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.
Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the chemical industry, including catalysis, materials science, pigments, surfactants, coatings, medications, fuels, and agriculture.
Valence shell electron pair repulsion (VSEPR) theory is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm.
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.
Reductive elimination is an elementary step in organometallic chemistry in which the oxidation state of the metal center decreases while forming a new covalent bond between two ligands. It is the microscopic reverse of oxidative addition, and is often the product-forming step in many catalytic processes. Since oxidative addition and reductive elimination are reverse reactions, the same mechanisms apply for both processes, and the product equilibrium depends on the thermodynamics of both directions.
Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)n, where n varies from 0 to 3. These are diamagnetic red-brown solids. The soluble trihydrated (n = 3) salt is the usual compound of commerce. It is widely used to prepare compounds used in homogeneous catalysis.
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 chemistry, the square planar molecular geometry describes the stereochemistry that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corners.
A spectrochemical series is a list of ligands ordered by ligand "strength", and a list of metal ions based on oxidation number, group and element. For a metal ion, the ligands modify the difference in energy Δ between the d orbitals, called the ligand-field splitting parameter in ligand field theory, or the crystal-field splitting parameter in crystal field theory. The splitting parameter is reflected in the ion's electronic and magnetic properties such as its spin state, and optical properties such as its color and absorption spectrum.
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.
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.
The biological term symbiosis was first used in chemistry by C. K. Jørgensen in 1964, to refer to the process by which a hard ligand on a metal predisposes the metal to receive another hard ligand rather than a soft one. Two superficially antithetical phenomena occur: symbiosis and antisymbiosis.
Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amido complexes of the parent amido ligand NH2− are rare compared to complexes with diorganylamido ligand, such as dimethylamido. Amide ligands have two electron pairs available for bonding.
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.
In inorganic chemistry, the cis effect is defined as the labilization of CO ligands that are cis to other ligands. CO is a well-known strong pi-accepting ligand in organometallic chemistry that will labilize in the cis position when adjacent to ligands due to steric and electronic effects. The system most often studied for the cis effect is an octahedral complex M(CO)
5X where X is the ligand that will labilize a CO ligand cis to it. Unlike the trans effect, which is most often observed in 4-coordinate square planar complexes, the cis effect is observed in 6-coordinate octahedral transition metal complexes. It has been determined that ligands that are weak sigma donors and non-pi acceptors seem to have the strongest cis-labilizing effects. Therefore, the cis effect has the opposite trend of the trans-effect, which effectively labilizes ligands that are trans to strong pi accepting and sigma donating ligands.
trans-Dichlorodiammineplatinum(II) is the trans isomer of the coordination complex with the formula trans-PtCl2(NH3)2, sometimes called transplatin. It is a yellow solid with low solubility in water but good solubility in DMF. The existence of two isomers of PtCl2(NH3)2 led Alfred Werner to propose square planar molecular geometry. It belongs to the molecular symmetry point group D2h.
In organometallic chemistry, transition metal complexes of nitrite describes families of coordination complexes containing one or more nitrite ligands. Although the synthetic derivatives are only of scholarly interest, metal-nitrite complexes occur in several enzymes that participate in the nitrogen cycle.
Transition metal azide complexes are coordination complexes containing one or more azide (N3−) ligands.
