Iminobisphosphines to (Non‐)Symmetrical Diphosphinoamine Ligands: Metal‐Induced Synthesis of Diphosphorus Nickel Complexes and Application in Ethylene Oligomerisation Reactions

We describe the synthesis of a range of novel iminobisphosphine ligands based on a sulfonamido moiety [R 1 SO 2 N=P(R 2 ) 2 ‐P(R 3 ) 2 ]. These molecules rearrange in the presence of nickel by metal‐induced breakage of the P–P bond to yield symmetrical and nonsymmetrical diphosphinoamine nickel complexes of general formula Ni{[P(R 2 ) 2 ]N(SO 2 R 1 )P(R 3 ) 2 }Br 2 . The complexes can be isolated and are very stable. Upon activation by MAO, these complexes oligomerise ethylene to small chain oligomers (mainly C 4 –C 8 ) with high productivity. Surprisingly fast codimerisation reactions of ethylene with butenes is observed, leading to a high content of branched C 6 products.