TY - JOUR
T1 - Photochemistry of Cp′Mn(CO) 2(NHC) (Cp′ = η 5-C 5H 4Me) species
T2 - Synthesis, time-resolved ir spectroscopy, and DFT calculations
AU - Batool, Madeeha
AU - Martin, Thomas A.
AU - Algarra, Andrés G.
AU - George, Michael W.
AU - MacGregor, Stuart A.
AU - Mahon, Mary F.
AU - Whittlesey, Michael K.
PY - 2012/7/23
Y1 - 2012/7/23
N2 - UV irradiation of Cp′Mn(CO) 3 (Cp′ = η 5-C 5H 4Me) in the presence of the free N-heterocyclic carbenes IEt 2Me 2, I iPr 2Me 2, IMes, and IPr affords the NHC dicarbonyl complexes Cp′Mn(CO) 2(NHC) (1-4). Time-resolved infrared spectroscopy in alkane solution reveals that 1-4 photodissociate CO to generate Cp′Mn(CO)(NHC) (1-CO, 2-CO, 3-CO, 4-CO), which exhibit solvent-independent second-order rate constants (k CO) for reaction with CO. These observations are consistent with 1-CO to 4-CO being stabilized by intramolecular agostic interactions with the NHCs rather than intermolecular alkane coordination. Density functional theory calculations provide support for this hypothesis and locate a series of agostic structures varying from δ-agostic (1-CO, 2-CO), to ε-agostic (3-CO), to φ-agostic (4-CO). The atoms-in-molecules approach is used to characterize these species, along with the γ-agostic interaction seen in the CpMn(CO)(PPh 3) analogue (5-CO), and shows that these species are distinguished primarily by the magnitude of the electron density at the agostic ring critical point.
AB - UV irradiation of Cp′Mn(CO) 3 (Cp′ = η 5-C 5H 4Me) in the presence of the free N-heterocyclic carbenes IEt 2Me 2, I iPr 2Me 2, IMes, and IPr affords the NHC dicarbonyl complexes Cp′Mn(CO) 2(NHC) (1-4). Time-resolved infrared spectroscopy in alkane solution reveals that 1-4 photodissociate CO to generate Cp′Mn(CO)(NHC) (1-CO, 2-CO, 3-CO, 4-CO), which exhibit solvent-independent second-order rate constants (k CO) for reaction with CO. These observations are consistent with 1-CO to 4-CO being stabilized by intramolecular agostic interactions with the NHCs rather than intermolecular alkane coordination. Density functional theory calculations provide support for this hypothesis and locate a series of agostic structures varying from δ-agostic (1-CO, 2-CO), to ε-agostic (3-CO), to φ-agostic (4-CO). The atoms-in-molecules approach is used to characterize these species, along with the γ-agostic interaction seen in the CpMn(CO)(PPh 3) analogue (5-CO), and shows that these species are distinguished primarily by the magnitude of the electron density at the agostic ring critical point.
UR - http://www.scopus.com/inward/record.url?scp=84864192562&partnerID=8YFLogxK
U2 - 10.1021/om300209a
DO - 10.1021/om300209a
M3 - Article
AN - SCOPUS:84864192562
SN - 0276-7333
VL - 31
SP - 4971
EP - 4979
JO - Organometallics
JF - Organometallics
IS - 14
ER -