Photochemistry of CpMn(CO)3 and Related Derivatives: Spectroscopic Observation of Singlet and Triplet CpMn(CO)2
详细信息 查看全文
- 作者：Carl R. Kemnitz ; Eric S. Ball ; Robert J. McMahon
- 刊名：Organometallics
- 出版年：2012
- 出版时间：January 9, 2012
- 年：2012
- 卷：31
- 期：1
- 页码：70-84
- 全文大小：715K
- 年卷期：v.31,no.1(January 9, 2012)
- ISSN：1520-6041
文摘
We report novel photochemistry derived from (畏5-C5H5)Mn(CO)3 (1a), (畏5-C5H4Me)Mn(CO)3 (1b),(畏5-C5Me5)Mn(CO)3 (1c), and (畏5-indenyl)Mn(CO)3 (1d). Photolysis (>261 nm, 1 h) of the parent tricarbonyl (1a鈥?b>d), matrix isolated in argon at 10 K, yields two species: the expected singlet dicarbonyl 1(畏5-L)Mn(CO)2 (12a鈥?b>d) and an additional compound assigned as the triplet dicarbonyl 3(畏5-L)Mn(CO)2 (32a鈥?b>d). Density functional theory calculations (B3LYP/LANL2DZ) support the structural assignments for 12 and 32. Natural bond orbital population analyses of 12a and 32a explain the source of the large coupling (螖谓CO 153 cm鈥?) between the carbonyl stretching vibrations in 32a. The triplet isomer (32) is metastable, even at temperatures as low as 10 K. We determined the rate constants for the thermal isomerization 32 鈫?12 using dispersive kinetic analysis. As revealed by these rate constants, the triplet complexes display the following order of stability in this system: Ind Cp 鈮?Cp鈥?> Cp*. The spectroscopy and kinetics observed in various matrices (Ar, CH4, and Xe) do not differ appreciably. Experimental and computational results suggest that the singlet鈥搕riplet energy gap (螖EST) of CpMn(CO)2 (2a) must be smaller than previous estimates.