Synthesis of 1-Phosphaspiro[2.n]alkanes by Addition of Terminal Phosphinidene Complexes to Exocyclic Olefins

The phosphinidene complexes PhPW(CO)₅ (1a) and MePW(CO)₅ (1b) have been added to exocyclic olefins to yield 1-phosphaspiro[2.n]alkanes (n = 2−5). The molecular structures of the parent phosphirane 10a and the parent phosphaspiro[2.2]pentane 6a that result from addition of PhPW-(CO)₅ to ethylene and methylenecyclopropane, respectively, have been determined by single-crystal X-ray analyses. The reactivity order for addition of both phosphinidene complexes to exocyclic olefins was determined as methylenecyclopentane (4) > methylenecyclobutane (3) > methylenecyclohexane (5) > methylenecyclopropane (2). PhPW(CO)₅ is more selective and less reactive in its additions than MePW(CO)₅. The relative rates for phosphinidene addition correlate with both ¹³C NMR chemical shifts of the spiro-carbon and the ¹J_CH coupling constants of the CH₂ group of the 1-phosphaspiro[2.n] alkanes products.