Cyclophosphazene hydrazides as scaffolds for multi-ferrocenyl assemblies: Synthesis, structure, and electrochemistry

Reactions of N-methylhydrazine with chlorocyclophosphazenes, N3P3Cl6 (1), N3P3(OPh)Cl-5 (2), gem-N3P3Ph2Cl4 (3), spiro-N3P3(O2Cl2H8)(2)Cl-2 (4), N3P3(OPh)(5)Cl(5), and diphenylphosphinic chloride, Ph2P(O)Cl (6), proceed in a regiospecific manner to afford the products N3P3[N(Me)NH2](6) (1a), N3P3(OPh)[N(Me)NH2](5) (2a), gem-N3P3Ph2[N(Me)NH2](4) (3a), spiroN(3)P(3)(O2C12H8)(2)[N(Me)NH2](2) (4a), N3P3(OPh)(5)[N(Me)NH2] (5a), and Ph2P(O)[N(Me)NH2] (6a). The terminal NH2 groups in all of these compounds are reactive and have been used in the condensation reaction involving ferrrocene-2-carboxaldehyde to afford the corresponding hydrazones N3P3[N(Me)N=CHC5H4FeC5H5](6) (1b), N3P3(OPh)[ N(Me)N=CHC5H4FeC5H5](5) (2b), gem-N3P3Ph2[N(Me)N=CHC5H4FeC5H5](4) (3b), spiro-N3P3(O2C12H8)(2)[N(Me)N=CHC5H4FeC5H5]2 (4b), N3P3(OPh)(5)[N(Me)N=CHC5H4FeC5H5] (5b), and Ph2P(O)[ N(Me)N=CHC5H4FeC5H5] (6b). The structures of 1-6(a,b) have been determined by the use of multinuclear NMR, mass spectroscopy, and elemental analysis. X-ray crystal structures of 1b, 3b, 4b, 5b, and 6b have also been determined, which confirm their molecular structures. Cyclic voltammetric experiments on the ferrocenyl derivatives 1b-6b reveal an essentially reversible oxidation peak. Further, all of these are electrochemically quite robust and do not decompose on oxidation.