| Research Abstract |
^<121> Sb mossbauer spectra of 16 antimony(III) compounds of accurately known crystal structure and 51 other such compounds of unknown structure have been measured at 20 K. The following three conclusions were drawn from the observed relationship between the mossbauer parameters (especially isomer shift, <delta> and quadrupole coupling constant, e^2gQ) and the type of configuration around the Sb(III) atoms with stereochemically active lone pair electrons(E).
1. In N-, O-coordinated compounds, (delta) (as well as e^2gQ) decreases in the order SbO_3E (psi.)-tetrahedral, Sb_2O_3 (approaches) SbO_4E (psi)-trigonal bipyramidal, [Sb_2(tart)_2]^<2->) > SbO_6E (E at axial position; (psi)-pentagonal bipyramidal, Sb(ox)_3^<3->) > SbX_6E (E at equatorial position; (psi)-pentagonal bipyramidal,(Hedta).
2. In S-, C1-coordinated compounds, <delta> (as well as e^2gQ) decreases in the order SBS_3E<psi>-tetrahedral, [Sb(SR)_3]) > SbS_4E <psi>-trigonal bipyramidal, KSbS_2) > Sb- S_3shortS_3longE (<psi>-monocapped octahedral, [Sb(S_2COR)_3], [Sb(S_2P(OR)_2)_3]) [ SbS_6E (<psi>- pentagonal bipyramidal, [Sb(S_2PPh_2)_3]) > SbCl_6 (octahedral, M_3[SbCl_6]). The character of the lone pair is considered to increase in the above order from left to right, the p-character decreasing in the same order.
3. The Sb(III) atoms coordinated by S or Cl atoms have smaller e^2gQ than those coordinated by O or N atoms, both of which have identical configurations.
In addition. ^<121>Sb Mossbauer technique was successfully applied to the studies on sturcture of the antimony(III) complexes in the frozen solution, pyrolysis as well as radiolysis of antimony(III) complexes, and structure and bonding of the organic antimony(V) complexes.
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