| Abstract: |
The chelation dynamics of [5-C5H4C(O)R]Mn(CO)3 complexes 1 (R = CH2(SCH3)3), 2 (R = CH(SCH3)2), and 3 (R = C(SCH3)3) in room temperature acetonitrile solution have been investigated on the picosecond timescale by UV-pump IR-probe transient absorption spectroscopy. Similar to the previously observed behavior in n-heptane solution, irradiation of 3 in acetonitrile at 289 nm induces CO loss to exclusively yield the Mn-S chelated (ring-closed) product in <100 ps and <13 ps, respectively. Unlike the behavior of 1 and 2 in n-hexane and n-heptane solution, UV excitation of either 1 or 2 in acetonitrile solution induces CO loss to also exclusively yield the chelated products in <13 ps, with no evidence of a competing solvation pathway. Faster vibrational cooling in acetonitrile versus alkane solution suggests stronger solute-solvent interaction, perhaps via hydrogen bonding. Results from the steady-state photolysis of the pendant sulfide s chelates, [1, 5-C5H4C(O)R2]Mn(CO)2, 4 (R = CH(SCH3)2) and 5 (R = C(SCH3)3) are also discussed. |
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