Additive model for the electric field gradient at antimony in some pentacoordinate organoantimony(V) derivatives

Abstract

to exist as a cubic pyrite structure when prepared and quenched from 800 to 8.50" and as a partially ordered (orthorhombic Pca2, space group) structure when synthesized between 700 and 800"; this partially ordered structure contained ordered As-S pairs. The compounds CoSbS and CoPSe crystallize with an orthorhombic structure, apparently similar to that of cr-NiAsz (pararammelsbergite). CoAsSe and CoSbSe are orthorhombic with the cla and c/b axial ratios of the anomalous marcasite.The temperature-independent magnetic data found for all CoXY materials studied is indicative of low-spin Co3+ (d6).The electrical data for these materials may reflect the specific effect of anions and crystallography on both the broadness and degree of separation of the valence and conduction bands."'Sb Mossbauer data are reported for several compounds of the types Ph,SbX and Ph,SbX, (Ph = C,H,; X = various electronegative groups) and are consistent with trigonal-bipyramidal structures in which the X groups occupy one or both axial positions, respectively. The first explicit application of an additive model for the electric field gradient at Sb in organoantimony(V) compounds has been made to these and other derivatives of like stoichiometries. Calculated and observed quadrupole coupling constants (e'qQ) are in good agreement, indicating the adequacy of such a model for these systems. For compounds of the type Ph,SbX, there is an approximately linear relation between isomer shift ( 6 ) and e'4Q. the slope of which is consistent with o-bonding effects being the dominant factor in determining the Mossbauer parameters. In derivatives containing Sb-0 bonds the S values are more positive than would be expected on the basis of electronegativity arguments alone. AIC30828T IntroductionAdditive models for the electric field gradient (efg) have been extensively employed to interpret Mossbauer quadrupole splitting data on organometallic Sn(1V) derivatives (and to a lesser extent, spin-paired Fe(I1) and Fe(-11) complexes).' Such models have had considerable success in predicting both signs and magnitudes of quadrupole splittings in compounds with fairly regular geometry, although the converse application of predicting molecular geometry from measured efg parameters has met with more limited success. This is due in part to the fact that similar efg parameters may arise from two or more possible structures, so that an unequivocal choice is not always possible. Moreover, no really satisfactory method has yet been devised to account for distortions from regular geometry.In view of the usefulness of the additive approximation for "'Sn quadrupole splittings in organotin(1V) compounds it is obviously of interest to extend the treatment to lZISb quadrupole splittings in organoantimony(V) complexes, since the model should be equally applicable here.la Although ' "Sb Mossbauer results for only a few organoantimony(V) deriva-

Moessbauer study of stibonic and stibinic acids: structural implications from orbital population analysis

“…It is reasonable to postulate that the overall reaction of PF3 with S02 is a two-step process: pf3 + so, opf3 + so 2SO -* SO, + S Since this reaction shows pressure dependence at relatively low All experiments were for 24 h. 6 The amount of sulfur can be calculated from the material balance. " Based on mmol of PF3 consumed.…”

“…Based on mmol of PF3 consumed. All experiments were for 24 h. 6 The amount of hydrogen can be calculated from the material balance.…”

121Sb Mössbauer Spectra of Hypervalent Complexes Having an Antimony-transition Metal Bond and Partial Quadrupole Coupling Constants

“…Ruddick et al have applied the model to 2 of 121 Sb Mössbauer spectra to give a quantitative explanation of the electronic states of organoatimony(V) compounds [31]. We will extend the model to our hypervalent antimony compounds.…”

“…According to the so-called point-charge model, the principal component of the EFG are written as [30,31] tbe , respectively [29]. Since we cannot obtain the absolute pqs values, they are referred to [Cl] tba .…”

Structure and bonding in organic derivatives of antimony(V)

“…MOssbauer spectral data of a number of triorgano (as well as a few tetraorgano) antimony(V) halides at liquid nitrogen and/or helium temperatures have been determined to establish the bond hybridization and the structure of the compoundS2, 82,83,85,86,[159][160][161][162] M6ssbauer data for Ph3SbX2 and Ph4SbX (X = an eleetronegative group) have been found to be consistent with trigonal bipyramidal geometry in which X groups occupy one or both axial positions 52,82,83,85,159). In the compounds, Ph3SbX2, an approximately linear relation between isomer shift (6) and quadrupole splitting constant (e2qQ) has been observed 83).…”