Patent GB-988943-A (GB)
Title: Process for the preparation of metal complexes
IPC: C07F15/04
Filed: 1961-07-20
Abstract: A complex which can be used as catalyst in the preparation of aldehydes and/or alcohols from an olefin, CO and H2 e.g. as in Specification 988,941 obtained by reducing a salt of a transition metal having an atomic number from 23 to 32, 40 to 51 or 57 to 84 in a liquid medium with an alkali metal dithionite and contacting the reduction product with a biphyllic ligand containing trivalent phosphorus, arsenic or antimony or by reducing a salt of the said transition metal in a liquid medium with an alkali metal dithionite in the presence of the said biphyllic ligand.  Other biphyllic ligands, e.g. carbon monoxide may also be present.  The transition metal is preferably a Group VIII metal e.g. Fe, Co, Ni, Ru, Rh, Pd, Os, Ir or Pt. The biphyllic ligand is preferably one containing trivalent phosphorus, the three valences of which may be satisfied by any organic group, e.g. aliphatic, cycloaliphatic, heterocyclic or atomatic groups which groups may contain a carbonyl, carboxyl, nitro, amino or hydroxy group or an unsaturated carbon-to-carbon linkage. One organic group may be bound to more than one of the valences of the phosphorus atom thus forming a heterocyclic compound, thus two valences of the phosphorus atom may be satisfied by one alkylene or dioxyalkylene group.  The biphyllic ligand may be polydentate, e.g. a compound of the formula <FORM:0988943/C2/1> and <FORM:0988943/C2/2> Preferred complexes are those having the general formula [(R1zA)x-L-Ry]pM(CO)n wherein (R1zA)x-L-Ry represents the biphyllic ligand, M is the transition metal, L is phosphorus, arsenic or antimony, R and R1 are alkyl, aryl, aralkyl or alkaryl groups, A is oxygen, nitrogen or sulphur, x ranges from 0 to 3, y = 3 - x, p ranges from 1 to the co-ordination number of the transition metal, n + p is equal to the co-ordination number and Z is 1 when A is oxygen or sulphur or is 2 when A is nitrogen. The reduction with the dithionite is preferably carried out in an aqueous medium but other water-miscible solvents e.g. pyridine, dimethylformamide, methanol, acetone, dioxane or 1,2-dimethoxyethane may be present. The biphyllic ligand may be added after the reduction of the salt of the transition metal or the reduction may be carried out in the presence of the biphyllic ligand and in the latter case the biphyllic ligand if used in excess may also serve as the liquid medium.  The salt of the transition metal may be a water-soluble inorganic or organic salt e.g. a salt of a hydrohalic acid, HCN, or a carboxylic acid. Specified salts are chlorides, bromides, cyanides, nitrates, acetates, propionates, butyrates and salts of polybasic acids e.g. sulphuric, phosphoric, or a sulphonic or phosphonic acid.  As mentioned above the reduction may be carried out in the presence of carbon monoxide and in this case the complex will comprise the transition metal held in complex combination with one or more biphyllic ligands containing P, As or Sb and one or more carbon monoxide molecules.  The reduction may suitably be carried out at from 0 DEG  to 150 DEG  C. and it is preferred to use atmospheric pressure, although higher or lower pressures may be used.  The alkali metal dithionite may be sodium, potassium or rubidium dithionite, the former being preferred.  The ligand is preferably used in stoichiometric excess over the transition metal salt, a molar ratio of ligand to metal of from 10:1 to 50:1 being suitable.  The dithionite should be present in at least the amount required for reduction of the transition metal to the zero valence state.  When water is used as solvent it is desirable to add a complexing agent; e.g. ammonia, an alkali metal cyanide, acetate or thiocyanate.  Also, the reduction should preferably be carried out in a medium having a pH greater than 7, e.g. by using aqueous ammonia as the reaction medium. Examples are given for the production of tetrakis - (triethyl phosphite) - nickel (O), a cobalt-triethylphosphite complex and a tricresyl phosphite-nickel complex.  Several other complexes obtainable by the process are also specified. Specification 946,062 is referred to.