Architecture and synthesis of P,N-heterocyclic phosphine ligands

Abstract

Diverse P,N-phosphine ligands reported to date have performed exceptionally well as auxiliary ligands in organometallic catalysis. Phosphines bearing 2-pyridyl moieties prominently feature in literature as compared to phosphines with five-membered N-heterocycles. This discussion seeks to paint a broad picture and consolidate different synthetic protocols and techniques for N-heterocyclic phosphine motifs. The introduction provides an account of P,N-phosphine ligands, and their structural and coordination benefits from combining heteroatoms with different basicity in one ligand. The body discusses the synthetic protocols which focus on P–C, P–N-bond formation, substrate and nucleophile types and different N-heterocycle construction strategies. Selected references are given in relation to the applications of the ligands.

Coinage Metal Complexes of Bis(quinoline‐2‐ylmethyl)phenylphosphine‐Simple Reactions Can Lead to Unprecedented Results

“…This versatile coordination behavior is very beneficial and needed in catalysis, for the preparation of MOFs or even luminescent materials. [1][2][3][4][5][6][7][8][9][10][11][12][13] Hemilabile tertiary phosphines are preferably used due to their outstanding flexibility which can be modified by changing the substituents accordingly. The modification of the substituents can result in the adaptation of their steric and electronic properties, their bite angle and solubility, and even chiral phosphine ligands can be formed.…”

“…Multidentate P,N ligands stand out due to their hemilability, as they contain two electronically different coordination atoms (soft phosphorus and hard nitrogen). This versatile coordination behavior is very beneficial and needed in catalysis, for the preparation of MOFs or even luminescent materials [1–13] . Hemilabile tertiary phosphines are preferably used due to their outstanding flexibility which can be modified by changing the substituents accordingly.…”

Investigation of Structural Changes of Cu(I) and Ag(I) Complexes Utilizing a Flexible, Yet Sterically Demanding Multidentate Phosphine Oxide Ligand

“…The versatile coordinating behavior of hemilabile P–N-compounds is a widely used property not only in coordination chemistry but also in the fields of catalysis, bioinorganic chemistry, or material science. − A comprehensive design of such multidentate phosphine ligands is beneficial when trying to provoke or improve specific properties of the resulting metal complex, e.g., luminescence or catalytic activity. A broad variety of phosphine and phosphine oxide ligands with nitrogen containing aromatic substituents directly bonded to phosphorus have been published. − Despite the fact that these compounds do not allow for any flexibility of the ligand, they show impressive material properties, such as luminescence or catalytic activity in addition to a rich coordination chemistry. − For the application in transition-metal catalysis, a certain conformational flexibility of the ligand can be beneficial, as possible transition states can be stabilized more easily. − The benefit of flexibility in catalysis has been demonstrated for enzymatic systems and has recently been discussed for a variety of other catalyst classes by Sigman et al − The steric demand of the phosphine ligand when coordinating to a metal can be varied by changing the substituents on phosphorus accordingly. The increased steric demand can result in the ligand bridging across two metal centers, which has been demonstrated previously for some transition metals and can be a promising feature in catalytical application. ,− Such ligands can even support metallophilic interactions, which leads to interesting photophysical properties. , …”

Recent Progress in Cyclic Aryliodonium Chemistry: Syntheses and Applications

“…Heteroatoms-containing molecules or heterocyclic compounds are widely present in pharmaceutical drugs ,,− and organic materials. ,, Due to their unique chemical properties, the development of new methodologies to access structurally diversified heteroatom-containing scaffolds is of high importance. ,− The advances in synthesis of such heterocyclic compounds from cyclic aryliodoniums have been made.…”