Polarographic Observations of some Iron Organometallic Compounds in Acetonitrile

Abstract

Polarography in acetonitrile is useful for the study of the electrochemical behavior of organometallic compounds because acetonitrile is a suitable solvent for this class of compounds and provides a wide potential range over which their electrochemical behavior can be investigated. This inquiry was undertaken to enhance the understanding of the chemistry of these compounds. The polarographic behavior of three related iron compounds was studied and attempts were made to identify the products of the electrochemical reactions.Canadian Journal of Chemistry, 49, 398 (1971) Experimental Polarographic ResultsReagent-grade acetonitrile was purified by distillation from sodium hydride followed by distillation from phosphorous pentoxide. Tetraethyl ammonium perchlorate was prepared according to ref. 1, recrystallized four times from water, and dried over phosphorous pentoxide.The purified acetonitrile was stored in a glass container under helium and was metered into a polarographic cell with a Metrohm piston buret through a glass and teflon system. Oxygen was removed from the acetonitrile by bubbling helium previously saturated with acetonitrile through it.Polarograrns were obtained by using a three-electrode system and a Metrohm Polarecord equipped with a n infrared (i.r.) compensator. The supporting electrolyte, tetraethyl ammonium perchlorate, was used at a concentration of 0.05 M. The reference electrode was a Ag/O.Ol M A g N 0 3 electrode in acetonitrile. The reference electrode was isolated from the solution by a small piece of porous glass sealed in glass tubing with silicone rubber cement (G.E. Silicone Seal). The working counter electrode was a platinum wire sealed in glass. The polarographic cells were flat-bottom glass tubes about 7 cm long and 2.8 cm in diameter. The supporting electrolyte and compound were weighed into the cell, then the cell was flushed with helium and a known volume of acetonitrile metered into it.The same apparatus was also used to control the potential of a mercury-pool electrode for coulometric measurements. The solution was stirred with a magnetic stirrer. The counter working electrode was isolated behind two glass frits. Electrical connection between the working counter electrode and the solution was maintained through acetonitrile saturated with electrolyte (approximately 0.5 M). The total corrent passed was determined with the aid of a hydrazine coulometer (2).Infrared spectra were determined with 1-mm KBr cells and a Perkin-Elmer 337 infrared spectrophotometer. Spectra in the far i.r. were obtained with Nujol mulls, polyethylene cells, and a Beckman IR-I1 spectrophotometer.The polarographic behavior of cyclopentadienecarbonylhydridobis(trichlorosilyl)iron (1) in acetonitrile was examined. This compound is known (3) to ionize in acetonitrile according t o the equationIn the polarogram for this compound shown in Fig. 1A two waves with half-wave potentials of about -1.5 and -2.4 V are evident. The diffusion current for both these waves is a linear function of concentration. The dif...

Organic polarography

“…Polarographic data were reported for a series of bridged and nonbridged ferrocenes (298), for ferrocene, acetyl ferrocene, and acetoacetyl ferrocene (311), mononitrosyl iron bis(diaryl-l,2dithiolene) complexes ( 574), for Fe and Co dithiolene complexes (38), benzoyl ferrocene and ferrocenyl aldehyde at a rotating Au amalgam disk electrode (658), arene-Fe-cyclopentadienyl compounds where arene is benzene, naphthalene, fluorene, diphenyl, and phenanthrene (663), and for the ferrocene-ferricinium system (981). A mechanism for the polarographic behavior of cyclopentadiene carbonylhydridobis (trichlorosilyl) iron (I) in acetonitrile (97) and for cyclopentadienyl (benzene) iron derivatives in 50% ethanol (26) was proposed. Half-wave potentials for twelve 3-ferrocenyl-l (Xsubstituted-phenyl)-2-propen-l-one derivatives as a function of pH were correlated to Taft and Hammett constants (825).…”