Cyclophosphazene Hydrazides as Scaffolds for Multi-Ferrocenyl Assemblies:  Synthesis, Structure, and Electrochemistry

Abstract

Reactions of N -methylhydrazine with chlorocyclophosphazenes, N 3 P 3 Cl 6 ( 1 ), N 3 P 3 (OPh)Cl 5 ( 2 ), gem -N 3 P 3 Ph 2 Cl 4 ( 3 ), spiro -N 3 P 3 (O 2 C 12 H 8 ) 2 Cl 2 ( 4 ), N 3 P 3 (OPh) 5 Cl ( 5 ), and diphenylphosphinic chloride, Ph 2 P(O)Cl ( 6 ), proceed in a regiospecific manner to afford the products N 3 P 3 [N(Me)NH 2 ] 6 ( 1a ), N 3 P 3 (OPh)[N(Me)NH 2 ] 5 ( 2a ), gem -N 3 P 3 Ph 2 [N(Me)NH 2 ] 4 ( 3a ), spiro -N 3 P 3 (O 2 C 12 H 8 ) 2 [N(Me)NH 2 ] 2 ( 4a ), N 3 P 3 (OPh) 5 [N(Me)NH 2 ] ( 5a ), and Ph 2 P(O)[N(Me)NH 2 ] ( 6a ). The terminal NH 2 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 N 3 P 3 [N(Me)N CHC 5 H 4 FeC 5 H 5 ] 6 ( 1b ), N 3 P 3 (OPh)[ N(Me)N CHC 5 H 4 FeC 5 H 5 ] 5 ( 2b ), gem -N 3 P 3 Ph 2 [N(Me)N CHC 5 H 4 FeC 5 H 5 ] 4 ( 3b ), spiro -N 3 P 3 (O 2 C 12 H 8 ) 2 [N(Me)N CHC 5 H 4 FeC 5 H 5 ] 2 ( 4b ), N 3 P 3 (OPh) 5 [N(Me)N CHC 5 H 4 FeC 5 H 5 ] ( 5b ), and Ph 2 P(O)[ N(Me)N CHC 5 H 4 FeC 5 H 5 ] ( 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.