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41-503: (Redirected from Inner Sphere ) Inner Sphere may refer to: Inner sphere complex , a type of ion-surface binding Inner sphere electron transfer , a chemical reaction involving closely associated atoms Inner Sphere (BattleTech) , the primary setting of the BattleTech universe Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

82-407: A cation and surface. This affinity to surface sites can be attributed to covalent bonding. When compared to outer sphere complexes that have water molecules separating ions from ligands, inner sphere complexes have surface hydroxyl groups that function as σ {\displaystyle \sigma } -donor ligands , increasing the coordinated metal ion 's electron density . This

123-399: A Lewis acid is an atomic or molecular species with a localized empty atomic or molecular orbital of low energy. This lowest-energy molecular orbital ( LUMO ) can accommodate a pair of electrons. A Lewis base is often a Brønsted–Lowry base as it can donate a pair of electrons to H ; the proton is a Lewis acid as it can accept a pair of electrons. The conjugate base of a Brønsted–Lowry acid

164-407: A chloride ion lone-pair, forming AlCl − 4 and creating the strongly acidic, that is, electrophilic , carbonium ion. A Lewis base is an atomic or molecular species where the highest occupied molecular orbital (HOMO) is highly localized. Typical Lewis bases are conventional amines such as ammonia and alkyl amines. Other common Lewis bases include pyridine and its derivatives. Some of

205-657: A large application of Lewis bases is to modify the activity and selectivity of metal catalysts . Chiral Lewis bases, generally multidentate , confer chirality on a catalyst, enabling asymmetric catalysis , which is useful for the production of pharmaceuticals . The industrial synthesis of the anti-hypertension drug mibefradil uses a chiral Lewis base ( R -MeOBIPHEP), for example. Lewis acids and bases are commonly classified according to their hardness or softness. In this context hard implies small and nonpolarizable and soft indicates larger atoms that are more polarizable. For example, an amine will displace phosphine from

246-550: A metal ion completely immersed in a liquid ligand solution does not have a change in liquid-gas interface. This reaction can be modeled by − Δ G i = γ S G − γ S L {\displaystyle -\Delta G_{i}=\gamma _{SG}-\gamma _{SL}} = γ L G c o s θ {\displaystyle =\gamma _{LG}cos\theta } From these models, metal ions can be influenced by contact angle, and as

287-460: A redox reaction, the sorption phenomenon are then referred to as adsorption . This is of particular importance because different surfaces and ligands have varying redox intensity that can catalyze various reactions. When exposed to water, the metal oxide that was previously an inner sphere complex will become saturated with water, which is known as a dissolution reaction. This can also be observed in cases where hydroxyl groups are also present. pH

328-469: A result, inner sphere complexes are influenced by wetting agents and wetting procedures. An example of sorption of ligands occurs in metallic oxides and silicate surfaces. In a mineral surface, the metal ion acts as a Lewis acid , and the ligands act as the Lewis base. For ligands that have protons, the sorption is dependent on the pH . In cases of where ligands affect the surface coordination by performing

369-486: A result. For nonpolar ligands, van der Waals forces instead play a larger role in sorption interactions. Hydrogen bonding does also occur, but is not a part of the adsorption process itself. Due to these factors, the soil quality influences the retention and depletion of nutrients, pollutants, and other ligands that perform sorption with the soil. Generally, the charged surface of a metallic ion can become charged via crystalline imperfections , chemical reactions at

410-521: Is The W term represents a constant energy contribution for acid–base reaction such as the cleavage of a dimeric acid or base. The equation predicts reversal of acids and base strengths. The graphical presentations of the equation show that there is no single order of Lewis base strengths or Lewis acid strengths. and that single property scales are limited to a smaller range of acids or bases. The concept originated with Gilbert N. Lewis who studied chemical bonding . In 1923, Lewis wrote An acid substance

451-415: Is a Lewis base, because it can donate its lone pair of electrons. Trimethylborane [(CH 3 ) 3 B] is a Lewis acid as it is capable of accepting a lone pair. In a Lewis adduct, the Lewis acid and base share an electron pair furnished by the Lewis base, forming a dative bond. In the context of a specific chemical reaction between NH 3 and Me 3 B, a lone pair from NH 3 will form a dative bond with

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492-453: Is a consideration within these reactions, but the symmetrical, molecular adsorption of water is considered unstable and possesses a high activation energy . As a result, the rate determining step relies on the breakage of a critical oxo bond that may increase inductive effects through changes in electron density. This causes nucleophilic attacks and further dissolution to occur. Sorption reactions of inner sphere complexes are applicable in

533-516: Is also a Lewis base as loss of H from the acid leaves those electrons which were used for the A—H bond as a lone pair on the conjugate base. However, a Lewis base can be very difficult to protonate , yet still react with a Lewis acid. For example, carbon monoxide is a very weak Brønsted–Lowry base but it forms a strong adduct with BF 3 . In another comparison of Lewis and Brønsted–Lowry acidity by Brown and Kanner, 2,6-di- t -butylpyridine reacts to form

574-456: Is an example of competitive complex formation, in which ligands will compete for space on an activation site of a metal ion. Surface structures are able to reduce and oxidize ligands, whereas transport phenomena do not. Therefore, surface structure serves an important role in surface reactivity, with the coordination environment at the solid-water interface changing intensity or rate of a reaction. One method to achieve inner sphere complexes

615-470: Is described by the Gibb's Free Energy over the area S = − Δ G s / A {\displaystyle S=-\Delta G_{s}/A} The Gibb's Free Energy is spontaneous only when S is positive or zero. Another method of wetting is adhesional wetting , where the liquid makes contact with the solid surface for the first time. However, this initial wetting decreases

656-407: Is not very clear-cut. For example, in the formation of an ammonium ion from ammonia and hydrogen the ammonia molecule donates a pair of electrons to the proton ; the identity of the electrons is lost in the ammonium ion that is formed. Nevertheless, Lewis suggested that an electron-pair donor be classified as a base and an electron-pair acceptor be classified as acid. A more modern definition of

697-461: Is one of the strongest but is also one of the most complicated Lewis acids. It is convention to ignore the fact that a proton is heavily solvated (bound to solvent). With this simplification in mind, acid-base reactions can be viewed as the formation of adducts: A typical example of a Lewis acid in action is in the Friedel–Crafts alkylation reaction. The key step is the acceptance by AlCl 3 of

738-498: Is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms. The Brønsted–Lowry acid–base theory was published in the same year. The two theories are distinct but complementary. A Lewis base is also a Brønsted–Lowry base, but a Lewis acid does not need to be a Brønsted–Lowry acid. The classification into hard and soft acids and bases ( HSAB theory ) followed in 1963. The strength of Lewis acid-base interactions, as measured by

779-401: Is through wetting : a phenomenon where one fluid, known as a wetting agent, replaces another medium, like water or air, on a surface. In the case of a solid-water to a solid-liquid interface, the liquid spreads to increase the solid-liquid and liquid-gas interfacial area , and decreases the solid-gas interfacial and solid-water area as a result. The spreading coefficient of the liquid

820-468: The American physical chemist Gilbert N. Lewis ) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct . A Lewis base , then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH 3

861-428: The Lewis acid I 2 . Some Lewis acids bind with two Lewis bases, a famous example being the formation of hexafluorosilicate : Most compounds considered to be Lewis acids require an activation step prior to formation of the adduct with the Lewis base. Complex compounds such as Et 3 Al 2 Cl 3 and AlCl 3 are treated as trigonal planar Lewis acids but exist as aggregates and polymers that must be degraded by

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902-401: The Lewis base. A simpler case is the formation of adducts of borane. Monomeric BH 3 does not exist appreciably, so the adducts of borane are generated by degradation of diborane: In this case, an intermediate B 2 H − 7 can be isolated. Many metal complexes serve as Lewis acids, but usually only after dissociating a more weakly bound Lewis base, often water. The proton (H )

943-494: The Lewis basicity and Lewis acidity emphasize the thermodynamic aspect of Lewis adduct formation. In many cases, the interaction between the Lewis base and Lewis acid in a complex is indicated by an arrow indicating the Lewis base donating electrons toward the Lewis acid using the notation of a dative bond — for example, Me 3 B ← NH 3 . Some sources indicate the Lewis base with a pair of dots (the explicit electrons being donated), which allows consistent representation of

984-501: The adduct with the acid BF 3 . In the same way, bases could be classified. For example, bases donating a lone pair from an oxygen atom are harder than bases donating through a nitrogen atom. Although the classification was never quantified it proved to be very useful in predicting the strength of adduct formation, using the key concepts that hard acid—hard base and soft acid—soft base interactions are stronger than hard acid—soft base or soft acid—hard base interactions. Later investigation of

1025-425: The bond between carbon and iodine (S N 2 reaction). Textbooks disagree on this point: some asserting that alkyl halides are electrophiles but not Lewis acids, while others describe alkyl halides (e.g. CH 3 Br) as a type of Lewis acid. The IUPAC states that Lewis acids and Lewis bases react to form Lewis adducts, and defines electrophile as Lewis acids. Some of the most studied examples of such Lewis acids are

1066-407: The boron trihalides and organoboranes : In this adduct, all four fluoride centres (or more accurately, ligands ) are equivalent. Both BF 4 and BF 3 OMe 2 are Lewis base adducts of boron trifluoride. Many adducts violate the octet rule , such as the triiodide anion: The variability of the colors of iodine solutions reflects the variable abilities of the solvent to form adducts with

1107-420: The development of a stern layer . Additionally, water remediation can also be considered a by-product of inner sphere complexes found in clay and other mineral complexes. This is theorized to occur due to metal-metal precipitation, such as in the case of iron-arsenic. However, pH can greatly affect the surface binding effectiveness in this case as well. Lewis acids and bases A Lewis acid (named for

1148-548: The dissolution and weathering of these metals. Reductive dissolution in these environments may take longer or be non-existent as a result. However, an understanding of this has led to greater usage of oxyanions in built environments where corrosion and weathering needs to be limited. Ion size of the central metal and of inorganic ligands also play a role in the weathering. Alkali earth metals have reduced sorption as their ion size increases due to decreased affinity to anionic charges, which increases their mobility through weathering as

1189-402: The empty orbital of Me 3 B to form an adduct NH 3 •BMe 3 . The terminology refers to the contributions of Gilbert N. Lewis . The terms nucleophile and electrophile are sometimes interchangeable with Lewis base and Lewis acid, respectively. These terms, especially their abstract noun forms nucleophilicity and electrophilicity , emphasize the kinetic aspect of reactivity, while

1230-533: The liquid-gas interface that can be modeled by the Dupré equation W a = − Δ G a / A {\displaystyle W_{a}=-\Delta G_{a}/A} Or by the revised Dupré-Young equation W a = − γ L G ( 1 + c o s ( θ ) ) {\displaystyle W_{a}=-\gamma _{LG}(1+cos(\theta ))} Immersional wetting that has

1271-504: The main classes of Lewis bases are The most common Lewis bases are anions. The strength of Lewis basicity correlates with the pK a of the parent acid: acids with high pK a 's give good Lewis bases. As usual, a weaker acid has a stronger conjugate base . The strength of Lewis bases have been evaluated for various Lewis acids, such as I 2 , SbCl 5 , and BF 3 . Nearly all electron pair donors that form compounds by binding transition elements can be viewed ligands . Thus,

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1312-399: The pentahalides of phosphorus, arsenic, and antimony. In the same vein, CH + 3 can be considered to be the Lewis acid in methylation reactions. However, the methyl cation never occurs as a free species in the condensed phase, and methylation reactions by reagents like CH 3 I take place through the simultaneous formation of a bond from the nucleophile to the carbon and cleavage of

1353-493: The standard enthalpy of formation of an adduct can be predicted by the Drago–Wayland two-parameter equation. Lewis had suggested in 1916 that two atoms are held together in a chemical bond by sharing a pair of electrons. When each atom contributed one electron to the bond, it was called a covalent bond . When both electrons come from one of the atoms, it was called a dative covalent bond or coordinate bond . The distinction

1394-407: The strength of Lewis acid base interactions, −ΔH. The model assigned E and C parameters to many Lewis acids and bases. Each acid is characterized by an E A and a C A . Each base is likewise characterized by its own E B and C B . The E and C parameters refer, respectively, to the electrostatic and covalent contributions to the strength of the bonds that the acid and base will form. The equation

1435-412: The surface, or sorption at the surface-active ion. Clay minerals are an example of these interactions, and as such can explain chemical homeostasis in the ocean, biogeochemical cycling of metals, and even radioactive waste disposal . In engineering applications, the clay minerals can promote sodium ion adsorption in petroleum extraction , alongside the creation of environmental liners through

1476-529: The thermodynamics of the interaction suggested that hard—hard interactions are enthalpy favored, whereas soft—soft are entropy favored. Many methods have been devised to evaluate and predict Lewis acidity. Many are based on spectroscopic signatures such as shifts NMR signals or IR bands e.g. the Gutmann-Beckett method and the Childs method. The ECW model is a quantitative model that describes and predicts

1517-652: The title Inner sphere . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Inner_sphere&oldid=533384617 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Inner sphere complex Inner sphere complexes describe active surface sites that are involved in nucleation , crystal growth , redox processes , soil chemistry , alongside other reactions taking place between

1558-497: The transition from the base itself to the complex with the acid: A center dot may also be used to represent a Lewis adduct, such as Me 3 B·NH 3 . Another example is boron trifluoride diethyl etherate , BF 3 ·Et 2 O . In a slightly different usage, the center dot is also used to represent hydrate coordination in various crystals, as in MgSO 4 ·7H 2 O for hydrated magnesium sulfate , irrespective of whether

1599-463: The transport and retention of trace elements in soil systems. In particular, the sorbent materials found in nature are often metal-oxide inner sphere complexes. In nature, this is particularly important for iron and manganese cycling, as both are effected by the redox potential of their environments for weathering to occur. Oxyanions such as SO 4 2 − {\displaystyle {\ce {SO4^2-}}} can hinder

1640-406: The use of the dative bond arrow is just a notational convenience for avoiding the drawing of formal charges. In general, however, the donor–acceptor bond is viewed as simply somewhere along a continuum between idealized covalent bonding and ionic bonding . Lewis acids are diverse and the term is used loosely. Simplest are those that react directly with the Lewis base, such as boron trihalides and

1681-520: The water forms a dative bond with the metal. Although there have been attempts to use computational and experimental energetic criteria to distinguish dative bonding from non-dative covalent bonds, for the most part, the distinction merely makes note of the source of the electron pair, and dative bonds, once formed, behave simply as other covalent bonds do, though they typically have considerable polar character. Moreover, in some cases (e.g., sulfoxides and amine oxides as R 2 S → O and R 3 N → O ),

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