Synthesis and Reactions of Ethynylferrocene-Derived Fluoro- and Chlorocyclotriphosphazenes

The reactions of lithiated ethynylferrocene, FcCCLi (Fc = ferrocenyl), with fluoro- and chlorocyclotriphosphazenes, N3P3X6 (X = F, Cl), resulted in the formation of stable mono-FcCCP3N3X5 [X = F (1), Cl (2)] and geminal bis[(FcCC)2PN](X2PN)2 [X = F (3), Cl (4)], ethynylferrocene-substituted cyclophosphazenes. The reactions of 1 and 2 with CpCo(COD) were found to differ in the nature of the sandwich compounds (η5-Cp)Co{η4-C4[Fc2(N3P3X5)2]} formed. While the fluorophosphazene-derived compound 1 yielded both cis and trans isomers of the cyclobutadiene complexes 5 and 6, the chlorophosphazene-derived compound 2 was found to give only the trans-cyclophosphazene-disubstituted cyclobutadiene compound 7. The reaction of 3 with CpCo(COD) was found to give the compound (η5-Cp)Co{η4-C4-1,3-(Fc)2-2,4-[NP(CCFc)(NPF2)2]2} (8) having one of the alkyne units of the cyclophosphazene moiety of 3 remaining unreacted even after reaction with an excess of CpCo(COD). The first click reactions of ethynylferrocene-derived cyclophosphazenes have been carried out by reacting 1 and 4 with benzyl azide, resulting in novel mono- and disubstituted cyclophosphazene-derived 1,2,3-triazoles. The reaction of 1 with benzyl azide yielded two positional isomers of the 1,2,3-triazole, (1-PhCH2, 4-Fc, 5-P3N3F5)C2N3 (9), and (1-PhCH2, 4-P3N3F5, 5-Fc)C2N3 (10), with the latter having a benzyl group in the vicinity of the ferrocene unit as the major product. A similar reaction of 4 with benzyl azide was found to yield five triazole-based products, with two, [(1-PhCH2-4-FcC2N3)(CCFc)PN](PNCl2)2 (11) and [(1-PhCH2-5-Fc-C2N3)(CCFc)PN](PNCl2)2 (12), having one unreacted alkyne unit in the molecule. Among the bis-triazole-derived chlorophosphazenes [(1-PhCH2-4-Fc-C2N3)2PN](PNCl2)2 (13), [(1-PhCH2-4-Fc-C2N3)(1-PhCH2-5-Fc-C2N3)PN](PNCl2)2] (14), and [(1-PhCH2-5-Fc-C2N3)2PN](PNCl2)2 (15), the unsymmetrically disubstituted bis-triazole compound 14 was found to be the major product. The fluorophosphazene-derived triazole 10 was found to readily form a disubstituted square-planar complex trans-[(1-PhCH2-4-P3N3F5-5-Fc)C2N3]2PdCl2 (16) with PdCl2(PhCN)2. All of the new ferrocene- and cyclophosphazene-derived compounds except 8 and 12 have also been structurally characterized.