Synthesis and molecular structures of fluorophosphoranes, r3pf2, isoelectronic with anionic fluorosilicates

Abstract

The new difluorophosphoranes Ph(o-Tol)2PF2 (1), Mes3PF2 (2), Ph(1-Np)2PF2 (3), (o-Tol)3PF2, (p-Tol3PF2, Ph(t-Bu)2PF2, and (Ph2PF2)2CH2 containing bulky substituents were prepared by the fluori-nation reaction of precursor organophosphines with dimethylaminosulfur trifluoride. They were characterized by 1H, 3IP, and 19F NMR spectra. The molecular structures of 1-3 revealed trigonal bipyra-midal geometries. Comparison of the structural data with that of isoelectronic anionic fluorosilicates along with the NMR data suggests the operation of a steric effect that increases bond lengths in the difluorophosphoranes 1-3 and in related anionic silicates. The data are discussed relative to enhanced reactivity observed for anionic silicates. 1 crystallizes in the monoclinic space group C2/c with a = 11.819(3) Å, b = 10.163(2) Å, c = 13.992(3) Å, β = 99.14(2)°, and Z = 4. 2 crystallizes in the monoclinic space group C2/c with a = 10.531(2) Å, b = 12.667(2) Å, c = 18.110(4) Å, β = 104.21(2)°, and Z = 4. 3 crystallizes in the monoclinic space group P21/c with a = 15. 868(2) Å, b = 7.434(1) Å, c = 18.213(4) Å, p = 112. 34(2)°, and Z = 4. The final conventional unweighted residuals are 0.063 (1), 0.060 (2), and 0.040 (3). © 1995, Taylor & Francis Group, LLC. All rights reserved.