Abstract
Neutral hexacoordinate phosphorus(V) compounds of a number of univalent bidentate ligands are known.l,2 The silylated forms of tridentate, dianionic Schiff base ligands: N-(2-hydroxyphenyl)salicylideneamine H2LI, N-(4-tert-butyl-2-hydroxyphenyl)-salicylideneamine H2LII, N-(2-hydroxy-4-nitrophenyl)salicylidene-amine H2LIII, and 2,2′-azodiphenol H2LIV gave, with halogeno- and (trifluoromethyl)halogenophosphoranes, neutral hexa-coordinate derivatives with bis-chelate structures. The ligands form bicyclic five- and six-membered chelate rings in a meridional conformation, with two P-O bonds and one N→P donor bond. Hexacoordinate structures were evidenced by high-field 31P NMR chemical shifts (-136 to -148 ppm), characteristic J PF coupling patterns and was further substantiated by crystal structures of Cl3LII (A) and F3PLII (B).