Density Functional Theory-Based Prediction of Some Aqueous-Phase Chemistry of Superheavy Element 111. Roentgenium(I) Is the ‘Softest' Metal Ion

A previous approach (Hancock, R. D.; Bartolotti, L. J. Inorg. Chem. 2005, 44, 7175) using DFT calculations to
predict log K1 (formation constant) values for complexes of NH3 in aqueous solution was used to examine the
solution chemistry of Rg(I) (element 111), which is a congener of Cu(I), Ag(I), and Au(I) in Group 1B. Rg(I) has as
its most stable presently known isotope a t1/2 of 3.6 s, so that its solution chemistry is not easily accessible. LFER
(Linear free energy relationships) were established between ΔE(g) calculated by DFT for the formation of
monoammine complexes from the aquo ions in the gas phase, and ΔG(aq) for the formation of the corresponding
complexes in aqueous solution. For M2+, M3+, and M4+ ions, the gas-phase reaction was [M(H2O)6]n+(g) + NH3(g)
= [M(H2O)5NH3]n+(g) + H2O(g) (1), while for M+ ions, the reaction was [M(H2O)2]+(g) + NH3(g) = [M(H2O)NH3]+(g)
+ H2O(g) (2). A value for ΔG(aq) and for ΔE for the formation of M = Cu2+ in reaction 1, not obtained previously,
was calculated by DFT and shown to correlate well with the LFER obtained previously for other M2+ ions, supporting
the LFER approach used here. The simpler use of ΔE values instead of ΔG(aq) values calculated by DFT for
formation of monoamine complexes in the gas phase leads to LFER as good as the ΔG-based correlations.
Values of ΔE were calculated by DFT to construct LFER with M+ = H+, and the Group 1B metal ions Cu+, Ag+,
Au+, and Rg+, and with L = NH3, H2S, and PH3 in reaction 3:  [M(H2O)2]+(g) + L(g) = [M(H2O)L]+(g) + H2O(g) (3).
Correlations involving ΔE calculated by DMol3 for H+, Cu+, Ag+, and Au+ could reliably be used to construct LFER
and estimate unknown log K1 values for Rg(I) complexes of NH3, PH3, and H2S calculated using the ADF (amsterdam
density Functional) code. Log K1 values for Rg(I) complexes are predicted that suggest the Rg(I) ion to be a very
strong Lewis acid that is extremely ‘soft' in the Pearson hard and soft acids and bases sense.