V, Nb, and Ta hydride molecules in deuterium and rare-gas matrices: Infrared and electron spin resonance spectra

Abstract

The VH 2 molecule was found to have Sϭ3/2 and a 4 ⌺ ground state with a zero-field splitting parameter ͉D͉ϭ0.315 cm Ϫ1 . 51 V ͑Iϭ7/2͒ hyperfine splitting was observed in the ESR spectra, but the hydrogen hyperfine was unresolved. The narrowest lines were observed for VD 2 in solid deuterium at ϳ2 K. Efforts to observe VH 4 via ESR were not successful presumably because it could not be prepared in a high enough concentration. The infrared spectra of NbH 2 molecules and their deuterated isotopomers were observed in solid deuterium and rare-gas matrices. NbH 2 was found to be bent at 130°, in accord with theoretical calculations. NbH 2 was not observed in ESR spectra although it presumably has a 4 B 1 ground state; this is attributed to a large ͑Ͼ4 cm Ϫ1 ͒ negative D value. NbH 4 was observed via ESR as a tetragonally distorted (D 2d ) tetrahedral molecule in its 2 B 1 lowest state resulting from a static Jahn-Teller effect. 93 Nb ͑Iϭ9/2͒ and also H hyperfine splittings were observed. A corresponding TaH 4 spectrum was attributed to a similarly distorted tetrahedral Sϭ1/2 molecule.

Matrix infrared spectra and density functional calculations of transition metal hydrides and dihydrogen complexes

“…[13][14][15] The use of pure normal hydrogen and deuterium as reagent and matrix is promising for the future discovery of new higher metal hydride molecules. 18,19,78,96,99 One advantage of molecular matrices is that the matrix itself can be monitored through weak induced infrared absorptions. 96,100,101 Finally, solid para-hydrogen has found application as a medium for spectroscopic investigations of atoms, molecules, and charged hydrogen clusters.…”

“…The Nd:YAG laser fundamental (1064 nm, 10 Hz repetition rate with 10 ns pulse width) was focused onto a rotating metal target, and the laser energy was varied from 10-40 mJ pulse 21 . Thus, laser-ablated metal atoms were co-deposited with hydrogen molecules in excess argon, neon, or pure hydrogen as the matrix and reagent 18,19 onto a 3.5 K CsI cryogenic window using a Sumitomo Heavy Industries Model RDK-205D closedcycle cryocooler. Hydrogen, D 2 , HD, and H 2 + D 2 mixtures were used in different experiments.…”

“…The second-row transition metal dihydrides have been observed except for radioactive Tc, noble Pd which forms only the complex, and Ag. 18,23,29,30,[40][41][42][43] The strong b 2 modes for the second-row dihydrides (Table 2) in solid argon (except where noted) are higher than their first row counterparts in all cases. This is particularly so for RuH 2 and RhH 2 , where the second-row dihydrides are lower spin states.…”

σ‐Organoniobium Compounds with [NbR4]− and NbR4 Stoichiometries

“…Since a similar reduction (0.63) was observed in the V iv homologous compound, [12] it follows that the outer NbCl 4 shell in 2 does not significantly affect the radial distribution of the unpaired-electron ground-state function. By applying the same formalism to the matrix-confined species Nb iv D 4 , [23] however, a significantly higher reduction is obtained, P/P 0 = 0.45, which points to more covalent metal-ligand bond character in that case. According to the structural and magnetic properties of compounds 1 and 2, the secondary ortho-Cl···Nb interactions defining the outer NbCl 4 shell exert a shielding effect on the NbC 4 core without significantly altering its geometry or electronic state.…”

“…An elongated T-4 structure was also assigned to the matrixconfined deuteride Nb iv D 4 on the basis of its EPR spectroscopic properties. [23] Since g k < g ? < g e (g e = 2.0023 for the free electron), it can be concluded that the ground state of compound 2 in an S 4 environment is 2 B, that is, the Nb iv center has a (d xy ) 1 electron configuration.…”