Migratory Insertion of Hydrogen Isocyanide in the Pentacyano(methyl)cobaltate(III) Anion

Abstract

The preparation of the pentacyano(iminiumacetyl)cobaltate(III) anion and its N-methyl and N,N-dimethyl derivatives is reported. The iminiumacetyl group is formed by migratory insertion of cis hydrogen isocyanide in the pentacyano(methyl)cobaltate(III) anion. The new compounds have been spectroscopically characterized by (1)H, (13)C, (15)N, and (59)Co NMR spectroscopy and by absorption spectroscopy. The iminium carbon atoms yield (13)C NMR signals at 256.7, 247.7, and 240.4 ppm for the parent iminiumacetyl compound and its N-methyl and N,N-dimethyl derivatives, respectively. The (15)N resonance frequencies of the iminium groups and the lack of rotation of the carbon-nitrogen bond both show that this bond is best described as a double bond. The structure of (Et(4)N)(Ph(4)As)(2)[Co(CN)(5)(CH(3))] was determined by X-ray crystallography at 122.0(5) K. The structure displays disorder.

Substitution Behaviour of an Alkylcobaltamine Complex − Evidence for a Limiting Dissociative Mechanism

“…This is most probably due to the strong trans labilizing effect of the cobaltϪcarbon bond and the competition with the excess ammonia in solution. The reaction with cyanide leading to the formation of [Co(CN) 5 (CH 3 )] 3Ϫ was recently reported by Kofod, [28] but the reaction was not studied kinetically. We therefore employed bidentate ligands that would lead to thermodynamically more stable products as a result of the chelate effect.…”

“…Following this fast reaction, a slow subsequent step could be observed which then led to the final UV/Vis spectrum of trans-[Co(en) 2 (NH 3 )(CH 3 )] 2ϩ (see Figure 2). Important to note is that in the presence of a high NH 3 concentration in solution, the formation of the amine complex was observed in the UV/Vis spectra, but when the NH 3 concentration was systematically decreased, the shoulder around 300 nm, which was assigned to the trans-amine complex, [28] disappeared. The final spectrum of the slower reaction at low [NH 3 ] was identical to that of the trans-[Co(en) 2 (H 2 O)(CH 3 )] 2ϩ .…”

“…[27] The X-ray structure shows a large increase in the length of the CoϪN bond trans to the metalϪcarbon bond compared to those of the equatorial positions. [28] An interesting question is to what extent the introduction of a single metalϪcarbon σ-bond affects the substitution behaviour of this Co III complex.…”

Synthesis, Spectroscopic and X-ray Structural Study ofcis-diazidobis- (ethylenediamine)Cobalt(III) Thiocyanate

“…The bond lengths S-C ¼ 1.675(3) Å , C-N ¼ 1.185(3) Å and bond angle S-C-N ¼ 178.1 (2) for cis-[Co(en) 2 (N 3 ) 2 ]SCN while corresponding value for NH 4 SCN are S-C ¼ 1.645(9) Å , C-N ¼ 1.173(5) Å , bond angle S-C-N ¼ 179.6 (4) .…”

“…Cobalt(III) complexes continue to receive attention [1][2][3] owing to their important role in the development of inorganic chemistry. Cobalt is one of those trace metals that is present in the human body as a metal cofactor in the form of biologically important molecules such as the B 12 coenzyme and vitamin B 12 [4][5][6][7].…”