Accessing Alkyl- and Alkenylcyclopentanes from Cr-Catalyzed Ethylene Oligomerization Using 2-Phosphinophosphinine Ligands

Desilylation of the 2-phosphinophosphinine 2-PPh2-3-Me-6-SiMe3-PC5H2 with HCl gave 2-PPh2-3-Me-PC5H3, demonstrating the late-stage modification of this bidentate heterocyclic ligand. Group 6 metal carbonyl complexes of these ligands showed κ2 binding and very small bite angles of 65.1–68.3°, and also demonstrated that the donor properties of 2-phosphinophosphinines can be tuned readily by the presence of the SiMe3 group, which gives a more π accepting phosphinine ligand. The properties of 2-phosphinophosphinines were compared to those of bidentate diphosphorus ligands computationally, contextualizing them in the ligand knowledge base for bidentate P,P donor ligands (LKB-PP), and were found to occupy an area of ligand space adjacent to Ar2PN(R)NAr2 ligands that have been successfully used in ethylene oligomerization reactions, but with well-separated properties in the second principal component. Testing 2-phosphinophosphinines in Cr-catalyzed ethylene oligomerization reactions showed key differences from s...