In coordination chemistry, the first coordination sphere refers to the array of molecules and ions (the ligands) directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere.
cis-[CoCl2(NH3)4]+ The NH3 and Cl groups form a coordination sphere around the central cobalt ion.
The first coordination sphere refers to the molecules that are attached directly to the metal. The interactions between the first and second coordination spheres usually involve hydrogen-bonding. For charged complexes, ion pairing is important.
Hexamminecobalt(III) chloride is a salt of a coordination complex wherein six ammonia ("ammine") ligands occupy the first coordination sphere of the ion Co3+.
In hexamminecobalt(III) chloride ([Co(NH3)6]Cl3), the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN6 core "decorated" by 18 N−H bonds that radiate outwards.
Second coordination sphereedit
In crystalline FeSO4.7H2O, the first coordination sphere of Fe2+ consists of six water ligands. The second coordination sphere consists of a water of crystallization and sulfate, which interact with the [Fe(H2O)6]2+ centers.
Metal ions can be described as consisting of series of two concentric coordination spheres, the first and second. More distant from the second coordination sphere, the solvent molecules behave more like "bulk solvent." Simulation of the second coordination sphere is of interest in computational chemistry. The second coordination sphere can consist of ions (especially in charged complexes), molecules (especially those that hydrogen bond to ligands in the first coordination sphere) and portions of a ligand backbone. Compared to the first coordination sphere, the second coordination sphere has a less direct influence on the reactivity and chemical properties of the metal complex. Nonetheless the second coordination sphere is relevant to understanding reactions of the metal complex, including the mechanisms of ligand exchange and catalysis.
Role in catalysisedit
Mechanisms of metalloproteins often invoke modulation of the second coordination sphere by the protein.[1]
The rates at which ligands exchange between the first and the second coordination sphere is the first step in ligand substitution reactions. In associative ligand substitution, the entering nucleophile resides in the second coordination sphere. These effects are relevant to practical applications such as contrast agents used in MRI.[4]
Solvent effects on colors and stability are often attributable to changes in the second coordination sphere. Such effects can be pronounced in complexes where the ligands in the first coordination sphere are strong hydrogen-bond donors and acceptors, e.g. respectively [Co(NH3)6]3+ and [Fe(CN)6]3−. Crown-ethers bind to polyamine complexes through their second coordination sphere. Polyammonium cations bind to the nitrogen centres of cyanometallates.[5]
Role in supramolecular chemistryedit
Macrocyclic molecules such as cyclodextrins act often as the second coordination sphere for metal complexes. [6][7]
^Zhao, Meng; Wang, Hai-Bo; Ji, Liang-Nian; Mao, Zong-Wan (2013). "Insights into metalloenzyme microenvironments: biomimetic metal complexes with a functional second coordination sphere". Chemical Society Reviews. 42 (21): 8360–8375. doi:10.1039/c3cs60162e. ISSN 0306-0012. PMID 23881282.
^Yang, J. Y.; Chen, S.; Dougherty, W. G.; Kassel, W. S.; Bullock, R. M.; DuBois, D. L.; Raugei, S.; Rousseau, R.; Dupuis, M.; Rakowski DuBois, M. (2010). "Hydrogen oxidation catalysis by a nickel diphosphine complex with pendant tert-butyl amines". Chem. Commun. 46 (45): 8618–8620. doi:10.1039/c0cc03246h. PMID 20938535.
^Bullock, R. M.; Helm, M. L. (2015). "Molecular Electrocatalysts for Oxidation of Hydrogen Using Earth-Abundant Metals: Shoving Protons Around with Proton Relays". Acc. Chem. Res. 48 (7): 2017–2026. doi:10.1021/acs.accounts.5b00069. OSTI 1582563. PMID 26079983.
^R. M. Supkowski, W. DeW. Horrocks Jr. "On the determination of the number of water molecules, q, coordinated to europium(III) ions in solution from luminescence decay lifetimes" Inorganic Chimica Acta 2002, Volume 340, pp. 44–48. doi:10.1016/S0020-1693(02)01022-8
^Lehn, J. M. Supramolecular Chemistry: Concepts and Perspectives; VCH: Weinhiem, 1995.
^Z. Liu, S. T. Schneebeli, J. F. Stoddart "Second-sphere coordination revisited" Chimia 2014, 68, 315-320. doi:10.2533/chimia.2014.315
^Z. Liu, M. Frasconi, J. Lei, Z. J. Brown, Z. Zhu, D. Cao, J. Iehl, G. Liu, A. C. Fahrenbach, O. K. Farha, J. T. Hupp, C. A. Mirkin, Y. Y. Botros, J. F. Stoddart "Selective isolation of gold facilitated by second-sphere coordination with alpha-cyclodextrin" Nature Communications 2013, 4, 1855. doi:10.1038/ncomms2891
February 27, 2024
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In coordination chemistry the first coordination sphere refers to the array of molecules and ions the ligands directly attached to the central metal atom The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere cis CoCl2 NH3 4 The NH3 and Cl groups form a coordination sphere around the central cobalt ion Contents 1 First coordination sphere 2 Second coordination sphere 2 1 Role in catalysis 2 2 Role in mechanistic inorganic chemistry 2 3 Role in spectroscopy 2 4 Role in supramolecular chemistry 3 See also 4 Further reading 5 ReferencesFirst coordination sphere editThe first coordination sphere refers to the molecules that are attached directly to the metal The interactions between the first and second coordination spheres usually involve hydrogen bonding For charged complexes ion pairing is important nbsp Hexamminecobalt III chloride is a salt of a coordination complex wherein six ammonia ammine ligands occupy the first coordination sphere of the ion Co3 In hexamminecobalt III chloride Co NH3 6 Cl3 the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere The coordination sphere of this ion thus consists of a central MN6 core decorated by 18 N H bonds that radiate outwards Second coordination sphere edit nbsp In crystalline FeSO4 7H2O the first coordination sphere of Fe2 consists of six water ligands The second coordination sphere consists of a water of crystallization and sulfate which interact with the Fe H2O 6 2 centers Metal ions can be described as consisting of series of two concentric coordination spheres the first and second More distant from the second coordination sphere the solvent molecules behave more like bulk solvent Simulation of the second coordination sphere is of interest in computational chemistry The second coordination sphere can consist of ions especially in charged complexes molecules especially those that hydrogen bond to ligands in the first coordination sphere and portions of a ligand backbone Compared to the first coordination sphere the second coordination sphere has a less direct influence on the reactivity and chemical properties of the metal complex Nonetheless the second coordination sphere is relevant to understanding reactions of the metal complex including the mechanisms of ligand exchange and catalysis Role in catalysis edit Mechanisms of metalloproteins often invoke modulation of the second coordination sphere by the protein 1 nbsp In metal complexes of 1 5 diaza 3 7 diphosphacyclooctanes and related ligands amine groups occupy the second coordination sphere 2 3 Role in mechanistic inorganic chemistry edit The rates at which ligands exchange between the first and the second coordination sphere is the first step in ligand substitution reactions In associative ligand substitution the entering nucleophile resides in the second coordination sphere These effects are relevant to practical applications such as contrast agents used in MRI 4 The energetics of inner sphere electron transfer reactions are discussed in terms of second coordination sphere Some proton coupled electron transfer reactions involve atom transfer between the second coordination spheres of the reactants Fe H2O 6 2 Fe H2O 5 OH 2 Fe H2O 6 3 Fe H2O 5 OH 2 Role in spectroscopy edit Solvent effects on colors and stability are often attributable to changes in the second coordination sphere Such effects can be pronounced in complexes where the ligands in the first coordination sphere are strong hydrogen bond donors and acceptors e g respectively Co NH3 6 3 and Fe CN 6 3 Crown ethers bind to polyamine complexes through their second coordination sphere Polyammonium cations bind to the nitrogen centres of cyanometallates 5 Role in supramolecular chemistry edit Macrocyclic molecules such as cyclodextrins act often as the second coordination sphere for metal complexes 6 7 See also editCoordination number Ligand cone angle Coordination geometryFurther reading editWhat Is A Coordination Compound References edit Zhao Meng Wang Hai Bo Ji Liang Nian Mao Zong Wan 2013 Insights into metalloenzyme microenvironments biomimetic metal complexes with a functional second coordination sphere Chemical Society Reviews 42 21 8360 8375 doi 10 1039 c3cs60162e ISSN 0306 0012 PMID 23881282 Yang J Y Chen S Dougherty W G Kassel W S Bullock R M DuBois D L Raugei S Rousseau R Dupuis M Rakowski DuBois M 2010 Hydrogen oxidation catalysis by a nickel diphosphine complex with pendant tert butyl amines Chem Commun 46 45 8618 8620 doi 10 1039 c0cc03246h PMID 20938535 Bullock R M Helm M L 2015 Molecular Electrocatalysts for Oxidation of Hydrogen Using Earth Abundant Metals Shoving Protons Around with Proton Relays Acc Chem Res 48 7 2017 2026 doi 10 1021 acs accounts 5b00069 OSTI 1582563 PMID 26079983 R M Supkowski W DeW Horrocks Jr On the determination of the number of water molecules q coordinated to europium III ions in solution from luminescence decay lifetimes Inorganic Chimica Acta 2002 Volume 340 pp 44 48 doi 10 1016 S0020 1693 02 01022 8 Lehn J M Supramolecular Chemistry Concepts and Perspectives VCH Weinhiem 1995 Z Liu S T Schneebeli J F Stoddart Second sphere coordination revisited Chimia 2014 68 315 320 doi 10 2533 chimia 2014 315 Z Liu M Frasconi J Lei Z J Brown Z Zhu D Cao J Iehl G Liu A C Fahrenbach O K Farha J T Hupp C A Mirkin Y Y Botros J F Stoddart Selective isolation of gold facilitated by second sphere coordination with alpha cyclodextrin Nature Communications 2013 4 1855 doi 10 1038 ncomms2891 Retrieved from https en wikipedia org w index php title Coordination sphere amp oldid 1197952718, wikipedia, wiki, book, books, library,
