Preparation of metal alkyls

Abstract

A method of preparing a methyl alkyl of formula (R 3 M) x where R 3 represents three alkyl groups R which may be the same or different, M represents a Group III metallic element and x is 1 or 2, which method comprises (a) forming a trialkyl adduct of formula (R 3 M) y . L wherein L represents an aryl-containing Group V, preferably phosphorus, donor ligand provided by an organic Lewis base which is stable at 20° C., and wherein Y is an integer equal to the number of Group V atoms presents in the ligand, and (b) heating the adduct to provide thermal dissociation thereof thereby releasing the alkyl as a gaseous product.

We claim: 
     
       1. A method of preparing a Group III metal alkyl which comprises (a) .[.combining a.]. .Iadd.forming an adduct of the .Iaddend.metal alkyl .[.with a ligand to form an adduct of said alkyl with said ligand.]. and (b) heating the adduct to provide thermal dissociation thereof thereby releasing the Group III metal alkyl as a gaseous product, characterized in that the adduct formed is of formula (R 3  M) y .L wherein R 3  represents three alkyl groups R which may be the same or different, M represents a Group III metallic element, L represents an aryl-containing Group V donor ligand provided by an organic Lewis base which is stable at 20° C. .Iadd.both the organic Lewis base and the ligand L are of general formula I ##STR8## wherein Ar 1 , Ar 2  are aryl groups, X is a Group V atom and Ar 3  is an aryl group which may be the same or different to one or both of Ar 1  and Ar 2 , Z is ##STR9## wherein D is an aromatic or aliphatic group and Ar 4  is an aryl group, n is an integer from 1 to 5 .Iaddend.and y is an integer equal to or less than the number of Group V donor atoms present in the ligand. 
     
     
       2. A method according to claim 1 characterised in that L is an aryl-containing phosphorus donor ligand. .[. 
     
     
       3.  A method according to claim 1 or claim 2 characterised in that the organic Lewis base has a melting point of from 50° C. to 200° C..]. .[.4. A method according to claim 1 characterised in that the heat of formation of the adduct is between 5 and 15 kcal mol -1 ..]. .[.5. A method according to claim 4 characterised in that the heat of formation of the adduct is from 6 to 12 kcal mol -1 ..]. .[.6. A method according to claim 1 characterised in that the Lewis base for providing the ligand L is selected from aryl-containing Group V Lewis bases in which each group V donor atom present in the base is trivalent and is bonded directly to at least one adjacent aryl group..]. .[.7. A method according to claim 6 characterised in that the organic Lewis base and the ligand L are both of general formula I ##STR10## wherein Ar 1  and Ar 2  are the same or different and are aryl groups,   X is a Group V atom, and   
     
     
       Y is an aryl or aryl-containing group..]. .[.8.  A method according to claim 7 characterised in that the organic Lewis base and the ligand L are both of general formula II ##STR11## wherein Ar 1 , Ar 2  and X are as defined in claim 7, Ar 3  is an aryl group which may be the same or different to one or both of Ar 1  and Ar 2 ,   Z is ##STR12## wherein D is an aromatic or aliphatic group and   
     
     
       Ar 4  is an aryl group, and n is an integer from 1 to 5..]. 9. A method according to claim .[.8.]. .Iadd.1 .Iaddend.characterised in Ar 1 , Ar 2 , Ar 3  and Ar 4  are independently selected from phenyl, 
     
     
        substituted phenyl, p-diphenyl and naphthyl. 10. A method according to claim 9 characterised in that Ar 1 , Ar 2 , Ar 3  and Ar 4   
     
     
        are each phenyl. 11. A method according to claim .[.8.]. .Iadd.1 .Iaddend.characterised in that D is an aliphatic chain of formula 
     
     
        (CH 2 ) m  where m is an integer from 1 to 12. 12. A method 
     
     
        according to claim 11 characterised in that m is from 2 to 4. 13. A method according to claim .[.8.]. .Iadd.1 .Iaddend.characterised in that n is from 1 to 3.