Department of Chemistry, Tongji University , Shanghai 200092, China.
Inorg Chem. 2013 Sep 16;52(18):10275-85. doi: 10.1021/ic400560k. Epub 2013 Sep 5.
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 H2ThS ((1)A') and H2US ((3)A″) molecules. The lowest three spin states of triplet H2US are calculated to be within 3 kcal/mol using all three methods, just as in H2UO. The major products are compared with the oxygen analogues H2ThO and H2UO, and the sulfides have 71-85 cm(-1) higher 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 H2ThS and H2US.
钍和铀原子在 4 K 时与过量的稀有气体基质中的硫化氢共沉积。观察到每种锕系元素的主要二氢化物硫化物反应产物，并基于 S-34 和 D 同位素取代进行了鉴定。这些分配通过使用密度泛函理论与 B3LYP 和 PW91 交换相关函数和 CCSD(T)方法对三角锥形 H2ThS((1)A')和 H2US((3)A'')分子进行频率和结构计算得到了证实。使用所有三种方法，三重态 H2US 的最低三个自旋态计算在 3 kcal/mol 以内，就像在 H2UO 中一样。主要产物与氧类似物 H2ThO 和 H2UO 进行了比较，并且硫化物的氢锕系元素伸缩频率高 71-85 cm(-1)。通过 S 3p 电子对到空的 6d 轨道的反向键合，氢化物取代基、三角锥形结构和硫的较低电负性似乎增强了锕系元素的氢键，这种独特的共价键有利于氢化物取代基的诱导效应。硫的反向键合赋予 US 和 ThS 键以极化的三键特征，并增强了 H2ThS 和 H2US 中的金属氢化物键合。
