Preparation and crystal structures of five organoantimony halides; ( p-tolyl)antimony(III) dichloride and dibromide, diphenylantimony(III) bromide, 2′-diyl)antimony(III) chloride and bis-(2′-chlorobiphenyl-2-yl)antimony(V) trichloride

Abstract

Crystal structures are reported for four organoantimony(III) halides, i.e. ( p-tolyl)antimony dichloride ( 1) and dibromide ( 2), diphenylantimony bromide ( 3), (biphenyl-2,2′-diyl) antimony chloride ( 4) and a new antimony(V) compound, bis(2′-chlorobiphenyl-2-yl)antimony(V) trichloride ( 5), obtained by oxidising ( 4) with an excess of chlorine. The two tolyl compounds ( 1) and ( 2), which are isostructural and also isostructural with the corresponding phenyl derivatives, contain pyramidal CSbX 2 units. These are interlinked by (a) two weak intermolecular Sb ⋯ halogen interactions (mean 3.54 and 3.69 Å for the chloride and bromide, respectively), raising the antimony coordination number to five giving infinite chains, and (b) weak contacts between antimony and three of the carbon atoms of a symmetry-related tolyl group (mean 3.41 and 3.42 Å for the chloride and bromide, respectively). There are no intermolecular Sb ⋯ Br contacts in 3 but two Sb ⋯ C interactions (mean 3.64 Å) interconnect the pyramidal monomers. Such Sb ⋯ C interactions (mean 3.43 Å) are also present in the biphenylyl derivative 4, in which the CSbC angle in the pyramidal monomer is constrained to 81.0° by the short bite of the biphenylyl group. Loose dimers are formed in the solid state by Sb ⋯ Cl contacts at 3.71 Å. In contrast to the chlorine bridged dimeric structure of Ph 2SbCI 3, compound 5 is a distorted trigonal bipyramidal monomer in the solid state, providing the first example of an antimony(V) compound with chlorine atoms in both axial and equatorial sites. As expected, distances to the two axial chlorines are substantially longer (2.420(3), 2.421(3) Å) than that to the equatorial atom (2.280(3) Å). The greatest distortion is shown by the equatorial CSbC angle, which is increased to 137.1°, probably as a consequence of the steric requirements of the bulky chlorobiphenylyl groups.