5-Methylquinoxaline as a versatile mono-, bi- and tridentate ligand in palladium(II) chemistry. Crystal structures of [Pd(OAc)(C, N4-CH2C8H5N2-5) (PPh 3)]

José Vicente, M. Cristina Lagunas, Elke Bleuel, M. Carmen Ramírez De Arellano

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)

Abstract

To study the potential coordination versatility of 5-methylquinoxaline, the preparation of complexes which contain it as a mono-, bi- or tridentate ligand was carried out. On reaction with [Pd(OAc)2] 3 it coordinates to the metal through its less sterically blocked nitrogen atom (N(1), distal to the Me group) to give trans-[Pd(OAc)2(N1-C8H5N2 Me-5)2] (1). Reflux of 1, or a mixture of [Pd(OAc)2]3 and 5-methylquinoxaline, in glacial acetic acid gave the cyclometallated acetate-bridged dimer [Pd(C, N4-CH2C8H5N2-5) (μ-OAc)]2 (2). Complex 2 reacted with: (i) LiCl to give [Pd(C, N4-CH2C8H5N2-5) (μ-Cl)]2 (3); (ii) PPh3 to give [Pd(C, N4-CH2C8H5N2-5) (OAc)(PPh3)] (4); (iii) PR3 and LiCl to give [Pd(C, N4-CH2C8H5N2-5)Cl (PR3)][R = Ph (5), Me (6), Et (7)]; (iv) Tl(acac) to give [Pd(C, N4-CH2C8H5N 2-5)(O, O-acac)] (8); and (v) 2,2′-bipyridine (bpy)-NaClO4H2O to give [Pd(C, N4-CH 2C8H5N2-5) (bpy)]ClO 4 (9). Complex 5 reacted with [PdCl2(NCPh) 2] in a 2:1 molar ratio to form the C, N4, N1-coordinated tripalladium derivative [PdCl2(PdCl(C, N4, N1-CH2 C8H5N2-5)(PPh3)2] (10). By contrast, when this reaction was carried out with an excess or equimolecular amount of PdCl2(NCPh)2] compound 3 was obtained together with [PdCl(μ-Cl)(PPh3)]2. We present evidence for formation of novel multimetallic species of the type [Pd(C, N4, N1-CH2C8H5N2-5) (PR3)]nXn by reaction of 5 or 6 with TlOTf (OTf = O3SCF3), AgClO4 or TlClO 4. The crystal structures of 1 and 4·2CHCl3 were determined by X-ray diffraction studies. They conclusively prove that Pd is coordinated to N(1) in 1 and to N(4) in 4.

Original languageEnglish
Pages (from-to)62-71
Number of pages10
JournalJournal of Organometalic Chemistry
Volume648
Issue number1-2
DOIs
Publication statusPublished - 01 Apr 2002

Keywords

  • Cyclometallation
  • Methylquinoxaline
  • Palladium
  • X-ray diffraction

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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