Compounds with Complex Ions

The structures of ionic compounds comprising complex ions can in many cases be derived from the structures of simple ionic compounds. A spherical ion is substituted by the complex ion and the crystal lattice is distorted in a manner adequate to account for the shape of this ion. 

The structure of calcite (CaC03) can be derived from the NaCl structure by substituting the Cl- ions for CO2- ions. These are oriented perpendicular to one of the space diago- 

The structures of CaC2 and NaN3 (stereo views). Heavy outlines body-centered tetragonal unit cell of CaC2. Dashed line at NaN3 direction of the elongation of the NaCl cell 

The structures of CaC03 (calcite) and KjPtClg. The section of the calcite structure shown does not correspond to the unit cell (as can be seen from the orientations of the C03 groups on opposite edges) 

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H - Compounds with complex ions penta-atomic... 

Our goal in this chapter is to familiarize you with some properties of the elements, as well as the periodic trends that you can observe in these properties. You might want to review briefly the periodic trends we discussed in Chapter 8. We will also discuss coordination compounds and complex ions. Again— Practice, Practice, Practice. 

All the remaining halogens have unfilled d orbitals available and the covalency of the element can be expanded. Compounds and complex ions are formed both with other halogens and with oxygen in which the halogen can achieve a formal oxidation state as high as + 7. for example chlorine has formal oxidation states of +1 in the chlorate(I) anion CIO + 5 in the chlorate(V) anion CIO 3, and + 7 in the chlorate(VII) anion CIO4. ... 

In acidic aqueous solution the carbonato-compound [Ru(bpy)2C03] yields the diaquo complex which can be isolated72. Davies and Mullins had obtained this aquo complex by reaction of the dichloro-compound with silver ion in aqueous solution50. The interesting point in this latter work is that aquation is very rapid thus, if water is an acceptable solvent the dichloro-compound in hot aqueous solution may be the best reagent. 

Hydrogen cyanide is a weak acid, which has the result that its salts decompose slightly in the presence of stronger acids. One of these stronger acids is carbonic acid, which arises from the reaction between carbon dioxide and water. [Even] stronger acids, such as, for example, sulfuric acid, decompose cyanide even more easily. Complex compounds with cyanide ions with heavy metals are more durable. Among such compounds is the already mentioned Prussian Blue [=Iron Blue], but even this decomposes slowly in an acid environment. 

The formation of complex compounds with chloride ions in the case of samples polluted by heavy metals can lead to erroneous results (a solution of sodium chloride is added to the sample to obtain the appropriate conditions for bacteria).69... 

Upon the formation of CdS colloids, at the point when the colloidal particles stop their growth and the system reaches the quasiequilibrium state, the total amount of cadmium is distributed over CdS particles and the aqueous phase of the solution, where it appears both as activated Cd2+ ion and as the compounds with complexing admixtures. One may assume the thermodynamic equilibrium is reached between the different possible forms of cadmium occurrence. Assuming the presence of only one complexing agent L, which participates in a stepwise complexing, we may describe the above equilibrium by a system of chemical equations ... 

We studied the partition equilibria and structures of the ion pair of cationic complex of polyether compounds with picrate ion and reported that the dissociation of ion pair in the organic phase plays an important role for the partition equilibria.In the present paper, the ion-pair formation in 1,2-dichloroethane was studied by using the one of the most simple system of electrolyte, tetraalkylammonium picrate. The effect of the chain length of the alkyl group was studied for the symmetric and asymmetric tetraalkylammonium ions. 

Another helpful scheme is the classification of ions with hard and soft Lewis acids by Ahrland (82) and Pearson (83). While a specific definition or scale of softness is not universally accepted, the general principles are clear. They can be used to give somewhat more information for predictions of what compounds or complex ions might be expected for the superheavy elements. 

Pearson s Hard-Soft-Acid-Base (HSAB) priciple is that hard add-base combinations form readily and are generally ionic compounds. The other group of stable compounds and complex ions involves the interaction between soft acid and soft bases. For these, the bonding is primarily covalent with interpenetrating orbitals. The combinations hard acid with soft base, or vice versa, have little stability. 

Werner presented his coordination theory in 1893, and his investigations and thoughts on cobalt compounds were presented in a series of 52 papers authored by him and 75 papers with associates (Table I). The names commonly used for these compounds are complex ions, Werner complexes, coordinated complexes, coordination compounds, or simply complexes. His first lecture on cobalt compounds was probably the one given on Neue Kobaltiake, September 1896, before the Schweizerische Naturforschende Gesellschaft of Zurich. A most important lecture in his life was no doubt his acceptance of the 1913 Chemistry Nobel Prize (4) in... 

Metal ions can act as electron-pair acceptors, reacting with electron donors to form coordination compounds or complex ions. The donor species, or ligand, must have at least one pair of unshared electrons to form the bond. Remarkable growth in the analytical applications of complex-formation reactions is attributable to a particular class of coordination compounds called chelates. These compounds are made by the reaction of a metal ion and a ligand that contains two or more donor groups. The properties of chelates can differ markedly from the parent cation. 

These are sometimes considered under two heads, those with complex ions, such asCOg and NOa", and those without complex ions. Only the latter will be discussed here. They are of two main types. In the first, the lattice structures are those of simple compounds in which random replacement of metal ions has occurred. LigTiOg has a random rock-salt structure with two thirds of the metal ion positions occupied by Li and one third by Ti. FeSb04 has a random rutile structure. 

The bonds in their simple unipositive compounds are largely covalent and the halides, oxides and sulphides are all, with the exception of silver fluoride, insoluble in water. The water-soluble compounds are those with complex ions, such as Cu(CN)3, Cu(NH3)2 and Ag(NH3)2, the solutions always being colourless. In these ions the metal is unipositive with a non-bonding d shell and the disposition of the ligands tends to be linear or trigonal planar as in non-transition metals. 

The only structurally characterized Np solid compound with azide ion is the [(Np02)(N3)(Phen)(H20)]2 3H2O complex (see Section 4.2). In contrast to uranyl(VI) compounds [135,136], in this structure azide ion acts as bidentate ligand connecting different metal centers. 

The simplest systems containing ionic bonds are the gaseous molecules of alkali halides and oxides, the structures of which are noted in Chapters 9 and 12 we refer later to the halide molecules in connection with polarization. The importance of the ionic bond lies in the fact that it is responsible for the existence at ordinary temperatures, as stable solids, of numerous metallic oxides and halides (both simple and complex), of some sulphides and nitrides, and also of the very numerous crystalline compounds containing complex ions, particularly oxy-ions, which may be finite (CO3 , NO3, SOl", etc.) or infinite in one, two, or three dimensions. 

Use Forms a complex compound with ferrous ions used as an indicator drier in coatings industry. 

Dilituric acid (5-nitrobarbituric acid) forms a sparingly soluble compound with potassium ions. The decrease in absorbance of the reagent gives a measure of the K content in the solution. Potassium ions can be precipitated by tetraphenylborate. The excess reagent forms an ion-pair with the cationic Cu(I)-neocuproine complex, and this ion-pair is extractable into methyl acetate. The absorbance of the extract is measured at 456 nm [83]. An indirect method involving the reaction of potassium tetraphenylborate with mercury(II) ehloranilate is very sensitive [84]. 

Complex oxides are compounds containing complex ions, which appear as discrete structural units. For example, calcium carbonate has a structure based on rocksalt with the different sites... 

The most distinctive aspect of transition metal ehemistry is the formation of coordination compounds (also called complexes). These are substances that contain at least one complex ion, a species consisting of a central metal cation (either a transition metal or a main-group metal) that is bonded to molecules and/or anions called ligands. In order to maintain charge neutrality in the eoordination compound, the complex ion is typically associated with other ions, ealled counter ions. 

All of the elements can be found naturally as ions, most often as 2- ions (except for Po). Oxidation states of -i2, -i4, and +6 also can be fonnd for members S - Po when combined with O, F, or Cl. The difference in oxidation states can be explained by the electronic structure of the elements. Oxygen is able to use only s and p orbitals for bonding. The larger members of the group use d orbitals in the hybridization and thus can participate in the use of an expanded octet. This is shown in compounds and complex ions such as SOF4, SF4, Se04 -, TeFg —. 

USE Forms a complex compound with ferrous ions which is used under the name of Terrain as an indicator in oxidation reduction systems, eg., titration of ferrous salts. Also used in determination of nickel, ruthenium, silver and other metals. 

Detailed surveys of the theory and experimental determination of the stability constants of complexes were published by Locke [26] and De Ligny [27]. To interpret experimental results on the formation of complexes of ogranic compounds with metal ions it is necessary to use not only the complex formation constants but also the entropy and heat of formation of the complexes [7]. Silver-containing sorbents are mainly used to separate unsaturated compounds. The stability of complexes of silver ion with organic compounds and therefore their retention depend on the number of double bonds, their type and the molecular structure of the unsaturated compound. The following characteristics of retention of unsaturated compounds on stationary phases containing silver ion (see, e.g., refs. 12, 22, 23, 27, 28 and 38) were formulated in surveys by Guha and Janak [4]. 

Azido complexes are coordination compounds with azide ions as inner-sphere ligands and may be cationic, such as azidopentaaquocobalt(III) (d) or anionic, such as hexaazidocuprate (e) or neutral, such as dipyridine diazidozinc (0- There are mixed-ligand complexes, such as (d) and (f), and all-azido... 

Notes on the addition reactions of nitric oxide. Nitric oxide is an odd molecule, with an odd number of electrons. Probably because of this fact it is unusually active in forming coordination compounds. Examples of such coordination compounds and complex ions are (FeNO)++, [Co(NH3)6NO]++, CuNOCls-, FeNOCls, AINOCI3, Fe(CN)BNO", and the nitrosyl carbonyls, such as Co(CO)3NO. Many of these complexes are unstable and decompose on heating. They appear to be formed by the donation of either one or three electrons from the NO molecule thus in the nitroprusside ion, Fe(CN)5NO , produced by the action of nitric acid on a ferrocyanide, the nitric oxide is considered to contribute three electrons to the iron atom, leaving the latter in the ferrous rather than the ferric condition. Likewise the existence... 

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