This thesis describes the results of re-investigations into the solution behavior and interaction with molecular hydrogen of several triarylphosphine and -arsine complexes of ruthenium(ll) and ruthenium(III)
The complex RuCl₂(PPh₃)₃ was found to exist in N,N-dimethyl-acetamide (DMA) solutions in equilibrium with, a triply chloro-bridged bis(phosphine) dimer, I (L = DMA). Addition of chloride ion caused
[Figure 1]
substitution of the solvent to form an anionic dimer, I (L = CI ), and this is discussed, with respect to the stability of this bridging arrangement.
In the presence of added base, Proton Sponge® (1,8-bis(dimethyl-
amino)naphthalene) , the complexes RuX₂YL₂ (X = Y = CI, Br, or X = CI,
Br, Y = 0₂CR; L = PPh₃, Ptol₃, or AsPB₃), [RuCl₂ (PPh₃)₂]₂,
[RuCl(DMA)(PPh₃)₂(0₂CCH₂)]₂, and HRuCl(nbd)(PPh₃)₂ were found to react
with H₂ in DMA or toluene to give complexes of the form [H₂RuXL₂]₂
(X = CI, Br). The ruthenium(III) product. [H₂RuCl(Ptol₃)₂]₂ has been
characterized by analytical, molecular weight, ¹H- and ³¹P-n.m.r. methods and chemical reactions, and the data indicate an asymmetric dichloro-bridged dimer, II. The reaction of II with Ptol₃ in DMA to form HRuCl(Ptol₃)₃ has been studied kinetically; the results suggest that II is in equilibrium with the ruthenium(ll) dimer, [HRuClCPtol₃)₂]₂.
The reaction between RuCl₂(PPh₃)₃ and H₂ in DMA to form
HRuCl(PPh₃)₃ has also been re-investigated. In the presence of a
large excess of PPh₃, the reaction is believed to proceed by way of a
bis(phosphine) monomer species, consistent with previous findings.
However, in the presence of excess chloride, where the precursor
exists as I (L = CI⁻), spectrophotometry evidence indicates the
presence of a long-lived intermediate. Investigations .of the v
corresponding bis (phosphine) complex, [RuCl₂(PPh₃)₂]₂, have made it
possible to formulate the nature of the intermediate. Based mainly on ³¹P-n.m.r. and hydrogen uptake data, the intermediate is believed to be H₃Ru₂Cl₃(PPh₃)₄, a cogener of II. This allows for an overall scheme for the tris(phosphine) system under the conditions of excess chloride:
[Figure 2]
A similar scheme can be invoked to explain the reactivity of the bis-(phosphine) system.
Investigations of the corresponding reactivity toward H₂ of other bis(phosphine) systems for comparison led to the discovery of a new method of preparing carboxylato complexes. Based on a presumed, but not detected, alkyl intermediate, it was possible to prepare the dimer [RuCl(DMA)(PPh₃)₂(O₂CCH₂]₂, containing a bridging succinic acid linkage, and a series of RuCl(0₂CR)(PPh₃)₃ complexes. These have been characterized
and their reactivity towards in toluene investigated. At concentrations sufficiently high for n.m.r. studies, the tris(phosphine) species react with to form HRuCl(PPh₃)₃ by a pathway involving initial formation of HRu(₂CR) (PPh₃)₃. The bis (phosphine) system, [RuCl(DMA)(PPh₃)₂(O₂CCH₂)]₂, forms the tetrahydride dimer, II, but the mechanism of formation could not be elucidated.
The nature of HRuCl(nbd)(PPh₃)₂ has be en examined; the species possesses the coplanar arrangement of metal, hydride, and olefin deemed requisite for olefin insertion reactions. Indeed, reaction with CO gives an acyl-dicarbonyl derivative, III, which results from consecutive olefin and CO insertion reactions. The HRuCl(nbd)(PPh₃)₂ complex reacts
[Figure 3]
cleanly with hydrogen in the absence of added base in toluene to form [H₂RuCl(PPh₃)₂]₂. Studies show that the reaction proceeds by a disproportionate
reaction to form HRuCl(PPh₃)₃ and subsequent conproportionation with an unobserved phosphine deficient species to form the final product. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/24282 |
| Date | January 1983 |
| Creators | Dekleva, Thomas William |
| Publisher | University of British Columbia |
| 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 0.0024 seconds