Names of complex compounds

Since the lUPAC nomenclature system relies totally on the pivotal concept of the parent structure to which, in a second sphere, substituents are assigned, it appeared advisable to maintain this division also for the chapters of this book. Thus, we begin with the exposition of the nomenclature rules for parent structures and, in the second chapter, proceed with the discussion of the different types of nomenclature for substituted systems, radicals, and ions in the third chapter specific classes of functional compounds are addressed, followed, in the forth chapter, by the treatment of metal organyls and, in the fifth, of carbohydrates. The concluding sixth chapter takes up once again the construction of the final names of complex compounds including isotopic modifiers and stereochemical descriptors. 

Some six hundred structures of naturally occurring carbogenic molecules appe on the pages which follow, together with the name of each compound and references to the original literature of successful chemical synthesis. Thus, Part Three of this book is effectively a key to the literature of chemical synthesis as applied to the complex molecules of nature. The survey does not include oligomeric or polymeric structures, such as peptides, proteins, carbohydrates and polynucleotides, which fall outside the scope of this book because they can be assembled by repetitive procedures. 

Nomenclature of complex ions and organic compounds. We believe that this material is of little value in a beginning course. The students promptly forget how to name a complex ion, because they have litde chance to use the rules. The naming of organic compounds seems better left to a course in organic chemistry. 

For the naming of monoazo compounds R —N2 —R, in which the linked radicals are derived from identical parent hydrocarbons, the prefix azo is added to the name of the parent hydrocarbon hydride, e.g., 1,2-azonaphthalene. Complex compounds with two or more azo groups are named in a similar manner (see Rule C-9.11.3). 

The names of coordination compounds can become awesomely long because the identity and number of each type of ligand must be included. In most cases, chemists avoid the problem by using the chemical formula rather than the name itself. For instance, it is much easier to refer to [FeCl(H20)5]+ than to pen-taaquachloroiron(II) ion, its formal name. However, names are sometimes needed, and they can be constructed and interpreted, in simple cases at least, by using the rules set out in Toolbox 16.1. Table 16.4 gives the names of common ligands and their abbreviations, which are used in the formulas of complexes. 

Under general headings such as Cobalt(III) complexes and Ammines, used for grouping coordination complexes of similar types having names considered unsuitable for individual headings, formulas or names of specific compounds are not usually given. Hence it is imperative to consult the Formula Index for entries for specific complexes. 

In addition to the structure and the systematic name of each compound, some of the more frequently occurring complexes are given special names. The table also contains information as to the nature of the central atom and literature references. 

The nomenclature,particularly of complex compounds, is not always satisfactory in spite of the good work of the nomenclature commissions of the International Union of Pure and Applied Chemistry. Occasionally, a competent chemist would, not be able to write the correct structure based on a given name. This is particularly noticeable in the naming of open chain and cyclic polynitrogen compounds... 

To find the formula and charge of the complex cation or anion, note the number of ligands of each type, their charge, and the oxidation state of the metal in the name of the compound or ion. If the name refers to an electrically neutral compound, balance the charge of the complex cation or anion with the appropriate number of ions of opposite charge. 

For each of the following, (i) give the systematic name of the compound and specify the oxidation state of the transition metal, (ii) draw a crystal field energy-level diagram and assign the d electrons to orbitals, (iii) indicate whether the complex is high-spin or low-spin (for dA-d7 complexes), and (iv) specify the number of unpaired electrons. 

Rule 6, To form the complete name of a compound, arrange the names of the substituents in the alphabetical or complexity order (in Chart 6 the Chemical Abstracts alphabetical order has been followed) then prefix this part of the name to the correct cyclo part of the name. Such a systematic cyclohexane-type name forms a single word. For example /S-cyclogeraniolene (Formula 31, Chart 6) is named... 

The names of anions usually end in -ide if there are monatomic or homopolyatomic, or -ate for heteropolyatomic anions and coordination compounds. Anionic ligands usually end in -o. Thus CP is chloride, I3 is triiodide and S042 is sulfate but become, chloro, triiodo and sulfato if they are coordinated as ligands. The names of complex anions are not always derived from the familiar name... 

Ending of Name Names of complex cations and neutral molecules have no distinguishing termination but in the case of anionic complexes the suffix "ate" is attached to the name of central atom. For example, the names of some compounds with anionic complexes are ... 

The name for the complex group is placed in parentheses to avoid confusion when the entire compound is named. The number designating the position of the complex group on the main chain is placed outside the parentheses. Therefore, the name of the compound is 2-methyl-5-(2-methylpropyl)nonane. 

H+ + Cu(NH3)42+ —> Cu2+ + 4NH4+. If the name of the compound confused you, we ll be going over complex ions later. This is a redox reaction. 

Identify the materials used and give information on the degree of and criteria for purity, but do not reference standard laboratory reagents. Give the chemical names of all compounds and the chemical formulas of compounds that are new or uncommon. Use meaningful nomenclature that is, use standard systematic nomenclature where specificity and complexity require, or use trivial nomenclature where it will adequately and unambiguously define a well-established compound. 

Reminder Simple chemical structures can often be represented by a line formula or by the systematic name of the compound, but complex chemical structures depend on structural representations exhibiting the atom-atom connectivity, including the order and stereochemistry of the bonds. 

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