Fast Propene Dimerization Using Upper Rim‐Diphosphinated Calix[4]arenes as Chelators

The complexes [NiBr 2 ⋅ 1 ] and [NiBr 2 ⋅ 2 ], containing the upper rim‐diphosphinated calixarenes 5,17‐bis(diphenylphosphino)‐25,26,27,28‐tetrapropoxycalix[4]arene ( 1 ) and 5,17‐dibromo‐11,23‐bis(diphenylphosphino)‐25,26,27,28‐tetrapropoxycalix[4]arene ( 2 ) were assessed as propene dimerization catalysts. Combined with methylaluminoxane, both complexes result in highly efficient dimerization catalysts displaying C 6 selectivities in the range 80–97% and activities that compare with the best reported systems, the latter using PCy 3 as ligand. The origin of the remarkable activities of the calixarene derivatives may be the ability of the diphosphine to undergo a periodic bite angle increase that incidentally favors the insertion step. Calixarenes such as 1 or 2 , which each incorporate two “stable” Ph 2 PAr moieties, constitute interesting alternatives to the use PCy 3 in propene dimerization.