Palladium(II) co-ordination by linear N-methylated polyamines: A solution and solid-state study

Carla Bazzicalupi, Andrea Bencini, Haim Cohen, Claudia Giorgi, Gilad Golub, Dan Meyerstein, Nadav Navon, Piero Paoletti, Barbara Valtancoli

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12 Scopus citations

Abstract

Palladium(II) co-ordination by the tertiary polyamines 2,5,8-trimethyl-2,5,8-triazanonane, 2,5,8,11-tetramethyl-2,5,8,11-tetraazadodecane, 2,5,9,12-tetramethyl-2,5,9,12-tetraazatridecane, 2,6,9,13-tetramethyl-2,6,9,13-tetraazatetradecane, 2,5,8,11,14-pentamethyl-2,5,8,11,14-pentaazapentadecane, 2,5,8,11,14,17-hexamethyl-2,5,8,11,14,17-hexaazaoctadecane and by the new compound 2,5,8,11,14,17,20,23-octamethyl-2,5,8,11,14,17,20,23-octaazatetracosane has been investigated by means of potentiometric (0.1 M NMe4Cl aqueous solution, 298.1 K) and spectrophotometric measurements. The species present in solution and their stability constants have been determined. The first five amines form only mononuclear complexes, while the last two can give both mono- and bi-nuclear complexes in aqueous solution. The thermodynamic data show that the complexes with N-methylated polyamines are tremendously less stable than their non-methylated counterparts. The UV/VIS spectra of the complexes exhibit a marked red shift of the L → M charge-transfer bands with respect to the complexes of the non-methylated ligands. As a consequence of the reduced thermodynamic stability, both mono- and bi-nuclear complexes show a particular acid-base behavior with respect to those of the non-methylated amines. Such complexes can easily bind a proton or a hydroxide anion in aqueous solution, with consequent detachment of a co-ordinated nitrogen. The crystal structures of two binuclear complexes were determined. In both the metals show distorted square-planar arrangements of the donors.

Original languageEnglish
Pages (from-to)1625-1631
Number of pages7
JournalJournal of the Chemical Society. Dalton Transactions
Issue number10
DOIs
StatePublished - 21 May 1998

ASJC Scopus subject areas

  • Chemistry (all)

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