First structural study of a thiophosphorane containing a six-membered ring. Phosphorus-sulfur vs phosphorus-oxygen ligand preferences

Abstract

Oxidative addition of phenanthrenequinone to the newly synthesized dithiaphosphorinane, (Xylyl-O)P-S(CH₂)₃S (1), results in a new thiophosphorane containing a sulfur-bonded six-membered ring. X-ray analysis on separate crystals reveals both a monoclinic and triclinic modification. This represents the first structural study of a six-membered ring containing thiophosphorane. The structure which is a trigonal bipyramid has the ring sulfur atoms located in apical-equatorial sites instead of the expected diequatorial arrangement. As a consequence, the more electronegative xylyloxy oxygen atom is relegated to an equatorial position. A slightly twisted boat conformation exists for the dithiaphosphorinane ring. ^IH NMR spectroscopy is consistent with the retention of the solid-state structure in solution which undergoes rapid intramolecular ligand exchange.