Reactions of Metal Chelates. VI.^1,2 The Synthesis and Reactions of a Stable Chelate Diazonium Salt³

Abstract

A monoamine derivative L of chromium(III) acetylacetonate has been prepared by reduction of a mononitro derivative I. The chelate amine L was" transformed into a stable chelate diazonium fluoroborate N. The diazonium salt was converted into a monofluoro chelate O. Nitration of mono-and dichloro chromium acetylacetonates afforded a series of chloro-, nitro-substituted chelates. Apparent displacement of chloro by nitro was observed during nitration of the dichloro chelate C.Recent reports from this and other laboratories have described the quasiaromatic properties of metal complexes of acetylacetone.16-13 These chelates undergo a wide variety of electrophilic substitution reactions under relatively mild conditions. Stereochemical studies indicate that these substitutions are not attended by opening of the chelate rings.1416 The proton magnetic resonance spectra of unsymmetrically substituted metal acetylacetonates7 and of certain acetylacetone-ethylene diamine complexes16 suggest the presence of aromatic ring current in these substances. Classically, one of the most significant chemical indications of aromatic character is the stabilization of a diazonium ion. This paper reports a successful preparation of a chelate diazonium salt and its chemical properties.Our first attempts to synthesize amino-substituted metal acetylacetonates A, the logical precursors of chelate diazonium salts, were unsuccessful. Attempts at direct amination of the chelate ring failed. Nitro-substituted chelates B, available from a previous study,6seemed fo offer a route to the desired amino chelates A.However, all attempts to reduce nitro groups on the nitrocobalt(III) or rhodium(III) chelates led to reduction of the metals and subsequent decomposition of the complexes.6 On the other hand, chemical or catalytic reductions of the nitro chromium chelate B either afforded unchanged starting material or resulted in intractable mixtures of unidentified products. We had previously experienced difficulty in carrying out trans-

The busy student's guide to the nitration of trisacetylacetonates of cobalt(III) and chromium(III)

“…The reliable nitration procedures reported by them have been formalized as standard methods by inclusion in "Inorganic Syntheses" (5). In all cases reported (3,5,6), the method involves the following steps 1) generation of the nitrating agent (presumably acetyl nitrate) by stirring finely ground copper nitrate with acetic anhydride at 0°C for 15 min…”

Kinetic Studies of Reduction of Tris‐(1,1,1,5,5,5‐hexafluoroacetylacetonato) ruthenium(III) in Methanol, Ethanol and Propanol

“…Metal 1,3-diketone systems behave as sensitive heterocycles possessing at least some aromatic character. Holm and cotton 15 have expressed doubt in such aromaticity but collman et al 16 and other workers have recognized their quasi-aromatic character and have reported electrophilic substitution reactions in these systems.…”

Sind β‐Diketon‐Metallkomplexe aromatisch?

“…Forsch. 6, 479 (1966) (3) oder Methylferrocen-a-carbonsaure hinsichtlich der Ursache der optischen Aktivitiit Bhnlich sind.…”