A novel hemilabile calix[4],quinoline-based P,N-ligand: coordination chemistry and complex characterisation

Abstract

The synthesis of the calix[4]arene-based P,N-ligand 3 (5,11,17,23-tetra-tert-butyl-25-[(2-quinolylmethyl)oxy]-26,27,28-(mu3-phosphorustrioxy)calix[4]arene), in which the nitrogen atom-containing moiety has been introduced at the lower rim of the cavity prior to P-functionalisation, is described and its coordination properties investigated. In the crystal structure, the calix[4]-cavity adopts a cone conformation with an exo orientation of the phosphorus lone pair enabling P-N chelation. 1H, 13C, 31P and 1H{15N} HMQC NMR spectra indicated that, in complexes [PdCl(CH3)(3)] (4) and [Rh(CO)Cl(3)] (5), ligand 3 coordinates in a chelating fashion, while in cis-[PtC12(3)2] (6) and [Rh(acac)(CO)(3)] (7) it behaves as a monodentate ligand, coordinating via the phosphorus atom only. X-Ray crystal structure determinations were performed for [PdCl(CH3)(3)] (4) and cis-[PtCl2(3)2] (6). The cationic Pd complex [Pd(CH3)(CH3CN)(3)][PF5] (8) was found to be active in a CO/ethylene copolymerisation reaction. Good selectivities were observed for the Pd-catalysed allylic alkylation of cinnamyl acetate with in situ prepared catalysts. [Rh(acac)(CO)2] modified with ligand 3 catalyses the hydroformylation of 1-octene with low selectivities towards linear aldehydes. High-pressure NMR experiments on the hydrido carbonyl rhodium(3) were inconclusive, different species were formed.

Calixarene-monophosphines as supramolecular chelators

“…To answer this question, the three phosphines 2, 4, and 5 in which two phenoxy rings bear no p-substituent were reacted with [RuCl 2 (p-cymene)] 2 . In all three cases, complexes similar to those above were formed (17)(18)(19), with the p-cymene ligand confined at the cavity entry (Scheme 6). Again, the Me-Ar( i Pr) vectors point downwards, as deduced from the presence of highfield-shifted Me signals for all three complexes.…”

“…12 To date, most phosphine ligands constructed on a calix [4]arene backbone have been multidonor systems based on coordinating atoms which are anchored to the same rim of the calixarene moiety, that is, either the phenolic oxygen atoms or the p-carbon atoms of the phenol units. 13,14 Prominent examples of ligands of this type that have found applications in transition metal chemistry include hemispherical, 15 hemilabile, 16, 17 and chiral, 18 as well as highly strained diphosphines. 19 Surprisingly, calixarenes substituted by a single P(III) unit and no other functional group have been only sparingly used in coordination chemistry.…”

Organocatalyzed Synthesis of Functionalized Quinolines

“…Quinoline was discovered by Runge in 1834 as a colorless hygroscopic liquid and was first synthesized in 1897. The application of quinoline is diverse, the scaffold could be found among natural products (alkaloids), pharmaceuticals, agrochemicals, dyestuffs, and materials; it is also used to chelate metallic ions as N ‐donor ligands in coordination chemistry. Additionally, the wide range of pharmacological activities of quinoline has been found out more and more.…”

Metal-free domino one-pot protocols for quinoline synthesis

“…In coordination chemistry, quinolines are used to chelate metallic ions as N-donor ligands. 2 The quinoline scaffold has been reported to possess diverse range of pharmacological activities [3][4][5][6][7][8][9][10][11][12][13][14] including antiprotozoal, [15][16][17][18][19][20] antitubercular, 21,22 anticancer, 4,23,24 antipsychotics, 25 antiinammatory, 26,27 antioxidant, 3 anti-HIV, 28 antifungal, 29 as efflux pump inhibitors, 30 and for treatment of neurodegenerative diseases, 19 and treatment of lupus, 31 etc.…”