Terpyridines 2,2 :6 ,2"-terpyridine

The unstable pale blue-green bis(2,276, 2 -terpyridine)iron(3+) ion [47779-99-7], [Fe(terpy)2], has been obtained by oxidation of [Fe(terpy)2]. It is very unstable with respect to reduction by solvent and ligand dissociation. The perchlorate salt [2153642-5] has been reported. 

Like mthenium, amines coordinated to osmium in higher oxidation states such as Os(IV) ate readily deprotonated, as in [Os(en) (NHCH2CH2NH2)] [111614-75-6], This complex is subject to oxidative dehydrogenation to form an imine complex (105). An unusual Os(IV) hydride, [OsH2(en)2] [57345-94-5] has been isolated and characterized. The complexes of aromatic heterocycHc amines such as pyridine, bipytidine, phenanthroline, and terpyridine ate similar to those of mthenium. Examples include [Os(bipy )3 [23648-06-8], [Os(bipy)2acac] [47691-08-7],... 

Newkome employed this methodology in his synthesis of halogenated terpyridines. The requisite pyridinium ion 62 was prepared from the corresponding... 

Construction of one-dimensional multicomponent molecular arrays, transition metal complexes with terpyridines and/or porphyrins as ligands 98EJI1. 

Electrochemistry of supramolecular systems with heterocyclic fragments as host molecules (porphirinoids, complexes on the basis of 2,2 -bipyridine and 2,2, 2"-terpyridine, hetero- and heteracyclophanes) 98AG(E)216. 

Vectorial transfer of electronic energy in rod-like ruthenium-osmium complexes with bis-2,2, 2"-terpyridine ligands 97CC333. 

The crude 2,2 -bipyridine obtained from the reaction of pyridine and degassed Raney nickel was found to contain 1.5% of 2 6, 2"-terpyridine, but no 2,2 2, 2" 6 ",2 "-quaterpyridine could be detected. Moreover, experiments with 2,2 -bipyridine and Raney nickel have failed to yield quaterpyridine, and the amount of terpyridine formed in experiments with mixtures of pyridine and 2,2 -bipyridine was found to be no higher than in the reaction with pyridine itself. " ... 

From the dimensions of the lattice of W-6 Raney nickel, it seems that the formation of 2,2 6, 2"-terpyridine would be expected when one molecule of 2,2 -bipyridine and one molecule of pyridine are... 

Abbreviations edta = ethylenediamine-tetraacetic acid, bipy terpyridine, TPMPyP = tetrakis(4-N-methylpyridyl)porphyrin... 

Pyridine-based N-containing ligands have been tested in order to extend the scope of the copper-catalyzed cyclopropanation reaction of olefins. Chelucci et al. [33] have carefully examined and reviewed [34] the efficiency of a number of chiral pyridine derivatives as bidentate Hgands (mainly 2,2 -bipyridines, 2,2 6, 2 -terpyridines, phenanthrolines and aminopyridine) in the copper-catalyzed cyclopropanation of styrene by ethyl diazoacetate. The corresponding copper complexes proved to be only moderately active and enantios-elective (ee up to 32% for a C2-symmetric bipyridine). The same authors prepared other chiral ligands with nitrogen donors such as 2,2 -bipyridines 21, 5,6-dihydro-1,10-phenanthrolines 22, and 1,10-phenanthrolines 23 (see Scheme 14) [35]. 

Kwong and Lee [39] prepared various chiral 2,2 6, 2"-terpyridines and tested them as copper ligands for the cyclopropanation of alkenes. High enantioselectivities were obtained, the presence of bulky alkyl groups at the 8-position of the tetrahydroquinoline ring being crucial (structure 29 in Scheme 17). Thus when = Bu, up to 90% ee for the trans and 94% for the cis isomer were obtained by performing the reaction at 0 °C (transIds = 69/31). 

Chelucci et al. [41] synthesized further chiral terpyridines derived from (-)-yd-pinene, (-i-)-camphor, and (-l-)-2-carene and tested their ability to chelate copper or rhodium for the asymmetric cyclopropanation of styrene. The copper catalysts were poorly efficient and selective in this reaction. The corresponding rhodium complexes led to the best result (64% ee) with the ligand derived from (-l-)-2-carene (ligand 33 in Scheme 17). 

To mimic the square-pyramidal coordination of iron bleomycin, a series of iron (Il)complexes with pyridine-containing macrocycles 4 was synthesized and used for the epoxidation of alkenes with H2O2 (Scheme 4) [35]. These macrocycles bear an aminopropyl pendant arm and in presence of poorly coordinating acids like triflic acid a reversible dissociation of the arm is possible and the catalytic active species is formed. These complexes perform well in alkene epoxidations (66-89% yield with 90-98% selectivity in 5 min at room temperature). Furthermore, recyclable terpyridines 5 lead to highly active Fe -complexes, which show good to excellent results (up to 96% yield) for the epoxidation with oxone at room temperature (Scheme 4) [36]. 

With the iron complex [Fe(Cl3terpy)2]( 104)2 (Clsterpy = 4,4, 4"-trichloro-2,2 6, 2"-terpyridine) as catalyst, sulfamate esters react with Phl(OAc)2 to generate iminoiodanes in situ which subsequently undergo intramolecular nitrenoid C-H insertion to give amidation products in good yields (Scheme 30) [48]. 

MeOPh-terpy = 4 -(4-methoxyphenyl)-2,2, 6. 2"-terpyridine. 4-MeS-terpy = 4 -(4-methylsulfanyl-2,2, 6. 2"-terpyridine. bimm = bis(l-methyl-2-imidazolyl)methoxymethane. BPMA= HN(CH2-2-C5H4N)2. 

Constable, E.C., Henney, R.P.G., Leese, T.A. and Tocher, D.A. (1990) Cyclometallation reactions of 6-phenyl-2,2 -bipyridine a potential C,N,N-donor analogue of 2,2 6, 2"-terpyridine. Crystal and molecular structure of dichlorobis (6-phenyl-2,2 -bipyridine)ruthenium(II). Journal of the Chemical Society, Dalton Transactions, (2), 443. 

Pitteri, B., Marangoni, G., Visentin, F., Bobbo, T., Bertolasi, V. and Gilli, P. (1999) Equilibrium and kinetic studies of (2,2 6, 2"-terpyridine)gold(III) complexes. Preparation and crystal structure of [Au(terpy)(0H)][C104]2. Journal of the Chemical Society, Dalton Transactions, (5), 677. 

---