Cobalt complexes with hydrocarbons

As a result, the reduction of cobalt from the divalent to the zero-valent state changes the chemistry of the system, since Co° readily forms complexes with hydrocarbons. This was confirmed by subsequent adsorption of propene, which produced the EPR spectrum shown in Figure 1.23D, with spin Hamiltonian parameters ofg, = 2.096, gy = 1.924, = 2.297, A = 12, Ay = 52, = 99G. This... 

Diketonate cobalt(III) complexes with alkyl peroxo adducts have been prepared recently and characterized structurally, and their value in hydrocarbon oxidation and olefin epoxidation examined.980 Compounds Co(acac) 2(L) (O O / - B u) with L = py, 4-Mepy and 1-Meim, as well as the analog of the first with dibenzoylmethane as the diketone, were prepared. A distorted octahedral geometry with the monodentates cis is consistently observed, and the Co—O bond distance for the peroxo ligand lies between 1.860(3) A and 1.879(2) A. 

Careful studies by Doyle et al. (163) have also shown that soluble ruthenium species are inactive for hydrocarbon formation. A soluble system could be maintained in heptane solvent at 250°C under 100 atm of 1 1 H2/CO for many hours by taking precautions to avoid the possible introduction of impurities into the system and by slowly raising the temperature. No hydrocarbon formation was observed in this reaction. Only upon heating to about 260°C was the disappearance of soluble ruthenium complexes noted, along with the formation of linear alkanes. These results may suggest that metastable homogeneous ruthenium solutions can be formed, as has been reported for cobalt complexes (56) precipitation of the metal may be an autocatalytic process. 

Cobalt vapor interacts with norbornene to produce Co(C7H10)3, a 15-electron complex, apparently isostructural with Ni(C7H10)3. The cobalt complex is soluble in hydrocarbon solvents to afford deep blue solutions decomposing rapidly and autocatalytically at -15° (5a, 134). It has not yet been possible to isolate this complex in a pure state but some of the reactions have been examined by trapping experiments ... 

When triethylamine is added to cobalt salts in hydrocarbon solvents, bright blue complexes are produced which are soluble in solvents such as benzene. With cobalt chloride, adding diethylaluminum chloride increases... 

The trimeric lithium-cobalt complex [LiCo(C2H4)(PMe3)3]3 (69) 94), the first lithium carrier in hydrocarbon solvents, clearly involves interactions of the lithium atom with the hydrocarbon ligands as well as the cobalt atoms, but further ligation with solvent donor atoms is not required. 

Another cobalt complex having only hydrocarbon ligands, (1,3-butadiene)cyclopentadienylcobalt, has been obtained as a volatile red solid melting at 103°-105°C by reaction of the diene with dicyclopenta-dienylcobalt or (1-benzoyl-1,3-cyclopentadiene)cyclopentadienylcobalt (489). The compound decomposes slowly in air. 

The sodium salt of IBA proved to be quite stable, selective, and sensitive, unfortunately the reaction was not reversible, and the sensitivity decreased with each sample injection. However, a cobalt complex of IBA was made, and found to remedy the situation. Further improvement of the coating could be obtained by the addition of small amount of pesticide to the methylene chloride solution of the cobalt-lBA complex. A modified coating with paraoxon was found to be more sensitive to parathion than DDVP and DIMP. No serious interference was observed from SO2, CO2, CO, NO2, NH3, and chlorinated hydrocarbon pesticides except if combined by solvent. 

Formation of free radicals in the presence of transition metal compounds may be the result of their interaction with hydrocarbon or dioxygen. Such catalysts as cobalt and manganese salts are usually introduced in the bivalent state. An inaease of chain initiation rate here may be connected with the activation of dioxygen by a metal complex via the following reaction [8] ... 

Chelating agents can be used as metal deactivators. But prior to their use in a given plastic formulation, it is necessary to know the entire composition of the mixture. The activity of some metals bound in complexes might exceed that of simple systems and thus accelerate self-oxidation. For example, bis-salicyli-dene-ethylenediamine, when used with hydrocarbons, strongly accelerates their oxidation in the presence of iron and cobalt ions, but in the presence of copper, in concentration four times larger than that of the metal, it inhibits selfoxidation of hydrocarbons [59]. 

A preliminary report is published of work which, though incomplete mechanistically, is of sufficient interest in connection with the Co-C bond to justify inclusion here/ Hydrocarbons R , RH, and R2, are formed from the alkyl-mer- AT-(2-aminoethyl)-7-methylsalicylideneminato (ethyl-enediamine)cobalt ion, [RCo(7-Mesalen)(en)], in aqueous perchloric acid. Use of DCIO4 in D2O shows that RH is formed from the cobalt complex although RN(0)(t-Bu) radicals could be trapped on addition of t-BuNO. There is an induction period this is decreased and the steady-state concentration of RN(0)(t-Bu) is increased as acidity rises. Two diol-dehydrase reactions catalyzed by B12 coenzyme can also be made to occur using this system. 

Treatment of dicobalt octarbonyl with a 2 1 mixture of t-butylacety-lene and acetylene forms a remarkable cobalt complex of stoicheimometry Co2(CO)4(C2HBu )2(C2H2). The structure of this compound, 9.7, provides a fascinating insight into a mechanism of polymerization of acetylenes. The bonding of the hydrocarbon residue in complex, 9.7, may be described in terms of a fly-over , bis-enyl system. The distance Co—C3 (fl enyl) is 2-04 A. 

Two known cobalt complexes of cyclooctatetraene are of the type CgHg(CoC5H5) , with = 1 or 2. In the mononuclear complex COT acts as a 1,5-diene with the eight-membered hydrocarbon in the tub configuration 153,154), while the binuclear complex probably has a central CgHg ligand with a plane tetragonal structure 147,154). 

Fluorination of aliphatic hydrocarbons with cobalt trifluoride gives complex mixtures Isobutane (2-methylpropane) fluorinated at 140-200 °C affords a mixture of 30 products of different degrees of fluorination and of isobutane as well as butane skeletons. The tertiary hydrogen is replaced preferentially Products containing 5-10 atoms of fluorine including a small amount of perfluoroisobutane were isolated [10]. 

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