Synthesis and properties of antimony(iii) and bismuth(iii) halide complexes of diphosphines and diarsines. Crystal structures of [Bi2I6{o-C6H4(AsMe2)2}2], [Sb2Br6{o-C6H4(PPh2)2}2], [Sb2Cl6{o-C6H4(AsMe2)2}], and [BiCl3{o-C6H4(P(O)Ph2)2}(thf)]

Abstract

The reaction of SbX₃ or BiX₃ (X = Cl, Br or I) with the diarsines o-C₆H₄(AsMe₂)₂ or Ph₂AsCH₂CH₂AsPh₂, the triarsine MeC(CH₂AsMe₂)₃, or the diphosphines o-C₆H₄(PMe₂)₂ or o-C₆H₄(PPh₂)₂ (L), yield complexes of 1 ∶ 1 stoichiometry MX₃L irrespective of the reactant ratios used. X-Ray structures of [Bi₂I₆{o-C₆H₄(AsMe₂)₂}₂] and [Sb₂Br₆{o-C₆H₄(PPh₂)₂}₂] reveal distorted octahedral Bi or Sb coordination spheres, linked via asymmetric halide-bridges. Bond lengths suggest a bonding model based upon primary bonding in pyramidal MX₃ groups with weaker secondary interactions to the diphosphine or diarsine and the longer distance bridging halide. [Sb₂Cl₆{o-C₆H₄(AsMe₂)₂}] is obtained by partial decomposition of [Sb₂Cl₆{o-C₆H₄(AsMe₂)₂}₂] in hot ethanol and contains Sb{o-C₆H₄(AsMe₂)₂}Cl₂ and SbCl₄ units linked via asymmetric chlorine bridges into puckered chains, which associate further through long Sb⋯Cl contacts to produce a polymeric sheet structure. The mononuclear species [BiCl₃{o-C₆H₄(P(O)Ph₂)₂}(thf)] obtained from BiCl₃ and o-C₆H₄(P(O)Ph₂)₂ in thf is a distorted octahedron with a BiCl₃O₃ donor set.