title: Time-resolved infrared absorption study of cyclopentadienyl manganese tricarbonyl derivatives: Chelation of pendant sulfides in acetonitrile.
abstract: The chelation dynamics of [Mn{eta5-C5H4C(O)R}(CO)3] complexes 1 (R = CH2(SCH3)), 2 (R = CH(SCH3)2), and 3 (R = C(SCH3)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{eta5-C5H4C(O)CH(SCH3)2-kappaS}(CO)2] (4) and [Mn{eta5-C5H4C(O)C(SCH3)3-kappaS}(CO)2] (5), is also discussed.
authors.affiliation: Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8443, USA.
authors.forename: Tung T
authors.initials: TT
authors.lastname: To
authors.forename: Edwin J
authors.initials: EJ
authors.lastname: Heilweil
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Burkey