NEW SQUARE-PYRAMIDAL ORGANOANTIMONY(V) COMPOUNDS - CRYSTAL-STRUCTURESOF (BIPHENYL-2,2'-DIYL)PHENYLANTIMONY(V) DIBROMIDE, DICHLORIDE AND DIISOTHIOCYANATE, SB(2,2'-C12H8)PHX2 (X=BR, CL OR NCS), AND OF OCTAHEDRAL SBPH(O-O2C6CL4)CL-2-CENTER-DOT-OET2

Oxidative addition between (biphenyl-2,2'-diyl)phenylantimony(III), Sb (2,2'-C12H8)Ph 1 and Br-2 or SO2Cl2 gave Sb(2,2'-C12H8)PhBr2 2 and Sb( 2,2'-C12H8)PhCl2, 3, respectively, while the corresponding fluoride Sb (2,2'-C12H8)PhF2 4 and the thiocyanate Sb(2,2'-C12H8)Ph(NCS)(2) 5 were obtained by metathesis reactions between 3 and KF and KSCN, respectiv ely. Compounds 2 and 3 are isostructural but, in contrast to the close ly related SbPh3X2 species, individual molecules have square-pyramidal geometry. Again in contrast to SbPh3X2 compounds, secondary antimony- halogen interactions trans to the apical carbon atom lead to solid-sta te dimers, implying Lewis acidity at antimony. Antimony in the thiocya nate 5 showed similar square-pyramidal geometry with N-bonded thiocyan ate groups but bridging by one thiocyanate again gives dimers in the s olid. Oxidative addition between SbPhCl2 and tetrachloro-ortho-benzoqu inone in ether solution gave the tetrachlorocatechol analogue of 3 as a six-co-ordinate ether solvate, SbPb(o-O2C6Cl4). OEt2 6. If the weak bond to ether is ignored, antimony again has square-pyramidal geometry but formation of the adduct again points to antimony Lewis acidity. A non-solvated substituted catecholate, SbPh(o-O2C6H2Bu2t-3,5)Cl-2 8, w as also synthesized but crystals suitable for X-ray diffraction could not be obtained.