Iron complex compounds, anions

Iron (II) complex compounds, anions, carbonyl, H2Fe(CO)4, and potassium salt, 2 243, 244... 

Iron(III) complex compounds, anions, oxalato, K2[Fe(C204)a]-3H20, 1 36... 

Iron(III) compounds of 3-OEt-salAPA have been widely studied [127, 128, 139-145]. Both the anion and the incorporated solvent molecule influence the spin crossover behaviour of the complex salts. Thus T1/2 for [Fe(3-OEt-salAPA)2]ClC>4 is 295 K, whereas that for the dichloromethane solvate is 152 K [140]. The transition in [Fe(3-0Et-salAPA)2]C104 and [Fe(3-OEt-salA-PA)2]BPh4 is more gradual and occurs at a somewhat higher temperature than that for the benzene solvate [Fe(3-0Et-salAPA)2]C104-C6H6 [141]. 

Unfortunately, many compounds contain bonds that are a mixture of ionic and covalent. In such a case, a formal charge as written is unlikely to represent the actual number of charges gained or lost. For example, the complex ferrocyanide anion [Fe(CN)6]4- is prepared from aqueous Fe2+, but the central iron atom in the complex definitely does not bear a +2 charge (in fact, the charge is likely to be nearer +1.5). Therefore, we employ the concept of oxidation number. Oxidation numbers are cited with Roman numbers, so the oxidation number of the iron atom in the ferrocyanide complex is +11. The IUPAC name for the complex requires the oxidation number we call it hexacyanoferrate (II). 

Dissertation Washington University St. Louis, 1979]. From data for the analogous cobalt(III) complex with perchlorate and hexafluorophosphate as anions, he found association constants of about 900 and 300, with distances of closest approach of 5 or 6 8, respectively. These values seem reasonable. For the iron(II) compound with the hexafluorophosphate or perchlorate, the ion association constants were too small to measure (< - 50). 

The previously reported susceptibility of the iron complex 35 toward fluoride ion to give the anionic compound 30 (see Section III,D) suggested that nucleophiles might react similarly with 64 to give anionic derivatives. Indeed, reaction of 64 with the soft nucleophile PMe3 yields the 1 1 adduct 68 (145). 

Cationic iron-alkene complexes also participate in an unusual cycloaddition process, wherein electron-deficient alkenes are attacked by nucleophilic o -allylic Fp complexes, generating stabilized carb-anions and cationic alkene-iron complexes. Attack of the carbanion on the alkene forming a five-membered ring completes this process (Scheme 13). Oxidative removal of the iron produces useful organic compounds.19-21... 

There are also carboxylates15 (Section 17-E-10), phosphates, catecholates, and oxalates. Most of the divalent iron oxalato compounds have a chain structure but the product of photoreduction of mononuclear [bipyH] [Feni(ojc)2(H20)2] gives a three-dimensional anionic polymeric network of [Fe2I(ox)3]2 1 and [Fen(bipy)3]2+ ions.16 Magnetic exchange typically occurs through the oxalate bridges.17 Six-coordinate iron(II) a-amino acid complexes are readily obtained from the reaction of the 4-coordinate Fe(mes)2(phen) and the protic amino add, AH, in THF 18... 

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