TY - JOUR
T1 - Assessing metal-metal multiple bonds in Cr-Cr, Mo-Mo, and W-W compounds and a hypothetical U-U compound
T2 - A quantum chemical study comparing DFT and multireference methods
AU - Li Manni, Giovanni
AU - Dzubak, Allison L.
AU - Mulla, Abbas
AU - Brogden, David W.
AU - Berry, John F.
AU - Gagliardi, Laura
PY - 2012/2/6
Y1 - 2012/2/6
N2 - To gain insights into the trends in metal-metal multiple bonding among the Group 6 elements, density functional theory has been employed in combination with multiconfigurational methods (CASSCF and CASPT2) to investigate a selection of bimetallic, multiply bonded compounds. For the compound [Ar-MM-Ar] (Ar=2,6-(C 6H 5) 2-C 6H 3, M=Cr, Mo, W) the effect of the Ar ligand on the M 2 core has been compared with the analogous [Ph-MM-Ph] (Ph=phenyl, M=Cr, Mo, W) compounds. A set of [M 2(dpa) 4] (dpa=2,2′-dipyridylamide, M=Cr, Mo, W, U) compounds has also been investigated. All of the compounds studied here show important multiconfigurational behavior. For the Mo 2 and W 2 compounds, the σ 2π 4δ 2 configuration dominates the ground-state wavefunction, contributing at least 75 %. The Cr 2 compounds show a more nuanced electronic structure, with many configurations contributing to the ground state. For the Cr, Mo, and W compounds the electronic absorption spectra have been studied, combining density functional theory and multireference methods to make absorption feature assignments. In all cases, the main features observed in the visible spectra may be assigned as charge-transfer bands. For all compounds investigated the Mayer bond order (MBO) and the effective bond order (EBO) were calculated by density functional theory and CASSCF methods, respectively. The MBO and EBO values share a similar trend toward higher values at shorter normalized metal-metal bond lengths.
AB - To gain insights into the trends in metal-metal multiple bonding among the Group 6 elements, density functional theory has been employed in combination with multiconfigurational methods (CASSCF and CASPT2) to investigate a selection of bimetallic, multiply bonded compounds. For the compound [Ar-MM-Ar] (Ar=2,6-(C 6H 5) 2-C 6H 3, M=Cr, Mo, W) the effect of the Ar ligand on the M 2 core has been compared with the analogous [Ph-MM-Ph] (Ph=phenyl, M=Cr, Mo, W) compounds. A set of [M 2(dpa) 4] (dpa=2,2′-dipyridylamide, M=Cr, Mo, W, U) compounds has also been investigated. All of the compounds studied here show important multiconfigurational behavior. For the Mo 2 and W 2 compounds, the σ 2π 4δ 2 configuration dominates the ground-state wavefunction, contributing at least 75 %. The Cr 2 compounds show a more nuanced electronic structure, with many configurations contributing to the ground state. For the Cr, Mo, and W compounds the electronic absorption spectra have been studied, combining density functional theory and multireference methods to make absorption feature assignments. In all cases, the main features observed in the visible spectra may be assigned as charge-transfer bands. For all compounds investigated the Mayer bond order (MBO) and the effective bond order (EBO) were calculated by density functional theory and CASSCF methods, respectively. The MBO and EBO values share a similar trend toward higher values at shorter normalized metal-metal bond lengths.
KW - bond theory
KW - density functional calculations
KW - electronic states
KW - metal-metal interactions
KW - quantum chemistry
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U2 - 10.1002/chem.201103096
DO - 10.1002/chem.201103096
M3 - Article
C2 - 22237933
AN - SCOPUS:84856355303
SN - 0947-6539
VL - 18
SP - 1737
EP - 1749
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 6
ER -