Editing Dubnium (section)

== Experimental chemistry ==
Experimental results of the chemistry of dubnium date back to 1974 and 1976. JINR researchers used a [[wikt:thermochromatography|thermochromatographic]] system and concluded that the volatility of dubnium bromide was less than that of niobium bromide and about the same as that of hafnium bromide. It is not certain that the detected fission products confirmed that the parent was indeed element 105. These results may imply that dubnium behaves more like [[hafnium]] than niobium.<ref name="Haire" />

The next studies on the chemistry of dubnium were conducted in 1988, in Berkeley. They examined whether the most stable oxidation state of dubnium in aqueous solution was +5. Dubnium was fumed twice and washed with concentrated [[nitric acid]]; [[sorption]] of dubnium on glass [[cover slip]]s was then compared with that of the group 5 elements niobium and tantalum and the group 4 elements zirconium and hafnium produced under similar conditions. The group 5 elements are known to sorb on glass surfaces; the group 4 elements do not. Dubnium was confirmed as a group 5 member. Surprisingly, the behavior on extraction from mixed nitric and [[hydrofluoric acid]] solution into [[methyl isobutyl ketone]] differed between dubnium, tantalum, and niobium. Dubnium did not extract and its behavior resembled niobium more closely than tantalum, indicating that complexing behavior could not be predicted purely from simple extrapolations of trends within a group in the periodic table.<ref name="Haire" />

This prompted further exploration of the chemical behavior of complexes of dubnium. Various labs jointly conducted thousands of repetitive chromatographic experiments between 1988 and 1993. All group 5 elements and [[protactinium]] were extracted from concentrated [[hydrochloric acid]]; after mixing with lower concentrations of hydrogen chloride, small amounts of hydrogen fluoride were added to start selective re-extraction. Dubnium showed behavior different from that of tantalum but similar to that of niobium and its pseudohomolog protactinium at concentrations of hydrogen chloride below 12 [[Molar concentration|moles per liter]]. This similarity to the two elements suggested that the formed complex was either {{chem|DbOX|4|-}} or {{chem|[Db(OH)|2|X|4|]|-}}. After extraction experiments of dubnium from [[hydrobromic acid|hydrogen bromide]] into [[diisobutyl carbinol]] (2,6-dimethylheptan-4-ol), a specific extractant for protactinium, with subsequent elutions with the hydrogen chloride/hydrogen fluoride mix as well as hydrogen chloride, dubnium was found to be less prone to extraction than either protactinium or niobium. This was explained as an increasing tendency to form non‐extractable complexes of multiple negative charges. Further experiments in 1992 confirmed the stability of the +5 state: Db(V) was shown to be extractable from cation‐exchange columns with α‐hydroxyisobutyrate, like the group 5 elements and protactinium; Db(III) and Db(IV) were not. In 1998 and 1999, new predictions suggested that dubnium would extract nearly as well as niobium and better than tantalum from halide solutions, which was later confirmed.<ref name="Haire" />

The first isothermal gas chromatography experiments were performed in 1992 with <sup>262</sup>Db (half-life 35 seconds). The volatilities for niobium and tantalum were similar within error limits, but dubnium appeared to be significantly less volatile. It was postulated that traces of oxygen in the system might have led to formation of {{chem|DbOBr|3}}, which was predicted to be less volatile than {{chem|DbBr|5}}. Later experiments in 1996 showed that group 5 chlorides were more volatile than the corresponding bromides, with the exception of tantalum, presumably due to formation of {{chem|TaOCl|3}}. Later volatility studies of chlorides of dubnium and niobium as a function of controlled partial pressures of oxygen showed that formation of oxychlorides and general volatility are dependent on concentrations of oxygen. The oxychlorides were shown to be less volatile than the chlorides.<ref name="Haire" />

In 2004–05, researchers from Dubna and Livermore identified a new dubnium isotope, <sup>268</sup>Db, as a fivefold alpha decay product of the newly created [[moscovium|element 115]]. This new isotope proved to be long-lived enough to allow further chemical experimentation, with a half-life of over a day. In the 2004 experiment, a thin layer with dubnium was removed from the surface of the target and dissolved in [[aqua regia]] with tracers and a [[lanthanum]] carrier, from which various +3, +4, and +5 species were precipitated on adding [[ammonium hydroxide]]. The precipitate was washed and dissolved in hydrochloric acid, where it converted to nitrate form and was then dried on a film and counted. Mostly containing a +5 species, which was immediately assigned to dubnium, it also had a +4 species; based on that result, the team decided that additional chemical separation was needed. In 2005, the experiment was repeated, with the final product being hydroxide rather than nitrate precipitate, which was processed further in both Livermore (based on reverse phase chromatography) and Dubna (based on anion exchange chromatography). The +5 species was effectively isolated; dubnium appeared three times in tantalum-only fractions and never in niobium-only fractions. It was noted that these experiments were insufficient to draw conclusions about the general chemical profile of dubnium.<ref>{{cite report |first1=N. J. |last1=Stoyer |first2=J. H. |last2=Landrum |first3=P. A. |last3=Wilk |display-authors=etal |title=Chemical Identification of a Long-Lived Isotope of Dubnium, a Descendant of Element 115 |year=2006 |publisher=IX International Conference on Nucleus Nucleus Collisions |url=https://e-reports-ext.llnl.gov/pdf/338922.pdf |access-date=October 9, 2017 |url-status=live |archive-url=https://web.archive.org/web/20170131161312/https://e-reports-ext.llnl.gov/pdf/338922.pdf |archive-date=January 31, 2017 }}</ref>

In 2009, at the JAEA tandem accelerator in Japan, dubnium was processed in nitric and hydrofluoric acid solution, at concentrations where niobium forms {{chem|NbOF|4|-}} and tantalum forms {{chem|TaF|6|-}}. Dubnium's behavior was close to that of niobium but not tantalum; it was thus deduced that dubnium formed {{chem|DbOF|4|-}}. From the available information, it was concluded that dubnium often behaved like niobium, sometimes like protactinium, but rarely like tantalum.<ref>{{Cite journal |last1=Nagame |first1=Y.|last2=Kratz |first2=J. V. |last3=Schädel |first3=M.|date=2016 |title=Chemical properties of rutherfordium (Rf) and dubnium (Db) in the aqueous phase|journal=EPJ Web of Conferences|language=en|volume=131|doi=10.1051/epjconf/201613107007|page=07007|bibcode=2016EPJWC.13107007N|url=https://jopss.jaea.go.jp/pdfdata/BB2016-0022.pdf |archive-url=https://web.archive.org/web/20190428145306/https://jopss.jaea.go.jp/pdfdata/BB2016-0022.pdf |archive-date=2019-04-28 |url-status=live|doi-access=free}}</ref>

In 2021, the volatile heavy group 5 oxychlorides MOCl<sub>3</sub> (M = Nb, Ta, Db) were experimentally studied at the JAEA tandem accelerator. The trend in volatilities was found to be NbOCl<sub>3</sub> > TaOCl<sub>3</sub> ≥ DbOCl<sub>3</sub>, so that dubnium behaves in line with periodic trends.<ref>{{cite journal |last1=Chiera |first1=Nadine M. |last2=Sato |first2=Tetsuya K. |first3=Robert |last3=Eichler |first4=Tomohiro |last4=Tomitsuka |first5=Masato |last5=Asai |first6=Sadia |last6=Adachi |first7=Rugard |last7=Dressler |first8=Kentaro |last8=Hirose |first9=Hiroki |last9=Inoue |first10=Yuta |last10=Ito |first11=Ayuna |last11=Kashihara |first12=Hiroyuki |last12=Makii |first13=Katsuhisa |last13=Nishio |first14=Minoru |last14=Sakama |first15=Kaori |last15=Shirai |first16=Hayato |last16=Suzuki |first17=Katsuyuki |last17=Tokoi |first18=Kazuaki |last18=Tsukada |first19=Eisuke |last19=Watanabe |first20=Yuichiro |last20=Nagame |display-authors=3 |date=2021 |title=Chemical Characterization of a Volatile Dubnium Compound, DbOCl<sub>3</sub> |url= |journal=Angewandte Chemie International Edition |volume=60 |issue=33 |pages=17871–17874 |doi=10.1002/anie.202102808 |pmid=33978998 |pmc=8456785 |access-date=}}</ref>