Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is hard and ductile. Pure nickel, powdered to maximize the reactive surface area, shows a significant chemical activity, but larger pieces are slow to react with air under standard conditions because an oxide layer forms on the surface and prevents further corrosion. So, pure native nickel is found in Earth's crust only in tiny amounts in ultramafic rocks, in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere. Meteoric nickel is found in combination with iron, a reflection of the origin of those elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earth's outer and inner cores. Use of nickel has been traced as far back as 3500 BCE. Nickel was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who mistook the ore for a copper mineral, in the cobalt mines of Los, Hälsingland, Sweden.
The element's name comes from a mischievous sprite of German miner mythology, who personified the fact that copper-nickel ores resisted refinement into copper. An economically important source of nickel is the iron ore limonite, which contains 1–2% nickel. Nickel's other important ore minerals include pentlandite and a mixture of Ni-rich natural silicates known as garnierite. Major production sites include the Sudbury region in Canada, New Caledonia in the Pacific, Norilsk in Russia. Nickel is oxidized by air at room temperature and is considered corrosion-resistant, it has been used for plating iron and brass, coating chemistry equipment, manufacturing certain alloys that retain a high silvery polish, such as German silver. About 9% of world nickel production is still used for corrosion-resistant nickel plating. Nickel-plated objects sometimes provoke nickel allergy. Nickel has been used in coins, though its rising price has led to some replacement with cheaper metals in recent years. Nickel is one of four elements that are ferromagnetic at room temperature.
Alnico permanent magnets based on nickel are of intermediate strength between iron-based permanent magnets and rare-earth magnets. The metal is valuable in modern times chiefly in alloys. A further 10% is used for nickel-based and copper-based alloys, 7% for alloy steels, 3% in foundries, 9% in plating and 4% in other applications, including the fast-growing battery sector; as a compound, nickel has a number of niche chemical manufacturing uses, such as a catalyst for hydrogenation, cathodes for batteries and metal surface treatments. Nickel is an essential nutrient for some microorganisms and plants that have enzymes with nickel as an active site. Nickel is a silvery-white metal with a slight golden tinge, it is one of only four elements that are magnetic at or near room temperature, the others being iron and gadolinium. Its Curie temperature is 355 °C; the unit cell of nickel is a face-centered cube with the lattice parameter of 0.352 nm, giving an atomic radius of 0.124 nm. This crystal structure is stable to pressures of at least 70 GPa.
Nickel belongs to the transition metals. It is hard and ductile, has a high for transition metals electrical and thermal conductivity; the high compressive strength of 34 GPa, predicted for ideal crystals, is never obtained in the real bulk material due to the formation and movement of dislocations. The nickel atom has two electron configurations, 3d8 4s2 and 3d9 4s1, which are close in energy – the symbol refers to the argon-like core structure. There is some disagreement. Chemistry textbooks quote the electron configuration of nickel as 4s2 3d8, which can be written 3d8 4s2; this configuration agrees with the Madelung energy ordering rule, which predicts that 4s is filled before 3d. It is supported by the experimental fact that the lowest energy state of the nickel atom is a 3d8 4s2 energy level the 3d8 4s2 3F, J = 4 level. However, each of these two configurations splits into several energy levels due to fine structure, the two sets of energy levels overlap; the average energy of states with configuration 3d9 4s1 is lower than the average energy of states with configuration 3d8 4s2.
For this reason, the research literature on atomic calculations quotes the ground state configuration of nickel as 3d9 4s1. The isotopes of nickel range in atomic weight from 48 u to 78 u. Occurring nickel is composed of five stable isotopes. Isotopes heavier than 62Ni cannot be formed by nuclear fusion without losing energy. Nickel-62 has the highest mean nuclear binding energy per nucleon of any nuclide, at 8.7946 MeV/nucleon. Its binding energy is greater than both 56Fe and 58Fe, more abundant elements incorrectly cited as having the most tightly-bound nuclides. Although this would seem to predict nickel-62 as the most abundant heavy element in the universe, the high rate of photodisintegration of nickel in stellar interiors causes iron to be by far the most abundant. Stable isotope nickel-60 is the daughter product of the extinct radionuclide 60Fe, whi
A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds. A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved. There are four types of compounds, depending on how the constituent atoms are held together: molecules held together by covalent bonds ionic compounds held together by ionic bonds intermetallic compounds held together by metallic bonds certain complexes held together by coordinate covalent bonds. A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H2O. Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service: its CAS number.
A compound can be converted to a different chemical composition by interaction with a second chemical compound via a chemical reaction. In this process, bonds between atoms are broken in both of the interacting compounds, bonds are reformed so that new associations are made between atoms. Any substance consisting of two or more different types of atoms in a fixed stoichiometric proportion can be termed a chemical compound, it follows from their being composed of fixed proportions of two or more types of atoms that chemical compounds can be converted, via chemical reaction, into compounds or substances each having fewer atoms. The ratio of each element in the compound is expressed in a ratio in its chemical formula. A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H2O.
In the case of non-stoichiometric compounds, the proportions may be reproducible with regard to their preparation, give fixed proportions of their component elements, but proportions that are not integral. Chemical compounds have a unique and defined chemical structure held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be molecular compounds held together by covalent bonds, salts held together by ionic bonds, intermetallic compounds held together by metallic bonds, or the subset of chemical complexes that are held together by coordinate covalent bonds. Pure chemical elements are not considered chemical compounds, failing the two or more atom requirement, though they consist of molecules composed of multiple atoms. Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service: its CAS number. There is varying and sometimes inconsistent nomenclature differentiating substances, which include non-stoichiometric examples, from chemical compounds, which require the fixed ratios.
Many solid chemical substances—for example many silicate minerals—are chemical substances, but do not have simple formulae reflecting chemically bonding of elements to one another in fixed ratios. It may be argued that they are related to, rather than being chemical compounds, insofar as the variability in their compositions is due to either the presence of foreign elements trapped within the crystal structure of an otherwise known true chemical compound, or due to perturbations in structure relative to the known compound that arise because of an excess of deficit of the constituent elements at places in its structure. Other compounds regarded as chemically identical may have varying amounts of heavy or light isotopes of the constituent elements, which changes the ratio of elements by mass slightly. Compounds are held together through a variety of different types of bonding and forces; the differences in the types of bonds in compounds differ based on the types of elements present in the compound.
London dispersion forces are the weakest force of all intermolecular forces. They are temporary attractive forces that form when the electrons in two adjacent atoms are positioned so that they create a temporary dipole. Additionally, London dispersion forces are responsible for condensing non polar substances to liquids, to further freeze to a solid state dependent on how low the temperature of the environment is. A covalent bond known as a molecular bond, involves the sharing of electrons between two atoms; this type of bond occurs between elements that fall close to each other on the periodic table of elements, yet it is observed between some metals and nonmetals. This is due to the mechanism of this type of bond. Elements that fall close to each other on the periodic table tend to have similar electronegativities, which means they have a similar affinity for electrons. Since neither element has a stronger affinity to donate or gain electrons, it causes the elements to share electrons so both elements have a more stable octet.
Ionic bonding occurs when valence electrons are transferred between elements. Opposite to covalent bonding, this chemical bond creates two oppositely charged ions; the metals in ionic bonding
Lev Aleksandrovich Chugaev was a Russian chemist. At the height of his career, he was professor of chemistry at the University of Petersburg, being the successor to Dmitri Mendeleev, he was active in the fields of inorganic chemistry platinum group complexes, as well as organic chemistry. He is known as Leo Aleksandrovich Tschugaeff or Tschugaev. Chugaev discovered; this reaction was one of the first "spot tests" for a metal ion. An adherent to the theories of Alfred Werner, Chugaev made several contributions to the chemistry of platinum; the salt Cl3 containing the chloropentammineplatinum ion, is called "Chugaev's salt". Other complexes prepared in his laboratory include, Cl3, Cl3. H2O. Chugaev studied complexes of hydrazine. One of his complexes, since called Chugaev's salt, was the product of the reaction of platinum salts with methyl isocyanide and hydrazine. After many decades, this compound was shown to be a carbene complex the first metal carbene complex reported, he discovered the Chugaev reaction during his work on thujene and terpene
Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Safety data sheet
A safety data sheet, material safety data sheet, or product safety data sheet is a document that lists information relating to occupational safety and health for the use of various substances and products. SDSs are a used system for cataloging information on chemicals, chemical compounds, chemical mixtures. SDS information may include instructions for the safe use and potential hazards associated with a particular material or product, along with spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements. A SDS for a substance is not intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. There is a duty to properly label substances on the basis of physico-chemical, health or environmental risk. Labels can include hazard symbols such as the European Union standard symbols; the same product can have different formulations in different countries. The formulation and hazard of a product using a generic name may vary between manufacturers in the same country.
The Globally Harmonized System of Classification and Labelling of Chemicals contains a standard specification for safety data sheets. The SDS follows a 16 section format, internationally agreed and for substances the SDS should be followed with an Annex which contains the exposure scenarios of this particular substance; the 16 sections are: SECTION 1: Identification of the substance/mixture and of the company/undertaking 1.1. Product identifier 1.2. Relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4. Emergency telephone number SECTION 2: Hazards identification 2.1. Classification of the substance or mixture 2.2. Label elements 2.3. Other hazards SECTION 3: Composition/information on ingredients 3.1. Substances 3.2. Mixtures SECTION 4: First aid measures 4.1. Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3. Indication of any immediate medical attention and special treatment needed SECTION 5: Firefighting measures 5.1.
Extinguishing media 5.2. Special hazards arising from the substance or mixture 5.3. Advice for firefighters SECTION 6: Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2. Environmental precautions 6.3. Methods and material for containment and cleaning up 6.4. Reference to other sections SECTION 7: Handling and storage 7.1. Precautions for safe handling 7.2. Conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION 8: Exposure controls/personal protection 8.1. Control parameters 8.2. Exposure controls SECTION 9: Physical and chemical properties 9.1. Information on basic physical and chemical properties 9.2. Other information SECTION 10: Stability and reactivity 10.1. Reactivity 10.2. Chemical stability 10.3. Possibility of hazardous reactions 10.4. Conditions to avoid 10.5. Incompatible materials 10.6. Hazardous decomposition products SECTION 11: Toxicological information 11.1. Information on toxicological effects SECTION 12: Ecological information 12.1.
Toxicity 12.2. Persistence and degradability 12.3. Bioaccumulative potential 12.4. Mobility in soil 12.5. Results of PBT and vPvB assessment 12.6. Other adverse effects SECTION 13: Disposal considerations 13.1. Waste treatment methods SECTION 14: Transport information 14.1. UN number 14.2. UN proper shipping name 14.3. Transport hazard class 14.4. Packing group 14.5. Environmental hazards 14.6. Special precautions for user 14.7. Transport in bulk according to Annex II of MARPOL73/78 and the IBC Code SECTION 15: Regulatory information 15.1. Safety and environmental regulations/legislation specific for the substance or mixture 15.2. Chemical safety assessment SECTION 16: Other information 16.2. Date of the latest revision of the SDS In Canada, the program known as the Workplace Hazardous Materials Information System establishes the requirements for SDSs in workplaces and is administered federally by Health Canada under the Hazardous Products Act, Part II, the Controlled Products Regulations. Safety data sheets have been made an integral part of the system of Regulation No 1907/2006.
The original requirements of REACH for SDSs have been further adapted to take into account the rules for safety data sheets of the Global Harmonised System and the implementation of other elements of the GHS into EU legislation that were introduced by Regulation No 1272/2008 via an update to Annex II of REACH. The SDS must be supplied in an official language of the Member State where the substance or mixture is placed on the market, unless the Member State concerned provide otherwise; the European Chemicals Agency has published a guidance document on the compilation of safety data sheets. The German Federal Water Management Act requires that substances be evaluated for negative influence on the physical, chemical or biological characteristics of water; these are classified into numeric water hazard classes. WGK nwg: Non-water polluting substance WGK 1: Slightly water polluting substance WGK 2: Water polluting substance WGK 3: Highly water polluting substance This section contributes to a better understanding of the regulations governing SDS within the South African framework.
As regulations may change, it is the responsibility of the reader to verify the validity of the regulations mentioned in text. As globalisation increased and countries engaged in cross-border trade, the quantity of hazardous material crossing international borders a
Butanone known as methyl ethyl ketone, is an organic compound with the formula CH3CCH2CH3. This colorless liquid ketone has a sweet odor reminiscent of butterscotch and acetone, it is produced industrially on a large scale, occurs in trace amounts in nature. It is soluble in water and is used as an industrial solvent. Butanone may be produced by oxidation of 2-butanol; the dehydrogenation of 2-butanol using a catalyst is catalyzed by copper, zinc, or bronze: CH3CHCH2CH3 → CH3CCH2CH3 + H2This is used to produce 700 million kilograms yearly. Other syntheses that have been examined but not implemented include Wacker oxidation of 2-butene and oxidation of isobutylbenzene, analogous to the industrial production of acetone; the cumene process can be modified to produce phenol and a mixture of acetone and butanone instead of only phenol and acetone in the original. Both liquid-phase oxidation of heavy naphtha and the Fischer-Tropsch reaction produce mixed oxygenate streams, from which 2-butanone is extracted by fractionation.
Butanone is an effective and common solvent and is used in processes involving gums, cellulose acetate and nitrocellulose coatings and in vinyl films. For this reason it finds use in the manufacture of plastics, textiles, in the production of paraffin wax, in household products such as lacquer, paint remover, a denaturing agent for denatured alcohol, as a cleaning agent, it has similar solvent properties to acetone but boils at a higher temperature and has a slower evaporation rate. Unlike acetone, it forms an azeotrope with water, making it useful for azeotropic distillation of moisture in certain applications. Butanone is used in dry erase markers as the solvent of the erasable dye; as butanone dissolves polystyrene and many other plastics, it is sold as "model cement" for use in connecting parts of scale model kits. Though considered an adhesive, it is functioning as a welding agent in this context. Butanone is the precursor to methyl ethyl ketone peroxide, a catalyst for some polymerization reactions such as crosslinking of unsaturated polyester resins.
Dimethylglyoxime can be prepared from butanone first by reaction with ethyl nitrite to give diacetyl monoxime followed by conversion to the dioxime: In the Peroxide process on producing hydrazine, the starting chemical ammonia is bonded to butanone, oxidized by hydrogen peroxide, bonded to another ammonia molecule. In the final step of the process, a hydrolysis produces the desired product hydrazine and regenerates the butanone. MeC=NN=CMe + 2 H2O → 2 MeC=O + N2H4 Butanone can react with most oxidizing materials, can produce fires, it spark to cause a vigorous reaction. Butanone fires should be extinguished with dry agents, or alcohol-resistant foam. Concentrations in the air high enough to be flammable are intolerable to humans due to the irritating nature of the vapor. Butanone is a constituent of tobacco smoke, it is an irritant. Serious health effects in animals have been seen only at high levels; these included skeletal birth defects and low birth weight in mice, when they inhaled it at the highest dose tested.
There are no long-term studies with animals breathing or drinking it, no studies for carcinogenicity in animals breathing or drinking it. There is some evidence that butanone can potentiate the toxicity of other solvents, in contrast to the calculation of mixed solvent exposures by simple addition of exposures; as of 2010, some reviewers advised caution in using butanone because of reports of neuropsychological effects. Butanone is listed as a Table II precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances. Emission of butanone was regulated in the US as a hazardous air pollutant, because it is a volatile organic compound contributing to the formation of tropospheric ozone. In 2005, the US Environmental Protection Agency removed butanone from the list of hazardous air pollutants. Butane n-Butanol International Chemical Safety Card 0179 National Pollutant Inventory: Methyl Ethyl Ketone Fact Sheet NIOSH Pocket Guide to Chemical Hazards US EPA Datasheet Record in the Household Products Database of NLM
Palladium is a chemical element with symbol Pd and atomic number 46. It is a lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston, he named it after the asteroid Pallas, itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, rhodium, ruthenium and osmium form a group of elements referred to as the platinum group metals; these have similar chemical properties, but palladium has the lowest melting point and is the least dense of them. More than half the supply of palladium and its congener platinum is used in catalytic converters, which convert as much as 90% of the harmful gases in automobile exhaust into less noxious substances. Palladium is used in electronics, medicine, hydrogen purification, chemical applications, groundwater treatment, jewelry. Palladium is a key component of fuel cells, which react hydrogen with oxygen to produce electricity and water. Ore deposits of palladium and other PGMs are rare; the most extensive deposits have been found in the norite belt of the Bushveld Igneous Complex covering the Transvaal Basin in South Africa.
Recycling is a source from scrapped catalytic converters. The numerous applications and limited supply sources result in considerable investment interest. Palladium belongs to group 10 in the periodic table, but the configuration in the outermost electrons are in accordance with Hund's rule. Electrons in the s-shell migrate to fill the d orbitals. Palladium is a soft silver-white metal, it has the lowest melting point of the platinum group metals. It is soft and ductile when annealed and is increased in strength and hardness when cold-worked. Palladium dissolves in concentrated nitric acid, in hot, concentrated sulfuric acid, when finely ground, in hydrochloric acid, it dissolves at room temperature in aqua regia. Palladium does not react with oxygen at standard temperature. Palladium heated to 800 °C will produce a layer of palladium oxide, it tarnishes in a moist atmosphere containing sulfur. Palladium films with defects produced by alpha particle bombardment at low temperature exhibit superconductivity having Tc=3.2 K.
Occurring palladium is composed of seven isotopes, six of which are stable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with 17 days, 100Pd with 3.63 days. Eighteen other radioisotopes have been characterized with atomic weights ranging from 90.94948 u to 122.93426 u. These have half-lives of less than thirty minutes, except 101Pd, 109Pd, 112Pd. For isotopes with atomic mass unit values less than that of the most abundant stable isotope, 106Pd, the primary decay mode is electron capture with the primary decay product being rhodium; the primary mode of decay for those isotopes of Pd with atomic mass greater than 106 is beta decay with the primary product of this decay being silver. Radiogenic 107Ag is a decay product of 107Pd and was first discovered in 1978 in the Santa Clara meteorite of 1976; the discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus Ag correlations observed in bodies, which have been melted since accretion of the solar system, must reflect the presence of short-lived nuclides in the early solar system.
Palladium compounds exist in the 0 and +2 oxidation state. Other less common states are recognized; the compounds of palladium are more similar to those of platinum than those of any other element. Palladium chloride is the principal starting material for other palladium compounds, it arises by the reaction of palladium with chlorine. It is used to prepare heterogeneous palladium catalysts such as palladium on barium sulfate, palladium on carbon, palladium chloride on carbon. Solutions of PdCl2 in nitric acid react with acetic acid to give palladium acetate a versatile reagent. PdCl2 reacts with ligands to give square planar complexes of the type PdCl2L2. One example of such complexes is the benzonitrile derivative PdX22. PdCl2 + 2 L → PdCl2L2. Palladium forms a range of zerovalent complexes with the formula PdL4, PdL3 and PdL2. For example, reduction of a mixture of PdCl22 and PPh3 gives tetrakispalladium: 2 PdCl22 + 4 PPh3 + 5 N2H4 → 2 Pd4 + N2 + 4 N2H5+Cl−Another major palladium complex, trisdipalladium, is prepared by reducing sodium tetrachloropalladate in the presence of dibenzylideneacetone.
Palladium, as well as palladium, are catalysts in coupling reactions, as has been recognized by the 2010 Nobel Prize in Chemistry to Richard F. Heck, Ei-ichi Negishi, Akira Suzuki; such reactions are practiced for the synthesis of fine chemicals. Prominent coupling reactions include the Heck, Sonogashira coupling, Stille reactions, the Kumada coupling. Palladium acetate, tetrakispalladium (Pd4, trisdipalladium serve either as catalysts or precatalysts. Although Pd compounds are comparatively rare, one example is sodium hexachloropalladate