Time-resolved infrared absorption study of cyclopentadienyl manganese tricarbonyl derivatives: Chelation of pendant sulfides in acetonitrile


The chelation dynamics of [Mn{η 5-C 5H 4C(O)R}(CO) 3] complexes 1 (R = CH 2(SCH 3)), 2 (R = CH(SCH 3) 2), and 3 (R = C(SCH 3) 3) in room-temperature acetonitrile solution have been investigated on the picosecond time scale 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 a Mn-S chelated dicarbonyl product. Unlike the behavior of 1 and 2 in n-hexane and n-heptane solutions, UV excitation of either 1 or 2 in acetonitrile solution induces CO loss to also exclusively yield the chelated products, with no evidence of a competing solvation pathway. All three complexes exhibit ultrafast chelation in <13 ps. Faster vibrational cooling in acetonitrile vs alkane solutions suggests stronger solute-solvent interaction, perhaps via hydrogen bonding. Ring-opening resulting from continuous irradiation of the pendant sulfide's chelates, [Mn{η 5-C 5H 4C(O)CH(SCH 3) 2-κS}(CO) 2] (4) and [Mn{η 5-C 5H 4C(O)C(SCH 3) 3-κS}(CO) 2] (5), is also discussed. © 2006 American Chemical Society.

Publication Title

Journal of Physical Chemistry A