A cavity-shaped cis-chelating P,N ligand for highly selective nickel-catalysed ethylene dimerisation

Abstract

The presence of a cyclodextrin cavity in a chelating P,N ligand promotes the exclusive formation of 1 : 1 ligand/metal complexes. A Ni(ii) complex of the ligand is a very selective catalyst for ethylene dimerisation as a result of metal confinement.

Stabilization of Luminescent Mononuclear Three‐Coordinate CuI Complexes by Two Distinct Cavity‐Shaped Diphosphanes Obtained from a Single α‐Cyclodextrin Precursor

“…Such monoanion can undergo a first nucleophilic substitution with dimesylate 6 a , and the resulting CD secondary phosphane can then cyclize upon deprotonation by the remaining LDA to give the P‐bridged diphosphane 2 in 57 % yield (Scheme 2). Similar cyclizations have been previously performed with phenylphosphane [10] and N , N ‐dimethyl‐2‐phosphanylaniline, [11] which, unlike 4 , do not rearrange in the presence of excess n ‐BuLi. As for the latter primary phosphanes, the cyclization reaction is 100 % stereoselective, the second possible diastereomer in which the phosphorus lone pair is pointing outside the cavity was not detected in the reaction mixture.…”

“…of base or the formation of small amounts of a tetraphosphane side product (Table S1 and Figure S1). Although some of the P(III) atoms of 1 a and 2 are seemingly quite basic (δ 31P =−27.2 and −19 ppm for 1 a and −28.7 and −14.7 ppm for 2 ), these ligands are considerably more stable against air oxidation than their PhP‐bridged counterpart (δ 31P =−16.2 ppm) and can be purified by standard column chromatography as in the case of an analogous cavity‐shaped P,N ligand without noticeable formation of phosphane oxides [11] . The presence of through‐space PC couplings involving the triarylphosphane P‐atom and C‐6 carbon atoms of the glucose units C and F ( TS J P,C =7.7 Hz and 3 Hz, respectively) is in agreement with a triarylphosphane unit sitting just above the CD unit (Figure S4e).…”

“…The ability of these new cavity-shaped, cis-chelating P,P ligands to promote the exclusive formation of mononuclear complexes showing metal encapsulation is also currently exploited for catalytic purposes, [27] notably in ethylene oligomerization. [11]…”

“…Theoretical studies are currently in progress to rationalize these differences and have a complete elucidation of the ground and excited state properties of these intriguing classes of metal complexes that incorporate a simple trigonal coordination motif within a complex, cage‐like architecture. The ability of these new cavity‐shaped, cis ‐chelating P,P ligands to promote the exclusive formation of mononuclear complexes showing metal encapsulation is also currently exploited for catalytic purposes, [27] notably in ethylene oligomerization [11] …”