Cobalt acetylacetonate-oxygen

The liquid-phase oxidation of acrolein (AL), the reaction products, their routes of formation, reaction in the absence or presence of catalysts such as acetylacetonates (acac) and naphthenates (nap) of transition metals and the influence of reaction factors were discussed in an earlier paper (22). The coordinating state of cobalt acetylacetonate in the earlier stage of the reaction depends on the method of addition to the reaction system (25, 26). The catalyst, Co(acac)2-H20-acrolein, which was synthesized by mixing a solution of Co(acac)2 in benzene with a saturated aqueous solution, decreases the induction period of oxygen uptake and increases the rate of oxygen absorption. The acrolein of the catalyst coordinated with its cobalt through the lone pair of electrons of the aldehyde oxygen. Therefore, it is believed that the coordination of acrolein with a catalyst is necessary to initiate the oxidation reaction (10). 

Hexaammineplatinum(IV) salts also undergo imine-forming reactions with acetylacetone (equation 49).172 A cobalt(III) acetylacetone complex can be formed as a result of intramolecular addition of cobalt-bound hydroxide ion to acetylacetone. The cobalt-bound oxygen atoms are retained in the new chelate ring (equation 50).173... 

The polymerization of butadiene to 1.2 polymers with anionic Ziegler type catalysts has been studied by Natta and co-workers (46). They have shown that isotactic 1.2-polybutadiene can be produced by the use of catalysts which are made up of components which have basic oxygen and nitrogen structures such as triethylaluminum with cobalt acetylacetonate or with chromium acetylacetonate. Natta and co-workers have shown that either syndiotactic or isotactic structures are produced depending on the ratio of aluminum to chromium. Syndiotactic structures are obtained at low aluminum to chromium ratios while isotactic polybutadiene is obtained at high ratios. The basic catalyst component is characteristic of syndiotactic catalysts. Natta, Porri, Zanini and Fiore (47) have also produced 1.2 polybutadiene using... 

There are now numerous, metal-linked oligomeric (and polymeric) systems that fall into this category. For example, the acetylacetonates of manganese(II), nickel(II) and zinc(II) have long been known to be trimeric while the cobalt(II) complex is tetrameric, with three (3-diketonate oxygen atoms bridging adjacent metal centres in a linear array in each case. Other more recent examples include systems built... 

Chemoselective oxidation of the ring sulfur of penicillin derivatives 100 and 101 has been reported in the presence of cobalt(lll) acetylacetonate and either isobutyraldehyde or propionaldehyde under oxygen to afford the corresponding sulfoxides 102 and 103 in excellent yields as shown in Scheme 35. Overoxidation was not observed and additional functional groups were not affected under these conditions <1996T2343>. 

Because oxidations with oxygen are free-radical reactions, free radicals should be good initiators. Indeed, in the presence of hydrogen bromide at high enough temperatures, lower molecular weight alkanes are oxidized to alcohols, ketones, or acids [5 7]. Much more practical are oxidations catalyzed by transition metals, such as platinum [5, 6, 55, 56], or, more often, metal oxides and salts, especially salts soluble in organic solvents (acetates, acetylacetonates, etc.). The favored catalysts are vanadium pent-oxide [3] and chlorides or acetates of copper [2, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66], iron [67], cobalt [68, 69], palladium [60, 70], rhodium [10], iridium [10], and platinum [5, 6, 56, 57]. 

The cobalt(ll) thiocyanate complex can be extracted with oxygen-containing solvents, such as a mixture of diethyl ether with isoamyl alcohol (1+1), MIBK, or acetylacetone [23,24], The molar absorptivity, e, of the complex in the ether-isoamyl aleohol mixture is about 30% smaller than in the aqueous acetone media. 

Oxidative carbonylation of amines to carbamates and ureas in the presence of cobalt complexes was recently reported (24-25), We have found that Co(II) complexes bearing nitrogen and oxygen-donor ligands such as carboxylates, acetylacetonates and Schiff bases produce DMC with high selectivity in methanol under CO and Oj. (Table VII) (26-27),... 

An interesting approach to the synthesis of phthalimides has been reported that starts from aminoquinoline benzamides (Scheme 3.85) [89]. The reaction entailed the carbonylation of the substrate using a cobalt(II) acetylacetonate as the catalyst. The reaction conditions were remarkably mild and could be carried out without exclusion of air. Indeed, air was critical to the success of the reaction, and the oxygen in air was proposed to act as a terminal oxidant for the process. 

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