The first free 7 lambda(3)-phosphanorbornadiene

The first uncoordinated 7 lambda(3)-phosphanorbornadiene 10 is reported. Th is missing member of the class of 7-heteranorbornadienes was prepared by de complexation of its pentacarbonyltungsten complex 6 with iodine and N-methy limidazole It is moderately stable at room temperature toward loss of the p hosphinidene bridge (PhP:) because the aromatic fragment, [5]metacyclophane (5), is a highly strained compound. For this reason, 10 may be considered to be a hyperstable compound. An analysis of the energetics of the system b y density functional calculations supports this rationalization.