Patent GB-785760-A (GB)
Title: Process for the production of cyclopentadiene compounds of transition elements
IPC: C07F17/00
Filed: 1954-09-15
Abstract: The higher halides of transition elements may be reduced to lower halides by reaction with iron, aluminium, zinc or other reducing metal in glycol dialkyl ether solution.  The process is applicable to halides of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and actinium as well as to those of the inner transition elements of the lanthanide and actinide series.  The preferred glycol dialkyl ethers are ethylene glycol dimethyl and diethyl ethers and the dimethyl ethers of diethylene glycol and tetraethylene glycol. Example II describes the reduction of FeCl3 to FeCl2 by use of finely divided iron in ethylene glycol dimethyl ether, and Example V the reduction of CrCl3 to CrCl2 by use of chromium powder in the same solvent medium.  Anhydrous manganese dibromide is prepared by reacting manganese powder and bromine in ethylene glycol dimethyl ether (Example IV).ALSO:The invention comprises compounds of formula R2MXz, wherein R is an alicyclic cyclopentadienyl ring or an alkyl-, alkenyl-, acyl-, aryl- or aralkyl-substituted alicyclic cyclopentadienyl ring, M is a transition element (as defined below), X is a halogen atom and z is 0, 1, 2 or 3.  The compounds may be prepared by reacting in an organic solvent medium a halide or oxyhalide of a transition element and sodium cyclopentadiene or an alkyl-, alkenyl-, acyl-, aryl or aralkyl-substitution derivative thereof.  The preparation of cyclopentadienyl iron and cyclopentadienyl nickel by reacting an alkali metal cyclopentadiene with an iron or nickel halide is disclaimed, except when using a dialkyl ether of an alkylene glycol as reaction medium.  Alicyclic cyclopentadiene rings include cyclopentadiene itself and indene and their substitution derivatives only.  Transition elements are defined as having an inner d level of electrons partially occupied but not filled to capacity, namely, xandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, yttrium, zirconium, niobium, molybdenum, technetium, ruthernium, rhodium, palladium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum and actinium as well as the inner transition elements of the lanthanide and actinide series. Solvents specified include diethyl ether, ethylene glycol methyl phenyl ether, propylene glycol dimethyl ether, diethyl acetal, dibutyl acetal, methyl phenyl ether, methyl morpholine, triethylamine, benzene, ethylene glycol dimethyl and diethyl ethers, diethylene glycol dimethyl ether, tetramethylene glycol dimethyl ether dioxane and tetrahydrofuran.  Of these the glycol dialkyl ethers are preferred.  They are suitable solvents for the preparation of the sodium cyclopentadiene and for the conversion of this into the transition metal derivative.  The alkali metal derivative may be prepared from sodium sand or sodium wire, or from caustic soda (in stoichiometric excess) or sodamide.  Liquid ammonia may also be used as the solvent for this stage.  The product of the reaction of the invention may contain halogen or not according to whether the reaction halogen or not according to whether the reaction is carried out under oxidizing or reducing conditions.  In general using MX2 as the halide the product is non-halogenated, MX3 gives a non-halogenated product, a halogenated product or the cationic form (R2M+) depending on ratio of reagents and reaction temperature, and MX4 gives R2MX2 though R2MX or a nonhalogenated product may result under reducing conditions.  The higher valency halide may be reduced in situ in the glycol dialkyl ether medium by reduction with aluminium, zinc or other reducing metal, or in the case of FeCl3 or CrCl3 by reduction with finely-divided Fe or Cr, respectively. Example 1 describes the preparation of cyclopentadienyl sodium from finely-divided sodium and cyclopentadiene in ethylene glycol dimethyl ether, and in Example 2 this is added to a slurry of ferrous chloride prepared by reducing ferric chloride in ethylene glycol dimethyl ether with finely-divided iron powder to give dicyclopentadienyl iron.  Other examples describe the preparation of bis-(cyclopentadienyl) zirconium dichloride, bis-(cyclopentadienyl) manganese, bis-(cyclopentadienyl) manganese bromide, bis - (cyclopentadienyl) chromium, bis - (methylcyclopentadienyl) iron, bis - (allylcyclopentadienyl) iron, bis - (indenyl) iron, bis-(cyclopentadienyl) titanium dichloride, bis-(cyclopentadienyl) titanium, bis-(methylcyclopentadienyl) cobalt tribromide, bis-(cyclopentadienyl) cobalt chloride, bis-(cyclopentadienyl) cobalt, bis-(cyclopentadienyl) hafnium dichloride, bis-(cyclopentadienyl) vanadium dichloride, bis-(cyclopentadienyl) nickel, bisbenzylcyclopentadienyl) iron, and bis-(acetylcyclopentadienyl) iron.