Ali, Shahbano Amjad; (2001) Ruthenium and osmium clusters containing imido and sulfido ligands and their reactions with unsaturated organic molecules. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Chapter 1 is an introduction to our research in triosmium and triruthenium clusters and details the different types of trinuclear clusters and capping ligands available. The uses of clusters in catalysis are then discussed. Chapter 2 describes the synthesis of amido and imido systems derived from [M3(CO)12] and NH2SO2tolyl. The formation and crystal structure of [Ru3(μ3-H)2(μ3-NSO2tolyl)(CO)9] is presented with its thermal decarbonylation to give [{Ru3(μ-H)2 (μ4-NSO2tolyl)(CO)7}2] (based on spectroscopic evidence) and protonation to give [Ru3(μ-H)3(μ3-NSO2tolyl)(CO)9]⁺. The deprotonation of [Os3(μ-H)(μ-NHSO2tolyl)(CO)10] to give the pyramidal μ2-imido system [OS3(μ-H)(μ-NSO2tolyl)(CO)10] which has been crystallographically characterised, is also discussed Chapter 3 reports the formation of the MeCN-substituted derivatives by treatment of [M3(μ-H)2(μ3-NSO2tolyl)(CO)9] with Me3NO.2H2O/MeCN. Important new discoveries on how alkynes are incorporated into these clusters are described, including single insertions into M-H bonds and coupling of alkenyl ligands formed by double insertions to give butadiene clusters. The crystal structures of [Os3(μ-trans-σ, η2-CH=CHBu)(μ3-NSO2tolyl)(CO)8] and [Ru3(μ-η2, η2-C4H6)(μ3-NSO2tolyl)(μ3- CO)(CO)7] are given. Chapter 4 studies the reactions of [M3(μ-H)2(μ3-S)(CO)8(MeCN)] (M = Ru or Os) with alkynes. Here evidence for the formation of double insertion products is presented as well as for single insertion products and butadiene clusters. The mode of coordination for the butadiene ligand in this case was different to those in Chapter 3. The crystal structure of [Os3(η4-PhCH=CHCPh=CH2)(μ3-S)(CO)8] is discussed. Studies on the reductive coupling of alkynes to give butadienes are described. Comparisons between the different effects of μ3-NSO2tolyl compared with μ3-S and Ru compared with Os are presented. Chapter 5 focuses on the coupling of high-valent with low-valent transition metal units within a single molecular cluster. For instance, the synthesis and characterisation of the high-low valent clusters [Ru3(CO)12MoX2] where MoX2 is the high-valent fragment is reported. The crystal structure of [Ru3(CO)12{Mo(N-2,6- Me2C6H3)2}] results on protonating this cluster are presented.

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