Abstract
A series of [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)PXS] complexes (Ru 2 -S 2 -PXS, X = phosphine ligands, S = 1–8) have been synthesized and evaluated for their photocatalytic H 2 generation efficiencies from formic acid decomposition. The [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)P(o-C 6 H 4 CH 3 ) 3 ] (Ru 2 -S 2 -PX4) catalyst + P(CH 3 ) 3 ligand exhibited a high turnover frequency of 15,840 h −1 and turnover number of 24,536. A mechanistic investigation of the Ru 2 -S 2 -PX4 + FA/TEA catalyzed photocatalytic H 2 generation reaction using ATR-IR, EI-MS, and NMR techniques suggested that when Ru 2 -S 2 -PX4 was photoirradiated, the P(o-C 6 H 4 CH 3 ) 3 was dissociated from the complex to form a new species, [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)]* (I). The free P(o-C 6 H 4 CH 3 ) 3 then attacks a second molecule of Ru 2 -S 2 -PX4 to form Ru 2 -S 2 -(PX4) 2 and release of free CO, which is then combined with species I to form Ru 2 -S 2 . Subsequent attachment of formate ion to species Ru 2 -S 2 -PX4, Ru 2 -S 2 , and Ru 2 -S 2 -(PX4) 2 to form [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)]-HCOO − (II), Ru 2 -S 2 -HCOO − (II′) and Ru 2 -S 2 -PX4-HCOO − (II″), respectively. Rearrangement of complex II (or II′ or II″) and evolution of CO 2 generate a transient complex [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)H] (III), which then undergoes a protonation process to yield complex [Ru 2 (CO) 5 (μ-SCH 2 CH 2 CH 2 S)H 2 ] (IV). Release of H 2 and re-incorporation of the formate anion as well as evolution of CO 2 regenerates the active complex III and the cycle begins again.
| Original language | American English |
|---|---|
| Pages (from-to) | 9784-9794 |
| Number of pages | 11 |
| Journal | International Journal of Hydrogen Energy |
| Volume | 42 |
| Issue number | 15 |
| DOIs | |
| State | Published - 13 Apr 2017 |
Keywords
- Biomimetic photocatalyst
- Hydrogen generation
- Ruthenium H-cluster
