4.4- Dimethyl-2,2-bipyridyl ligand

The element symbols within each formula are arranged according to a modified Hill system in which the order is metal(s), C, H and then any remaining symbols arranged alphabetically. Compounds containing two (or more) different metals appear twice (or more), being listed under each metal. Common ligand abbreviations which appear in the text have also been used in the index. These include acac (acetylacetone), bipy (2,2 -bipyridyl), diars [o-phenylenebis(dimethyl-arsine)], dien (diethylenetriamine), etc. 

Bis(bipyridyl)nickel(0) has been prepared by metal-vapor methods and electrochemical data were obtained for it. In these low-valence states, a significant proportion of the electron density lies on the bipy ligand.2469 Also, the crystal and molecular structure of 4,6-dimethyl-2,2 -dipyr-idyldicarbonylnickel(O) (1021) has been determined. The coordination geometry about Ni is tetrahedral.2470... 

Interesting complexes have been prepared from the chiral ligands derived from 3,3 -dimethyl-2,2 -bipyridyl Af,JV -dioxide (216,217).955,956 A number of diastereomeric tris complexes were isolated. These could be interconverted photochemically. 

Abbreviations arene, i/6-benzene or substituted benzene derivative bipy, 2,2 -bipyridyl Bu, Bu", Bu, iso-, n-, or rerf-butyl COD, 1,5-cyclo-octadiene Cp, /5-C5H5 DAD, dimethyl-acetylene dicarboxylate dam, 1,2-bis(diphenylarsino)methane DBA, dibenzylideneacetone DMF, A. A -dimethylformamide dpe, l,2-bis(diphenylphosphino)ethane dpen, os-l,2-bis(di-phenylphosphino)ethylene dpm, 1,2-bis(diphenylphosphino)methane ESR, electron spin resonance F6-acac, hexafluoroacetylacetone FN, fumaronitrile MA, maleic anhydride Me, methyl MLCT, metal ligand charge transfer phen, 1,10-phenanthroline Pr , Pr", iso- or n-propyl py, pyridine RT, room temperature TCNE, tetracyanoethylene tetraphos, (Ph2PCH2CH2)jP THF, tctrahydrofuran Xylyl, 2,6-Me2C6H3. 

In many cases ligands are abbreviated by giving a substituent and its location followed by the ligand abbreviation (e.g., 4,4 -Me-bpy would be 4,4 -dimethyl-2,2 -bipyridyl). In tables collecting complexes of one ligand type only the substituent is given. Ligand structures appear in Fig. 1. 

Nakamaru, K. (1982) Synthesis, luminescence quantum yields, and lifetimes of trischelated ruthenium(II) mixed-ligand complexes including 3,3 -dimethyl-2,2 -bipyridyl, Bull. Chem. Soc. Jpn. 55, 2697-2705. 

When dibenzotellurophene dichloride in acetone was refluxed with the following ligands, adducts with one or two ligands per dibenzotellurophene dichloride molecule were formed1 dimethylacetamide (2), dimethyl sulfoxide (2), 1,2-diaminoethane (1), N,N -diphenylthiourea (2), bis[dimethylaminothiocarbonyl] disulfide (1). 4-methylpyridine (2), pyridine Af-oxide (2), bipyridyl (1), 1,10-phenanthroline (1). 

A recent study822 of the effect of steric interactions on the luminescence of 2,2 -bipyridyl complexes of Rh found luminescence from both ligand and metal-centered orbitals of [Rh(dmbpy)3]3+ (dmbpy = 3,3 -dimethyl-2,2 -bipyridyl). At 77 K the metal-centered luminescence dominates, but in fluid solution the ligand-centered emission is enhanced. As in the unsubstituted analogs, ligand-centered luminescence dominates under all conditions for [Rh(dmbpy)2Cl2]+. Luminescence from fluid solutions of [Rh(phen)3]3+ and [Rh(bipy)3]3+ is consistent with the 77K behavior,816 as ligand-centered emission is observed.822... 

A large number of mixed ligand complexes of cobalt(III) are known in which one ligand is either bipyridyl or phenanthroline and the other ligands are, for example, dimethyl glyoxime (569), 8-hydroxyquinoline... 

Substituted bipyridines and phenanthrolines have been used as ligands for copper(II) ions. 4,4 6,6 -Tetramethyl-2,2 -bipyridyl(L) gives monomeric CuL(N03)2, two sulfato complexes, and a series [CuL2X]+C104, as well as forming copper(I) complexes readily (309). 2,9-Dimethyl-1,10-phenanthroline affords 1 1 complexes with cupric... 

A mixed-valence complex of Ru(bpy)2 bridged by l,10-bis[4 -methyl(2,2 -bipyridyl)]-3,8-dimethyl-l,3,5,7,9-decapentene, i.e., with five double bonds constituting the spacer between 2,2 -bipyridine ligands, has been described by Lehn and co-workers [32b]. Hush s analysis of the intervalence transition gave = 0.018 eV for a 24 A metal-metal distance. 

Boron-substituted pyridine reagents can be used to construct the bipyridine ring system by coupling them with halopyridines in the presence of a Pd° catalyst and a base (Suzuki method). Various ligands have been made in this manner in moderate to high yields, including 2,3-bipyridine (85%)41 and 3,5-dimethyl bipyridine (60%) 42 One valuable feature of the Suzuki method is that it is compatible with stannanes. A pyridyl diethylborane has been coupled to a tributyl tin-functionalized pyridyl bromide.43 This compatibility is useful for polypyridine syntheses because subsequent Stille coupling of the bipyridyl stannane is possible. 

Rhodium3+ ions or their complexes with N-donor ligands such as 2,2 -bipyridyl (bipy), 1,10-phenanthroline (phen) or 2,9-dimethyl-1,10-phenanthroline (dmp) inserted... 

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