Abstract
A synthetic approach to the sandwich complex [Cp'''Co(η(4) -P(4) )] (2) containing a cyclo-P(4) ligand as an end-deck was developed. Complex 2 is the missing homologue in the series of first-row cyclo-P(n) sandwich complexes, and shows a unique tendency to dimerize in solution to form two isomeric P(8) complexes [(Cp'''Co)(2) (μ,η(4) :η(2) :η(1) -P(8) )] (3 and 4). Reactivity studies indicate that 2 and 3 react with further [Cp'''Co] fragments to give [(Cp'''Co)(2) (μ,η(2) :η(2) -P(2) )(2) ] (5) and [(Cp'''Co)(3) P(8) ] (6), respectively. Furthermore, complexes 2, 3, and 4 thermally decompose forming 5, 6, and the P(12) complex [(Cp'''Co)(3) P(12) ] (7). DFT calculations on the P(4) activation process suggest a η(3) -P(4) Co complex as the key intermediate in the synthesis of 2 as well as in the formation of larger polyphosphorus complexes via a unique oligomerization pathway.