Cyano ligand

Based on the donor sites of the ligands, as well as on the nuclearity and geometry, the high-valent complexes containing Mn + and Mn ions have been categorized into the ligand-based 

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The basis for the toxicological activity of this substance is the reaction of cobalt ion with cyanide ion to form a relatively nontoxic and stable ion complex. The hexacyanocobaltate ion contains a Co2+ central metal ion with six cyanide ions as ligands. This coordination complex involves six coordinate covalent bonds whereby each cyanide ion supplies a pair of electrons to form each covalent bond with the central cobalt ion. The formation constant for the hexacyanocobaltate ion is even larger than for dicobalt EDTA,3 and thus the cobalt ion preferentially exchanges an EDTA ligand for six cyano ligands ... 

Silver(m) Complexes with Alkyl, Alkynyl, and Cyano Ligands 241... 

Although its mode is uncertain, sodium nitroprusside (SNP) is one of the most valuable vasodilators. Its use in clinical practice is suspect as the cyano-ligands render cyanide poisoning a possibility. However for ex vivo experiments this consideration is less important but the possibility of some biological action due to these ions remains. The mechanism by which SNP acts as a vasodilator is not fully understood. With the discovery of a physiological role for NO there has been renewed interest in mechanistic studies of reactions involving SNP and a re-examination of studies of SNP undertaken before 1987. So far, only one simple reaction leading to the release... 

In isolation the electron distribution in the trivalent chromium (III) ion consists of three unpaired electrons in the d shell, as indicated in line (a) of Table 5.1. In line (b) the six electron pairs donated to the central chromium atom by oxygen atoms of water molecules give rise to sp3d2 hybridisation. This is characteristic of an octahedral structure. A similar situation arises with the trivalent cobalt(III) complex in line (e), where each of the three t2g levels is doubly occupied by an electron pair from each cyano ligand. 

Central metal displacement from plane formed by four cyano ligand carbon atoms. b pipe = piperidine. 

The correlation between the X-ray crystallographic data of the W—CN bond lengths and the first-order coupling constants between the 183W and 13C in the equatorial cyano ligands, as predicted by the Fermi-contact term (51), is fairly good (see Table III). This illustrates the increase in cis W—CN bond length induced by increased donor... 

In Table III is also given the distortion of the W(IV) complexes as demonstrated by the displacement from the plane as well as the change in bite angle of the equatorial cyano ligand with the M=0 moiety as well as the v(W = 0) as obtained from IR studies and the oxygen-17 NMR data. It is clear that a reasonable correlation between all these parameters, excluding the chemical shift for the [WO(CN)5]3 complex (Fig. 4a), exists. 

Furthermore, protonation results in a significant distortion of the coordination polyhedron, i.e., the metal ion is displaced from the plane formed by the four cyano ligand carbon atoms toward the oxo along the M = 0 axis by as much as 0.34 A, which represents about 20% of the total metal-oxo bond length. In spite of this distortion stronger metal-cyano bonds are observed crystallographically, suggesting a better n back-donation by the metal center to the cyano carbons since d-ff overlap is increased. This observation is in line with both the 13C and 15N chemical shift and kinetic data (Section V) for the protonated complexes (8). 

The proton transfer processes described above induce interesting effects on the geometry of these metal complexes upon protonation (see also Section II). If it is assumed that the equatorial cyano ligands form a reference plane and are stationary for any of these distorted octahedral cyano oxo complexes, the protonation/deprotonation process as illustrated in Scheme 3 is responsible for the oxygen exchange at the oxo sites. This process effectively induces a dynamic oscillation of the metal center along the O-M-O axis at a rate defined by kmv, illustrated in Fig. 15. This rate of inversion is determined by the rate at which the proton is transferred via the bulk water from the one... 

Angelici, R.J. Quick, M.H., Kraus, G.A. and Plummer, D.T. (1982) Synthesis of chelating bidentate isocyano and cyano ligands and their metal complexes. Inorg. Chem., 21, 2178-84. 

Mixed-valence complexes terminated in other than ammine and cyano ligands include [([9]aneS3)ClRu(/x-243)RuCl([9]aneS3)] which exhibits a strong intermetallic interaction consistent with a Robin-Day class III (delocalized) species. The synthesis of the Ru Ru complex [ P(OMe)3 2(MeCN)Ru(u-S2)(/u-NH2NH2)Ru P(OMe)3 2(MeCN)] + has been reported. Oxidation of the (M = Ru or Os) complexes [ 4 -(4-MeC6H4 tpy)M(u-L)M 4 -(4-... 

Nitroprusside is capable of ligating redox partners through a cyano ligand to participate in inner-sphere electron-transfer reactions. With hemoglobin an electron is transferred in this fashion from the porphyrin center to yield [Fe(CN)4(NO)] , methemoglobin and NO (see below) [92]. 

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