Cobalt complexes imines

The metal-catalyzed oxidation of imines using molecular oxygen as the final oxidant and aldehydes as co-reductants has been studied223. Various transition metal complexes have been tested as catalysts and it is found that cobalt complexes can catalyze the selective oxidation of imines to oxaziridines in good yield (ca 80%) (Scheme 4). 

Acyclic /V-alkylimines, asymmetric hydrogenation, 10, 56 Acyclic ( j3-allyl)cobalt complexes, oxidation reactions, 7, 58 Acyclic allylic esters, alkylation, 11, 76 Acyclic aromatic imines, asymmetric hydrogenation, 10, 56 Acyclic 1-buly l-( )5-pencadienyl) iron cations, preparation and reactivity, 6, 156... 

There are some reports on the asymmetric catalytic hydrogenation of C=N double bonds. Rhodium phosphine complexes do not have high activity, and the stereoselectivity is low. - Homogeneous hydrogenation of oximes, Schiff s bases and cyclic imines " have been reported. A cyano cobalt complex has been used for the homogeneous catalytic hydrogenation of oximes and Schiff s bases but the degree of asymmetric induction is unknown. 

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]. 

A cobalt complex 8 containing a redox active tetradentate bis-iminopyridine framework has been reported to support a water reduction catalyst, with activities of observed rate constant, of 10 M s derived from voltammetry measurements (Scheme 3) [16]. Ligand-centered reduction of the coordinated imine function has been proposed as the first electrocatalytic step followed by protonation. Notably, this compound was shown to operate even under basic conditions at pH 8 (buffer) to give 10 liter of H (mol catalyst" h" ) albeit with a modest Faradaic efficiency of only 60%. 

Table 5. Iron and Cobalt Complexes Bearing Pyridylbis(imine) Ligands...

Cyclometalation Reactions Involving C-Cl Bond Activation of Ortfio-Chlorinated Substrated with Imines as Anchoring Groups by Cobalt Complexes... 

In 2015, Kempe and co-workers reported the first cobalt-catalyzed A-alkylation of (hetero)arylamines with alcohols under mild conditions (80 °C) with a relatively low catalyst loading (2 mol%) (Elq. 32) [133]. In 2016, Zhang and co-workers developed another pincer cobalt complex 19, which is an active catalyst for both imination and A-alkylation reactions of aromatic and aliphatic amines with alcohols under base-free conditions [134]. By using complex 19, monoalkylated amine products rather than the imines can be selectively achieved by simply adding 4 A molecular sieves to the reaction mixture (Eq. 33). 

Although the same experiment could be carried out with an aqueous solution of a low molecular weight amine—cobalt(II) complex, the cobalt-poly (ethylene imine) solution provides the crucial advantage of no amine odor. The cobalt complex attached to the poly(ethyleneimine) cross-linked with poly(epichlorohydrin) was prepared as a rubbery gel or film and studied for its oxygen-absorbing properties [24]. 

Palladium complexes also catalyze the carbonylation of halides. Aryl (see 13-13), vinylic, benzylic, and allylic halides (especially iodides) can be converted to carboxylic esters with CO, an alcohol or alkoxide, and a palladium complex. Similar reactivity was reported with vinyl triflates. Use of an amine instead of the alcohol or alkoxide leads to an amide. Reaction with an amine, AJBN, CO, and a tetraalkyltin catalyst also leads to an amide. Similar reaction with an alcohol, under Xe irradiation, leads to the ester. Benzylic and allylic halides were converted to carboxylic acids electrocatalytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions. ... 

A series of complexes in which the cyanide ligands are modified or replaced arises from the decomposition of methyl and pyridiomethylcobalt(111) pentacyanide derivatives in acid solution. The reactions include protonation of a cyanide ligand, insertion of a cyanide ligand between the organic group and the cobalt atom to produce an imine (see Section VI,D), decomposition of this imine to an acyl product, and replacement of a cyanide ligand by water 100, 101). The products are listed in Table III, 29. 

Highly c/s-selectivity and low molecular weight distribution polymerization of l -butadiene with cobalt(II) pyridyl bis(imine) complexes in the presence of ethylaluminum sesquischloride effect of methyl position in the ligand... 

Table 1. Solution polymerization results for butadiene usir cobalt(II) pyridyl bis(imine) complexes. Polymerization conditions [l,3-butadiaie]= 1 mol/L [Cal.] = 2.00 x 10" mol/L ...

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