Tethered Bis(amidate) and Bis(ureate) Supported Zirconium Precatalysts for the Intramolecular Hydroamination of Aminoalkenes

Tethered bis(amide) and bis(urea) proligands featuring a neutral chalcogen donor (O or S) in the backbone were synthesized and installed on zirconium via protonolysis. The bis(amidate) zirconium complexes adopt a kappa(4)(N,N,O,O) binding motif and were characterized in the solid state with a pyridine donor. Likewise, the bis(ureate)-supported complexes are also found to have a kappa(4)(N,N,O,O) binding motif in the solid state however no additional donor ligand is required for discrete complex formation. No evidence for interaction between the neutral chalcogen donor and the zirconium atom is found for any of the transition metal species. All complexes were screened as precatalysts for the intramolecular hydroamination reaction with both primary and secondary aminoalkene substrates. Interestingly, the bis(ureate) species show similar reactivity to the bis(amidate) species, in contrast to a recently reported alkyl-bridged bis(ureate) complex, which readily cyclizes secondary aminoalkenes.