2-(2-{Diphenylarsino}ethyl)-1,3-dioxane (L1) and 2-(diphenylarsinomethyl)tetrahydrofuran (L2) and their palladium(II), platinum(II) and mercury(II) complexes: synthesis and crystal structures of [PdBr2(L1)2] and [HgBr2(L2)]2

Novel and potentially hemilabile ligands of (As, O) type, 2-(2-{diphenylarsino}ethyl)-1,3-dioxane (L1) and 2-(diphenylarsinomethyl)tetrahydrofuran (L2), are synthesised by reacting Ph2AsLi generated in situ under a nitrogen atmosphere with an appropriate organic halide. The complexes of L1 and L2 with Pd(II), Pt(II) and Hg(II) having composition [M(L1/L2)2X2] (M=Pd or Pt; X=Cl or Br) or [M(L1)Br2]2 (M=Hg) have been synthesised and characterised by elemental analyses, IR, 1H- and 13C{1H}-NMR spectra and molecular weight and conductivity measurements. The crystal structures of [PdBr2(L1)2] and [HgBr2(L2)]2 are solved. The potentially bidentate ligands L1 and L2 coordinate with Pd/ Hg through As only. The CH2O signals observed in 1H- and 13C{1H}-NMR spectra of the present complexes do not show any shift with respect to those of L1 and L2. The PdAs and HgAs bond lengths are 2.414(1) and 2.504(3) Å, respectively The Hg complex has bromo-bridges (2.792(3)–2.884(4) Å) that are asymmetric. The geometry of Hg is a distorted tetrahedral and that of Pd square planar. The As has tetrahedral geometry as three C atoms and Hg or Pd surround it. The [HgBr2(L2)]2 is the first example of a mercury(II)–arsine complex containing Hg(μ-Br)2Hg unit.