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 [Th-2(mu(2)-OH)(2)(NO3)(6)(H2O)(6)]H2O (1) is identical to that identified previously by Johansson. Two additional unreported compounds have been identified, [Th-2(mu(2)-OH)(2)(NO3)(4)(H2O)(8)](NO3)(2) (2) and [Th-2(mu(2)-OH)(2)Cl-2(H2O)(12)]Cl-4 center dot 2H(2)O (3). 1 crystallizes in the monoclinic space group P2(1)/c, with a = 6.792(2) angstrom, b = 11.710(4) angstrom, c = 13.778(5) angstrom, and beta = 102.714(5)degrees and 2 crystallizes in the monoclinic space group P2(1)/n, with a = 6.926(5) angstrom, b = 7.207(1) angstrom, c = 21.502(1) angstrom, and beta = 96.380(1)degrees. The chloride-containing dimer, 3, crystallizes in triclinic P (1) over bar, with a = 8.080(2) angstrom, b = 8.880(2) angstrom, c = 9.013(2) angstrom, alpha = 97.41(3)degrees, beta = 91.00(3), and gamma = 116.54(3)degrees. 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.