Cobalt complexes bidentate

Azo compounds o-am ino-o -hydroxy diary 1 transition metal complexes, 6,57 bidentate dyes, 6,42 o,o -diaminodiaryI cobalt complexes, 6,58,60 o,o -dihydroxydiaryl copper complexes. 6.55,57 pK 6,47... 

Formazan, l-(2-hydroxy-5-suIfophenyl)-3-phenyl-5-(2-carboxyphenyl)-zinc detection, 6, 83 Formazans cobalt complexes dyes, 6, 81 metal complexes bidentate, 6, 78 color photography, 6,111 dyes, 6, 77 tetradentate, 6, 81 tridentate, 6, 79... 

The cobalt complexes reported in Fig. 17.20 can be easily produced by mixing 1 equivalent of [ ( 20) ]2 + with 3 equivalents of a bidentate ligand or 2 equivalents of a tridentate ligand under magnetic stirring in refluxing methanol for 2 h. Addition of ethyl ether results in the precipitation and isolation the product that is then usually used without any further purification. 

Scheme 4 shows a platinum catalyst 1 containing such a bis-SPO bidentate ligand anion, designed for the hydroformylation of ethylene and of 1-heptene, and various other, similarly built, platinum catalysts. Catalyst 1 has an activity comparable to that of the commercial cobalt catalysts that were used at the time and displays a higher selectivity for linear products than the cobalt-containing catalysts (66). Like the latter, the platinum complex exhibits hydrogenation activity to give, in part, alcohols in addition to aldehydes and also produces alkanes (an undesired reaction that implies a loss of feedstock). The catalysts are also active for isomerization, as are the cobalt complexes, and for internal heptene hydroformylation (Table 1), with formation of 60% linear products. 

The effects of geometric and ligand stereoisomerism on Co shielding are reported for a series of tris(bidentate)cobalt complexes involving chiral and achiral -diketones. (231) Owing to the broad lines in some of the asymmetrically coordinated systems separate resonances are not always resolved. 

Not only palladium, but many more non-metallocene late (and early) transition metal catalysts for the coordination polymerization of ethene and 1-olefins were reported [11]. Among the most significant findings in this area are the disclosures of novel highly active and versatile catalysts based on (i) bidentate diimine [N,N] nickel and palladium complexes [12], (ii) tridentate 2,6-bis(imino)pyridyl [N,N,N] iron and cobalt complexes [13], and (iii) bidentate salicyl imine [N,O] nickel complexes [14]. 

Another case involving cobalt complexes was studied by Work (19), who prepared, among others, a compound containing three different bidentate amines—ethylenediamine, trimethylene-diamine, and neopentanediamine, [Co(en)(tn)(dan)]CI3, by following and extending a synthesis first described by Werner (20) ... 

Pyridine and related ligands. The crystal structures of [M(py)2(N03)2] (M = Co, Cu, or Zn) have been determined and the overall molecular geometries are very similar for all three compounds. In all of these complexes the nitrate groups are co-ordinated in an assymetric bidentate manner, the degree of assymetry following the order Co < Zn Cu. Cobalt complexes of the linear quinquedentate ligand pyDPT (75) have been isolated. They are [Co-(pyDPT)X]X,H20 (X = Cl, Br, 1, or NO3), [Co(pyDPT)](PF6)2, and... 

A single report documents the study of perfluoroalkyl poly(pyrazolyl)borate cobalt complexes however, their breadth and significance is appreciable. The compounds H B(pz)4 CpCo(Rf) (x = 0, 1,2) were prepared by the interaction of the respective K[H B(pz)4 J salt with CpCo(Rf)(CO)I, and in each case exhibit bidentate coordination of the poly(pyrazolyl)borate ligand, regardless of the number of pyrazole donors potentially available. 

In the context of unicyclic networks, one further case must be considered for completeness and this is the case of disjoint unicyclic mechanisms. In this case, assume that there are two precursors which independently and selectively effect alkene hydroformylation and that the mechanisms do not share any common intermediates whatsoever. Perhaps the first precursor is a bidentate phosphine-substituted monmiuclear cobalt complex, and the second precursor is a mononuclear rhodium complex. This situation can be represented in shorthand notation as shown in Fig. 6a. 

Of the three modes of coordination between a bidentate phosphine ligand and a metal complex (Fig. 8), the chelating mode (B) is most common. The active cobalt-catalyst generated by the reduction of Co " or Co " with EtjAlCl is probably a five-coordinated cobalt complex. Two olefins in NBD and the acetylene occupy three of the five coordi-... 

Chiral cobalt complexes have been used to control stereochemistry. A successful strategy described by Verdaguer uses bidentate ligands... 

There are few examples where the absolute stereochemistry is determined in the PKR. Verdaguer has demonstrated the use of a bidentate phosphorous-sulphur ligand to provide an enantiopure cyclopentenone in for the synthesis of the HIV drug (-)-abacavir. The achiral alkyne cobalt complex is generated first in 1 h at room temperature. Heating with enantiopure R,S-ligand 102 provides a separable mixture of diastereomeric... 

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