Photoelectron (PE) spectra have been obtained for the M(BH(4))(4) (M = Zr, Hf and U) molecules in the 20-60 eV photon-energy range, and for M = U, also in the 90-120 eV region. Derived branching ratios (BR) and relative partial-photoionization cross sections (RPPICS) of the valence bands are used to confirm band assignment and demonstrate d-orbital covalency for all three compounds and f-orbital covalency for U(BH(4))(4). Core ionizations are identified and used to confirm resonance features in the RPPICS. The absorption spectrum of Zr(BH(4))(4) between 20 and 60 eV shows 4p absorption at 35.5 eV, coincident with the 4p-4d resonance in the RPPICS of the 1e and 2t(2) ionization bands of Zr(BH(4))(4). Less intense absorption bands at 32.5 and 33.8 eV correspond with shape resonance features in the 1a(1) and 1t(2) PE bands. The RPPICS of the f band of U(BH(4))(4) shows two strong resonant features between 95 and 120 eV. Direct photoemission of the 5f electrons from U(BH(4))(4) results only in the observation of the (2)F(5/2) ion state of [U(BH(4))(4)](+), but in the 5d-5f resonant region, a weak band corresponding to the (2)F(7/2) ion state is also observed. The splitting of the 1t(2) band of U(BH(4))(4) is attributed to a small contribution of U 6p semi-core electrons to this MO. Density functional calculations give a good estimate of the pattern of ionization energies, although the calculated absolute values are lower than the experimental values, the first IE by 0.5 eV for Zr(BH(4))(4) and Hf(BH(4))(4) and 1.0 eV for U(BH(4))(4). The MO compositions are in very good agreement with the deductions made from the BR and RPPICS analyses.

OsH 4 (PPh 3 ) 3 ] (1) reacts with KH in THF in the presence of 18-crown-6 to form [K(THF)(18-crown-6)][OsH 3 (PPh 3 ) 3 ] (2), characterized by NMR spectroscopy and X-ray crystallography; cation-anion contact is achieved through three Os-H‚‚‚K moieties. In contrast, [IrH 3 (PPh 3 ) 3 ] (6) reacts with KH and 18crown-6 in THF with redistribution of ligands to produce the known bis-phosphine complex [K(18crown-6)][IrH 4 (PPh 3 ) 2 ] (7). This reaction has been followed by NMR spectroscopy, and [IrH 2 (PPh 3 ) 3 ]has been identified as a likely intermediate. K[OsH 3 (PPh 3 ) 3 ] (3) reacts with Bu n 3 SnCl to form the tinosmium complex [OsH 3 (SnBu n 3 )(PPh 3 ) 3 ] (8), characterized by NMR spectroscopy and X-ray crystallography. The molecule contains a seven-coordinate osmium center, which can be described approximately as a distorted fac-[OsH 3 (PPh 3 )] arrangement, with the SnBu n 3 moiety capping the OsH 3 face.

Ruthenium trihydrides containing N-heterocyclic carbene ligands display large quantum mechanical exchange couplings in their 1H NMR spectra: DFT calculations are used to explore this phenomenon and to compare them to their phosphine congeners.

Electron spectra D 6515Electronic Structure of M(BH 4 ) 4 , M: Zr, Hf, and U, by Variable Photon-Energy Photoelectron Spectroscopy and Density Functional Calculations. -Variable--energy photoelectron spectroscopy and DFT calculations demonstrate d-orbital covalency for all three title compounds. In U(BH4)4, the metal also uses its 5f orbitals for bond formation, and the 6p core orbitals interact with the ligand valence electrons. -(GREEN*, J. C.; DE SIMONE, M.; CORENO, M.; JONES, A.; PRITCHARD, H. M. I.; MCGRADY, G. S.; Inorg. Chem. 44 (2005) 22, 7781-7793; Inorg. Chem. Lab., Oxford Univ., Oxford OX1 3QR, UK; Eng.) -W. Pewestorf 03-008