Bipyridyl zinc complexes

The complexes of zinc and cadmium with Schiff bases derived from salicylaldehyde and propan-2-olamine or 2-aminomethylpropanol have been reported,57 as well as their complexes with ethanolamine and propan-2-olamine.58,59 Zinc complexes of stoicheiometry ZnL2X2 have been obtained where L = benzoyl- and salicyl-hydra-zones of vanilline. furfural, and cinnamaldehyde. Zinc complexes of several substituted o-bydroxybutyrophenones and their oximes have been reported.60-62 Complexes of stoicheiometery ZnL2U have been reported where L = the a-nitroketonato-anion obtained from nitroacetone, 3,3-dimethyl-l-nitrobutan-2-one or 3-nitrocam-phor and L — bipyridyl or 1,10-phenanthroline.63... 

Complexes of zinc dialkyldithiocarbamates with bidentate nitrogen ligands such as 1,10-phen-anthroline have been structurally characterized.563 The related complexes (4,4 -bipyridyl)... 

Other workers have employed different sensitiser systems, e.g. duel sensitisation by a zinc porphyrin and copper phthalocyanine on TiOj, Eosin Y or tetrabro-mophenol blue on ZnO, and a ZnO/SnOj mixture with a ruthenium bipyridyl complex, to produce good energy conversion factors. 

Reduction of a cobalt(II) halide in presence of 2,2 -bipyridyl with zinc in THF-ethanol leads to cobalt(I)-bipyridyl complexes which hydrogenate butadiene to cis-2-butene at 25 °C and normal pressure of hydrogen. For different halides the rate decreases in the order I>Br>Cl. 1,10-Phenanthroline complexes were also active.64 Here again, the catalyst does not tolerate an excess of diene. The proposed mechanism for the hydrogenation is given in Scheme 4. 

The open-isomer of DTE having two zinc porphyrin moieties could form coordination complex with 4,4-bipyridyl like a tweezer (see Scheme 4), but the closed isomer could not bind cooperatively because of its structural rigidity. The different binding behavior of ZnP-DTE-ZnP with 4,4-bipyridyl was though to make the photo-control of affinity to guest molecules possible. 

An extension of this work has resulted in the synthesis of related 6,6-disubsti-tuted (bipyridyl) ligand derivatives containing pyromellitimide spacers connected with propynyl, butynyl and propynyloxy linkers.The first of these ligands was shown to yield a chiral di-zinc(II) cationic complex of type [Zn2L2] . This species is stabilised by the presence of an aromatic guest p- or o-dimethoxybenzene) in its cavity. Related dinuclear species were also shown to form with cadmium(II) and nickel(II). 

Spectra have also been reported for alkaline earth complexes of bipyridyl, terpyridyl, and substituted bipyridyls and phenanthrolines (106,107) of the type M +(L )2. For Be, Mg, Ca, and Sr the spectra show the presence of a ground, orvery lowexcited, triplet state consistent with a divalent metal cation in a tetrahedral environment with one electron on each chelate ligand. The similarity in splittings for Be and Mg is thought to show that interligand interactions prevent the achievement of the small Be + ionic radius. Treatment of bipyridyl with zinc amalgam does... 

A number of stannyl-zinc and -cadmium compounds have been prepared by reaction of a tin-alkali metal compound with a zinc or cadmium halide, or a tin hydride with an alkyl-zinc or -cadmium compound. The coordination of a ligand such as a triphenyl-phosphine, TMEDA, or bipyridyl, or a solvating solvent such as DME, both enhances the nucleophilicity of the alkyl group in the alkylmetallic compounds and stabilises the stannylmetallic product. Thus triphenyltin hydride reacts with diethylzinc or diethylcad-mium in pentane or benzene with separation of metallic zinc or cadmium, but with a preformed complex, or in a coordinating solvent, the distannylmetallic compound is formed (e.g. equation 19-32). 

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