Patent GB-829574-A (GB)
Title: Method for the preparation of metallo-organic compounds
IPC: C10L1/30
Filed: 1956-10-03
Abstract: Catalysts comprising a transition element or its oxide on a support are prepared by adsorbing on the support either (a) a compound (Ar)2M, where M is the transition element and Ar either represents an aromatic hydrocarbon having a benzene ring with no double bond conjugated to the double bonds of the benzene ring either in a fused ring or a substituent group or represents an aryl substituted benzene, or (b) a salt of the cation (Ar)2M + or (Ar)2M + +, Ar and M being defined as above (see Group IV (b)), followed by thermal decomposition in an inert atmosphere to give the metal on the support or in air to give the oxide on the support.  Any transition element including the lanthanides and actinides may be used, but metals of Group IVb, Vb and VIb and iron, ruthenium and osmium from Group VIII of the Periodic Table are particularly suitable.  Temperatures of 80-400 DEG  C. or higher may be used depending on the decomposition temperature.  As inert atmospheres argon or krypton may be used. In an example, an aqueous solution of dibenzene molybdenum tetrachloroaluminate [(C6H6)2Mo] AlCl4 is mixed with diatomaceous earth, the complex being adsorbed.  The solid is filtered and heated to the decomposition temperature in air to give a catalytically active mixture of molybdena on alumina.ALSO:The Specification comprises cations of the formula (Ar)2M(y+) and compounds of the formula (Ar)2M in which formul  M represents a transition metal; Y represents the valency of the metal and is 1 or 2; and Ar represents a hydrocarbon containing an isolated benzene ring, defined as a benzene ring not having a double bond conjugated with the double bonds of the ring either in a ring fused to the benzene ring or in a substituent group, or represents an aryl substituted benzene. The cations (Ar)2 M(y+) may be prepared by reacting in the liquid phase under anhydrous conditions the hydrocarbon, a halide of the transition metal and an aluminium halide.  If the transition metal is in a higher valence state in the halide than is desired in the cation product, a reducing agent is added to the reaction mixture, this agent is conveniently a metal above antimony and the transition metal in the electromotive series and may be powdered aluminium, zinc, magnesium, chromium, iron, or manganese or if the hydrocarbon used is itself a reducing agent, such as tetrahydronaphthalene, this may be used in excess and no other reducing agent added.  Alternatively, triethyl aluminium may be used instead of an aluminium halide.  Under the reaction conditions this reduces the transition metal and gives an aluminium halide.  The reaction is carried out in an organic liquid which may be an excess of the hydrocarbon used in the reaction or an added inert diluent such as hexane, heptane, dodecane, cyclohexane or a paraffin gasoline fraction. Temperatures from - 30 DEG  to 300 DEG  C. can be used, slightly elevated temperatures being preferred to increase the rate of reaction without exceeding the decomposition temperature of the product and is preferably 40-150 DEG C. If a temperature above the boiling point of any liquid present is used, pressure must be applied to maintain the liquid phase.  Absence of air is preferred, the reaction being performed under nitrogen, argon or krypton.  The reactants are preferably maintained under the reaction conditions for at least 15 minutes, after which the product is cooled and hydrolysed, preferably in the absence of air, with, for example, methanol followed by water and, if desired, a base.  This precipitates aluminium and excess transition metal as their hydroxides leaving the cation product in aqueous solution.  The organic layer can be separated and discarded.  The cation product can be precipitated as an insoluble salt, e.g. in the case of dibenzene chromium the iodide, perchlorate, picrate, tetraphenyl boron, Reineckate, or cyclopentadienyl tricarbonyl chromium.  The compound (Ar)2M is prepared by reduction of the cation with sodium hyposulphite, hydroxylamine, hydrazine, hydroxy-methylene sulphinic acid, formamidine sulphinic acid, zinc and dilute acetic acid or aluminium and caustic alkali.  The latter two methods can be employed where zinc or aluminium has been used as a reducing agent in the production of the cation merely by addition of dilute acetic acid or caustic alkali respectively, the second of these not being generally applicable since some cations such as (Ar)2Fe+ + are unstable in alkaline solution. This reaction too is carried out in an inert atmosphere.  A layer of benzene or ether is added to the aqueous solution and then the reducing agent.  The product is soluble in organic solvents and not water and passes into the organic layer from which it may be recovered by evaporation, and purified by sublimation under high vacuum. The compounds may be re-converted to the cationic form by oxidation, by adding water to a solution of the compound in an organic solvent and bubbling air or oxygen through.  The cationic form appears in the aqueous phase.  Any transition metal including the lanthanide and actinide series may be used, but the process is particularly well adapted to the production of compounds wherein the metal is an element of Group IVB, VB and VIB or iron, ruthenium or osmium.  Metals of Group VIB, i.e. chromium, molybdenum and tungsten form particularly stable cations and compounds.  Hydrocarbons which may be used include benzene, alkyl substituted benzenes, aralkyl substituted benzenes, indane, tetrahydronaphthalene, 9,10-dihydroanthracene, and allyl benzene and aryl benzenes such as diphenyl, phenylnaphthalene, phenylanthracene and phenylphenanthrene. The salts of the cations and the compounds can be thermally decomposed at temperatures above 400 DEG  C. and this can be employed to produce coatings of the metal on objects for various purposes (see Groups II and III). Numerous examples are given.ALSO:A coating of a transition element on a metallic or non-metallic substrate may be obtained by the thermal decomposition preferably in an inert atmosphere of either (a) a compound of the formula (Ar)2M where M is the transition element and Ar represents an aromatic hydrocarbon having a benzene ring with no double bond conjugated with the double bonds of the benzene ring either in a fused ring or substituent group or represents an aryl substituted benzene or (b) a halide or otherother salt of the cation (Ar)2M + or (Ar)2M ++ where Ar and M are defined as above (see Group IV(b)).  The compounds are all decomposed by temperatures of 400 DEG C. and may decompose below. The process is carried out in the absence of air and preferably in an inert atmosphere such as argon or krypton or by heating in a slow stream of hydrogen at 750-1000 DEG C.  The metals which may be deposited include all the transition elements including the lanthonides and actinides.  They may be deposited on glass, glass cloth or resin to form strip conductors or resistors for electrical purposes or in desired places on a substrate, by conventional methods, to form printed circuits.  On metal substrates they enhance corrosion resistance and on glass cloth or asbestos provide decorative surfaces or designs.  Metals may also be deposited on supports such as diatomaceous earth to give supported metal catalysts by impregnating the support with a solution of the compound and heating in an atmosphere of argon or krypton to 80-400 DEG C.  This is particularly suitable for application to metals of Group IVB, VB, or VIB or iron, ruthenium or osmium. In examples, glass cloth and dibenzene chromium ((C6H6)2Cr) were sealed in an evacuated tube at 400 DEG C. for one hour.  The resultant cloth was found to be electrically conducting.  Dibenzene chromium was placed in a glass tube with some glass rings, small pieces of copper and a stainless steel wrench and the tube evacuated, sealed and heated at 380 DEG C. for 30 minutes.  The inner surface of the tube and the objects therein were coated with chromium metal.