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.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2013

Author dc:creator

• Ndambuki, Sylvester Wambua

Advisor dc:contributor.advisor

• Ziegler, Tom

• Chemistry--Inorganic

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

eng

DOI

http://dx.doi.org/10.11575/PRISM/24675

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:11023/553