The thesis describes some aspects of the aqueous solution chemistry of chlororuthenate(III) and chlorocarbonylruthenate(III or II) complexes including their reactivity toward carbon monoxide. This led to the synthesis and characterisation of a polymeric complex [HRu(CO)₃][sub n], which is formally a Ru(I) derivative. The use of these ruthenium complexes for activating CO catalytically was studied, especially for the carbonylation of amines.
The [HRu(CO)₃][sub n] polymer was characterised by microanalysis, infra-red and high-field ¹H n.m.r. , and its chemistry In donor solvents in which it was soluble. The polymer may be formed by reductive carbonylation of chloro complexes of Ru[sup II], Ru[sup III](CO), Ru[sup II] (CO), Ru[sup II] (C0)₂ and Ru[sup II]CO)₃, and stoichiometric evidence suggests processes such as:
[chemical reactions 1 to 4].
Increasing acidity and chloride concentration inhibit the reductive carbonylation process, which likely requires simultaneous coordination
of cis CO and OH ligands. Reactions (1) - (4) are
accompanied by formation of smaller amounts of low valent ruthenium complexes including Ru₃(CO)₁₂, which could result from a reductive carbonylation process such as
[chemical reaction 5]
or via 'combination' of Ru[sup I] and Ru[sup -I] species. Evidence is presented
for reaction (5) starting with CsRu(CO)₃Cl₃. Reductive carbonylation 2-
of Ru(CO)₂Cl₄⁻² (reaction (4)) shows autocatalytic gas uptake plots, indicating catalysis of the reaction via a Ru(0) or Ru(I) intermediate.
The kinetics for the carbonylation of piperidine to N-formyl piperidine catalysed by each of the complexes [HRu(CO)₃][sub n], [Ru(CO)₂(OAc)(pip)]₂, and CsRu(CO)₃Cl₃, have been studied under mild conditions. Mechanisms are proposed to explain the observed kinetics and in each case a tricarbonyl monomeric species appears to be the active catalyst. A CO insertion reaction in a Ru(CO)₃ (pip)[sub x] intermediate must be involved. A scheme such as (6) e.g.
[chemical reaction 6]
requires a hydride shift, likely metal activated. Alternatively, piperidine could behave as a proton acceptor with the reaction proceeding via a carbamoyl intermediate (reaction (7)).
[chemical reaction 7]
Both [HRu(CO)₃][sub n] and CsRu(C0)₃Cl₃ carbonylate piperidine in a stoichiometric reaction in the absence of CO, and in the case of the cesium salt evidence suggests the following reactions:
[chemical reactions 8-9]
Only secondary amines were carbonylated effectively. Attempts to isolate and characterise ruthenium complexes via the reactions [HRu(CO)₃][sub n] or CsRu(C0)₃Cl₃with piperidine proved frustrating, although one complex isolated from the polymer reaction is thought to be H₂Ru₂(CO)₄(pip)₃, and an oxygenated solution of [HRu(CO)₃][sub n] in piperidine yielded a complex which analysed well for [HRu(CO)₂(pip)]₂•0₂. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/20913 |
| Date | January 1977 |
| Creators | Plackett, David Victor |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
Page generated in 0.0014 seconds