Infrared
Spectra of H<sub>2</sub>ThS and H<sub>2</sub>US in Noble Gas Matrixes:
Enhanced H‑An‑S Covalent
Bonding
Xuefeng Wang
Lester Andrews
K. Sahan Thanthiriwatte
David A. Dixon
10.1021/ic400560k.s001
https://acs.figshare.com/articles/journal_contribution/Infrared_Spectra_of_H_sub_2_sub_ThS_and_H_sub_2_sub_US_in_Noble_Gas_Matrixes_Enhanced_H_An_S_Covalent_Bonding/2376667
Laser-ablated thorium and uranium
atoms have been co-deposited
at 4 K with hydrogen sulfide in excess noble gas matrixes. The major
dihydride sulfide reaction products were observed for each actinide
and identified on the basis of S-34 and D isotopic substitution. These
assignments were confirmed by frequency and structure calculations
using density functional theory with the B3LYP and PW91 exchange-correlation
functionals and the CCSD(T) method for the pyramidal H<sub>2</sub>ThS (<sup>1</sup>A′) and H<sub>2</sub>US (<sup>3</sup>A″)
molecules. The lowest three spin states of triplet H<sub>2</sub>US
are calculated to be within 3 kcal/mol using all three methods, just
as in H<sub>2</sub>UO. The major products are compared with the oxygen
analogues H<sub>2</sub>ThO and H<sub>2</sub>UO, and the sulfides have
71–85 cm<sup>–1</sup> <i>higher</i> hydrogen-actinide
stretching frequencies. The actinide-hydrogen bonding appears to be
enhanced in the actinide sulfides through back-bonding of a S 3p electron
pair to a vacant 6d orbital, which is delocalized over the H atoms.
This unique covalent bond is favored by the inductive effect of the
hydride substituents, the pyramidal structures, and the lower electronegativity
of sulfur. Sulfur back-bonding gives polarized triple bond character
to the US and ThS bonds and enhanced metal hydride bonding in H<sub>2</sub>ThS and H<sub>2</sub>US.
2016-02-18 21:45:35
triplet H 2US
H 2ThS
Noble Gas Matrixes
bond
frequency
H 2UO
dihydride sulfide reaction products
PW
actinide
method
S 3 p electron pair
3LYP
CCSD
oxygen analogues H 2ThO