# Cis‐Chelating Diphosphanes for Intracavity Nickel(II)‐Catalyzed Ethylene Oligomerization

## TL;DR

This paper describes the design of cavity-shaped diphosphanes that confine nickel catalysts to improve ethylene oligomerization, producing mostly 1-butene.

## Contribution

The novelty lies in using cyclodextrin-derived diphosphanes to control nickel catalysts' environment for selective ethylene oligomerization.

## Key findings

- Nickel complexes of the diphosphanes catalyze ethylene oligomerization with high selectivity for 1-butene.
- The cavity size and ligand structure influence the activity and selectivity of the reaction.
- Theoretical studies show the cyclodextrin cavity restricts olefin isomerization, enhancing α-olefin formation.

## Abstract

Four cis‐chelating diphosphanes derived from cyclodextrins (CDs), each featuring a distinct intracavity environment, compel NiII or PdII metal centers to reside within α‐ or β‐CD cavities. Nickel(II) complexes of these metal‐confining ligands act as active catalysts in ethylene oligomerization upon activation with modified methylaluminoxane (MMAO). The size of the cavity and the position of the P2Ni fragment relative to the cavity affect both the activity and selectivity of the reaction. In all instances, 1‐butene is the major product (up to 98% C4 products and 90% 1‐butene within the C4 fraction). Extensive theoretical studies with state‐of‐the‐art methods carried out on the most selective system suggest that the CD cavity restricts isomerization pathways by limiting the mobility of the coordinated olefin in this constrained supramolecular environment, thereby enhancing α‐olefin formation.

Four cavity‐shaped diphosphanes have been synthesized from both α‐ and β‐cyclodextrins. The metal‐confining properties of these ligands were exploited in nickel‐catalyzed ethylene oligomerization.
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