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Metal-metal bonded complexes of the early transition metals. 5. Direct hydrogenation of a metal-metal multiple bond

Journal Article · · Inorg. Chem.; (United States)
DOI:https://doi.org/10.1021/ic00142a014· OSTI ID:6800364
The tantalum(III) dimer Ta/sub 2/Cl/sub 6/(PMe/sub 3/)/sub 4/(Ta==TA) reacts readily and irreversibly with molecular hydrogen to form the tantalum(IV) dimer Ta/sub 2/Cl/sub 6/(PMe/sub 3/)/sub 4/H/sub 2/. The reaction proceeds under very mild conditions (25/sup 0/C, 1 atm H/sub 2/) and represents the first example of hydrogen addition to a metal-metal multiple bond. Ta/sub 2/Cl/sub 6/(PMe/sub 3/)/sub 4/H/sub 2/ has been characterized by /sup 1/H NMR, /sup 31/P NMR, and IR spectra and x-ray crystallography. It crystallizes in the monoclinic space group P2/sub 1//n with a = 13.650 (4) A, b = 11.285 (3) A, c = 22.479 (8) A, ..beta.. = 125.45 (1)/sup 0/, V = 2820.95 A/sup 3/, and rho(calcd) = 2.074 g cm/sup -3/ for mol wt 880.9 and Z = 4. Diffraction data were collected at -170 +- 4/sup 0/C, and full-matrix least-squares refinement has led to the discrepancy indices R/sub F/ = 0.062 and R/sub wF/ = 0.048. Ta/sub 2/Cl/sub 6/(PMe/sub 3/)/sub 4/H/sub 2/ is a quadruply bridged complex with two bridging hydride and two bridging chloride ligands. The bridging hydrides were not located in the final difference Fourier. Their presence and location were established by spectroscopic techniques and an analysis of the solid-state structure. The Ta-Ta separation in the dimer is 2.621 (1) A, and the coordination geometry about each tantalum atom is roughly square antiprismatic. Metal-metal and metal-bridge-metal bonding are discussed in a qualitative manner to explain the exceptionally short Ta-Ta bond in the complex. 5 figures, 5 tables.
DOE Contract Number:
FG02-80ER10125
OSTI ID:
6800364
Journal Information:
Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 21:12; ISSN INOCA
Country of Publication:
United States
Language:
English