Manganese carbonyl cations of the form Mn(CO)
n
+ (
n = 1−9) are produced in a molecular beam by laser vaporization in a pulsed nozzle source. Mass selected infrared photodissociation
spectroscopy in the carbonyl stretching region is used to study these complexes and their “argon-tagged” analogues. The geometries
and electronic states of these complexes are determined by comparing their infrared spectra to theoretical predictions. Mn(CO)
6+ has a completed coordination sphere, consistent with its predicted 18-electron stability. It has an octahedral structure
in its singlet ground state, similar to its isoelectronic analogue Cr(CO)
6. Charge-induced reduction in
π back-bonding leads to a decreased red-shift in Mn(CO)
6+ (υ
CO = 2106 cm
−1) compared with Cr(CO)
6 (υ
CO = 2003 cm
−1). The spin multiplicity of Mn
+(CO)
n
complexes gradually decreases with progressive ligand addition. MnCO
+ is observed as both a quintet and a septet, Mn(CO)
2+ is observed only as a quintet, while Mn(CO)
3,4+ are both observed as triplets. Mn(CO)
5+ and Mn(CO)
6+ are both singlets, as are all larger complexes.
相似文献