogen-free dicationic cluster containing the µ₄-oxotetracopper(II) core

A long Nb=O double bond in bis(pyridinium) tetrachlorooxo(pyridine-κN)niobate(V) chloride

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Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

Cited by 15 publications

References 28 publications

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ1-N1 Coordination

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ1-N1 Coordination

Preparation and characterization of azaindolyl-azaindole and structure of its halogen-free dicationic cluster containing the µ4-oxotetracopper(II) core

A long Nb=O double bond in bis(pyridinium) tetrachlorooxo(pyridine-κN)niobate(V) chloride

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Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

Homoleptic Transition Metal Complexes of the 7-Azaindolide Ligand Featuring κ¹-N1 Coordination

Preparation and characterization of azaindolyl-azaindole and structure of its halogen-free dicationic cluster containing the µ₄-oxotetracopper(II) core