Trianionic pincer and pincer-type metal complexes and catalysts

Abstract

Trianionic pincer and pincer-type ligands are the focus of this review. Metal ions from across the periodic table, from main group elements, transition metals, and the rare earths, are combined with trianionic pincer ligands to produce some of the most interesting complexes to appear in the literature over the past decade. This review provides a comprehensive examination of the synthesis, characterization, properties, and catalytic applications of trianionic pincer metal complexes. Some of the interesting applications employing trianionic pincer and pincer-type complexes include: (1) catalyzed aerobic oxidation, (2) alkene isomerization, (3) alkene and alkyne polymerization, (4) nitrene and carbene group transfer, (5) fundamental transformations such as oxygen-atom transfer, (6) nitrogen-atom transfer, (7) O2 activation, (8) C-H bond activation, (9) disulfide reduction, and (10) ligand centered storage of redox equivalents (i.e. redox active ligands). Expansion of the architecture, type of donor atoms, chelate ring size, and steric and electronic properties of trianionic pincer ligands has occurred rapidly over the past ten years. This review is structured according to the type of pincer donor atoms that bind to the metal ion. The type of donor atoms within trianionic pincer and pincer-type ligands to be discussed include: NCN(3-), OCO(3-), CCC(3-), redox active NNN(3-), NNN(3-), redox active ONO(3-), ONO(3-), and SNS(3-). Since this is the first review of trianionic pincer and pincer-type ligands, an emphasis is placed on providing the reader with in-depth discussion of synthetic methods, characterization data, and highlights of these complexes as catalysts.

Pincer Complexes of Lithium, Sodium, Magnesium and Related Metals: A Discussion of Solution and Solid-State Aggregated Structure and Reactivity

“…(38) will react cleanly with added LiCl in THF or toluene solution to regenerate 37. Such an observation suggests that 37 is the thermodynamically stable heteroaggregate complex and not simply a result of the "trapping" of a LiCl molecule during the formation of the two amido moieties.…”

“…Note that "E" can also be formally anionic applications in the synthesis of other metal and non-metal pincer derivatives. Hence, metal metathesis reactions are their main use; this aspect has been discussed previously [38,43].…”

“…A thorough introduction to this whole class of ligands can be found in the earlier reports and hence will not be repeated here; cf. [36][37][38][39][40][41][42]. This chapter will deal specifically with pincer ligands of the Group 1 elements (Li, Na) with some relationships drawn to the complexes of Mg, Cu and Zn where appropriate [43].…”

Unsymmetrical palladium PCN pincer complexes containing pyrazolyl aminophosphine ligands

“…Bis(benzonitrile)dichloropalladium (II), 3-nitrobenzyl bromide, chlorodiphenylphosphine, chlorodiisopropylphosphine, and 3,5-dimethylpyrazole were purchased from Sigma-Aldrich Canada Ltd. 4-N,N-dimethylaminopyridine (DMAP) and phenylboronic acid were purchased from Alfa Aesar (a John Matthey company). 1 H, 13 C, and 31 P NMR spectra were recorded on a Bruker Avance 500 spectrometer and referenced to SiMe 4 ( 1 H, 13 C) and 85% H 3 PO 4 ( 31 P). Infrared spectra were collected on a Nicolet Avatar 330 FT-IR spectrometer.…”

“…Their steric and electronic features can be finetuned at the donor sites as well as the metal centers to afford desirable properties and activities. The chemistry of pincer complexes is a topic of frequent reviews and continues to attract extensive research interest [1][2][3][4][5][6][7][8]. In the pincer complexes, the most commonly studied ligands are the symmetrical types (e.g.…”