The Reactions of Alkynlcyclophosphazenes with Metal Carbonyls

Abstract

The reaction of N₃P₃F₅C≡CR (R=Ph, Me₃Si, n-C₄H₉) with CO₂(CO)₈, leads to N₃P₃F₅C≡CR·CO₂ (CO)₆. The corresponding reaction with 2,2-N₃P₃F₄,(C≡CPh)₂, produces the novel, structurally characterized, tetracobalt species 2,2-N₃P₃F₄ C≡CR·CO₂ (CO)₆)₂. In the case of the previously reported N₃P₃F₅C≡CPh complex, we now report that reaction with excess phosphazene leads to the cyclotrimerized material 1,2,4-(N₃P₃F₅)₃Ph₃C₆(I). Detailed dynamic ¹⁹F NMR spectroscopy studies of this material shows detectable barriers to rotation about the phosphorus-carbon bond of the central arene. The reaction of a more reactive catalyst, η⁵-C₅H₅Co(CO)₂, with N₃P₃F₅ C≡CPh gives rise to a variety of cyclooligomerized products. A cyclodimerized material, (N₃P₃F₅)₂Ph₂C₂(II) is isolated as the colbalt stabilized entity II·CoCp. The carbonyl insertion product of the cyclodimerized complex has been isolated as well as I and its colbalt complex I·CoCp (which is believed to contain an η⁴ arene). The reaction of Fe(CO)₅, with N₃P₃F₅C≡CPh gives the iron stabilized cyclodimer, II·Fe(CO)₅. The corresponding reaction with FeACO), gives a plethora of products including the cyclodimerized material noted above and its carbonyl insertion product. Other characterized products include I·Fe(CO)₃, (also believed to be an η⁴ material), an iron containing metallocycle and unique derivative in which the alkyne bridges iron and cyclopentadienone fragments.