Dicobalt-Hexacarbonyl Complexes of Acetylenic Phosphazenes

π-Complexes have been prepared between propynylcyclophosphazenes 4 and 6 and dicobalt hexacarbonyl. These complexes are models for phosphazene high polymers that bear pendent metalloacetylenic side units. The complexes 8 and 9 are catalysts for the cyclotrimerization of phenylacetylene or diphenylacetylene, for the cotrimerization of acetylenic cyclophosphazenes with phenylacetylene or diphenylacetylene, and for the self-trimerization of 4 or 6 to 1,2,4-tri(cyclophosphazenyl)benzenoid derivatives. Complexes of types 8 and 9 were studied by mass spectrometric, infrared, ¹H, ¹³C, and ³¹P NMR techniques and by X-ray diffraction methods. The spectroscopic data revealed the existence of strong electronic interactions between the acetylenic dicobalt carbonyl side unit and the phosphazene ring when the organometallic unit was linked to a 1,2-ynyl function (9) but not when the organometallic component was insulated from the ring by a methylene spacer group (8). The X-ray diffraction results showed that, for three typical complexes (17, 18, and 19), the organometallic unit induced distortions in the cyclophosphazene ring, the effect being greater when the metalloacetylenic unit was closest to the skeleton. Both steric and electronic influences appear to be responsible for these phenomena. Crystal structure data: N₃P₃Cl₄(CH₃)[C₃H₃Co₂(CO)₆] (2-yne) (17), a = 17.238 (2) Å, b = 7.470 (7) Å, c = 17.853 (4) Å, β = 99.92 (1)°, V = 2264 (3) ų P2₁/c (No. 14, C_2h⁵), Z = 4; N₃P₃Cl₄(C₃H₅)[C₃H₃-Co₂(CO)₆ (2-yne) (18), a = 8.038 (3) Å, b = 22.080 (4) Å, c = 13.064 (3) Å, β = 91.51 (3)°, V = 2418 (2) ų, P2_l/n (No. 14, C_2h⁵), Z = 4; N₃P₃Cl₄(CH₃)[(CH₃.Co₂(CO)₆] (1-yne) (19), a = 8.592 (2) Å, b = 14.58 (1) Å, c = 17.787 (4) Å, V = 2228 (3) ų, Pnma (No. 62, D_2h¹⁶), Z = 4.