Synthesis and Reactions of Ethynylferrocene-Derived Fluoro- and Chlorocyclotriphosphazenes

Abstract

The reactions of lithiated ethynylferrocene, FcC[triple bond]CLi (Fc = ferrocenyl), with fluoro- and chlorocyclotriphosphazenes, N(3)P(3)X(6) (X = F, Cl), resulted in the formation of stable mono-FcC[triple bond]CP(3)N(3)X(5) [X = F (1), Cl (2)] and geminal bis[(FcC[triple bond]C)(2)PN](X(2)PN)(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 (eta(5)-Cp)Co{eta(4)-C(4)[Fc(2)(N(3)P(3)X(5))(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 (eta(5)-Cp)Co{eta(4)-C(4)-1,3-(Fc)(2)-2,4-[NP(C[triple bond]CFc)(NPF(2))(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-PhCH(2), 4-Fc, 5-P(3)N(3)F(5))C(2)N(3) (9), and (1-PhCH(2), 4-P(3)N(3)F(5), 5-Fc)C(2)N(3) (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-PhCH(2)-4-FcC(2)N(3))(C[triple bond]CFc)PN](PNCl(2))(2) (11) and [(1-PhCH(2)-5-Fc-C(2)N(3))(C[triple bond]CFc)PN](PNCl(2))(2) (12), having one unreacted alkyne unit in the molecule. Among the bis-triazole-derived chlorophosphazenes [(1-PhCH(2)-4-Fc-C(2)N(3))(2)PN](PNCl(2))(2) (13), [(1-PhCH(2)-4-Fc-C(2)N(3))(1-PhCH(2)-5-Fc-C(2)N(3))PN](PNCl(2))(2)] (14), and [(1-PhCH(2)-5-Fc-C(2)N(3))(2)PN](PNCl(2))(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-PhCH(2)-4-P(3)N(3)F(5)-5-Fc)C(2)N(3)](2)PdCl(2) (16) with PdCl(2)(PhCN)(2). All of the new ferrocene- and cyclophosphazene-derived compounds except 8 and 12 have also been structurally characterized.