Dioxygen complexes are coordination compounds that contain O2 as a ligand.[1][2] The study of these compounds is inspired by oxygen-carrying proteins such as myoglobin, hemoglobin, hemerythrin, and hemocyanin.[3] Several transition metals form complexes with O2, and many of these complexes form reversibly.[4] The binding of O2 is the first step in many important phenomena, such as cellular respiration, corrosion, and industrial chemistry. The first synthetic oxygen complex was demonstrated in 1938 with cobalt(II) complex reversibly bound O2.[5]
O2 binds to a single metal center either “end-on” (η1-) or “side-on” (η2-). The bonding and structures of these compounds are usually evaluated by single-crystal X-ray crystallography, focusing both on the overall geometry as well as the O–O distances, which reveals the bond order of the O2 ligand.
Complexes of η1-O2 ligands
A picket-fence porphyrin complex of Fe, with axial coordination sites occupied by methylimidazole (green) and dioxygen (R = amide groups).[6]
O2adducts derived from cobalt(II) and iron(II) complexes of porphyrin (and related anionic macrocyclic ligands) exhibit this bonding mode. Myoglobin and hemoglobin are famous examples, and many synthetic analogues have been described that behave similarly. Binding of O2 is usually described as proceeding by electron transfer from the metal(II) center to give superoxide (O− 2) complexes of metal(III) centers. As shown by the mechanisms of cytochrome P450 and alpha-ketoglutarate-dependent hydroxylase, Fe-η1-O2 bonding is conducive to formation of Fe(IV) oxo centers. O2 can bind to one metal of a bimetallic unit via the same modes discussed above for mononuclear complexes. A well-known example is the active site of the protein hemerythrin, which features a diiron carboxylate that binds O2 at one Fe center. Dinuclear complexes can also cooperate in the binding, although the initial attack of O2 probably occurs at a single metal.
Complexes of η2-O2 ligands
η2-bonding is the most common motif seen in coordination chemistry of dioxygen. Such complexes can be generated by treating low-valent metal complexes with oxygen. For example, Vaska's complex reversibly binds O2 (Ph = C6H5):
IrCl(CO)(PPh3)2 + O2 ⇌ IrCl(CO)(PPh3)2O2
The conversion is described as a 2 e−redox process: Ir(I) converts to Ir(III) as dioxygen converts to peroxide. Since O2 has a triplet ground state and Vaska's complex is a singlet, the reaction is slower than when singlet oxygen is used.[7] The magnetic properties of some η2-O2 complexes show that the ligand, in fact, is superoxide, not peroxide.[8]
Most complexes of η2-O2 are generated using hydrogen peroxide, not from O2. Chromate ([CrO4)]2−) can for example be converted to the tetraperoxide [Cr(O2)4]2−. The reaction of hydrogen peroxide with aqueous titanium(IV) gives a brightly colored peroxy complex that is a useful test for titanium as well as hydrogen peroxide.[9]
Binuclear complexes of O2
O2-bound form of hemocyanin, the O2 carrier for certain molluscs.
These binding modes include μ2-η2,η2-, μ2-η1,η1-, and μ2-η1,η2-. Depending on the degree of electron-transfer from the dimetal unit, these O2 ligands can again be described as peroxo or superoxo. Hemocyanin is an O2-carrier that utilizes a bridging O2 binding motif. It features a pair of copper centers.[10]
Salcomine, the cobalt(II) complex of salen ligand is the first synthetic O2 carrier.[12] Solvated derivatives of the solid complex bind 0.5 equivalent of O2:
2 Co(salen) + O2 → [Co(salen)]2O2
Reversible electron transfer reactions are observed in some dinuclear O2 complexes.[13]
Oxidation of the dicobalt peroxy complex gives the complex of superoxide (O2−). The Co-O-O-Co core flattens in the process and the O-O distance contracts by 10%.
Relationship to other oxygenic ligands and applications
Dioxygen complexes are the precursors to other families of oxygenic ligands. Metal oxo compounds arise from the cleavage of the O–O bond after complexation. Hydroperoxo complexes are generated in the course of the reduction of dioxygen by metals. The reduction of O2 by metal catalysts is a key half-reaction in fuel cells.
Metal-catalyzed oxidations with O2 proceed via the intermediacy of dioxygen complexes, although the actual oxidants are often oxo derivatives. The reversible binding of O2 to metal complexes has been used as a means to purify oxygen from air, but cryogenic distillation of liquid air remains the dominant technology.
References
^Yee, Gereon M.; Tolman, William B. (2015). "Chapter 5: Transition Metal Complexes and the Activation of Dioxygen". In Kroneck, Peter M. H.; Sosa Torres, Martha E. (eds.). Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. Vol. 15. Springer. pp. 131–204. doi:10.1007/978-3-319-12415-5_5. PMID 25707468.
^Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego, CA: Academic Press. ISBN0-12-352651-5.
^Lippard, S. J.; Berg, J. M. (1994). Principles of Bioinorganic Chemistry. Mill Valley, CA: University Science Books. ISBN0-935702-73-3.
^Berry, R. E. (2004). "Reactivity and Structure of Complexes of Small Molecules: Dioxygen". Comprehensive Coordination Chemistry II. Vol. 1. pp. 625–629. doi:10.1016/B0-08-043748-6/01161-0. ISBN9780080437484.
^Tsumaki, Tokuichi (1938). "Nebenvalenzringverbindungen. IV. Über einige innerkomplexe Kobaltsalze der Oxyaldimine" [Secondary valence ring compounds. IV. On some inner-complex cobalt salts of oxyaldimine]. Bulletin of the Chemical Society of Japan. 13 (2): 252–260. doi:10.1246/bcsj.13.252.
^S. J. Lippard, J. M. Berg “Principles of Bioinorganic Chemistry” University Science Books: Mill Valley, CA; 1994. ISBN0-935702-73-3.
^Selke, M.; Foote, C. S. (1993). "Reactions of Organometallic Complexes with Singlet Oxygen. Photooxidation of Vaska's Complex". J. Am. Chem. Soc. 115 (3): 1166–1167. doi:10.1021/ja00056a061.
^Egan, James W.; Haggerty, Brian S.; Rheingold, Arnold L.; Sendlinger, Shawn C.; Theopold, Klaus H. (1990). "Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand". Journal of the American Chemical Society. 112 (6): 2445–2446. doi:10.1021/ja00162a069.
^Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN0-7506-3365-4.
^Elwell, Courtney E.; Gagnon, Nicole L.; Neisen, Benjamin D.; Dhar, Debanjan; Spaeth, Andrew D.; Yee, Gereon M.; Tolman, William B. (2017). "Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity". Chemical Reviews. 117 (3): 2059–2107. doi:10.1021/acs.chemrev.6b00636. PMC5963733. PMID 28103018.
^M. Calligaris, G. Nardin, L. Randaccio, A. Ripamonti (1970). "Structural Aspects of the Synthetic Oxygen-Carrier NN′-Ethylenebis(Salicylideneiminato)cobalt(II): Structure of the Addition Compound with Oxygen Containing Dimethylformamide". J. Chem. Soc. A: 1069. doi:10.1039/j19700001069.{{cite journal}}: CS1 maint: uses authors parameter (link)
^Tokuichi Tsumaki (1938). "Nebenvalenzringverbindungen. IV. Über einige innerkomplexe Kobaltsalze der Oxyaldimine". Bulletin of the Chemical Society of Japan. 13 (2): 252–260. doi:10.1246/bcsj.13.252.
^Schaefer, William Palzer (1968). "Structure of Decaammine-μ-Peroxo-Dicobalt Disulfate Tetrahydrate". Inorganic Chemistry. 7 (4): 725–731. doi:10.1021/ic50062a022.
March 24, 2023
transition, metal, dioxygen, complex, dioxygen, complexes, coordination, compounds, that, contain, ligand, study, these, compounds, inspired, oxygen, carrying, proteins, such, myoglobin, hemoglobin, hemerythrin, hemocyanin, several, transition, metals, form, c. Dioxygen complexes are coordination compounds that contain O2 as a ligand 1 2 The study of these compounds is inspired by oxygen carrying proteins such as myoglobin hemoglobin hemerythrin and hemocyanin 3 Several transition metals form complexes with O2 and many of these complexes form reversibly 4 The binding of O2 is the first step in many important phenomena such as cellular respiration corrosion and industrial chemistry The first synthetic oxygen complex was demonstrated in 1938 with cobalt II complex reversibly bound O2 5 Contents 1 Mononuclear complexes of O2 1 1 Complexes of h1 O2 ligands 1 2 Complexes of h2 O2 ligands 2 Binuclear complexes of O2 3 Relationship to other oxygenic ligands and applications 4 ReferencesMononuclear complexes of O2 EditO2 binds to a single metal center either end on h1 or side on h2 The bonding and structures of these compounds are usually evaluated by single crystal X ray crystallography focusing both on the overall geometry as well as the O O distances which reveals the bond order of the O2 ligand Complexes of h1 O2 ligands Edit A picket fence porphyrin complex of Fe with axial coordination sites occupied by methylimidazole green and dioxygen R amide groups 6 O2 adducts derived from cobalt II and iron II complexes of porphyrin and related anionic macrocyclic ligands exhibit this bonding mode Myoglobin and hemoglobin are famous examples and many synthetic analogues have been described that behave similarly Binding of O2 is usually described as proceeding by electron transfer from the metal II center to give superoxide O 2 complexes of metal III centers As shown by the mechanisms of cytochrome P450 and alpha ketoglutarate dependent hydroxylase Fe h1 O2 bonding is conducive to formation of Fe IV oxo centers O2 can bind to one metal of a bimetallic unit via the same modes discussed above for mononuclear complexes A well known example is the active site of the protein hemerythrin which features a diiron carboxylate that binds O2 at one Fe center Dinuclear complexes can also cooperate in the binding although the initial attack of O2 probably occurs at a single metal Complexes of h2 O2 ligands Edit h2 bonding is the most common motif seen in coordination chemistry of dioxygen Such complexes can be generated by treating low valent metal complexes with oxygen For example Vaska s complex reversibly binds O2 Ph C6H5 IrCl CO PPh3 2 O2 IrCl CO PPh3 2O2The conversion is described as a 2 e redox process Ir I converts to Ir III as dioxygen converts to peroxide Since O2 has a triplet ground state and Vaska s complex is a singlet the reaction is slower than when singlet oxygen is used 7 The magnetic properties of some h2 O2 complexes show that the ligand in fact is superoxide not peroxide 8 Most complexes of h2 O2 are generated using hydrogen peroxide not from O2 Chromate CrO4 2 can for example be converted to the tetraperoxide Cr O2 4 2 The reaction of hydrogen peroxide with aqueous titanium IV gives a brightly colored peroxy complex that is a useful test for titanium as well as hydrogen peroxide 9 Binuclear complexes of O2 Edit O2 bound form of hemocyanin the O2 carrier for certain molluscs These binding modes include m2 h2 h2 m2 h1 h1 and m2 h1 h2 Depending on the degree of electron transfer from the dimetal unit these O2 ligands can again be described as peroxo or superoxo Hemocyanin is an O2 carrier that utilizes a bridging O2 binding motif It features a pair of copper centers 10 Structure of Co salen dmf 2O2 11 Salcomine the cobalt II complex of salen ligand is the first synthetic O2 carrier 12 Solvated derivatives of the solid complex bind 0 5 equivalent of O2 2 Co salen O2 Co salen 2O2Reversible electron transfer reactions are observed in some dinuclear O2 complexes 13 Oxidation of the dicobalt peroxy complex gives the complex of superoxide O2 The Co O O Co core flattens in the process and the O O distance contracts by 10 Relationship to other oxygenic ligands and applications EditDioxygen complexes are the precursors to other families of oxygenic ligands Metal oxo compounds arise from the cleavage of the O O bond after complexation Hydroperoxo complexes are generated in the course of the reduction of dioxygen by metals The reduction of O2 by metal catalysts is a key half reaction in fuel cells Metal catalyzed oxidations with O2 proceed via the intermediacy of dioxygen complexes although the actual oxidants are often oxo derivatives The reversible binding of O2 to metal complexes has been used as a means to purify oxygen from air but cryogenic distillation of liquid air remains the dominant technology References Edit Yee Gereon M Tolman William B 2015 Chapter 5 Transition Metal Complexes and the Activation of Dioxygen In Kroneck Peter M H Sosa Torres Martha E eds Sustaining Life on Planet Earth Metalloenzymes Mastering Dioxygen and Other Chewy Gases Metal Ions in Life Sciences Vol 15 Springer pp 131 204 doi 10 1007 978 3 319 12415 5 5 PMID 25707468 Holleman A F Wiberg E 2001 Inorganic Chemistry San Diego CA Academic Press ISBN 0 12 352651 5 Lippard S J Berg J M 1994 Principles of Bioinorganic Chemistry Mill Valley CA University Science Books ISBN 0 935702 73 3 Berry R E 2004 Reactivity and Structure of Complexes of Small Molecules Dioxygen Comprehensive Coordination Chemistry II Vol 1 pp 625 629 doi 10 1016 B0 08 043748 6 01161 0 ISBN 9780080437484 Tsumaki Tokuichi 1938 Nebenvalenzringverbindungen IV Uber einige innerkomplexe Kobaltsalze der Oxyaldimine Secondary valence ring compounds IV On some inner complex cobalt salts of oxyaldimine Bulletin of the Chemical Society of Japan 13 2 252 260 doi 10 1246 bcsj 13 252 S J Lippard J M Berg Principles of Bioinorganic Chemistry University Science Books Mill Valley CA 1994 ISBN 0 935702 73 3 Selke M Foote C S 1993 Reactions of Organometallic Complexes with Singlet Oxygen Photooxidation of Vaska s Complex J Am Chem Soc 115 3 1166 1167 doi 10 1021 ja00056a061 Egan James W Haggerty Brian S Rheingold Arnold L Sendlinger Shawn C Theopold Klaus H 1990 Crystal structure of a side on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand Journal of the American Chemical Society 112 6 2445 2446 doi 10 1021 ja00162a069 Greenwood N N Earnshaw A 1997 Chemistry of the Elements 2nd ed Oxford Butterworth Heinemann ISBN 0 7506 3365 4 Elwell Courtney E Gagnon Nicole L Neisen Benjamin D Dhar Debanjan Spaeth Andrew D Yee Gereon M Tolman William B 2017 Copper Oxygen Complexes Revisited Structures Spectroscopy and Reactivity Chemical Reviews 117 3 2059 2107 doi 10 1021 acs chemrev 6b00636 PMC 5963733 PMID 28103018 M Calligaris G Nardin L Randaccio A Ripamonti 1970 Structural Aspects of the Synthetic Oxygen Carrier NN Ethylenebis Salicylideneiminato cobalt II Structure of the Addition Compound with Oxygen Containing Dimethylformamide J Chem Soc A 1069 doi 10 1039 j19700001069 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint uses authors parameter link Tokuichi Tsumaki 1938 Nebenvalenzringverbindungen IV Uber einige innerkomplexe Kobaltsalze der Oxyaldimine Bulletin of the Chemical Society of Japan 13 2 252 260 doi 10 1246 bcsj 13 252 Schaefer William Palzer 1968 Structure of Decaammine m Peroxo Dicobalt Disulfate Tetrahydrate Inorganic Chemistry 7 4 725 731 doi 10 1021 ic50062a022 Retrieved from https en wikipedia org w index php title Transition metal dioxygen complex amp oldid 1108257627, wikipedia, wiki, book, books, library,
