Structural Diversity in Supramolecular Complexes of MCl₃ (M = As, Sb, Bi) with Constrained Thio- and Seleno-Ether Ligands

MCl3 react with o-C6H4(EMe)2 (E = S, Se) or o-C6H4(CH2ER)2 (E = S, R = Me or Et; E = Se, R = Me) in anhydrous CH2Cl2 or MeCN to give the yellow (Bi) or white (Sb) complexes, [MCl3{o-C6H4(EMe)2}], [(MCl3)2{o-C6H4(CH2SMe)2}3], [MCl3{o-C6H4(CH2SEt)2}], and [(BiCl3)4{o-C6H4(CH2SeMe)2}3], which were characterized by IR/Raman, 1H NMR spectroscopy, and microanalysis. The corresponding reactions with AsCl3 gave oils. Using the tetrachalcogenoethers, 1,2,4,5-C6H2(CH2EMe)4 (E = S or Se), gave [(MCl3)2{1,2,4,5-C6H2(CH2EMe)4}] (E = S: M = As, Sb or Bi; E = Se: M = As) as powdered solids. The structures adopted are extremely diverse within this related series. Crystal structure determinations show infinite chains for [MCl3{o-C6H4(EMe)2}] (M = Bi, E = S or Se; M = Sb, E = S), although the structures differ significantly in detail. [BiCl3{o-C6H4(SMe)2}] is formed through chains of orthogonal μ-Bi2Cl2 units linked together, with one dithioether ligand chelating per Bi atom, and seven-coordinate Bi; [SbCl3{o-C6H4(SMe)2}] comprises weakly associated Sb2Cl6 dimer units linked into chains by weakly bridging dithioethers, where both available lone pairs on each S atom are used. [BiCl3{o-C6H4(SeMe)2}] comprises distorted square pyramidal units involving pyramidal BiCl3 primary coordination and a weakly chelating diselenoether ligand, and assembled into infinite chains through long bridging Bi···Cl interactions via all three Clʼs. The 2:3 M:L complexes [(MCl3)2{o-C6H4(CH2SMe)2}3] (M = Bi or Sb) are isostructural, and also show one-dimensional polymers, but this time the coordination is based upon pyramidal MCl3 units, with secondary bonding via three long M···S contacts from bridging dithioethers, and a further long M···Cl bridge which completes a distorted seven-coordinate environment at M. The Et-substituted thioether analogue gives the 1:1 [MCl3{o-C6H4(CH2SEt)2}] for both Bi and Sb; the former showing a chain polymer structure based upon seven-coordinate Bi and bridging dithioethers and the latter a weakly Cl-bridged dimer with distorted octahedral coordination at Sb, with a chelating dithioether. The 4:3 [(BiCl3)4{o-C6H4(CH2SeMe)2}3] complexes are based upon a central BiCl6 octahedron linked to each of the other three Bi atoms via two bridging Cl atoms; the outer Bi atoms are also bonded to two mutually trans Se donor atoms from distinct diselenoethers, and two terminal Cl atoms, giving a distorted octahedral coordination environment at Bi. One of the two crystallographically independent tetrabismuth units is discrete, while the other shows further Cl-bridges to adjacent units giving an infinite network. [(AsCl3)2{1,2,4,5-C6H2(CH2SMe)4}] also forms an infinite network based upon square pyramidal As(III), and comprises pyramidal AsCl3 units each weakly coordinated to two (mutually cis) S-donor atoms from two different thioether ligands. The Sb-analogue is structurally very similar; however, in this case a solvent MeCN occupies the sixth coordination site. Finally, [(AsCl3)2{1,2,4,5-C6H2(CH2SeMe)4}] forms an infinite chain based upon distorted octahedral coordination at As through three terminal (pyramidal) Cl atoms, two Se atoms from κ2-μ2-selenoethers, although unexpectedly the chelation is through Se atoms that are mutually meta on the aromatic ring; with one Se atom on each ligand using both of its lone pairs to bridge (weakly) between two As atoms. These MCl3-chalcogenoether adducts are mostly weakly associated, and lead to very diverse structures which result from a combination of intra- and intermolecular interactions and crystal packing.