Palladium(ii)-based cis,trans-1,3,5-triaminocyclohexane complexes demonstrating a variety of coordination modes and architectures

Abstract

The reaction of cis,trans-1,3,5-triaminocyclohexane·3HX (L·3HX) with PdX₂ (X = Br, Cl) affords a wide range of coordination complexes that represent the different coordination modes available to L. Monoligand complexes [Pd(LH)Cl₂]Cl (1) and [Pd(LH)Br₂]₂[PdBr₄] (2) demonstrate the bidentate coordination of L with the two cis amino ‘head’ groups chelating the palladium(II) ion and the third trans amino ‘tail’ group being protonated. Diligand complexes [Pd(LH)₂]X (X = (NO₃)₄3, (SO₄)₂4) show a ‘head-to-head’ coordination mode with the protonated trans amino groups adopting a conformation that positions them opposite to each other. Both sets of amino groups are engaged in coordination in a cyclic ‘head-to-tail’ fashion found in the hexanuclear ring clusters [{Pd(L)X}₆]X₆ (X = Cl 5, Br 6). 5 and 6 are isostructural, both in the solid state and in solution, despite accommodating six chloro or bromo ligands into the cluster framework. A trinuclear complex [Pd{Pd(L)Cl₂}₂Cl₂] (7) reveals ‘tail-to-tail’ coordination of two ligands for the centre palladium(II) ion in addition to their ‘head’ amino groups individually chelating other palladium(II) ions. Complexes 1–7 were characterised by single-crystal X-ray diffraction, elemental analysis, IR and by NMR spectroscopy (1–6).