4 - -2,2 :6 ,2"terpyridine

Evaporation of the filtrate and trituration of the oily solid with 10 1 hexanes/cyclohexane affords an additional 2.80 g (mp 85-86°C) for an overall yield of 25.25 g (54%). Yields for this step are typically in the range 45-55%. The filtrate of this second crop and the orange band from the chromatography still contain more of this valuable ligand. Further chromatography does not appreciably improve this material, as the major impurities coelute with the terpyridine. This additional amount of terpyridine can be isolated from the mixture as Fe(terpy)2(PF6)2 and the ligand separated from the complex by the method of Constable.9 A total of 3.40 g of the iron(II) complex (which corresponds to 1.95 g of terpyridine) can be isolated in this manner. Including this product increases the overall yield to 58%.  

The checkers performed this reaction on 1/5 the scale and reported a yield of 40%. 

Submitted by DONALD L. JAMESON and RONALD K. CASTELLANO Checked by DANIEL L. REGER and JAMES E. COLLINS  

The recent report of a chiral bis(l-pyrazolyl)methane provides the first example of L not based on pyrazole or 3,5-dimethylpyrazole.13-14 The substituted bis(pyrazolyl)methane was prepared by Method A, which gave 

Tris(l-pyrazolyl)methane was first prepared by Hiickel and Bretschneider by the reaction of sodium pyrazolate with chloroform.17 Trofimenko prepared the tris(3,5-dimethyl-l-pyrazolyl)methane by a similar method.2 More recent preparations have utilized both liquid-liquid18 and solid-liquid12 phase-transfer catalysis. The preparation of tris(l-pyrazolyl)methane (E) given below is a modification of the solid-liquid phase-transfer procedure.12 

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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... 

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). 

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. 

The [Co(terpy)2]+ ion (terpy = 2,2 6, 2"-terpyridine) has been found to catalyze the reduction of C02 when the divalent precursor is immobilized on electrode surfaces. The vinyl-substituted terpy analog was electropolymerized to give a film that reduced the overpotential for C02 reduction in DMF and MeCN by more than 1V.104 The activity of this surface-confined species was superior to that of the complexes in solution.105 Similarly, in water, the [Co(terpy)2]2+ ion immobilized and reduced in situ within a Nafion film also catalyzes the reduction of C02106 and H+ ions.107... 

Reaction of 3-(2-pyridyl)pyrazole and 6-(3-pyrazolyl)-2,2 -bipyridine with zinc salts results in mononuclear pseudo-octahedral complexes [ZnL3](PF6)2 and [ZnL2](PF6)2 respectively. The ligands coordinate as neutral mononucleating chelates in a similar fashion to the bidentate 2,2 -bipyridine or tridentate 2,2 6, 2"-terpyridine respectively.153... 

Bipyridines were efficiently used in supramolecular chemistry [104], Since the molecule is symmetric no directed coupling procedure is possible. In addition, 2,2 6/,2//-terpyridine ligands can lead to several metal complexes, usually bis-complexes having octahedral coordination geometries [105,106], Lifetimes of the metal-polymeric ligand depend to a great extent on the metal ion used. Highly labile complexes as well as inert metal complexes have been reported. The latter case is very important since the complexes can be treated as conventional polymers, while the supramolecular interaction remains present as a dormant switch. 

A general strategy developed for the synthesis of supramolecular block copolymers involves the preparation of macromolecular chains end-capped with a 2,2 6/,2//-terpyridine ligand which can be selectively complexed with RUCI3. Under these conditions only the mono-complex between the ter-pyridine group and Ru(III) is formed. Subsequent reaction with another 2,2 6/,2"-terpyridine terminated polymer under reductive conditions for the transformation of Ru(III) to Ru(II) leads to the formation of supramolecular block copolymers. Using this methodology the copolymer with PEO and PS blocks was prepared (Scheme 42) [ 107]. 

E. C. Constable and S. Mundwiler, Metal-ion control of molecular recognition-sugar-functionalised 2,2 6, 2"-terpyridines, Polyhedron, 18 (1999) 2433-2444. 

E. C. Constable, B. Kariuki, and A. Mahmood, New approaches to sugar-functionalised 2,2 6, 2"-terpyridines based upon tetrafluorophenoxy spacers crystal and molecular structures of 4 -(tetrafluoro-4-hydroxyphenyl)-2,2 6, 2"-terpyridine and 4 -(4-methoxytetrafluorophenyl)-2, 2 6, 2" -terpyridine, Polyhedron, 22 (2003) 687-698. 

Di(5-nonyl)-2,2 -bipyridine A-propyl(2-pyridyl)methanimine 2,2 6, 2" -Terpyridine 4,4, 4"-Tris(5-nonyl)-2,2 6, 2"-terpyridine N, N, N, N", /V -Pentamethy ldie(hyelenetriamine 1,1,4,7,10,10-Hexamethyltriethylenetetramine Tris[2-(dimethylaminoethyl]amine Tris[(2-pyridyl)methyl]amine... 

Ru-Os-bis(2,2 6, 2") terpyridine complexes attached to biphenyl spacer groups [273] and the electron transport characteristics of ferrocene covalently bound to OPE rods [274] or oligoaniline junctions [275]. 

The classic low spin [FeN6]2+ systems are those derived from the bidentate diimines 2,2/-bipyridine 1 (bpy) and 1,10-phenanthroline 2 (phen) and the tridentate terimine 2,2/ 6/,2//-terpyridine 3 (trpy). 

Terpyridine moieties have been introduced as a terminal unit of macromolecules. In a subsequent procedure the two-step self-assembly process based on Rum/Run chemistry was used for polymers end-capped with the 2,2/ 6/,2 -terpyridine ligand. More precisely, the terpyridine-functionalized polymers were complexed with RUCI3 to selectively form a mono-complex. In a further step, this mono-complex was reacted under reducing conditions with other uncomplexed 2,2/ 6/,2/-terpyridine-terminated polymer blocks in order to form an asymmetrical AB ruthenium(II) frzs-complex. 

A complete description of the synthetic methodology and the characterization of the obtained metallosupramolecular block copolymers was reported in a recent paper [324]. These compounds have been referred to as metallosupramolecular block copolymers and designated by the acronym Ax-[Ru]-By, where A and B are the two different polymer blocks, -[Ru]- denotes the fczs-2,2/ 6/,2/terpyridine-ruthenium(II) linkage between the A and B blocks, and x and y represent the average degree of polymerization of the A and B blocks, respectively. The chemical structure of a PEB-[Ru]-PEO metallosupramolecular copolymer is depicted in Fig. 23. 

In a very recent set of papers [48,54,59,60,131,132,324-328], the synthesis and characterization of metallosupramolecular amphiphilic block copolymers containing a hydrophilic PEO block linked to a hydrophobic PS or PEB block through a fozs-2,2/ 6/,2/terpyridine-ruthenium(II) complex have been described. These copolymers form the so-called metallosupramolecular micelles . 

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