TY - JOUR
T1 - The QTAIM approach to chemical bonding between transition metals and carbocyclic rings
T2 - a combined experimental and theoretical study of (η5-C5H5)Mn(CO)3, (η6-C6H6)Cr(CO)3, and (E)-{(η5-C5H4)CF=CF(η5- C5H4)}(η5-C5H5)2Fe2
AU - Farrugia, Louis J.
AU - Evans, Cameron
AU - Lentz, Dieter
AU - Roemer, Max
PY - 2009
Y1 - 2009
N2 - Experimental charge densities for (C5H5)Mn(CO) 3 (2), (η6-C6H6)Cr(CO) 3 (3), and (E)-{(η5-C5H4)- CF=CF(η5-C5H4)}(η5-C5H5)2Fe2 (4) have been obtained by multipole refinement of high-resolution X-ray diffraction data at 100 K. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM). The electronic structures of these and related π-hydrocarbyl complexes have also been studied by ab initio density functional theory calculations, and a generally good agreement between theory and experiment with respect to the topological parameters was observed. The topological parameters indicate significant metal-ring covalency. A consistent area of disagreement concerns the topology of the metal-ring interactions. It is shown that because of the shared-shell bonding between the metal and the ring carbons, an annulus of very flat density ρ and very small ρ is formed, which leads to topologically unstable structures close to catastrophe points. This in turn leads to unpredictable numbers of metal-C bond paths for ring sizes greater than four and fewer M-C bond paths than expected on the basis of the formal hapticity. This topological instability is a general feature of metal-π-hydrocarbyl interactions and means that a localized approach based on individual M-Cring bond paths does not provide a definitive picture of the chemical bonding in these systems. However, other QTAIM indicators, such as the virial paths, the delocalization indices, and the source function, clearly demonstrate that for the n-hapto (ηn- CnH n)M unit, there is generally a very similar level of chemical bonding for all M-Cring; interactions, as expected on the basis of chemical experience.
AB - Experimental charge densities for (C5H5)Mn(CO) 3 (2), (η6-C6H6)Cr(CO) 3 (3), and (E)-{(η5-C5H4)- CF=CF(η5-C5H4)}(η5-C5H5)2Fe2 (4) have been obtained by multipole refinement of high-resolution X-ray diffraction data at 100 K. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM). The electronic structures of these and related π-hydrocarbyl complexes have also been studied by ab initio density functional theory calculations, and a generally good agreement between theory and experiment with respect to the topological parameters was observed. The topological parameters indicate significant metal-ring covalency. A consistent area of disagreement concerns the topology of the metal-ring interactions. It is shown that because of the shared-shell bonding between the metal and the ring carbons, an annulus of very flat density ρ and very small ρ is formed, which leads to topologically unstable structures close to catastrophe points. This in turn leads to unpredictable numbers of metal-C bond paths for ring sizes greater than four and fewer M-C bond paths than expected on the basis of the formal hapticity. This topological instability is a general feature of metal-π-hydrocarbyl interactions and means that a localized approach based on individual M-Cring bond paths does not provide a definitive picture of the chemical bonding in these systems. However, other QTAIM indicators, such as the virial paths, the delocalization indices, and the source function, clearly demonstrate that for the n-hapto (ηn- CnH n)M unit, there is generally a very similar level of chemical bonding for all M-Cring; interactions, as expected on the basis of chemical experience.
UR - http://www.scopus.com/inward/record.url?scp=67749145487&partnerID=8YFLogxK
U2 - 10.1021/ja808303j
DO - 10.1021/ja808303j
M3 - Article
C2 - 19102692
AN - SCOPUS:67749145487
VL - 131
SP - 1251
EP - 1268
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 3
ER -