Binding of molecular magnesium hydrides to a zirconocene-enyne template

An enyne-zirconium complex stabilizes molecular magnesium hydride ('MG''H IND. 2') and even a molecular hydride, n'C IND. 4''H IND. 9''MG'H. These systems feature magnesium olefin "pi" complexation.Deutsche ForschungsgemeinschaftNRW Forschungsschule “Molecules and Materials

A Computational Analysis of Supported and Unsupported Group 6 Transition Metal-Metal Bonds Based on the Natural Orbitals for Chemical Valence (NOCV) and the Extended Transition State (ETS) Techniques

A computational study has been carried out on the nature of the metal-metal bond of group 6 transition metal complexes based on the extended transition state (ETS) and natural orbitals for chemical valence (NOCV) methods. The analysis of the unsupported triple (M2L6) and quadruple (M2L2L´2; M=Cr,Mo,W; L,L´=π-acceptor/σ-donor ligands) metal-metal bonds demonstrated that the M-M bond strength follows the trend Cr<<Mo<W, a trend that is influenced largely by the higher steric repulsion between metal fragments that diminish down the triand with increasing M-M distances. The five bonding components of the putative Cr-Cr quintuple (σ2,π2,π´2,δ2,δ´2) bond in Ar´CrCrAr´ (Ar´=C6H3-2,6(C6H3-2,6-Pri2)2) are also presented in this thesis. It is shown that the presence of isopropyl (Pri) groups stabilizes the system by 20kcal/mol through van der Waal dispersions. Finally, the ETS-NOCV is applied on the analysis of the shortest (1.73Å) fully supported Cr-Cr bond in Cr2(Ar´NC(NMe2)NAr´)2 (Ar´= C6H3-2,6(C6H3-2,6-Pri2)2) and the quadruply (σ2, π4, δ2) bonded paddlewheel complexes

Analysis of the Putative Cr–Cr Quintuple Bond in Ar′CrCrAr′ (Ar′ = C₆H₃-2,6(C₆H₃-2,6-Prⁱ₂)₂ Based on the Combined Natural Orbitals for Chemical Valence and Extended Transition State Method

The nature of the putative Cr–Cr quintuple bond in Ar′CrCrAr′ (Ar′ = C₆H₃-2,6­(C₆H₃-2,6-Prⁱ₂)₂) is investigated with the help of a newly developed energy and density decomposition scheme. The new approach combines the extended transition state (ETS) energy decomposition method with the natural orbitals for chemical valence (NOCV) density decomposition scheme within the same theoretical framework. The results show that in addition to the five bonding components (σ²π²π′²δ²δ′²) of the Cr–Cr bond, the quintuple bond is augmented by secondary Cr–C interactions involving the Cr-<i>ipso</i>-carbon of the flanking aryl rings. The presence of isopropyl groups (Prⁱ) is further shown to stabilize Ar′CrCrAr′ by 20 kcal/mol compared to the two Ar′Cr monomers through stabilizing van der Waals dispersion interactions