Synthesis and coordinating properties of the facultative Sb2O- and As2O-donor ligands O{(CH2)2ER2}2 (E = Sb or As; R = Ph or Me)

The new mixed Sb2O-donor ligands O{(CH2)2SbR2}2 (R = Ph, 1; R = Me, 2) with flexible backbones have been prepared in good yields as air-sensitive oils from reaction of NaSbR2 with 0.5 mol equivalents of O(CH2CH2Br)2 in thf solution. The As2O-donor analogues, O{(CH2)2AsR2}2 (R = Ph, 3; R = Me, 4) were obtained similarly from LiAsPh2 or NaAsMe2, respectively and O(CH2CH2Br)2, although ligand 4 appears to be considerably less stable with respect to C–O bond fission under some conditions than the other ligands. Using O(CH2CH2Cl)2 leads only to partial substitution by the SbPh2− or AsPh2− nucleophile. These ligands behave as bidentate chelating Sb2- or As2-donors in the distorted tetrahedral [M(L–L)2]BF4 (M = Cu or Ag; L–L = 1–4) on the basis of solution 1H and 63Cu NMR spectroscopic studies, mass spectrometry and microanalyses. Crystal structures of three representative examples with Cu(I) and Ag(I) confirm the distorted tetrahedral Sb4 or As4 coordination at the metal and allow comparisons of geometric parameters. The crystallographic identification of an unexpected Cu(I)–Cu(I) complex, [Cu2{Me2As(CH2)2OH}3](BF4)2, obtained as a by-product via C–O bond fission within ligand 4 is also reported. The distorted octahedral [RhCl2(L–L)2]Cl and the distorted square planar cis-[PtCl2(L–L)] (L–L = 1 or 2) are also described. The ether O atoms are not involved in coordination to the metal ion in any of the late transition metal complexes isolated.

The preparations and characterisation of four flexible Sb2O- and As2O-donor ligands, O{(CH2)2ER2}2 (R = Me or Ph; E = Sb or As), incorporating dimethylene linkages between the donor atoms are described, together with their reactivity with selected late transition metal ions and the crystal structures of representative examples and an unexpected dinuclear Cu(I)–Cu(I) product containing a fragmented ligand.Figure optionsDownload as PowerPoint slide