ing :atomic numbers greater than 25 and less than 29; and of this group, nickel is particularly preferred. 

The actual chemical structure of the catalyst complex of the present invention is not known. 

Depending upon which metal salt is employed, when from about ’2-5 moles of a trialkyl or triaryl Group III metal, for example, triethylaluminum or triphenyl-alu› minum, are added to one formula weight of the 3-d complex metal salt, a highly active hydrogenation cata› lyst results. A chemical reaction takes place, as gen› erally evidenced by evolution of heat of reaction and the formation of hydrocarbon by-product. 

For the preparation of the effective hydrogenation catalysts of the present invention, particular amounts of organometallic compound must be used for each formula weight of the 3-d complex metal organic acid salt. Thus, when less than one mole of organometallic compound, for example, a trialkylaluminum, fa used for each formula weight of 3-d complex metal salt, the resulting unit hy› drogenation activity of the reaction product is unsatis› factory. Similarly, when more than about 6 moles of the organometallic component is used for each formula weight of the 3-d complex metal salt, unit hydrogenation activity is substantially lower than the values found for the prefer.red ratios, namely, from about 2-5 moles of an organometallic compound per formula weight of the metal salt. Although some variation ,is noted, depending upon the particular 3-d complex element salt being used, the particula11ly preferred range is 2.5-4.5 moles of tri› alkylaluminum per formula weight of salt. 

Although the preparation of the active hydrogenation catalyst complexes of the present invention can be ac› complished by mixing the necessary proportions of es› sentially anhydrous finely divided solid metal salt and organometallic compound, in the presence of an inert atmosphere, preferably, catalyst preparation is accom› plished by reaction in the presence of an inert liquid diluent. An inert atmosphere is one substantially free of oxygen, water vapor, :and other compounds known to be reactive toward organometallics, as well as compounds such as amines, ethers, etc., containing atoms having unshared electron pairs, such as oxygen. Similarly, :an inert diluent is one free of reactive groups (relative to the organometallic component of the catalyst) and elec› tron-pair donor atoms, such as oxygen. Once prepared, the hydrogenation catalysts, surprisingly, appear to suffer no ill effects from contact with ethers, ,alcohols, ketones, esters, amines, nitriles, and the like, whereas prior con› tacting of the organometallic compound and the metal salt in the presence of an ether, such as tetrahydrofuran, does not result in the production of :active hydrogenation catalysts. 

Inert diluents useful in catalyst preparation are, in general, hydrocarbons, including benzene, toluene, t-butyl› benzene, white oils, hydrocarbon waxes, pentane, heptane, and olefins. Where the unsaturated feed to be hydro› genated is a hydrocarbon, naturally preparation in situ is particularly convenient because subsequent purifica› tions, if required, are greatly simplified. Similarly, where an unsaturated hydrocarbon diluent is used in catalyst preparation, some hydrogen may be consumed in saturat› ing it, but no substantial disadvantages are experienced. 

Except in their use as hydrogenation catalysts for the !!"eduction of unsaturated hydrocarbons, preferably ,and advantageously, the catalyst complexes of the present invention are prepared in advance of use in an inert dilu› ent. The catalyst components react rapidly, even at moderate :temperatures, i.e., from about 0°-100° C., as well as at reduced and elevated temperatures, i.e., from about -50° to about 200° C., and higher, but below the well-known thermal decomposition temperature of the 3-d complex metal salts and the organometallic com› pounds. In general, but with some relatively minor vari› ation, depending upon the nature of the material to be hydrogenated, and the particular metal salt employed, 

the hydrogenation catalysts may be used as catalysts over a wide range of temperature, such ,as, for example, -10° C. to as high as 300° C. Preferably, useful tem- peratures are in the range from about ’20° to 200° C. 

The 3-d complex metal salts useful in the preparation of the hydrogenation catalysts must be salts of acidic organic compounds. In general, salts of organic acids having pKa values as measured in an ether medium at 25° C. in the range 1-20 are satisfactory metal salts for use in the catalyst preparation. Preferably, the acid is composed of only carbon, hydrogen, and oxygen, and contains 1 or 2 acidic hydrogen atoms. 

The preferred metal salts are salts of monobasic, strongly-acidic, organic acids having pKa’s less than 9. In general, these acids are carboxylic acids having from 1-25 carbon atoms per molecule, containing only hydro› gen, carbon, and oxygen. 

By monobasic is meant an organic acid having only one acidic ,hydrogen per molecule within the pKa range from 1-20. 

Particularly preferred for catalyst preparation are the 3-d complex metal salts of monobasic, strongly-acidic, organic acids, the salts of which are soluble in benzene at 25 ° C. to some appreciable degree, i.e., of the order of about 0.1 weight percent and higher, based on ben› zene solvent. In general, these metal salts will be those of organic acids having from about 6-25 carbon atoms per molecule, and these limits can vary in some slight degree, depending upon the particular metal cation and upon the carbon structure of the hydrocarbon skeleton of the metal salt anion. 

Of the 3-d complex metal hydrogenation catalysts con› templated in the present invention, those catalysts pre› pared by the use of hydrocarbon or inert-medium solu- ble nickel salt are most preferred, because of substantial advantages experienced in their use in catalyst prepara› tions and because of the exceptionally high unit activity of the resulting nickel hydrogenation catalyst complexes in the hydrogenation of reducible organic compounds. Thus, while the medium insoluble nickel salts of organic acids upon reaction with the required amount of the or› ganometallic compound generally yield active but par› tially agglomerated catalyst complexes, the catalyst ob› tained from the medium soluble nickel salts are stable complexes of extremely fine division, generally capable of remaining dispersed even in ultra-high centrifuge force fields, such as one generated at 60,000 r.p.m. for long periods. 

Less desirble than the metal salts of strongly-acidic organic acids, but nonetheless useful for hydrogenatio~ catalyst preparation, are the metal salts of weakly acidic, organic acids having pKa values in the range from about 9-20, having from 1-25 carbon atoms, 1-2 acidic hydro› gen atoms, and containing only carbon, hydrogen, and oxygen. Included among the weak acids whose 3-d com- plex metal salts are contemplated for use in hydrogena› tion catalyst preparation are those of the carbinols, such as methanol, butanol, hexyl alcohol, 2-ethylhexanol, lauryl alcohol, stearyl alcohol, C$_{25}$H$_{51}$OH, octyl alcohol, cyclo hexanol, octanol, isobutanol, eicosanol, oleyl al- cohol, octadecenol, phenol, lauryl phenols, t-butyl phe› nols, naphthols, glycols, n-C10H$_{21}$ CHOHCH$_{2}$ OH and of the {3-diketones, such as acetylacetonate, and higher molecular weight analogs of acetylacetonate, and the like, The metal salts of weak organic acids are less desirable for a number of reasons, including, in general, the rela› tive difficulty in preparation in the required essentially anhydrous salt form, the susceptibility of most of these metal salts to hydrolysis, a tendency to form agglomer- ated catalysts of somewhat lesser unit activity, and the like. 

Included among metal salts of the preferred mono› basic, strongly-acidic, organic acids are the salts of the acids: formic, acetic, propionic, n-butyric, isobutyric, n- pentanoic, isopentanoic, hexanoic, valeric, isovaleric, ben, 

