For maintenance: the two lists are compared in this /datacheck, to gain mutual improvements. As of December 2020, for 11 compared elements a diff has to be solved (in list of their states, or bolding).
↑ 1,01,11,21,31,4Na(−1), K(−1), Rb(−1), and Cs(−1) are known in alkalides; the table by Greenwood and Earnshaw shows −1 only for Na and also erroneously for Li; no lithides are described.
↑B(0) has been observed in diborynes, see Braunschweig, H.; Dewhurst, R. D.; Hammond, K.; Mies, J.; Radacki, K.; Vargas, A. (2012). »Ambient-Temperature Isolation of a Compound with a Boron-Boron Triple Bond«. Science. 336 (6087): 1420–2. Bibcode:2012Sci...336.1420B. doi:10.1126/science.1221138. PMID22700924.
↑Al(II) has been observed in aluminium(II) oxide (AlO); see Tyte, D.C. (1964). »Red (B2Π–A2σ) Band System of Aluminium Monoxide«. Nature. 202 (4930): 383–384. Bibcode:1964Natur.202..383T. doi:10.1038/202383a0, and in dialanes (R2Al—AlR2); see Uhl, Werner (2004). »Organoelement Compounds Possessing Al—Al, Ga—Ga, In—In, and Tl—Tl Single Bonds«. Advances in Organometallic Chemistry. 51: 53–108. doi:10.1016/S0065-3055(03)51002-4.
↑Al(−2) has been observed in Sr14[Al4]2[Ge]3, see Wemdorff, Marco; Röhr, Caroline (2007). »Sr14[Al4]2[Ge]3: Eine Zintl-Phase mit isolierten [Ge]4–- und [Al4]8–-Anionen / Sr14[Al4]2[Ge]3: A Zintl Phase with Isolated [Ge]4–- and [Al4]8– Anions«. Zeitschrift für Naturforschung B (v nemščini). 62 (10): 1227. doi:10.1515/znb-2007-1001.
↑P(0) has been observed, see Wang, Yuzhong; Xie, Yaoming; Wei, Pingrong; King, R. Bruce; Schaefer, Iii; Schleyer, Paul v. R.; Robinson, Gregory H. (2008). »Carbene-Stabilized Diphosphorus«. Journal of the American Chemical Society. 130 (45): 14970–1. doi:10.1021/ja807828t. PMID18937460.
↑The equilibrium Cl2O6⇌2ClO3 is mentioned by Greenwood and Earnshaw, but it has been refuted, see Lopez, Maria; Juan E. Sicre (1990). »Physicochemical properties of chlorine oxides. 1. Composition, ultraviolet spectrum, and kinetics of the thermolysis of gaseous dichlorine hexoxide«. J. Phys. Chem. 94 (9): 3860–3863. doi:10.1021/j100372a094., and Cl2O6 is actually chlorine(V,VII) oxide. However, ClO3 has been observed, see Grothe, Hinrich; Willner, Helge (1994). »Chlorine Trioxide: Spectroscopic Properties, Molecular Structure, and Photochemical Behavior«. Angew. Chem. Int. Ed. 33 (14): 1482–1484. doi:10.1002/anie.199414821.
↑Ca(I) has been observed; see Krieck, Sven; Görls, Helmar; Westerhausen, Matthias (2010). »Mechanistic Elucidation of the Formation of the Inverse Ca(I) Sandwich Complex [(thf)3Ca(μ-C6H3-1,3,5-Ph3)Ca(thf)3] and Stability of Aryl-Substituted Phenylcalcium Complexes«. Journal of the American Chemical Society. 132 (35): 12492–501. doi:10.1021/ja105534w. PMID20718434.
↑Sc(0) has been observed; see F. Geoffrey N. Cloke; Karl Khan & Robin N. Perutz (1991). »η-Arene complexes of scandium(0) and scandium(II)«. J. Chem. Soc., Chem. Commun. (19): 1372–1373. doi:10.1039/C39910001372.
↑Sc(I) has been observed; see Polly L. Arnold; F. Geoffrey; N. Cloke; Peter B. Hitchcock & John F. Nixon (1996). »The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring«. J. Am. Chem. Soc. 118 (32): 7630–7631. doi:10.1021/ja961253o.
↑Sc(II) has been observed; see Woen, David H.; Chen, Guo P.; Ziller, Joseph W.; Boyle, Timothy J.; Furche, Filipp; Evans, William J. (Januar 2017). »Solution Synthesis, Structure, and CO Reduction Reactivity of a Scandium(II) Complex«. Angewandte Chemie International Edition. 56 (8): 2050–2053. doi:10.1002/anie.201611758. PMID28097771.
↑Ti(I) has been observed in [Ti(η6-1,3,5-C6H3iPr3)2][BAr4] (Ar = C6H5, p-C6H4F, 3,5-C6H3(CF3)2); see Calderazzo, Fausto; Ferri, Isabella; Pampaloni, Guido; Englert, Ulli; Green, Malcolm L. H. (1997). »Synthesis of [Ti(η6-1,3,5-C6H3iPr3)2][BAr4] (Ar = C6H5, p-C6H4F, 3,5-C6H3(CF3)2), the First Titanium(I) Derivatives«. Organometallics. 16 (14): 3100–3101. doi:10.1021/om970155o.
↑Ti(−1) has been reported in [Ti(bipy)3]−, but was later shown to be Ti(+3); see Bowman, A. C.; England, J.; Sprouls, S.; Weihemüller, T.; Wieghardt, K. (2013). »Electronic structures of homoleptic [tris(2,2'-bipyridine)M]n complexes of the early transition metals (M = Sc, Y, Ti, Zr, Hf, V, Nb, Ta; n = 1+, 0, 1-, 2-, 3-): an experimental and density functional theoretical study«. Inorganic Chemistry. 52 (4): 2242–56. doi:10.1021/ic302799s. PMID23387926. However, Ti(−1) occurs in [Ti(η-C6H6]− and [Ti(η-C6H5CH3)]−, see Bandy, J. A.; Berry, A.; Green, M. L. H.; Perutz, R. N.; Prout, K.; Verpeautz, J.-N. (1984). »Synthesis of anionic sandwich compounds: [Ti(η-C6H5R)2]– and the crystal structure of [K(18-crown-6)(µ-H)Mo(η-C5H5)2]«. Inorganic Chemistry. 52 (4): 729–731. doi:10.1039/C39840000729.
↑Jilek, Robert E.; Tripepi, Giovanna; Urnezius, Eugenijus; Brennessel, William W.; Young, Victor G. Jr.; Ellis, John E. (2007). »Zerovalent titanium–sulfur complexes. Novel dithiocarbamato derivatives of Ti(CO)6: [Ti(CO)4(S2CNR2)]−«. Chem. Commun. (25): 2639–2641. doi:10.1039/B700808B. PMID17579764.
↑Fe(VII) has been observed in [FeO4]−; see Lu, Jun-Bo; Jian, Jiwen; Huang, Wei; Lin, Hailu; Zhou, Mingfei (2016). »Experimental and theoretical identification of the Fe(VII) oxidation state in FeO4−«. Physical Chemistry Chemical Physics. 18 (45): 31125–31131. Bibcode:2016PCCP...1831125L. doi:10.1039/C6CP06753K. PMID27812577.
↑Fe(VIII) has been reported; see Yurii D. Perfiliev; Virender K. Sharma (2008). »Higher Oxidation States of Iron in Solid State: Synthesis and Their Mössbauer Characterization – Ferrates – ACS Symposium Series (ACS Publications)«. Platinum Metals Review. 48 (4): 157–158. doi:10.1595/147106704X10801. However, its existence has been disputed.
↑ 25,0025,0125,0225,0325,0425,0525,0625,0725,0825,09Fe(−4), Ru(−4), and Os(−4) have been observed in metal-rich compounds containing octahedral complexes [MIn6−xSnx]; Pt(−3) (as a dimeric anion [Pt–Pt]6−), Cu(−2), Zn(−2), Ag(−2), Cd(−2), Au(−2), and Hg(−2) have been observed (as dimeric and monomeric anions; dimeric ions were initially reported to be [T–T]2− for Zn, Cd, Hg, but later shown to be [T–T]4− for all these elements) in La2Pt2In, La2Cu2In, Ca5Au3, Ca5Ag3, Ca5Hg3, Sr5Cd3, Ca5Zn3(structure (AE2+)5(T–T)4−T2−⋅4e−), Yb3Ag2, Ca5Au4, and Ca3Hg2; Au(–3) has been observed in ScAuSn and in other 18-electron half-Heusler compounds. See Changhoon Lee; Myung-Hwan Whangbo (2008). »Late transition metal anions acting as p-metal elements«. Solid State Sciences. 10 (4): 444–449. Bibcode:2008SSSci..10..444K. doi:10.1016/j.solidstatesciences.2007.12.001. and Changhoon Lee; Myung-Hwan Whangbo; Jürgen Köhler (2010). »Analysis of Electronic Structures and Chemical Bonding of Metal-rich Compounds. 2. Presence of Dimer (T–T)4– and Isolated T2– Anions in the Polar Intermetallic Cr5B3-Type Compounds AE5T3 (AE = Ca, Sr; T = Au, Ag, Hg, Cd, Zn)«. Zeitschrift für Anorganische und Allgemeine Chemie. 636 (1): 36–40. doi:10.1002/zaac.200900421.
↑Ni(−2) has been observed in Li2[Ni(1,5-COD)2], see Jonas, Klaus (1975). »Dilithium-Nickel-Olefin Complexes. Novel Bimetal Complexes Containing a Transition Metal and a Main Group Metal«. Angew. Chem. Int. Ed. 14 (11): 752–753. doi:10.1002/anie.197507521. and Ellis, John E. (2006). »Adventures with Substances Containing Metals in Negative Oxidation States«. Inorganic Chemistry. 45 (8): 3167–86. doi:10.1021/ic052110i. PMID16602773.
↑Cu(0) has been observed in Cu(tris[2-(diisopropylphosphino)-
phenyl]borane), see Moret, Marc-Etienne; Zhang, Limei; Peters, Jonas C. (2013). »A Polar Copper–Boron One-Electron σ-Bond«. J. Am. Chem. Soc. 135 (10): 3792–3795. doi:10.1021/ja4006578. PMID23418750.
↑Zn(0) has been observed; see Singh, Amit Pratap; Samuel, Prinson P.; Roesky, Herbert W.; Schwarzer, Martin C.; Frenking, Gernot; Sidhu, Navdeep S.; Dittrich, Birger (2013). »A Singlet Biradicaloid Zinc Compound and Its Nonradical Counterpart«. J. Am. Chem. Soc. 135 (19): 7324–9. doi:10.1021/ja402351x. and Soleilhavoup, Michèle; Bertrand, Guy (2015). »Cyclic (Alkyl)(Amino)Carbenes (CAACs): Stable Carbenes on the Rise«. Acc. Chem. Res. 48 (2): 256–266. doi:10.1021/ar5003494.
↑Ge(−1), Ge(−2), and Ge(−3) have been observed in germanides; see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). »Germanium«. Lehrbuch der Anorganischen Chemie (v nemščini) (101 izd.). Walter de Gruyter. str. 953–959. ISBN978-3-11-012641-9.
↑As(0) has been observed; see Abraham, Mariham Y.; Wang, Yuzhong; Xie, Yaoming; Wei, Pingrong; Shaefer III, Henry F.; Schleyer, P. von R.; Robinson, Gregory H. (2010). »Carbene Stabilization of Diarsenic: From Hypervalency to Allotropy«. Chemistry: a European Journal. 16 (2): 432–5. doi:10.1002/chem.200902840.
↑As(I) has been observed in arsenic(I) iodide (AsI); see Ellis, Bobby D.; MacDonald, Charles L. B. (2004). »Stabilized Arsenic(I) Iodide: A Ready Source of Arsenic Iodide Fragments and a Useful Reagent for the Generation of Clusters«. Inorganic Chemistry. 43 (19): 5981–6. doi:10.1021/ic049281s. PMID15360247.
↑As(IV) has been observed in arsenic(IV) hydroxide (As(OH)4) and HAsO-; see Kläning, Ulrik K.; Bielski, Benon H. J.; Sehested, K. (1989). »Arsenic(IV). A pulse-radiolysis study«. Inorganic Chemistry. 28 (14): 2717–24. doi:10.1021/ic00313a007.
↑Se(−1) has been observed in diselenides(2−) (Se22−).
↑Se(III) has been observed in Se2NBr3; see Lau, Carsten; Neumüller, Bernhard; Vyboishchikov, Sergei F.; Frenking, Gernot; Dehnicke, Kurt; Hiller, Wolfgang; Herker, Martin (1996). »Se2NBr3, Se2NCl5, Se2NCl−6: New Nitride Halides of Selenium(III) and Selenium(IV)«. Chemistry: A European Journal. 2 (11): 1393–1396. doi:10.1002/chem.19960021108.
↑ 41,0041,0141,0241,0341,0441,0541,0641,0741,0841,0941,1041,1141,1241,13Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). »Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides«. Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (15. december 2003). »Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation«. Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
↑Y(II) has been observed in [(18-crown-6)K][(C5H4SiMe3)3Y]; see MacDonald, M. R.; Ziller, J. W.; Evans, W. J. (2011). »Synthesis of a Crystalline Molecular Complex of Y2+, [(18-crown-6)K][(C5H4SiMe3)3Y]«. J. Am. Chem. Soc. 133 (40): 15914–17. doi:10.1021/ja207151y. PMID21919538.
↑Zr(−1) has been reported in [Zr(bipy)3]− (see Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2. izd.). Butterworth-Heinemann. str. 960. ISBN978-0-08-037941-8. and Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). »Zirconium«. Lehrbuch der Anorganischen Chemie (v nemščini) (101 izd.). Walter de Gruyter. str. 1413. ISBN978-3-11-012641-9.), but was later shown to be Zr(+4); see Bowman, A. C.; England, J.; Sprouls, S.; Weihemüller, T.; Wieghardt, K. (2013). »Electronic structures of homoleptic [tris(2,2'-bipyridine)M]n complexes of the early transition metals (M = Sc, Y, Ti, Zr, Hf, V, Nb, Ta; n = 1+, 0, 1-, 2-, 3-): an experimental and density functional theoretical study«. Inorganic Chemistry. 52 (4): 2242–56. doi:10.1021/ic302799s. PMID23387926.
↑ 45,045,1Zr(0) and Hf(0) occur in (η6-(1,3,5-tBu)3C6H3)2M (M=Zr, Hf) and [(η5-C5R5M(CO)4]−, see Chirik, P. J.; Bradley, C. A. (2007). »4.06 - Complexes of Zirconium and Hafnium in Oxidation States 0 to ii«. Comprehensive Organometallic Chemistry III. From Fundamentals to Applications. Zv. 4. Elsevier Ltd. str. 697–739. doi:10.1016/B0-08-045047-4/00062-5.
↑Complexes of Nb(0) and Ta(0) have been observed, see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (2003). »4.5.7. Niobium(0) and Tantalum(0)«. V J. A. McCleverty; T.J. Meyer (ur.). Comprehensive Coordination Chemistry II: From Biology to Nanotechnology. Zv. 4 (2 izd.). Newnes. str. 297–299. ISBN978-0-08-091316-2.
↑ 47,047,1Nb(I) and Ta(I) occur in CpNb(CO)4 and CpTa(CO)4, see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). »Tantal«. Lehrbuch der Anorganischen Chemie (v nemščini) (101 izd.). Walter de Gruyter. str. 1430. ISBN978-3-11-012641-9. and King, R. Bruce (1969). Transition-Metal Organometallic Chemistry: An Introduction. Academic Press. str. 11. ISBN978-0-32-315996-8.
↑George, G.N.; Klein, S.I.; Nixon, J.F. (1984). »Electron paramagnetic resonance spectroscopic studies on the zero-valent rhodium complex [Rh(P(OPri)3)4] at X-and Q-band frequencies«. Chemical Physics Letters. 108 (6): 627–630. Bibcode:1984CPL...108..627G. doi:10.1016/0009-2614(84)85069-1.
↑The Ag− ion has been observed in metal ammonia solutions: see Tran, N. E.; Lagowski, J. J. (2001). »Metal Ammonia Solutions: Solutions Containing Argentide Ions«. Inorganic Chemistry. 40 (5): 1067–68. doi:10.1021/ic000333x.
↑Cd(I) has been observed in cadmium(I) tetrachloroaluminate (Cd2(AlCl4)2); see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). »Cadmium«. Lehrbuch der Anorganischen Chemie (v nemščini) (91–100 izd.). Walter de Gruyter. str. 1056–1057. ISBN978-3-11-007511-3.
↑In(–5) has been observed in La3InGe, see Guloy, A. M.; Corbett, J. D. (1996). »Synthesis, Structure, and Bonding of Two Lanthanum Indium Germanides with Novel Structures and Properties«. Inorganic Chemistry. 35 (9): 2616–22. doi:10.1021/ic951378e.
↑In(−2) has been observed in Na2In, see [4], p. 69.
↑Sb(−2) has been observed in [Sb2]4−, e.g. in RbBa4[Sb2][Sb][O], see Boss, Michael; Petri, Denis; Pickhard, Frank; Zönnchen, Peter; Röhr, Caroline (2005). »Neue Barium-Antimonid-Oxide mit den Zintl-Ionen [Sb]3−, [Sb2]4− und 1∞[Sbn]n− / New Barium Antimonide Oxides containing Zintl Ions [Sb]3−, [Sb2]4− and 1∞[Sbn]n−«. Zeitschrift für Anorganische und Allgemeine Chemie (v nemščini). 631 (6–7): 1181–1190. doi:10.1002/zaac.200400546.
↑Sb(I) and Sb(II) have been observed in organoantimony compounds; for Sb(I), see Šimon, Petr; de Proft, Frank; Jambor, Roman; Růžička, Aleš; Dostál, Libor (2010). »Monomeric Organoantimony(I) and Organobismuth(I) Compounds Stabilized by an NCN Chelating Ligand: Syntheses and Structures«. Angewandte Chemie International Edition. 49 (32): 5468–5471. doi:10.1002/anie.201002209. PMID20602393.
↑Sb(IV) has been observed in [SbCl]2− , see Nobuyoshi Shinohara; Masaaki Ohsima (2000). »Production of Sb(IV) Chloro Complex by Flash Photolysis of the Corresponding Sb(III) and Sb(V) Complexes in CH3CN and CHCl3«. Bulletin of the Chemical Society of Japan. 73 (7): 1599–1604. doi:10.1246/bcsj.73.1599.
↑Te(V) is mentioned by Greenwood and Earnshaw, but they do not give any example of a Te(V) compound. What was long thought to be ditellurium decafluoride (Te2F10) is actually bis(pentafluorotelluryl) oxide, F5TeOTeF5: see Watkins, P. M. (1974). »Ditellurium decafluoride - A Continuing Myth«. Journal of Chemical Education. 51 (9): 520–521. Bibcode:1974JChEd..51..520W. doi:10.1021/ed051p520. However, Te(V) has been observed in HTeO-, TeO-, HTeO2-, and TeO3-; see Kläning, Ulrik K.; Sehested, K. (2001). »Tellurium(V). A Pulse Radiolysis Study«. The Journal of Physical Chemistry A. 105 (27): 6637–45. Bibcode:2001JPCA..105.6637K. doi:10.1021/jp010577i.
↑I(IV) has been observed in iodine dioxide (IO2); see Pauling, Linus (1988). »Oxygen Compounds of Nonmetallic Elements«. General Chemistry (3rd izd.). Dover Publications, Inc. str. 259. ISBN978-0-486-65622-9.
↑I(VI) has been observed in IO3, IO42−, H5IO6−, H2IO52−, H4IO62−, and HIO53−; see Kläning, Ulrik K.; Sehested, Knud; Wolff, Thomas (1981). »Laser flash photolysis and pulse radiolysis of iodate and periodate in aqueous solution. Properties of iodine(VI)«. J. Chem. Soc., Faraday Trans. 1. 77 (7): 1707–18. doi:10.1039/F19817701707.
↑Pr(I) has been observed in [PrB4]−; see Chen, Xin; Chen, Teng-Teng; Li, Wang-Lu; Lu, Jun-Bo; Zhao, Li-Juan; Jian, Tian; Hu, Han-Shi; Wang, Lai-Sheng; Li, Jun (13. december 2018). »Lanthanides with Unusually Low Oxidation States in the PrB3– and PrB4– Boride Clusters«. Inorganic Chemistry. 58 (1): 411–418. doi:10.1021/acs.inorgchem.8b02572. PMID30543295.
↑Pr(V) has been observed in [PrO2]+; see Zhang, Qingnan; Hu, Shu-Xian; Qu, Hui; Su, Jing; Wang, Guanjun; Lu, Jun-Bo; Chen, Mohua; Zhou, Mingfei; Li, Jun (6. junij 2016). »Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides«. Angewandte Chemie International Edition. 55 (24): 6896–6900. doi:10.1002/anie.201602196. ISSN1521-3773. PMID27100273.
↑ 75,075,175,275,375,4All the lanthanides (La–Lu) in the +2 oxidation state have been observed (except La, Gd, Lu) in dilute, solid solutions of dihalides of these elements in alkaline earth dihalides (see Predloga:Holleman&Wiberg) and (except Pm) in organometallic molecular complexes, see Lanthanides Topple Assumptions and Meyer, G. (2014). »All the Lanthanides Do It and Even Uranium Does Oxidation State +2«. Angewandte Chemie International Edition. 53 (14): 3550–51. doi:10.1002/anie.201311325. PMID24616202.. Additionally, all the lanthanides (La–Lu) form dihydrides (LnH2), dicarbides (LnC2), monosulfides (LnS), monoselenides (LnSe), and monotellurides (LnTe), but for most elements these compounds have Ln3+ ions with electrons delocalized into conduction bands, e. g. Ln3+(H−)2(e−).
↑Os(−1) has been observed in Na[Os(CO) 13]; see Krause, J.; Siriwardane, Upali; Salupo, Terese A.; Wermer, Joseph R.; Knoeppel, David W.; Shore, Sheldon G. (1993). »Preparation of [Os3(CO)11]2− and its reactions with Os3(CO)12; structures of [Et4N] [HOs3(CO)11] and H2OsS4(CO)«. Journal of Organometallic Chemistry. 454: 263–271. doi:10.1016/0022-328X(93)83250-Y. and Carter, Willie J.; Kelland, John W.; Okrasinski, Stanley J.; Warner, Keith E.; Norton, Jack R. (1982). »Mononuclear hydrido alkyl carbonyl complexes of osmium and their polynuclear derivatives«. Inorganic Chemistry. 21 (11): 3955–3960. doi:10.1021/ic00141a019.
↑Ir(VIII) has been observed in iridium tetroxide (IrO4); see Gong, Yu; Zhou, Mingfei; Kaupp, Martin; Riedel, Sebastian (2009). »Formation and Characterization of the Iridium Tetroxide Molecule with Iridium in the Oxidation State +VIII«. Angewandte Chemie International Edition. 48 (42): 7879–7883. doi:10.1002/anie.200902733. PMID19593837.
↑Ir(IX) has been observed in IrO+ 4; see Wang, Guanjun; Zhou, Mingfei; Goettel, James T.; Schrobilgen, Gary G.; Su, Jing; Li, Jun; Schlöder, Tobias; Riedel, Sebastian (21. avgust 2014). »Identification of an iridium-containing compound with a formal oxidation state of IX«. Nature. 514 (7523): 475–477. Bibcode:2014Natur.514..475W. doi:10.1038/nature13795. PMID25341786.
↑Pt(−1) and Pt(−2) have been observed in the barium platinides Ba2Pt and BaPt, respectively: see Karpov, Andrey; Konuma, Mitsuharu; Jansen, Martin (2006). »An experimental proof for negative oxidation states of platinum: ESCA-measurements on barium platinides«. Chemical Communications (8): 838–840. doi:10.1039/b514631c. PMID16479284.
↑Au(0) has been observed, see Mézaille, Nicolas; Avarvari, Narcis; Maigrot, Nicole; Ricard, Louis; Mathey, François; Le Floch, Pascal; Cataldo, Laurent; Berclaz, Théo; Geoffroy, Michel (1999). »Gold(I) and Gold(0) Complexes of Phosphinine‐Based Macrocycles«. Angewandte Chemie International Edition (21): 3194–3197. doi:10.1002/(SICI)1521-3773(19991102)38:21<3194::AID-ANIE3194>3.0.CO;2-O.
↑Tl(−5) has been observed in Na23K9Tl15.3, see Dong, Z.-C.; Corbett, J. D. (1996). »Na23K9Tl15.3: An Unusual Zintl Compound Containing Apparent Tl57−, Tl48−, Tl37−, and Tl5− Anions«. Inorganic Chemistry. 35 (11): 3107–12. doi:10.1021/ic960014z.
↑Tl(−1) has been observed in caesium thallide (CsTl); see King, R. B.; Schleyer, R. (2004). »Theory and concepts in main-group cluster chemistry«. V Driess, M.; Nöth, H. (ur.). Molecular clusters of the main group elements. Wiley-VCH, Chichester. str. 19. ISBN978-3-527-61437-0.
↑Tl(+2) has been observed in tetrakis(hypersilyl)dithallium ([(Me3Si)Si]2Tl—Tl[Si(SiMe3)]2), see Sonja Henkel; Dr. Karl Wilhelm Klinkhammer; Dr. Wolfgang Schwarz (1994). »Tetrakis(hypersilyl)dithallium(Tl—Tl): A Divalent Thallium Compound«. Angew. Chem. Int. Ed. 33 (6): 681–683. doi:10.1002/anie.199406811.
↑Pb(−2) has been observed in BaPb, see Ferro, Riccardo (2008). Nicholas C. Norman (ur.). Intermetallic Chemistry. Elsevier. str. 505. ISBN978-0-08-044099-6. and Todorov, Iliya; Sevov, Slavi C. (2004). »Heavy-Metal Aromatic Rings: Cyclopentadienyl Anion Analogues Sn56− and Pb56− in the Zintl Phases Na8BaPb6, Na8BaSn6, and Na8EuSn6«. Inorganic Chemistry. 43 (20): 6490–94. doi:10.1021/ic000333x.
↑Pb(+1) and Pb(+3) have been observed in organolead compounds, e.g. hexamethyldiplumbane Pb2(CH3)6; for Pb(I), see Siew-Peng Chia; Hong-Wei Xi; Yongxin Li; Kok Hwa Lim; Cheuk-Wai So (2013). »A Base-Stabilized Lead(I) Dimer and an Aromatic Plumbylidenide Anion«. Angew. Chem. Int. Ed. 52 (24): 6298–6301. doi:10.1002/anie.201301954. PMID23629949.
↑Bi(I) has been observed in bismuth monobromide (BiBr) and bismuth monoiodide (BiI); see Godfrey, S. M.; McAuliffe, C. A.; Mackie, A. G.; Pritchard, R. G. (1998). Nicholas C. Norman (ur.). Chemistry of arsenic, antimony, and bismuth. Springer. str. 67–84. ISBN978-0-7514-0389-3.
↑Bi(IV) has been observed; see A. I. Aleksandrov, I. E. Makarov (1987). »Formation of Bi(II) and Bi(IV) in aqueous hydrochloric solutions of Bi(III)«. Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science. 36 (2): 217–220. doi:10.1007/BF00959349.
↑Rn(IV) is reported by Greenwood and Earnshaw, but is not known to exist; see Sykes, A. G. (1998). »Recent Advances in Noble-Gas Chemistry«. Advances in Inorganic Chemistry. Zv. 46. Academic Press. str. 91–93. ISBN978-0-12-023646-6. Pridobljeno 22. novembra 2012.
↑U(II) has been observed in [K(2.2.2-Cryptand)][(C5H4SiMe3)3U], see MacDonald, Matthew R.; Fieser, Megan E.; Bates, Jefferson E.; Ziller, Joseph W.; Furche, Filipp; Evans, William J. (2013). »Identification of the +2 Oxidation State for Uranium in a Crystalline Molecular Complex, [K(2.2.2-Cryptand)][(C5H4SiMe3)3U]«. J. Am. Chem. Soc. 135 (36): 13310–13313. doi:10.1021/ja406791t. PMID23984753.
↑Pu(II) has been observed in {Pu[C5H3(SiMe3)2]3}−; see Windorff, Cory J.; Chen, Guo P; Cross, Justin N; Evans, William J.; Furche, Filipp; Gaunt, Andrew J.; Janicke, Michael T.; Kozimor, Stosh A.; Scott, Brian L. (2017). »Identification of the Formal +2 Oxidation State of Plutonium: Synthesis and Characterization ofref name="curium5" {PuII[C5H3(SiMe3)2]3}−«. J. Am. Chem. Soc. 139 (11): 3970–3973. doi:10.1021/jacs.7b00706. PMID28235179.
↑Pu(VIII) has been observed in PuO 4; see Nikonov, M. V.; Kiselev, Yu. M.; Tananaev, I. G.; Myasoedov, B. F. (Marec 2011). »Plutonium volatility in ozonization of alkaline solutions of Pu(VI) hydroxo complexes«. Doklady Chemistry. 437 (1): 69–71. doi:10.1134/S0012500811030104. Also see Kiselev, Yu. M.; Nikonov, M. V.; Dolzhenko, V. D.; Ermilov, A. Yu.; Tananaev, I. G.; Myasoedov, B. F. (17. januar 2014). »On existence and properties of plutonium(VIII) derivatives«. Radiochimica Acta. 102 (3). doi:10.1515/ract-2014-2146.
↑Am(VII) has been observed in AmO5-; see Americium, Das Periodensystem der Elemente für den Schulgebrauch (The periodic table of elements for schools) chemie-master.de (in German), Retrieved 28 November 2010 and Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2. izd.). Butterworth-Heinemann. str. 1265. ISBN978-0-08-037941-8.
↑ 109,0109,1109,2Kovács, Attila; Dau, Phuong D.; Marçalo, Joaquim; Gibson, John K. (2018). »Pentavalent Curium, Berkelium, and Californium in Nitrate Complexes: Extending Actinide Chemistry and Oxidation States«. Inorg. Chem. American Chemical Society. 57 (15): 9453–9467. doi:10.1021/acs.inorgchem.8b01450. PMID30040397.
↑Cm(VI) has been observed in curium trioxide (CmO3) and dioxidocurium(2+) (CmO2+); see Domanov, V. P.; Lobanov, Yu. V. (Oktober 2011). »Formation of volatile curium(VI) trioxide CmO3«. Radiochemistry. 53 (5): 453–6. doi:10.1134/S1066362211050018.
↑Cm(VIII) has been reported to possibly occur in curium tetroxide (CmO4); see Domanov, V. P. (Januar 2013). »Possibility of generation of octavalent curium in the gas phase in the form of volatile tetraoxide CmO4«. Radiochemistry. 55 (1): 46–51. doi:10.1134/S1066362213010098. However, new experiments seem to indicate its nonexistence: Zaitsevskii, Andréi; Schwarz, W H Eugen (april 2014). »Structures and stability of AnO4 isomers, An = Pu, Am, and Cm: a relativistic density functional study«. Physical Chemistry Chemical Physics. 2014 (16): 8997–9001. Bibcode:2014PCCP...16.8997Z. doi:10.1039/c4cp00235k. PMID24695756.{{navedi časopis}}: Vzdrževanje CS1: samodejni prevod datuma (povezava)
↑Sullivan, Jim C.; Schmidt, K. H.; Morss, L. R.; Pippin, C. G.; Williams, C. (1988). »Pulse radiolysis studies of berkelium(III): preparation and identification of berkelium(II) in aqueous perchlorate media«. Inorganic Chemistry. 27 (4): 597. doi:10.1021/ic00277a005.
↑Hs(VIII) has been observed in hassium tetroxide (HsO4); see »Chemistry of Hassium«(PDF). Gesellschaft für Schwerionenforschung mbH. 2002. Pridobljeno 31. januarja 2007.