The Crystal Structures of the Adducts SbCl5.POCl3, SbCl5.(CH3)3PO, and NbCl5.POCl3.

Abstract

The previously detd. crystal structures of SbCl5.POCl3 (I) (CA 53, 21022h) and SbCl5.Me3PO (II) (CA 55, 19416e) were refined by a least-squares method. The structure detn. of NbCl5.POCl8 (III) is also reported. It is isostructural with I and II: space group Pmnb, unit cell dimensions a 8.07 ± 0.01, b 16.23 ± 0.03, c 8.83 ± 0.02 A. The differences in the P-O and Sb-O bond lengths of adducts with POCl3 and Me3PO were confirmed and the values for III are consistent. The bond angles in the POCl3 mols. differ from regular tetrahedral coordination; the O-P-Cl bond angles are slightly larger and the Cl-P-Cl bond angles slightly smaller than for regular coordination. The Nb-Cl bond lengths exhibit a surprising variation, far beyond the significance limits, and are comparable with those for the nonbridging Nb-Cl bonds in Nb2Cl10. In both POCl3 adducts, very short Cl-Cl packing distances are found. [on SciFinder(R)]