Short syntheses of rigid acyclic or macrocyclic poly-imine ligands and their use in Ru(II), Fe(III), and alkali metal complexation

Abstract

ROBERT DASH and PIERRE G. POTVIN. Can. J. Chem. 70, 2249 (1992. Lipophilic derivatives of 2,6-bis(3-pyrazoly1)pyridine and 1,3-bis (3-pyrazoly1)benzene were obtained in acceptable yields by Stork reactions and transformed by N-alkylations into three pentadentates, three bis(bidentates), and one macrocyclic octadentate ligand. The parent bis(pyrazoly1) pyridine constituted a terpyridine analogue and readily formed a Ru(I1) complex. By comparison of 'H nuclear magnetic resonance patterns, it was found that the alkylations in the bis(pyrazoly1)pyridine series conferred an anti,anti conformation of the imino nitrogens. The pentadentates were then able to extract alkali metal ions into CHCI, with only modest strength and selectivity, but the preferred extraction of Li' by one of these was notable. By variation of the reaction conditions, a tri-iron(II1) and a di-iron(II1) complex were obtained from a bis(bidentate).ROBERT DASH et PIERRE G. POTVIN. Can. J. Chem. 70, 2249Chem. 70, (1992. Des derives lipophiles de la 2,6-bis(3-pyrazo1yle)pyridine et du 1,3-bis(3-pyrazoly1e)benzkne furent prepares en rendements acceptables par des reactions de Stork, puis N-alkylks pour fournir trois pentadentates, trois bis(bidentate) et un octadentate macrocyclique. En tant qu'analogue de la terpyridine, la bis(pyrazolyle)pyridine forma aisement un complexe au Ru(I1). D'aprks la resonance magnetique nuclkaire, les alkylations de la bis(pyrazoly1e)pyridine ont force l'adoption de conformations anti,anti et les pentadentates etaient donc de modestes recepteurs pour les cations alkalins et ont demontrk une faible sClectivit6 en extraction dans le chloroforme. Neanmoins, on souligne l'extraction preferentielle du Li' par l'un d'eux. Un bis(bidentate1 forma, selon les conditions employees, des complexes bi-et tri-nuclkaires avec le Fe(II1).

Mono- and Dinuclear Ruthenium(II) Complexes of 2,6-Di(pyrazol-3-yl)pyridines: Deprotonation, Functionalization, and Supramolecular Association

“…This facility has enabled us to prepare a variety of substituted tridentates 8,11,12 and a ditopic bis(tridentate) 11 as well as novel pentadentate and macrocyclic 7 ligands. We have also demonstrated how these ligands can bind alkali metal ions, Fe(III), Ru(II), ,, Zn(II), and Co(II). , The liposolubilities of H 1 and H 2 2 and their derivatives and complexes have proven to be synthetically very advantageous.

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“…We wished to similarly examine complexes of the tridentate analogue of H 1 , the symmetrical 2,6-di(tetrahydroindazol-3-yl)pyridine H 2 2 , which is also easily prepared. , Like H 1 but unlike the 1‘( N ‘),2-linkage isomers, , H 2 2 is amenable to modification at the 1( N )-H sites. This facility has enabled us to prepare a variety of substituted tridentates 8,11,12 and a ditopic bis(tridentate) 11 as well as novel pentadentate and macrocyclic 7 ligands.…”

Chelation-Controlled Regioselectivity in the Synthesis of Substituted Pyrazolylpyridine Ligands. 3. Unsymmetrically Substituted Tridentates and Ditopic Bis(tridentates) en Route to Singly Stranded Helicates

“…It has previously been shown that treatment of bis(pyrazolyl)pyridine 3 with NaH in THF, followed by alkylating agents, leads exclusively to out,out - or 1‘,1‘‘-disubstituted bis(indazol-3-yl)pyridines. , Thus, exhaustive methylation of 3 (2.4 equiv of NaH/THF/room temperature/2.3 equiv of CH 3 I) produced regiomerically pure 1a in 60% isolated yield . Metal chelation was apparently critical in directing the regiochemistry and organic bases, such as DBU or Et 3 N, generated complicated mixtures of out,out , in,out , and in,in regiomers.…”

“…A suitable class of tridentate building blocks are the 2,6-bis(tetrahydroindazol-3-yl)pyridines 1 . They and their bidentate cousins comprise a class of newly developed ligands for transition metals − which are readily prepared from commercially available materials by short routes and in good yields. They are lipophilic and readily form stable, organo-soluble Ru(II), ,, Zn(II), and Co(II) complexes.…”

“…They and their bidentate cousins comprise a class of newly developed ligands for transition metals − which are readily prepared from commercially available materials by short routes and in good yields. They are lipophilic and readily form stable, organo-soluble Ru(II), ,, Zn(II), and Co(II) complexes. Unlike the less versatile 2,1( N )-linked 2,6-bis(pyrazol-1-yl)pyridines 2 , − our 2,3( C )-linked analogues can be functionalized at N H sites, and this facility has been used to prepare pentadentate and macrocyclic octadentate species 2 as well as ligands bearing acetic or benzoic acid side-chains. , Ligands bearing peripheral ionizable groups are of particular interest as they provide access to anionic, neutral, or cationic complexes under pH control and we wished to employ this to modulate the interactions between photoexcited Ru II electron donors and cationic electron acceptors such as methylviologen.…”