Cobalt complexes, with nitrogen

Scope of Cobalt(II) and Organo-cobalt Complexes with Nitrogen and Oxygen Donors in OMRP... 

The final product is ferrocyanide and cobaltic EDTA, but this goes through an intermediate which can be isolated, and which is an adduct of these twro. Dr. Wilkins tried this system out in his rapid flow rate system and found a rate of association which was about right for substitution rates on a cobaltous ion. So this seemed to be a case where perhaps the nitrogen end of a cyanide was able to coordinate into a cobaltous complex, with either concomitant cr subsequent charge transfer. Yet no transfer of ligand occurs in the overall reaction. 

Co111 exhibits a greater tendency to form complexes with nitrogen-donor ligands than with oxygen-donor ligands. Thus the azo dye from diazotized 2-amino-1 -hydroxybenzene-5-sulfonamide and acetonylbenzthiazole affords the 1 2 cobalt... 

In 2004, we reported the Cobalt-catalyzed hydrohydrazination of olefins with di-ferf-butyl azodicarboxylate (5) and phenylsilane (Scheme 4.1). Our approach was based on a stepwise introduction of a hydride and an electrophilic nitrogen source, instead of the more classical approach based on electrophilic activation of the olefin followed by addition of a hydrazine nucleophile. This solution to override the inherently low reactivity of aUcenes was first introduced by Mukaiyama for the related Cobalt-catalyzed hydroperoxidation reaction. The introduction of new Cobalt-catalyst 4 was the key for an efficient hydrohydrazination reaction, as the Cobalt-complexes with acetylacetonate-derived ligands used by Mukaiyama promoted direct reduction of the azodicarboxylate. 

The metal ion, e.g. Fe or Co, when in its lower oxidation state can share electron charge with the oxygen molecule adduct. Several iron and cobalt prophyrin derivatives and cobalt-Schiff bases show the necessary reversibility and rates for successful application [e.g. 23]. a, a, a", a" -weso-tetrakis[(o-piralamidophenyl)-po phinato] Co (II) has been complexed with 1-methylimidazole to make a complex (CoPIm) which, when mixed with polybutyl methacrylate gave oxygen permeabilities on the order of 10-9 sec-cm/(cm2-s-cmHg) with a selectivity of about 5 over nitrogen [23]. 

Love and coworkers have reported a series of dinuclear cobalt complexes derived from a rigid binucleating macrocycle H4L 18 as shown in Fig. 26 (150). The synthesis of the dicobalt complex [Co2(L18)] (36) was achieved by an anaerobic transamination reaction between H4L18 and [Co(thf) N(SiMe3)2 2] in THF. The unsaturated species 36 forms a bis(pyridine) adduct, 36 py2 (py — pyridine), which has a cleft-like structure reminiscent of pacman diporphyrin complexes (151,152). Both cobalt ions are square pyramidal, with Col and Co2 displaced out of the N4-basal planes by 0.17 and 0.18 A, respectively. The apical sites are occupied by pyridine nitrogen atoms that are exo and endo to the cleft. Interestingly the endo pyridine is canted and reflects the... 

Pauson-Khand cyclopentenone synthesisThe cycloaddition of an alkene with an alkyne complexed with Co2(CO) usually furnishes a mixture of two cy-clopentenones when the alkene is unsymmetrical. The regioselectivity can be improved markedly if the alkene bears a heteroatom that can coordinate with the cobalt complex. Both sulfur and nitrogen ligands can improve the yield and regio-control of this reaction. 

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