Phosphines and other P(III)‐derivatives with Cavity‐shaped Subunits: Valuable Ligands for Supramolecular Metal Catalysis, Metal Confinement and Subtle Steric Control

Abstract

Tertiary phosphines and other P(III)‐derivatives are the par excellence ligands in industrially relevant homogeneous catalysis. A promising, recent development in this field concerns the use of P(III)‐compounds that incorporate cavity‐shaped subunits capable of assisting metal‐centred reactions, either by functioning as receptor moieties, creating confinement about the reactive centre or merely by influencing main catalytic steps via strong steric interactions exerted on the metal first coordination sphere. This Minireview, which is based on selected examples, illustrates the utility of covalently‐constructed phosphines that incorporate a cavity and highlights future directions that deserve development in ligand design.

Diametric calix[6]arene-based phosphine gold(I) cavitands

“…This crucial aspect prompted their application in supramolecular chemistry as well. Thus, a recent evolution of their chemistry concerns the development of novel architectures in which P(III) compounds are incorporated in cavity-shaped macrocycles [5][6][7][8]. In this scenario, calix [4]- [9][10][11][12][13] and resorcin [4]arene [14][15][16][17] are the most exploited cavitands due to their inherent limited flexibility and already proved their ability to control the catalytic activity of late-transition metals and particularly gold(I) catalysts [18][19][20][21][22][23][24][25].…”

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

“…Inwardly directed donor atoms rigidly grafted on a macrocyclic host molecule are capable of facilitating a metal centred reaction to take place inside the cavity-shaped ligand. [1][2][3][4][5] This feature is prone to produce high substrate recognition, [6][7][8][9][10][11][12][13][14] catalytic chemo- 15 and regioselectivity [16][17][18][19][20] as well as enantioselectivity if the receptor is optically active. 21 By connecting two C-6 carbon atoms of two glucose units of an α-, βor γ-CD with a single donor atom such as nitrogen 22 or phosphorus, [23][24][25] (Fig.…”

Diametric calix[6]arene gold(i) catalysts for intramolecular cyclopropanations of 1,6-dienynes

“…Differently, resorc[4]arene cavitands are more synthetically versatile. Their functionalisation with phosphine ligands, 8 along with their limited flexibility and their small cavity, was exploited to control the catalytic activity of the gold( i ) nuclei implanted on the macrocycle. 9 In this scenario, calix[6]arene platforms are definitely less employed.…”