FACILE SOLUTION ROUTES TO HYDROCARBON-SOLUBLE LEWIS BASE ADDUCTS OF THORIUM TETRAHALIDES - SYNTHESIS, CHARACTERIZATION, AND X-RAY STRUCTURE OF THBR4(THF)4

The direct combination of thorium metal turnings with 2 equiv of elemental bromine or iodine in THF solution at 0-degrees-C provides white crystalline ThX4(THF)4 (X = Br, 1; X = 1, 2; THF = tetrahydrofuran), in 70-80% isolated yield. These new compounds are soluble in hydrocarbon solvents and react readily with oxygen- and nitrogen-donor ligands in toluene solution to give ThBr4py4 (3), ThI4py4 (4), ThBr4(NCMe)4, (5), and ThBr4(DME)2 (6) in high yield (py = pyridine, DME = 1,2-dimethoxyethane). Compounds 1-6 have been characterized by elemental and thermogravimetric analysis, H-1 NMR, infrared, and diffuse-reflectance spectroscopy, and, for 1, a single-crystal X-ray structure determination. The X-ray diffraction study of 1 revealed a slightly distorted dodecahedral coordination geometry about the central thorium atom with two interpenetrating tetrahedra of bromide and THF ligands. Oxygen atoms of the THF ligands occupy A vertices (Th-O = 2.549 (17) angstrom, average) and bromide ions occupy B vertices (Th-Br = 2.859 (3) angstrom, average) of an irregular dodecahedron. 1 is an excellent synthetic precursor to thorium coordination and organometallic complexes and can be prepared on a 100-150-g scale in a single day. Crystal data for 1 (at -40-degrees-C): Rhombohedral space group R3BAR, with a = 26.317 (4) angstrom, c = 18.340 (4) angstrom, V = 11000 angstrom 3, d(calc) = 2.299 g cm-3, and Z = 18.