Synthesis, crystal structure, and reactions of an actinide metallocarborane complex, bis(eta/sup 5/-(3)-1,2-dicarbollyl)dichlorouranium(IV) dianion, (U(C/sub 2/B/sub 9/H/sub 11/)/sub 2/Cl/sub 2/)/sup 2/-

The reaction of UCl/sub 4/ with the C/sub 2/B/sub 9/H/sub 11//sup 2 -/ anion in tetrahydrofuran solution under inert atmosphere conditions has led to the formation of the complex anion (U(C/sub 2/B/sub 9/H/sub 11/)/sub 2/CL/sub 2/)/sup 2 -/, which has been isolated as several air-sensitive crystalline salts. The salt (Li(OC/sub 4/H/sub 8/)/sub 4/)/sub 2/(U(C/sub 2/B/sub 9/H/sub 11/)/sub 2/Cl/sub 2/) has been subjected to an x-ray crystal structure determination using counter intensity data. The complex anion is found to exhibit approximate C/sub 2..nu../ symmetry, with the ligands arranged in a distorted tetrahedral array about uranium. The average U-B distance to the pentahapto-bonded dicarbollide ligands is 2.73 (2) A, and the average U--Cl distance is 2.599 (6) A. The Cl--U--Cl angle is 90.3 (5)/sup 0/, and the dicarbollide bonding face centroids form an angle of 137/sup 0/ about the uranium atom. Refinement in space group Cc fitting 2020 data by 322 parameters led to agreement indices R = 0.058 and R/sub w/ = 0.061. Unit cell dimensions are a = 26.410 (7) A, b = 11.248 (5) A, c = 20.163 (6) A, ..beta.. = 102.35 molecules, with an average Li--O distance of 1.92 (3) A. The (U(C/sub 2/B/sub 9/H/sub 11/)/sub 2/Cl/submore » 2/)/sup 2 -/ anion reacts with C/sub 8/H/sub 8/ to yield uranocene, pentadienide. In actinide complexes, the dicarbollide dianion seems to have ligating properties which are intermediate between those of the cyclooctatetraene dianion and cyclopentadienide.« less