A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals, are coordination complexes.
Cis–trans isomerism, also known as geometric isomerism, describes certain arrangements of atoms within molecules. The prefixes "cis" and "trans" are from Latin: "this side of" and "the other side of", respectively. In the context of chemistry, cis indicates that the functional groups (substituents) are on the same side of some plane, while trans conveys that they are on opposing (transverse) sides. Cis–trans isomers are stereoisomers, that is, pairs of molecules which have the same formula but whose functional groups are in different orientations in three-dimensional space. Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes. Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms "syn" and "anti" are used.
Cisplatin is a chemical compound with formula cis-[Pt(NH3)2Cl2]. It is a coordination complex of platinum that is used as a chemotherapy medication used to treat a number of cancers. These include testicular cancer, ovarian cancer, cervical cancer, bladder cancer, head and neck cancer, esophageal cancer, lung cancer, mesothelioma, brain tumors and neuroblastoma. It is given by injection into a vein.
Nickel(II) chloride (or just nickel chloride) is the chemical compound NiCl2. The anhydrous salt is yellow, but the more familiar hydrate NiCl2·6H2O is green. Nickel(II) chloride, in various forms, is the most important source of nickel for chemical synthesis. The nickel chlorides are deliquescent, absorbing moisture from the air to form a solution. Nickel salts have been shown to be carcinogenic to the lungs and nasal passages in cases of long-term inhalation exposure.
Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble trihydrated (n = 3) salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid and hydroformylation.
In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The octahedron has eight faces, hence the prefix octa. The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. A perfect octahedron belongs to the point group Oh. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. For example, [Co(NH3)6]3+, which is not octahedral in the mathematical sense due to the orientation of the N−H bonds, is referred to as octahedral.
In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia ligand. "Ammine" is spelled this way for historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single "m". Almost all metal ions bind ammonia as a ligand, but the most prevalent examples of ammine complexes are for Cr(III), Co(III), Ni(II), Cu(II) as well as several platinum group metals.
In inorganic chemistry, the trans effect is the increased lability of ligands that are trans to certain other ligands, which can thus be regarded as trans-directing ligands. It is attributed to electronic effects and it is most notable in square planar complexes, although it can also be observed for octahedral complexes. The analogous cis effect is most often observed in octahedral transition metal complexes.
Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula C8H12, specifically [−(CH2)2−CH=CH−]2.
Platinum(II) chloride is the chemical compound PtCl2. It is an important precursor used in the preparation of other platinum compounds. It exists in two crystalline forms, but the main properties are somewhat similar: dark brown, insoluble in water, diamagnetic, and odorless.
Magnus's green salt is the inorganic compound with the formula [Pt(NH3)4][PtCl4]. This salt is named after Heinrich Gustav Magnus, who, in the early 1830s, first reported the compound. The compound is a linear chain compound, consisting of a chain of platinum atoms. It is dark green, which is unusual for platinum compounds.
Potassium tetrachloroplatinate(II) is the chemical compound with the formula K2PtCl4. This reddish orange salt is an important reagent for the preparation of other coordination complexes of platinum. It consists of potassium cations and the square planar dianion PtCl42−. Related salts are also known including Na2PtCl4, which is brown-colored and soluble in alcohols, and quaternary ammonium salts, which are soluble in a broader range of organic solvents.
Dichlorotetrakis(dimethyl sulfoxide) ruthenium(II) describes coordination compounds with the formula RuCl2(dmso)4, where DMSO is dimethylsulfoxide. Both cis and trans isomers are known, but the cis isomer is more common. The cis isomer is a yellow, air-stable solid that is soluble in some organic solvents. These sulfoxide complexes are used in the synthesis of various ruthenium(ii) complexes. They have also attracted attention as possible anti-cancer drugs.
Potassium hexachloroplatinate is the inorganic compound with the formula K2PtCl6. It is a yellow solid that is an example of a comparatively insoluble potassium salt. The salt features the hexachloroplatinate(IV) dianion, which has octahedral coordination geometry.
Dichlorotris(triphenylphosphine)ruthenium(II) is a coordination complex of ruthenium. It is a chocolate brown solid that is soluble in organic solvents such as benzene. The compound is used as a precursor to other complexes including those used in homogeneous catalysis.
The Kurnakov test, also known as Kurnakov's reaction, is a chemical test that distinguishes pairs of cis- and trans-isomers of [PtA2X2] (A = NH3, X = halogen or pseudohalide). Upon treatment with thiourea, the trans-dihalides give less soluble white products, whereas the cis-dihalides give more soluble yellow products. The test is still used to assay samples of the drug cisplatin, but it is mainly of pedagogical interest, as it illustrates the trans effect.
Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.
Nitropentaamminecobalt(III) chloride is an inorganic compound with the molecular formula [Co(NH3)5(NO2)]Cl2. It is an orange solid that is soluble in water. Although it has no applications, the compound has been of academic interest as a source of the transition metal nitrite complex [Co(NH3)5(NO2)]2+.
trans-Dichlorobis(ethylenediamine)cobalt(III) chloride is a salt with the formula [CoCl2(en)2]Cl (en = ethylenediamine). It is a green diamagnetic solid that is soluble in water. It is the monochloride salt of the cationic coordination complex [CoCl2(en)2]+. One chloride ion in this salt readily undergoes ion exchange but the two other chlorides are less reactive, being bound to the metal center. The more stable cis-dichlorobis(ethylenediamine)cobalt(III) chloride is also known.
Nitrate chlorides are mixed anion compounds that contain both nitrate (NO3−) and chloride (Cl−) ions. Various compounds are known, including amino acid salts, and also complexes from iron group, rare-earth, and actinide metals. Complexes are not usually identified as nitrate chlorides, and would be termed chlorido nitrato complexes.
