Infrared Spectra of the WH<sub>4</sub>(H<sub>2</sub>)<sub>4</sub> Complex in Solid Hydrogen Xuefeng Wang Lester Andrews Ivan Infante Laura Gagliardi 10.1021/ja077322o.s003 https://acs.figshare.com/articles/journal_contribution/Infrared_Spectra_of_the_WH_sub_4_sub_H_sub_2_sub_sub_4_sub_Complex_in_Solid_Hydrogen/2957821 The codeposition of laser-ablated tungsten atoms with neat hydrogen at 4 K forms a single major product with a broad 2500 cm<sup>-1</sup> and sharp 1860, 1830, 1782, 1008, 551, and 437 cm<sup>-1</sup> absorptions, which are assigned to the WH<sub>4</sub>(H<sub>2</sub>)<sub>4</sub> complex on the basis of isotopic shifts and agreement with isotopic frequencies calculated by density functional theory. This <i>D</i><sub>2</sub><i><sub>d</sub></i> structured complex was computed earlier to form exothermically from W atoms and hydrogen molecules. Annealing the matrix allows hydrogen to evaporate and the complex to aggregate and ultimately to decompose. Comparison of the H−H stretching mode at 2500 cm<sup>-1</sup> and the W−H<sub>2</sub> stretching mode at 1782 cm<sup>-1</sup> with 2690 and 1570 cm<sup>-1</sup> values for the Kubas complex W(CO)<sub>3</sub>(PR<sub>3</sub>)<sub>2</sub>(H<sub>2</sub>) suggests that the present physically stable WH<sub>4</sub>(H<sub>2</sub>)<sub>4</sub> complex has more strongly bound dihydrogen ligands. Our CASPT2 calculations suggest a 15 kcal/mol average binding energy per dihydrogen molecule in the WH<sub>4</sub>(H<sub>2</sub>)<sub>4</sub> complex. 2008-02-13 00:00:00 CASPT 2 calculations WH 2500 cm 4 K forms molecule dihydrogen Solid HydrogenThe codeposition mode