Reactions of Ferrocenyl- and Ruthenocenylphosphazenes with Lithiometallocenes and the X-ray Structures of N₃P3F₄(η-C₅H₄)₂Fe, [N₃P₃F₃{(η-C₅H₄)₂Fe}{(η-C₅H₄)Fe(η-C₅H₅)}], 1,5-N₄P₄F₆(η-C₅H₄)₂Fe, and 1,5,3,7-N₄P₄F₄[(η-C₅H₄)₂RU]₂¹

Cyclotri- and cyclotetraphosphazenes that bear fluoro and ferrocenyl or ruthenocenyl side groups undergo fluorine replacement with mono- or dilithioferrocene or mono- or dilithioruthenocene or with methyllithium or phenyllithium. The pattern of fluorine replacement is complex and depends on coordination of the incoming organolithium reagent with the skeletal nitrogen atoms and on steric hindrance factors. An unusual “double-transannular” ruthenocenylphosphazene was isolated from the cyclotetraphosphazene system. Four metallocenylphosphazenes have been studied by X-ray crystallography. Crystals of N₃P₃F₄(η-C₅H₄)₂Fe (1a) are triclinic, space group PI, with a = 8.074 (1) Å, b = 8.164 (1) Å, c = 11.521 (2) Å, a = 91.37 (2)°, β = 92.31 (2)°, γ = 118.2 (1)°, V = 667.9 ų, and Z = 2. The structure was refined to discrepancy indices R = 0.038 and R_w= 0.051. The phosphazene ring is severely distorted in response to the presence of the transannular ferrocenyl unit. cis-non-gem-[N₃P₃F₃{(η-C₅H₄)₂Fe}{(η-C₅H₄)Fe(η-C₅H₅)}] (7) gives orthorhombic crystals, space group P2₁2₁2₁, with a = 10.398 (2) Å, b = 10.644 (2) Å, c = 18.769 (2) Å, V = 2077.3 ų, and Z = 4. The structure was refined to discrepancy indices R = 0.042 and R_w= 0.059. The phosphazene ring is highly distorted in this molecule. The ferrocene transannular tetramer 1,5-N₄P₄F₆(η-C₅H₄)₂Fe (3a) gives monoclinic crystals, space group P2₁/n, with a = 8.668 (1) Å, b = 12.823 (1) Å, c = 14.560 (2) Å, β = 100.86 (1)°, V = 1589.3 ų, and Z = 4. The structure was refined to discrepancy indices R = 0.032 and R_w= 0.041. Even more distortion of the phosphazene ring is found in this molecule. Crystals of the double-transannular phosphazene tetramer 1,5,3,7-N₄P₄F₄{(η-C₅H₄)₂Ru}2 (10) are monoclinic, space group P2_ltwith a = 7.719 (1) Å, b = 12.151 (5) Å, c = 15.606 (2) Å, β = 101.93 (1)°, V = 1432.1 ų, and Z = 2. The eight-membered cyclotetraphosphazene ring is severely puckered to adapt to the constraints imposed by the two ruthenocene systems.