A synthetic route for the preparation of I, l '-heterosubstituted aminoferrocenes has been devised. The key precursor, 1-bromo- l '-aminoferrocene, is generated in a one-pot reaction from the readily available I, l '-dibromoferrocene, and has been additionally characterised as its N-borane adduct. l-Amino-1 '-ferrocenecarboxylic acid and its methyl ester are reported as the first examples of I , 1 '-heterosubstituted aminoferrocenes, and l-(diphenylphosphino)-1 '-aminoferrocene is representative of a new class of P,N-donor ferrocene ligands in which both heteroelements are bonded directly to the ferrocene
backbone. Protection of air-sensitive ferrocenylphosphines as their P-borane adducts has allowed for the synthesis of novel I, l '- and 1 ,2-substituted ferrocenylphosphine-boranes which, while air-stable and crystalline, can be readily deprotected to yield the corresponding 1, I'- or 1,2-diphosphines.
Nickel and palladium (II) chloride complexes of the previously reported ligand I, l 'bis(diisopropylphosphino)ferrocene and the palladium (II) chloride complex of I, I'bis(diisopropylphosphino )-2-[ (N,N-dimethy !amino )ethy 1 ]f errocene have been prepared and their single crystal X-ray structures determined: as with the ir diphenylphosphinoanalogues, the palladium complexes are square-planar and cis while the nickel complex is tetrahedral. The crystal structures are presented, together with preliminary electrochemical characterisation.
cis-Dichloro[ I, I '-bis( diisopropy lphosphino )ferrocene ]pall adium (II) has been tested as a catalyst precursor for carbon-carbon bond forming reactions and is found to be considerably more efficient than its phenylphosphino-analogue in catalysis of the Heck reaction. A range of related ( diisopropylphosphino )- and ( dipheny I phosphino )f errocenes is also compared and, in general, the complexes with (diisopropylphosphino)ferrocene ligands are shown to produce greater reaction rates. The scope of the new complexes in other cross-coupling reactions, namely the coupling of organomagnesium and organoboron reagents, is also assessed.