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The first stable macrocycles, 12-15, 16, 18, and 23, containing pentacovabnt phosphorus have been obtained by an Atherton-Todd reaction between the bis(hydridobicyc1ophosphorane.s) 3-7 and the corresponding binucleophile HO-(CHJ2-X-(CHJ2-OH. The tricyclic monclphosphoranes 8-1 1 as well as the noncyclic derivative 20 have also been isolated. A pathway that accounts for the formation of all these compounds is proposed. The X-ray crystal study of two 16-membered rings, 14, 15, confirms the diequatorial placement of the macrocyclic frame on the trigonal bipyramrdal phosphom which retains the most favorable axial-equatorial-axial annelation of the bicyclic moiety. Comparison of these two molecular structures points out the effect of the nature of X on the conformation of the macrocycle.