A preliminary chemical study of terminal allyl-, 3-butenyl-, and 4-pentenylphosphinidene complexes. Thermal rearrangement of 1-allylphosphirene complexes by insertion of the allylic C=C double bond into the phosphirene ring

Article abstract of DOI:10.1021/om00137a016

The reaction of dimethyl acetylenedicarboxylate with the appropriate phosphole complexes leads to the 7-allyl-, 7-(3-butenyl)-, and 7-(4-pentenyl)-7-phosphanorbornadiene P-W(CO)₅ complexes. In the 3-butenyl case, it is necessary to use a large excess of acetylenedicarboxylate in order to avoid an intramolecular [4 + 2] cycloaddition between the phosphole dienic system and the double bond of the butenyl P substituent. The thermal decomposition of the 7-phosphanorbornadiene complexes leads to the corresponding terminal phosphinidene tungsten pentacarbonyl complexes. The pentenylphosphinidene complex undergoes an internal cycloaddition involving the phosphorus atom and the C=C double bond to give a bicyclic phosphirane complex. The terminal allylphosphinidene complex reacts with olefins and acetylenes to give the expected phosphirane and phosphirene complexes. In the latter case, however, additional heating induces a brand new insertion of the allylic double bond within the phosphirene cycle leading to a new type of bicyclic phosphirane complex. The postulated mechanism implies an equilibrium between phosphirene complexes and 1-metalla-2-phosphacyclobutenes at high temperature. No such insertion has been observed with 1-(3-butenyl)phosphirene complexes nor with an external olefin and a phosphirene complex.