Coordination compounds structural formulae

Coordination compounds of formula MA4 might be square planar or tetrahedral. How many isomers would you predict to exist for compounds of formula MA2B2 for these two geometries Pt(NH3)2Cl2 has two known isomers, and [CoBr2l2] has only one. Speculate on the structures of these complexes. 

Compounds such as the one above, which contain a complex ion, are referred to as coordination compounds. The formula of the complex ion is set off by brackets, [ ], to make the structure of the compound clear. 

Besides structure and substructure searches, Gmclin provides a special search strategy for coordiuation compouuds which is found in no other database the ligand search system, This superior search method gives access to coordination compounds from a completely different point of view it is possible to retrieve all coordination compounds with the same ligand environment, independently of the central atom or the empirical formula of the compound. 

Free Radicals. In the formula of a polyatomic radical an unpaired electron(s) is(are) indicated by a dot placed as a right superscript to the parentheses (or square bracket for coordination compounds). In radical ions the dot precedes the charge. In structural formulas, the dot may be placed to indicate the location of the unpaired electron(s). 

A certain coordination compound has the simplest formula Pt HjC. It has a molar mass of about 600 g/mol and contains both a complex cation and a complex anion. What is its structure ... 

We have already mentioned the formulae for groups, such as S04 , without discussing the principles by which such formulae are assembled. These may (or may not) involve some reference to structure. The general approach is to select one or more atom(s) as the central or characteristic atom(s). This is so whether the ion or group is a coordination entity or not. Thus, I in ICl4 , V in V02 and Si and W in [SiW,204o] are all central atoms and are cited first. The subsidiary atoms then follow, in alphabetical order of symbols (this rule is slightly modified for coordination compounds). 

The formulae discussed so far rely on a minimum of structural information. Increasingly, chemists need to convey more than a list of constituents when providing a formula. They need to say something about structure to do this, simple line formulae (i.e. formulae written on a single line, as is text) need to be modified. How they are modified is determined by what information needs to be conveyed. Sometimes this can take a simple modification of a line formula to show extra bonds not immediately apparent, as in ring compounds, either organic or coordination compounds. 

It is usual for a coordination compound to write the formula of a ligand with the donor atom first. The nickel complex represented above has both S and P bonded to the metal (as well as all the carbon atoms of the C5H5). The ring structure for chlorocyclohexane should be obvious. 

A commonly found stoichiometry with transition metal salts is M(py)4(anion)2, in which the anions are often in a trans orientation.15 However, other stoichiometries have also been observed, such as M(py)2(anion)2 (often with halide anions), M(py)3(N03)2, MX3(py)3 and M(py)2(anion). The compounds of formula M(py)2X2 (X = halide) have been found in at least five different structures, examples of which are presented in Scheme 3. The dimers with a five-coordinate structure are usually found with substituted pyridines, such as 2-picoline.53... 

Not all coordination compounds are neutral molecules like Pt(NH3)2Cl2. Many are salts, such as [Ni(NH3)6]Cl2 and K3[Fe(CN)6], which contain a complex cation or anion along with enough ions of opposite charge to give a compound that is electrically neutral overall. To emphasize that the complex ion is a discrete structural unit, it is always enclosed in brackets in the formula of the salt. Thus, [Ni(NH3)6]Cl2 contains [Ni(NH3)6]2+ cations and Cl- anions. The term metal complex (or simply complex) refers both to neutral molecules, such as Pt(NH3)2Cl2, and to complex ions, such as [Ni(NH3)6]2+ and [Fe(CN)6]3-. 

CAS CHEMICAL REGISTRY 8,000,000 compounds CHEMICAL ABSTRACTS SERVICE The world s largest file of substance information, including coordination compounds, polymers, incompletely defined substances, alloys, mixtures, and minerals. In each record, the registry number is linked to molecular structure diagram, molecular formula, CA index name, synonyms, and the ten most recent references in Chemical Abstracts. Easy crossover to the bibliographic file... 

Prussian blue — iron(III) hexacyanoferrate(II) is the archetype of sparingly soluble mixed valence polymeric metal hexacyanometalates with the formula Me Me(N) [Me c (CN)6] with (i), (N), and (C) indicating the position in the crystal lattice, where (i) means interstitial sites, (N) means metal coordinated to the nitrogen of the cyanides, and (C) means metal ions coordinated to the carbon of the cyanides. It is one of the oldest synthetically produced coordination compounds and was widely used as pigment in paints because of the intensive blue color. The compound has been studied extensively by electrochemical and other methods. The importance of Prussian blue in electrochemistry is related to the fact that it has two redox-active metal centers and that it has an open structure that allows small cations to... 

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