Structures of Dimeric Hydrolysis Products of Thorium

Three unique thorium dimeric compounds have been crystallized from either direct hydrolysis of Th4+(aq)/HCl or
titration of Th(OH)4(am) with Th(NO3)4(aq) and their structures determined using single-crystal X-ray diffraction.
The compound [Th2(μ2-OH)2(NO3)6(H2O)6]H2O (1) is identical to that identified previously by Johansson. Two additional
unreported compounds have been identified, [Th2(μ2-OH)2(NO3)4(H2O)8](NO3)2 (2) and [Th2(μ2-OH)2Cl2(H2O)12]Cl4·2H2O (3). 1 crystallizes in the monoclinic space group P21/c, with a = 6.792(2) Å, b = 11.710(4) Å, c = 13.778(5)
Å, and β = 102.714(5)° and 2 crystallizes in the monoclinic space group P21/n, with a = 6.926(5) Å, b = 7.207(1)
Å, c = 21.502(1) Å, and β = 96.380(1)°. The chloride-containing dimer, 3, crystallizes in triclinic P1̄, with a =
8.080(2) Å, b = 8.880(2) Å, c = 9.013(2) Å, α = 97.41(3)°, β = 91.00(3), and γ = 116.54(3)°. We also present
high-energy X-ray scattering data demonstrating the presence of the hydroxo-bridged moiety in solution and discuss
our findings in the context of known solid-state structures. The three structures demonstrate 11-, 10-, and 9-coordinate
thorium, respectively, and coupled with the scattering experiments provide additional structural and chemical insight
into tetravalent actinide hydrolysis.