Isocyanidkomplexe, IV. Darstellung und Reaktionen Hg(CN)<sub>2</sub>‐verbrückter Metallcarbonyle

The nu(CN) vibrational spectra of cyanide groups bridging two metal atoms present a confused picture. Factors relevant to the interpretation of the available data are reviewed. Some mechanisms for frequency change, relative to the corresponding terminal species, are made more quantitative than previously described, and others are highlighted for the first time. The kinematic effect is much less important than previously assumed. It seems that an effect responsible for the major part of the frequency increase upon bridging commonly observed is the cation electric field, together with concomitant relaxation (the IVSE model). However, a contribution may well come from the change in the sigma bonding in the CN unit.

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“…For some Cr−(CN)−Hg species there is evidence that the isomers have a frequency difference of ca. 100 cm -1 …”

Section: Resultsmentioning

confidence: 99%

The Vibrational Spectra of the Cyanide Ligand Revisited. Bridging Cyanides

et al. 2007

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“…The first case involved the solvent-dependent equilibration between [(OC) 5 Cr(µ-CN)Hg(µ-NC)Cr(CO) 5 ] 7a and [(OC) 5 Cr(µ-NC)Hg(µ-CN)Cr(CO) 5 ] 7b. 51 More recently two cases of complexes containing central Ru(bipy) 2 (bipy = 2,2Јbipyridine) units were described for which both isomers could be isolated. In both the RuRe 2 and the RuCr 2 complexes (bipy 19 the isomers b having both cyanide C atoms attached to ruthenium are more stable and are accessible by thermal isomerization.…”

Section: Cyanide-isocyanide Isomerismmentioning

confidence: 99%

Cyanide-bridged oligonuclear complexes: features and attractions †

Vahrenkamp¹,

Gei²,

Richardson³

1997

J. Chem. Soc., Dalton Trans.

176

131

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The synthetic and structural chemistry as well as some physical and chemical properties of cyanide-bridged complexes containing two or more metal building blocks are discussed. Emphasis is laid on molecular shape and design and their consequences, including the effects of cyanide-isocyanide isomerism. Redox phenomena and molecular magnetism have been dealt with in relation to electronic communication across the cyanide bridges and metal-metal charge transfer. Long-range interactions between remote metal centers are discussed, and the few cases where they lead to remote chemical reactions are listed.Prussian Blue, [Fe 4 {Fe(CN) 6 } 3 ]ؒxH 2 O, which actually is the oldest known co-ordination compound, 1 has attracted the skills of many scientists seeking an understanding of its formation and composition, 2 structure, 3 colour 4 and physical properties like magnetism 5 and electrical conductivity. 6 Although it was soon obvious that the linking of two different metal ions by the cyanide ligand is the basis of all these phenomena, this did not initiate a variation of the theme. The systematic synthetic and physical exploration of Prussian Blue-like compounds had to await the popularity of the chemistry of materials. Only in recent years has a number of attractive two-and three-dimensional co-ordination polymers comprised of M᎐CN᎐MЈ units been prepared and subjected to the appropriate measurements. 7 While bulk magnetism and conductivity require extended interactions their basic fundamental property, the electronic communication between two metals across the cyanide bridge, is local and can be studied in simple dinuclear complexes. But classical co-ordination chemistry was not interested in this phenomenon, and hence the literature of more than 25 years ago contains only rare examples of cyanide-bridged systems 8 amongst the multitude of ligand-bridged dinuclear complexes. 9 It took the emerging discussion of mixed valence 10-12 and innersphere electron transfer 13,14 to move the M᎐CN᎐MЈ systems into the limelight. They were among the first to be studied in this respect, 15,16 and since then the electronic interactions between two metals across a cyanide bridge have proven to be a fertile area of research.In the last 15 years many di-and tri-nuclear complexes with bridging cyanide ligands have been investigated for the electronic communication and the electron transfer between their metal centers by means of electronic spectroscopy, electrochemistry, IR spectroscopy, fast kinetic methods and molecular orbital (MO) theory. Among others, the research groups of

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