Tetramethylguanidine and benzophenoneimine as ligands in gold chemistry

Wolfgang Schneider, Andreas Bauer, Annette Schier, Hubert Schmidbaur

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

(Tetramethylguanidine)gold(I) chloride (1) and bromide (2) are readily prepared in high yield from (Me2N)2C=NH and [AuCl(Me2S)] or [AuBr(tht)] (tht = tetrahydrothiophene), respectively. NMR spectra of chloroform solutions of the two products indicate equilibria of the type 2 LAuX L2Au+AuX2-. The cationic complex [Au{NH= C(NMe2)2)(PPh3)]4- is obtained as the triflate salt 3 from tetramethylguanidine and [Au(PPh3)]+O3SCF3-. In solution at low temperature (-60 °C), this compound adopts a rigid structure whereby the NMe2 groups are rendered non-equivalent, but at ambient temperature there is coalescence of the NMe2 signals in the 1H- and 13C-NMR spectra. The related benzophenoneimine complex Au(NH=CPh2)(PPh3)]+BF4- (4), which was synthesized as a reference compound, exhibits similar behaviour. In solution at low temperature (-60 °C) the two phenyl rings of the ligand are diastereotopic. In contrast, the triisopropylphosphane derivative [Au{NH= Ph2)(PJPr3)]+BF4- (5) is rigid on the NMR time scale, even at 25 °C. The solid-state structures of 2, 3, 4, and 5 have been determined by single-crystal X-ray diffraction. Compound 2 crystallizes in the ionic form with discrete Au -Au bonded ion pairs [Au{NH=C(NMe2)2)2]+ [AuBr2]-[Au-Au 3.1413(8) A). The cations of 3, 4, and 5 show the [Au(PPh3)]+ units N-coordinated to the imino groups, with the nitrogen atoms in a trigonal-planar configuration.

Original languageEnglish
Pages (from-to)1417-1422
Number of pages6
JournalChemische Berichte
Volume130
Issue number10
DOIs
StatePublished - 1997
Externally publishedYes

Keywords

  • (Imine)goid(I) complexes
  • Gold
  • Gold(I) complexes
  • Guanidines
  • Ketimines
  • N ligands

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