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Borderline hydrides typically refer to hydrides formed of hydrogen and elements of the periodic table in group 11 and group 12 and indium (In) and thallium (Tl).[ citation needed ] These compounds have properties intermediate between covalent hydrides and saline hydrides. Hydrides are chemical compounds that contain a metal and hydrogen acting as a negative ion.
Borderline hydrides exhibit bonding characteristics between ionic and covalent bond types. A specific examples of a borderline hydride CuH, copper hydride, that appears as a spongy reddish-brown substance is a moderate reducing agent. It will catalytically oxidize hypophosphorous acid to phosphorous acid at room temperature, and it gives off hydrogen gas when subjected to heat. [1] ZnH2 is also a solid at room temperature that breaks down at 90 °C, but even left alone decomposes over several days to zinc metal and hydrogen gas. [2] Hydrogen telluride (H2Te) and hydrogen selenide (H2Se) are both borderline hydrides of high volatility that produce strong, unpleasant odors.
Borderline hydrides are most commonly formed via the acidification or reduction of metal salts. For instance, copper hydride is formed by reacting copper sulphate and hypophosphorous acid at about 70 °C, forming a yellow precipitate that soon turns red-brown. [3] Zinc hydride, ZnH2, can be formed by the reduction of either a zinc halide or dimethylzinc.
A more recent definition of borderline hydrides refers to hydrides that exist between classic and non-classic dihydrides. The classic form is the dihydride M(H)2 configuration, where the metal is bound to two free hydrogen atoms. The non-classic form contains two hydrogen atoms bound to a central metal atom with an η2-H2 hapticity, indicating that a single coordination point on the metal atom bonds to two contiguous atoms from another molecule, in this case H2. [4] A well-known example of this is from the first such molecule to be synthesized with a coordinated hydrogen ligand (dihydrogen complex): W(CO)3(PPri3)2(η2-H2). [5] Classic dihydrides containing the dihydride M-(H)2 ligands are typically found as a tautomer with the non-classical dihydrogen complexes containing a M-(η2-H2) group.
Borderline hydrides exist with a bond character somewhere between the classical and non-classical hydrides. [6] Those that are thermally unstable exhibit stretching frequencies νHH greater than 2150 cm1 as a result of poor electron donation from the metal center. An electron dense metal center will yield hydride with a νHH less than 2060 cm1, while anything between is considered to be in the borderline region. Kubas, et al. state that a stretching frequency of 2090 cm1 is within the bounds of stable H2 complexes while 2060 cm1 is right on the borderline between dihydrogen and dihydrides. [5]
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkaline, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and tin, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide, cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.
In chemistry, a hydride is formally the anion of hydrogen, H−. The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms, are called hydrides: water is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.
In chemistry, a dihydrogen bond is a kind of hydrogen bond, an interaction between a metal hydride bond and an OH or NH group or other proton donor. With a van der Waals radius of 1.2 Å, hydrogen atoms do not usually approach other hydrogen atoms closer than 2.4 Å. Close approaches near 1.8 Å, are, however, characteristic of dihydrogen bonding.
Hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.
Organozinc compounds in organic chemistry contain carbon to zinc chemical bonds. Organozinc chemistry is the science of organozinc compounds describing their physical properties, synthesis and reactions.
Dihydrogen complexes are coordination complexes containing intact H2 as a ligand. The prototypical complex is W(CO)3(PCy3)2(H2). This class of compounds represent intermediates in metal-catalyzed reactions involving hydrogen. Hundreds of dihydrogen complexes have been reported. Most examples are cationic transition metals complexes with octahedral geometry.
Decamethyldizincocene is an organozinc compound with the formula [Zn2(η5–C5Me5)2]. It is the first and an unusual example of a compound with a Zn-Zn bond. Decamethyldizincocene is a colorless crystalline solid that burns spontaneously in the presence of oxygen and reacts with water. It is stable at room temperature and especially soluble in diethyl ether, benzene, pentane, or tetrahydrofuran.
Transition metal hydrides are chemical compounds containing a transition metal bonded to hydrogen. Most transition metals form hydride complexes and some are significant in various catalytic and synthetic reactions. The term "hydride" is used loosely: some so-called hydrides are acidic (e.g., H2Fe(CO)4), whereas some others are hydridic, having H−-like character (e.g., ZnH2).
Beryllium hydride is an inorganic compound with the chemical formula n. This alkaline earth hydride is a colourless solid that is insoluble in solvents that do not decompose it. Unlike the ionically bonded hydrides of the heavier Group 2 elements, beryllium hydride is covalently bonded.
Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of Nomenclature of Inorganic Chemistry. It is a collection of rules for naming inorganic compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
Zinc hydride is an inorganic compound with the chemical formula ZnH2. It is a white, odourless solid which slowly decomposes into its elements at room temperature; despite this it is the most stable of the binary first row transition metal hydrides. A variety of coordination compounds containing Zn-H bonds are used as reducing agents, however ZnH2 itself has no common applications.
Compounds of zinc are chemical compounds containing the element zinc which is a member of the group 12 of the periodic table. The oxidation state of most compounds is the group oxidation state of +2. Zinc may be classified as a post-transition main group element with zinc(II). Zinc compounds are noteworthy for their nondescript behavior, they are generally colorless, do not readily engage in redox reactions, and generally adopt symmetrical structures.
Binary compounds of hydrogen are binary chemical compounds containing just hydrogen and one other chemical element. By convention all binary hydrogen compounds are called hydrides even when the hydrogen atom in it is not an anion. These hydrogen compounds can be grouped into several types.
Cadmium hydride is an inorganic compound with the chemical formula (CdH
2)
n. It is a solid, known only as a thermally unstable, insoluble white powder.
Mercury(I) hydride is an inorganic compound with the empirical chemical formula HgH. It has not yet been obtained in bulk, hence its bulk properties remain unknown. However, molecular mercury(I) hydrides with the formulae HgH and Hg
2H
2 have been isolated in solid gas matrices. The molecular hydrides are very unstable toward thermal decomposition. As such the compound is not well characterised, although many of its properties have been calculated via computational chemistry.
Mercury(II) hydride is an inorganic compound with the chemical formula HgH
2. It is both thermodynamically and kinetically unstable at ambient temperature, and as such, little is known about its bulk properties. However, it known as a white, crystalline solid, which is kinetically stable at temperatures below −125 °C (−193 °F), which was synthesised for the first time in 1951.
Chromium(II) hydride, systematically named chromium dihydride and poly(dihydridochromium) is pale brown solid inorganic compound with the chemical formula (CrH
2)
n. Although it is thermodynamically unstable toward decomposition at ambient temperatures, it is kinetically metastable.
Iron(II) hydride, systematically named iron dihydride and poly(dihydridoiron) is solid inorganic compound with the chemical formula (FeH
2)
n. ). It is kinetically unstable at ambient temperature, and as such, little is known about its bulk properties. However, it known as a black, amorphous powder, which was synthesised for the first time in 2014.
Chlorobis(dppe)iron hydride is a coordination complex with the formula HFeCl(dppe)2, where dppe is the bidentate ligand 1,2-bis(diphenylphosphino)ethane. It is a red-violet solid. The compound has attracted much attention as a precursor to dihydrogen complexes.
Magnesium monohydride is a molecular gas with formula MgH that exists at high temperatures, such as the atmospheres of the Sun and stars. It was originally known as magnesium hydride, although that name is now more commonly used when referring to the similar chemical magnesium dihydride.
cuprous hydride.