Syntheses and crystal structures of the tetrakis(methyltrihydroborato) compounds of zirconium(IV), thorium(IV), uranium(IV), and neptunium(IV)

Zr(BH/sub 3/CH/sub 3/)/sub 4/, Th(BH/sub 3/CH/sub 3/)/sub 4/, U(BH/sub 3/CH/sub 3/)/sub 4/, and Np(BH/sub 3/CH/sub 3/)/sub 4/ have been synthesized and their molecular structures determined by single-crystal x-ray diffraction. Infrared spectroscopy and nuclear magnetic resonance data are presented for the Zr, Th, and U compounds. The space groups, unit cell parameters, and R factors are as follows: Zr(BH/sub 3/CH/sub 3/)/sub 4/, tetragonal, P4/sub 2//n, a = 10.311 (6) A, c = 5.851 (3) A, Z = 2, d/sub x/ = 1.103 g/cm/sup 3/, R = 0.013 (F/sup 2/ > 3sigma(F/sup 2/)); Th(BH/sub 3/CH/sub 3/)/sub 4/, triclinic, P1, a = 18.408 (6) A, b = 16.910 (6) A, c = 8.834 (3) A, ..cap alpha.. = 88.06 (4)/sup 0/, ..beta.. = 90.83 (4) /sup 0/, ..gamma.. = 88.08 (4)/sup 0/, Z = 8, d/sub x/ = 1.681 g/cm/sup 3/, R = 0.068 (F/sup 2/ > 3sigma(F/sup 2/)); U(BH/sub 3/CH/sub 3/)/sub 4/, monoclinic, P2/sub 1/n, a = 18.228 (6) A, b = 16.749 (6) A, c = 8.765 (2) A, ..beta.. = 90.69 (4)/sup 0/, Z = 8, d/sub x/ = 1.755 g/cm/sup 3/, R = 0.041 (F/sup 2/ > 3sigma(F/sup 2/)); Np(BH/sub 3/CH/sub 3/)/sub 4/, tetragonal, P4/sub 2//n, a = 10.552 (6) A, c = 5.950 (3) A, Z = 2, d/sub x/ = 1.767 g/cm/sup 3/, R = 0.016 (F/sup 2/ > 3sigma(F/sup 2/)). All compounds are monomolecular in the crystalline state. The metal atoms are tetrahedrally coordinated to the four BH/sub 3/CH/sub 3/ groups through tridentate hydrogen bridges. The M-B distances are 2.335 +- 0.003 A for Zr, 2.56 +- 0.05 A for Th, 2.49 +- 0.02 A for U, and 2.487 +- 0.006 A for Np. 17 references, 3 figures, 5 tables.